BIS 002C: Midterm #3

Examples of convergence: canine convergence in mammals

(3) Marsupial/eutherian convergence in mammals.

Evidence that choanoflagellates are the sister group of Metazoa

1. Collar cells: similar cells are present in sponges (choanocytes) and, in more modified form, in other animals. In other words, there is shared similarities in cell structure. 2. Choanoflagellates have homologs of metazoan cell signaling and adhesion genes, and these genes are not found in other eukaryotes. 3. DNA sequence data support choanoflagellate + metazoan clade.

Practice question: fossil mollusks

117,000 living species (~70,000 fossil species). Very large clade. Lots of fossils.

Cnidaria summary

12,500 species. Lack segmentation. Radial symmetry, around a longitudinal axis. Often with tentacles around the oral end. Incomplete gut: gastrovascular cavity. Diploblastic: two cell layers separated by gel-like mesoglea. Ectoderm (also known as epidermis). Endoderm (also known as gastrodermis). Two body forms: tube-shaped polyp, usually sessile, with oral end up; and bell-shaped medusa, motile, oral end facing down. Many cnidarians alternate between these two body forms. Cnidocyte: specialized cell with stinging or adhesive cnida. Coiled cnida is discharged suddenly by hydrostatic pressure, penetrating prey and injecting poison. Diffuse, noncentralized nervous system: nerve net. Very simple. Muscle cells present but simple. Present in both the endoderm and ectoderm. Polyps generally have few sensory structures, but medusae are often more specialized. Some cube jellies have eyes with epidermal cornea, cellular lens, and multi-layered retina. Similar in structure to the eyes of vertebrates. They have eyes, even though they don't have a brain. Not a lot of complicated sensory structures in cnidarians.

Annelid diversity

19,000 species. Less diverse than mollusks. Marine, freshwater and terrestrial. Two major groups: Polychaeta and Clitellata, but polychaetes are paraphyletic. Clitellata are a monophyletic group. Loss of parapodia is a synapomorphy of the Clitellata. Polychaetes have parapodia.

Basidiomycota (club fungi)

2nd largest group of fungi (1/3 species). Diagnostic spore structure, basidium with 4 spores on a club. Fruiting bodies can be highly specialized and unique. They also have species that have no fruiting bodies; some of such fungi are important plant pathogens.

Arbuscular mycorrhizae

A distinct type of endomycorrhiza formed by glomeromycete fungi, in which the tips of the fungal hyphae that invade the plant roots branch into tiny treelike structures called arbuscles. The Arbuscular Mycorrhizae fungi-plant symbiosis is > 400 million years old.

Pseudocoelom

A fluid-filled cavity derived from the blastocoel, and bounded partly by mesoderm and partly by endoderm.

Grazer

A grazer is any animal that relies on herbivory (feeds on plants) as its primary food source.

Bony fish

A paraphyletic group that consists of three living lineages. Lineages: ray finned fishes, coelacanths, lungfishes.

Phylogeny: major lineages of Metazoans

A polytomy exists at the base of the tree. Effects: under some reconstructions, you might conclude different things about digestion in a gut.

True coelom vs. reduced coelom

A reduced coelom is a true coelom, just reduced in size. This occurs, for example, in Mollusca and Arthropoda, where the coelom surrounds just a few organs, and the body has a hemocoel (derived from the blastocoel) which serves as an open circulatory system.

Bilateral symmetry

A single plane divides animal into left and right mirror-image halves. Characteristics of these animals: 1. Distinct anterior (front) and posterior (back) ends. 2. Cephalization: differentiation of anterior end into a head, with concentration of sensory organs. 3. Segmentation: serial repetition of body parts in well-defined segments. The circled animals in the image at left have these characteristics.

Problems associated with sea jellies

A single sea jelly tentacle is loaded with massive numbers of stinging cells. The mucous of clownfish was recreated to create a useful product to benefit humans, preventing them from getting stung by sea jellies.

Keystone species

A species that influences the survival of many other species in an ecosystem. One that has a disproportionately large effect on ecosystem dynamics.

Review: synapomorphy

A trait that arose in the MRCA of a group. Unique synapomorphy: A trait that arose only in the MRCA of the group (in no other organisms).

Dikarya

A vast fungal group that includes about 98% of all described fungal species and in which dikaryotic cells are formed (as part of their life cycle). This includes species that form typical mushroom fruiting bodies. They devised a way to fuse the cell but not to fuse the nucleus. The nuclei of the fused cells are still independent.

Practice question: Annelida and Mollusca

A. Spiral cleavage is a synapomorphy of the lophotrochozoans. That is the level at which it is a synapomorphy. It is a synapomorphy of a more inclusive group, not something specific like Annelida + Mollusca. B. This is a characteristic of deuterostomes. In protostomes, the mesoderm arises near the lip of the blastopore. C. Two synapomorphies of the lophotrochozoans: spiral cleavage and having a trochophore larva. The trochophore larva was lost in a few groups inside the Lophotrochozoans. It didn't independently arise in the two groups. It is probably a homologous character in Annelids and Mollusks. D. Both groups produce a coelom from splitting the bands of the mesoderm (schizocoely).

Practice question: Polychaeta

A. They are paraphyletic. Their characteristics is likely to be the original features of the common ancestor of Annelida. All of the features we see in Polychaeta must have been present in the ancestral Annelid. Refer to the phylogeny from the last card.

Practice question: synapomorphies

A: Not true because that would be the definition. B: Just because a synapomorphy is modified doesn't mean it isn't a synapomorphy. Cnidarians: incomplete gut. Ctenophores: complete gut. Explanation: We don't know what the ancestral condition is after gastrulation. We don't know what the original condition is between protostomes and deuterostomes. We might look at an outgroup. The outgroup to Bilateria is the cnidarians. We can't use them as an outgroup because they have an incomplete gut. The blastopore functions as both the mouth and anus. We can also look at placozoans (we can get suggestions). We can look at ctenophores because they have a complete gut. We don't know what happens with gastrulation with ctenophores. It is controversial. One paper said that the blastopore becomes the mouth.

Arthropoda: exoskeleton

Advantages: Support for walking on land. Protection against predators. Chitin reduces water loss. Disadvantages: Constraints growth. Organisms have to periodically shed their exoskeleton and grow a new skeleton that is slightly larger. This is a vulnerable stage, as the new exoskeleton is quite soft. The new skeleton has to be flexible. Ecdysis is the shedding of the exoskeleton.

Aflatoxin

Aflatoxin is produced by Aspergillus flavus and can have lethal effects on animals; especially those without a varied diet.

Synapomorphies of the TOF

All features listed are synapomorphies.

Spiders

All spiders produce silk, and many, but not all, produce webs that capture prey. A tarantula recently was caught consuming an opossum.

Nematodes (Nematoda)

Also known as "roundworms." Includes model organism Caenorhabditis elegans. Include many species of medical and agricultural importance. Contain a psuedocoelom. Only group that we discussed that contain this trait. This means that they retain the blastocoel. Nematodes are known from every habitat on earth including Antarctica and deep oceanic trenches. Nematodes are important agricultural pests. Nematodes are important parasites of plants and animals. Nematodes have a great diversity of mouthpart. Don't form a symbiotic relationship with fungi. Lack segmentation.

Phylogeny: amniotes

Amniotes: reptiles and mammals. Among reptiles, there are lizards and lizard like things called Lepidosaurs. Crocodilians and alligators fall in the same group. Within the dinosaur lineage lies the birds. Reptiles: Four major extant clades: lepidosaurs, turtles, crocodiles, and birds (within dinosaurs).

Symmetry

An animal is symmetrical if at least one plane can divide it into two mirror-image halves.

Absorptive heterotrophy

An organism (usually a fungus) that obtains its food by secreting digestive enzymes into the environment to break down large food molecules, then absorbing the breakdown products. Directly related to their life cycle. Defines fungi as a group.

Filter feeder

An organism that takes in water to filter out the food and then releases the extra water (clam, oysters, sponge, etc). Filter feeders are a subgroup of suspension feeders.

Radial symmetry

Animal in the form of a cylinder, parts arranged around the long axis, and with multiple imaginary planes that divide the animal into equal halves.

Animals

Animals are a large and diverse clade of eukaryotes. Monophyletic group. Diplontic life cycle.

Practice question: reduced coelom and open circulatory system

Annelids do not have a reduced coelom. The coelom is well developed. Each compartment has a proper coelom. The movement of the muscles around the coelom changes the shape of each segment. Blood flows through vessels. The group of mollusks that has a closed circulatory system is the cephalopods.

Practice question: metazoan phylogeny

Answer: C.

Practice question: wings

Answer: C. A. Wings evolved within insects. They evolved within a subgroup of insects. This is also why B is true. C. False. Mandibulate mouthparts are seen in insects as a whole and are shared with myriapods and other groups. D. True. E. Wings are characters that evolved within a subgroup of insects. Triploblastic is a character that evolved within a subgroup of metazoans.

Practice question: metazoan phylogeny

Answer: C. Option A: Option A would likely apply to placozoans because they have lost many of their features. Issue with A is that sponges lost all of these features, too. Why would they lose advantageous features? They help you defend yourself against predators. Arose in the MRCA. Got lost in many places, and regained in many places. Too many steps, at least in terms of parsimony. Argument against: Sometimes genomes leave signatures of past histories. Example: Are there genes in placozoa that are involved in gastrulation? Are there vestigial genes that suggest that a character was lost? Can we find intermediates in the fossil record? Option B: Argument in favor: most parsimonious option would be two steps. Problem: This would have to be a remarkable convergence. The fact that such complicated characters (guts, nerves, and muscles) evolved completely independently not once, but twice in the tree, is rare.

Chytrids

Aquatic and produce flagellated spores; they were the first fungi.

Placoderms

Armor-plated predators with jaws and teeth-like structures. First jawed vertebrates. Originated in Silurian, extinct by end of Devonian (360 mya). Extinct. Used to be common. Some placoderms were nine meters long and functioned as major predators.

Radula

Around the mouth is the structure called the radula. Using for eating. It allows them to break off pieces of tissue. Organ that consists of a muscular piece of cartilage called the odontophore. On top of that is a series of backward pointing sharp teeth made of chiton. The sharp teeth are moved back and forth due to the movement of the muscles of the odontophore. Many mollusks use this, but not all have a radula. The radula is unique to the mollusks, and is found in every class of mollusks except the bivalves.

Arthropoda

Arthropoda = "jointed foot." Extraordinary diversity, comprising about 3/4 of all described animal species. Mother species undescribed or undiscovered, perhaps 50+ million species altogether. Found in all habitats (marine, freshwater, terrestrial). This group has colonized land far more than the other groups we have discussed. Characteristics: Bilaterally symmetrical coelomate protostomes (same as Annelids). Segmented body, with structures repeated in each segment (same as Annelids). Paired jointed appendages with internal muscle attachments. Flexibility of movement. Tagmosis is the regional specialization of parts of the body. Specialized units are tagmata (singular: tagma). Tagmata are groups of segments that function in certain ways. Examples of tagmata: head, thorax, abdomen. Exoskeleton (composed of chitin and cuticle proteins) organized into articulating plates. Provides protection. Growth by periodic molting of exoskeleton (ecdysis). Paired compound eyes composed of many photoreceptive units (ommatidia). Not great for a sharp image, but is great for detecting movement. Reduced coelom and open circulatory system (hemocoel). The hemocoel is derived from the blastocoel. The blastocoel does not get completely displaced by a true coelom. It persists, and the hemocoel provides an open circulatory system. Complete gut with regional specialization. Different parts of the gut focused on different aspects of food processing. Food moves one way from mouth to anus. Also in Mollusca and Annelida, and other well developed protostomes. Well developed nervous system with dorsal brain and ventral nerve cord. Also in Mollusca and Annelida, and other well developed protostomes. Complex but variable excretory and respiratory systems. Reduced coelom. Persistent blastocoel becomes the hemocoel. Open circulatory system.

Differences between ascomycota and basidiomycota

Ascospores are formed. There is the same hyphae formation process in Ascomycota and Basidiomycota. There are different spores. Plasmogamy happens in both cases. The dikaryon is a mycelium that has two different nuclei. Ascomycota form an ascoma (cup shape). Forms the asci. Karyogamy, then meiosis and mitosis.

Importance of phylogeny

Aspergillus are also used in the production of soy sauce and other foods. But, it is a single 'species," A. oryzae. There is a single species that you should use to make soy sauces. All of the other species are toxic. We discovered this through phylogenies.

Characteristics of sponges (porifera)

Asymmetrical gutless animals. Sponges are not diploblasts or triploblasts. They do not have gastrulation. No gut, nerves, or muscles. Aquiferous system: branched water canals. Water flows continuously into incurrent pores (ostea). Differentiated cell types (such as choanocytes, pinacocytes, and amoebocytes), but no true tissues or organs. Cells arranged in gelatinous matrix (mesohyl) with collagen and usually spicules (skeletal elements) composed of silica or calcium carbonate. Spicules are hard structures made of silica or calcium carbonate that occur in the mesohyl in the cavity of the sponge. All aquatic, mostly marine. ~8500 species (7000 species of demosponges). Adults sessile, larvae motile. Mostly filter feeders on microscopic particles (bacteria, organic detritus, etc.), captured on microvilli, digested intracellularly. A few sponges live in freshwater. Most are part of the demosponges. Food is captured on the microvilli, and then taken inside by phagocytosis. Lack cephalization. Reproduction: Asexual: Through "budding" or fragmentation. Sometimes clones are formed. Sometimes broken pieces of sponge can grow back. A sponge can be thrown in a blender and the pieces can still grow back. Sexual: Most sponges are hermaphrodites but not self-fertilizing: sperm and eggs produced at different times (from choanocytes or other cells in the sponge body—no specialized gonads). One individual produces both sperms and eggs. The equivalent term in plants is monoecious (one house). Sponges are mostly monecious or hermaphrodites. Sperm released into the environment en masse through the aquiferous system ("smoking sponges"); then enter neighboring egg-containing sponges. They produce oocytes and sperm at different times. Released into the aqueous environment. Oocytes are kept in neighboring sponges. The eggs stay inside the parent sponge and the sperm have to get to the egg.

White-nose syndrome

Bats hibernate and slow down their metabolism while in humid, cold caves. This is a perfect place for fungi. It grows around mouth, nose and wings of hibernating bats. When bats are hibernating, both their body temperature and immune systems are depressed. The death of bats is important because they are insectivores that consume 6,000-8,000 insects per night. They control insect populations. Millions of bats have died from this fungus. The New York Times called this syndrome the most consequential wildlife disease of modern times.

Mollusca

Bilaterally symmetrical (some are secondarily asymmetrical) coelomate protostomes. Examples of asymmetrical organisms: Gastropoda (snails, slugs, conchs, sea hares, and sea butterflies). Not all mollusks are cephalized. Complete gut, regionally specialized. Cnidarians have an incomplete gut. Ctenophores have a complete gut. Reduced coelom (vestigial around heart, gonads, and some other organs). Open circulatory system (hemocoel), with heart—usually three-chambered—and associated vessels. Blood like fluids circulate in large, open cavities. The heart pumps the blood. At the end of the large vessels of the heart, the liquid flows in large open sinuses. Annelids and Chordata don't have this. In squid and octopus, they have a closed system (cephalopods). Characteristic body plan: mantle, visceral mass, and foot. Mouth with radula (rasping tongue-like organ). Well developed nervous system (especially in cephalopods). Nerves are concentrated into ganglia (singular ganglion). Some of the ganglia form a brain like structure in some mollusks. This contrasts the net nerves we see in cnidarians and ctenophores. Excretory system in form of nephridia. Nephridia are tubules. It is an organ system designed to get rid of wastes. Reduced coelom. Persistent blastocoel becomes the hemocoel. Open circulatory system.

Bird's nest fungi

Bird's nest fungi are dispersed by a combination of water (splash cups) and animals. The cup like structure is a cluster of spores. When they get wet, they fly. They have a tail that sticks to the plant.

Ratite birds

Birds that are only found in the Southern Hemisphere. They are all flightless. Traditional view: sister to Tinamous. Ratites are a monophyletic group. Tinamous can fly. Similar bone structure. These birds got isolated on different parts of ancient continents. But DNA sequence data revealed that tinamous are embedded phylogenetically within ratites.

Modifications to the molluscan body plan

Bivalves: In bivalves, the ventral foot has become a burrowing structure. Cephalopods: In the cephalopods, the ventral foot has developed into a complex series of arms and tentacles and a siphon (siphon used to bring water into the mantle cavity).

Pogonophorans (beard worms)

Bizarre gutless worms. Live in chitinous tubes, often at great depths. Species inhabiting hydrothermal vents have symbiotic bacteria that use hydrogen sulfide as energy source to fix carbon (chemoautotrophs). Bacteria live inside worms and provide them with nutrients. Beard worms were not originally thought to be Annelids. DNA sequence data has shown that they are Annelids.

Brown rot fungi

Break down cellulose, and hemicellulose, but leave lignin behind.

Echinodermata endoskeleton

Calcareous endoskeleton, composed of plates or ossicles, often with spines and pincer-like structures (pedicellariae). This is called an endoskeleton because it is derived from the mesoderm. It is covered with a thin epidermal layer. The epidermis is derived from the ectoderm. The skeletal features are derived from the mesoderm. The ossicles are connected to each other by collagen. Body can become rigid/tense with nerves. Muscles aren't needed.

Sea otters, sea urchins, and kelp forests

California sea otters eat urchins. Sea urchins consume kelp. Without sea otters and other predators the urchins become abundant and destroy underwater kelp forests. The forests are homes for organisms.

Sea cucumbers (Holothuroidea)

Can expel parts of their gut as anti-predator defense. Image: Sea cucumber with expelled Cuvierian tubules.

Cephalopod intelligence

Capable of learning and memory tasks. Can learn by observation of others (experiments with octopuses). Octopuses watch the trainings in one aquarium and are able to perform tasks that they saw their neighbor perform.

Otodus megalodon

Carcharodon megalodon: Megalodon: major predator, 1.8-1.5 million years ago. 50 feet long. Preyed on large marine fishes and mammals (including whales). Other sharks: Great white shark: largest predatory shark. Whale shark: largest shark (but a filter feeder).

Fish characteristics

Cartilaginous fish undergo respiration using gills. Water has dissolved oxygen and flows over the gills. Lungs and the swim bladder are homologous structures. An organism can't have them both. The swim bladder enables fish to control the amount of gas in their bodies, which affects their buoyancy. This structure occurs in the ray finned fish.

Radial cleavage

Cells divide parallel to, or at 90° to, the animal- vegetal axis, and accumulate in even, symmetrical layers. Cube shaped.

Cephalopod eyes

Cephalopods developed a single lens eye. Similar to vertebrates eyes. Cuddle fish, squid, and octopuses are have these eyes. Origins of eyes are an example of convergent evolution. The common ancestor of an octopus and vertebrate would be the split between protostome and deuterostomes. Octopuses are mollusks. The common ancestor did not have a complex eye. It was a worm like creature that didn't have an eye. Eyes must be a product of convergent evolution. Excellent visual acuity. Some common genes (rhodopsin, PAX6) involved in eye development in the two groups. Concept of "deep homology." Some of the same genes that are involved in the development of the eye are found in both cephalopods and vertebrates. Deep homology: although phenotype is a product of convergent evolution, at some deep level, there are homologous elements to the structures.

Sea slugs and photosynthesis

Certain sea slugs feed on algae. They digest most algal tissue but sequester the chloroplasts in their body, where they continue to function. Kleptoplasty: the stealing of plastids for use as photosynthetic machines. They can photosynthesize. They are kind of autotrophs. All animals can't undergo photosynthesis, but there are some exceptions. Sequester alga-derived chloroplasts for use as photosynthetic machines. How do they accomplish this, given that the functioning of such organelles in algae requires many nuclear-encoded genes? Acquire nuclear genes from algae that are used in regulating photosynthesis. This is a case of lateral gene transfer between two multicellular eukaryotes.

Bilateria

Characteristics: Triploblastic construction. Bilateral symmetry. Anterior/posterior axis. At the anterior, there tends to be a head (often with cephalization). Cephalization (concentration of nerves and sensory organs in a given area of the body).

Classic view of the phylogeny of Mollusca

Chitons and monoplacophora are shelled and somewhat segmented. Summary: some mollusks are segmented worm like animals that are not similar to traditional mollusks. Might have represented original mollusks. Residual effect of this worm like in the chitons and monoplacophora.

Modifications to the molluscan body plan

Chitons: In chitons, there is a series of shelled plates on the top of the animal, and repeated gills on the lower half. We see segmentation here. Gastropods: In gastropods, there is torsion, where the body is twisted in such a way that the anus comes to lie above the mouth. Twisting of the visceral mass so that the anus is now at the top of the body. Purpose of torsion: organisms are able to retract their head into their shells and protect themselves.

Chytrid vs zygomycota life cycle

Chytrids live in water. They have flagella. No flagella in the right life cycle (zygomycota). On the right, we see chemicals being produced; the hyphae get close and form gametangia. On the left, we don't have that union. On the right (zygomycota) plasmogamy is separated from karyogamy. A zygospore is produced on the right.

Sea star anatomy

Circular ring with series of side canals. Tube feet are connected to side canals. Tube feet are bulb like. Suction effect as a result of muscle action on the ampulla. Tube feet can extend or be retracted. Can help them capture prey and move. Tube feet are powered by the water vascular system. Water vascular system: water enters via an opening (madreporite), and circulates through a system of canals that culminate in a series of tube feet (with suckers). Tube feet are extensions of the water canals that extend into the arms. Movement of water allows for suction. Madreporite is where the water can enter and exit. It replenishes the system. Antagonistic muscle action on the tube feet can alternately extend and retract them.

Open vs. closed circulatory systems

Closed: deuterostomes. Chordates and echinoderms. Protostomes: closed in cephalopods and mollusks. Other mollusks have an open circulatory system. Annelids are closed. Arthropods are open. Open: still have veins and arteries. Blood is released into an open cavity. No elaborate system of capillaries. Blood would then be considered part of the extracellular matrix outside of cells.

Cnidarian feeding

Cnidarians are all carnivorous. There are exceptions. Myxozoas, for example, are parasites. Small animal prey captured with cnida-laden tentacles and conveyed into the gastrovascular cavity. Extracellular digestion occurs here. Occurs in the gut. Products are taken by phagocytosis into nutritive cells (of the gastrodermis) where digestion is completed intracellularly. Many cnidarians gain additional nutritional benefits from symbiotic photosynthetic protists. To have extracellular digestion means that digestion starts as extracellular. Most organism that are extracellular have a final stage that is intracellular. Example: sponges only have intracellular.

Cnidarian anatomy and body forms

Cnidarians are diploblasts (ectoderm and endoderm). Noncellular layer called the mesoglea (gel like substance). Mesoglea is an extracellular matrix found in Cnidarians. Area between endoderm and ectoderm. Contains proteoglycans. Particularly developed in sea jellies. It is similar to the mesohyl (mesophyll is found in sponges). Two body forms: tube-shaped polyp, usually sessile, with oral end up; and bell-shaped medusa, motile, oral end facing down. Many cnidarians alternate between these body forms during their life cycle. Blastocoel is called the mesoglea in cnidarians. Image: Yellow for endoderm, dark blue for ectoderm, and light blue for mesoglea.

Cnidaria nematocysts

Cnidocyte: specialized cell with unique stinging or adhesive structure called a cnida (most common type: nematocyst). Nematocyst has a long tube structure. Spine at base with toxins, used to wrap around and inject poison into its prey.

Cnidaria: predator mechanisms

Coiled cnida is discharged suddenly by hydrostatic pressure, penetrating prey and injecting poison. Trigger hair is stimulated.

Postanal tail

Combined with notochord and musculature --> propulsion.

Sea stars (Asteroidea)

Common, largely predatory. They can use their tube feet to hold open the shells of bivalves until the muscles weaken. They then release enzymes into the bivalve and feed.

Communication between cephalopods

Communication techniques: movements (of tentacles, fins, etc.) and body color changes. Chromatophores (cells with pigment): changes in shape --> changes in color. Squids can change their color using a cell called a chromatophore. It contains pigments and has muscles in it. It allows cells to change shape. The change in shape changes the color. Squid can do this. They have it best developed. Octopuses likely have this, too.

Hyphae and mycelium

Contain cells called hyphae. Each hyphae is one cell. Contain a mycelium, which is the main fungal body and is composed of a group of hyphae.

Hemichordates

Contain pharyngeal slits. Don't have the other three characteristics of Chordata. They are not part of Chordata. They are the reason why we don't think pharyngeal slits aren't a synapomorphy of chordates.

Trocophore

Contains a band of cilia. Movement of cilia allows the larva to move in its aquatic environment. Evolved in the Lophotrocozoans, as did spiral cleavage. it is not found in all protostomes (saying so would be a simplification).

Crustacean examples

Decapoda: includes crabs, crayfish, lobsters, prawns, shrimp. Krill: Feeds upon plankton and small organisms in the water. Krill are highly abundant. Important food for larger animals (seals and whales, etc). Barnacles: sessile, filter-feeding crustaceans. Not mollusks. They are a modified crustacean. They are sessile, which isn't consistent with the remainder of the clade. They are monecious, unlike their clade. Can move by virtue of settling on another organism. Sow bug (rolly polly): Kind of crustacean that has adapted to living on life in land. Most are active at night in gardens that are well irrigated. Other example: Shasta crayfish (California native, endangered by introduced species).

Dorsal hollow nerve chord

Develops from infolding of ectoderm above the notochord. In comparison, the ventral nerve chord is found in protostomes.

Notochord

Dorsal supporting rod, semi-rigid yet flexible. Develops in embryo (replaced by vertebrae in most vertebrates). Derived from the mesoderm. Made of collagen and glycoproteins. Similar to cartilage. A supporting structure.

Cross section of a polychaete worm

Each segment has paired appendages. Presented in blue. Involved in locomotion and respiration.

Cleavage

Early stages of cell division after zygote formation, resulting in multiple cells (blastomeres) and establishment of a longitudinal axis (animal-vegetal axis). Patterns of cleavage vary among different animal groups, especially as a function of how much yolk (stored nutrient) is in the egg. Two kinds: radial and spiral cleavage.

Phylogeny: deuterostomes

Echinoderms are sister to chordates. Three main subgroups within the chordates: vertebrates, tunicates, and lancelets. Two non-vertebrate clades are the lancelets and tunicates.

Modern-day view of the phylogeny of Mollusca

Established after DNA sequencing. Segmentation in Polyplacophora (chitons) and Monoplacophora.

Social insects

Eusocial insects live in colonies with division of labor: some individuals reproduce (queen, male), but most individuals belong to a non-reproductive worker caste. Eusocial = striking reproductive division of labor. Most members of a colony are workers. Reproduction is confined to one or a few individuals. Examples: (1) termites, (2) ants, (3) some bees and (4) some wasps. Social insects are often ecologically dominant species and reach high densities.

Mammals: Eutherians

Eutherians are sometimes called placental mammals. Well developed placenta. Main group of animals that is found everywhere.

Segmentation

Evolved three times: Annelida, Chordata, and Arthropoda.

Cnidarian clade: Hydrozoa

Example: hydrozoans. Includes lab animal Hydra (medusa stage lost) Colonial hydroids (such as Physalia, the Portuguese man-of-war) form large polymorphic floating colonies comprised of various types of polyps and attached medusae.

Cnidarian clade: Scyphozoa

Example: sea jellies (a.k.a. jelly fish). Sea jellies get their name due to their extensive mesoglea.

Arthropoda: Myriapoda

Examples: centipedes and millipedes (12,000 species). Two body tagmata: head and trunk. Numerous segments, each with one (centipede) or two (millipede) pairs of legs. Centipedes: carnivorous, with poison fangs. Millipedes: scavengers (some secrete cyanide in defense).

Molluscan diversity

Examples: chitons, snails, slugs, nudibranchs, clams, mussels, oysters, squids, octopuses, nautiluses, etc. Range in size from microscopic to very large (giant squid can achieve 900 kg). Mostly aquatic (marine and freshwater, but more are marine) but some gastropods are terrestrial. First major clade where we see both terrestrial and aquatic organisms. Can be herbivores, detritivores, carnivores, filter feeders, parasites, etc.

Bivalves

Examples: clams, mussels, scallops, oysters. Bivalves: two parts to the shell. Shell in two parts, hinged dorsally. Mostly sedentary filter feeders (using gills) No radula. Food and water brought in through siphon. Use gills to filter food particles, as well as for gas exchange. Loss of cephalization. They are sessile filter feeders, so they no longer move around or actively hunt prey. Cephalization is no longer needed.

Arthropoda: Crustaceans

Examples: crabs, shrimp, lobsters, barnacles, isopods, copepods, etc. (67,000 species). Paraphyletic group. Characteristics: Three body tagmata: head, thorax and abdomen. Head and thorax are closely integrated. Appendages (some two-branched) specialized for sensing, locomotion, respiration, etc. Hexapods and myriapods have single branched appendages. Dorsal carapace. Structure covering the head of the thorax. Diverse feeding habits (predators, filter feeders, scavengers, etc).

Cnidarian clade: Cubozoa

Examples: cube or box jellies (sea wasps). Cube jellies are very toxic. Small clade. Include species that have eyes. Sting is very toxic. Poisons from neotocites. Affect humans at beaches. Common in Australia beaches. Can kill people. Some beaches in Australia are closed for 7-8 months a year because of box jellies.

Oligochaetes

Examples: earthworms and related freshwater species. Characteristics: Classic deposit feeders (studied by Darwin who measured their prodigious earth-turning abilities). Cross-fertilizing hermaphrodites, held together during mating with mucus secreted by clitellum. Eggs and sperm placed in protective cocoon, from which small worms emerge. European earthworms have been introduced to America, which has caused ecological problems. Monecious. Each earthworm provides sperm to the other. They produce a protective cocoon, where fertilization occurs. They are often predators or detritivores.

Mammals: Prototherians

Examples: echidna, duck-billed platypus. Egg-laying mammals. Most mammals don't lay eggs.

Arthropoda: Chelicerata

Examples: horseshoe "crabs", sea "spiders", scorpions, mites, ticks, spiders, and kin (114,000 species). Characteristics: Two body tagmata: cephalothorax and abdomen. Two tagmata (instead of three that characterize insects). Characteristic appendages: chelicerae (pincers), pedipalps, usually 4 pairs legs Mostly predators and parasites. Spiders use silk (produced by glands in abdomen) to snare prey. Hexapods have three pairs and six legs. Spiders have 4 legs. Recent data suggests that they are modified arachnids.

Arthropoda: Hexapoda

Examples: insects and allies. Characteristics: Three tagmata: head, thorax and abdomen. One pair of antennae (two pairs in other crustaceans). Three pairs of legs (located on the thorax). Respiration by tracheae (system of air tubes extending into body). This is the main means of respiration for terrestrial organisms. Originally: mouthparts with mandibles, much modified in some groups. Crustaceans, myriapods, and hexapods all have mandibles. In mosquitoes, the mandible has been modified and is very reduced. Wings evolved (once) within the insects. Most insects have wings, but not all. Wings evolved more than once in the entire TOL. Wings are not a synapomorphy of insects. They evolved within the clade of insects (Hexapoda).

Chordates

Examples: lancelets, sea squirts, jawless fishes, jawed fishes, and tetrapods (amphibians, reptiles, mammals). Diverse and dominate. Land and water. Four characteristics (at least in embryo): 1. Notochord. 2. Dorsal hollow nerve chord. 3. Postanul tail. 4. Pharyngeal slits. Other innovations (apply to most chordates): 1. Internal skeleton with vertebrae. Found in vertebrates. 2. Jaws. 3. Two pairs of walking limbs. Found in tetrapods. 4. Segmented body muscles.

Clitellata

Examples: oligochaetes and leeches. Freshwater and terrestrial. Lack parapodia and tentacles. Clitellum: thickened band in middle of body that secretes a cocoon for protection of young. Prevents zygotes from desiccation. Monophyletic group. One synapomorphy is the loss of parapodia and the loss of tentacles. Key synapomorphy is the clitellum. Series of cells that secrete a cocoon that protects the young.

Annelida

Examples: polychaetes, earthworms, leeches, etc. Characteristics: Bilaterally symmetrical coelomate protostomes. Segmented (metameric = segmented)) body, with segments marked externally and internally; body structures repeated in each segment (modular units). Unlike the mollusks (where some groups have become secondarily asymmetrical like the bivalves). There is no secondary loss of bilateral symmetry. Each segment with paired bundles of chitinous setae (absent in leeches). Annelid setae are stiff bristles present on the body. They help, for example, earthworms to attach to the surface and prevent backsliding during peristaltic motion. Closed circulatory system; cutaneous respiration (gills in some polychaetes). Complete gut (like mollusks), with regional specialization. Well developed excretory system and central nervous system. Ventral nerve cord, series of ganglia, front of animal is a pair of ganglia that almost functions as a brain. Excretory organs (metanephridia) in each segment. Annelids are cephalized.

Polychaeta

Examples: sand worms, tube worms, clam worms, etc. Mostly marine worms. Just a few freshwater ones, similar to sponges. They are cephalized. Well developed head with tentacles and other sensory structures. Well developed parapodia and setae. Diverse feeding habits: predators, suspension feeders, deposit feeders.

Cnidarians and symmetry

Examples: sea anemones, corals, sea jellies, cube jellies, hydrozoans. Characteristics: Radial symmetry. Axis or axes of symmetry are around a longitudinal axis, which has oral (open) and aboral (closed) ends. Oral end often has tentacles.

Cnidarian clade: Anthozoa

Examples: sea anemones, corals, sea pens. Big clade that don't have a medusa stage. It could have been lost or was never present. Both solitary and colonial species. Solitary species: individuals live separately and are not connected. Colonial species: multiple polyps or medusae are attached and share a common gastrovascular cavity. Corals are sessile and colonial, with calcareous exoskeleton; calcium carbonate is secreted at the base of each polyp. These deposits accumulate and form coral reefs. Corals have intracellular photosynthetic protists (dinoflagellates) called zooxanthellae. Such dinoflagellates live inside of the coral cells (intracellular). The zooxanthellae provide the coral with photosynthates (glycerol and glucose), and the coral provide the zooxanthellae with protection and metabolic wastes (i.e. nitrogen and phosphorous). Coral reefs are the richest underwater marine environment we know of. Very diverse. House all kinds of organisms. Affected by water pollution, increased CO2, acidity, etc. Factors affect the relationship between corals and zooxanthellae. Sea anemones. Clown fish live in and around sea anemones. They are unaffected by the stings. They gain protection. They lure in prey and clean up food particles for the sea anemone.

Echinodermata

Examples: sea lilies, sea stars, brittle stars, sea urchins, sea cucumbers. Lack segmentation. Contain simple muscles. Bottom-dwelling marine organisms; predators, grazers, particle feeders. 7,500 extant species; 13,000 fossil species. All marine. Can't live in freshwater. Confined to salt water. Variable in feeding types. A lot more fossil species than extant species. This suggests that they did better in the past. Two dozen major classes of echinoderms. Most have gone extinct, and only about 5 main groups are present today.. Oral end can either face down or up. Complex water vascular system, derived from the coelom. Functions in gas exchange, locomotion and feeding. Complete gut with regional specialization. Diffuse nervous system (nerve net, nerve rings), no brain. Nervous system is more like that found in cnidarians and ctenophores. Respiration and excretion by diffusion across epidermis. Sexual reproduction: mostly dioecious, with external fertilization. Some mollusks have this (chitons and bivalves). Polychaetas are like this. They are marine. Most of the marine groups are dioecious and have external fertilization. Regeneration of body parts is common --> means of asexual reproduction.

Chondrichthyans (cartilaginous fish)

Examples: sharks, skates, rays. Skeleton made of flexible cartilage (bone lost secondarily). Generally predators, some scavengers. Powerful jaws, excellent swimmers.

Gastropods

Examples: snails, limpets, slugs, whelks, conchs, sea slugs (nudibranchs), sea hares, etc. Shell in one piece (univalve), usually coiled. Torsion: twisting of posterior end of body 180° so that anus lies above the head --> potential fouling problems. Mostly herbivores, but include some formidable carnivores.

Zombie ants

Explanation: Spores from a parasitic fungus infect the brains of ants. They disorient the ants. The colony sends these infected ants away from the colony. The fruiting body of the fungus erupts from the ant's head, killing them. It can take three weeks for the fruiting body to grow. The spores burst from the tip. Any nearby ants are at risk of death. It can wipe out entire colonies. It also infects other insects. Each of these fungi specialize on infecting just one species. Benefits: They stop one group of animals from becoming too prevalent. It is a density dependent way to control population growth.

Practice question: holometabolous insects

Extending life cycle doesn't necessarily mean fitness. Argument: With the larva and adult being so different, they can have completely different niches. They are almost two different organisms. This can't be done with incomplete metamorphosis.

Internal vs. external fertilization

External fertilization is typically found in animals that are mostly aquatic and internal fertilization is more characteristic of terrestrial animals.

Arthropoda: Trilobites

Extinct group of marine arthropods. Abundant and diverse 250-500 million years ago. Bottom dwellers, probably scavengers. Lived on ocean floor. Flattened, segmented creatures.

Features of protostomes

Features of Annelida, Mollusca and Arthropoda: All have well developed nervous systems (with a brain and ventral nerve cord); one-way gut with regional specialization; and excretory organs of some kind.

Sea stars (Asteroidea)

Feeds on corals. A problem in Australia. Have become common. Crown-of-thorns starfish: coral predator.

Fertilization vs. plasmogamy vs. karyogamy

Fertilization is the process in which plasmogamy and karyogamy occur at the same time.

Sexual reproduction in sponges

Fertilized egg (zygote) --> cleavage --> blastula-like stage. The zygote stays in the parent sponge, and forms a blastula, and develops into a larva. It is released into the environment. Sponges have a degree of parental investment in their young. Embryos are developed inside of them. The only part of the sponge that are mobile is the larval stage. Embryo retained on parent sponge for some period of time, then released as swimming (ciliated) larva, which eventually settles and develops into an adult form (settling on an appropriate substrate to develop).

Sea lilies, feather stars (Crinoidea)

Flower-shaped body; oral surface facing up. Sea lilies attached to stalk; feather stars more mobile. Not a lot of extant species, but lots of fossils.

Generalized molluscan body plan

Foot: Large ventral muscle mass (modified ventral body wall). Foot is a chunk of muscle on the ventral side of the organism. Chiefly for locomotion. Modified for burrowing in bivalves, and as arms/tentacles & siphon in cephalopods. Mantle: Dorsal body wall: fold of tissue that covers the visceral mass and encloses the mantle cavity (containing gills). Shell (when present) is secreted by the mantle. Visceral mass: Body proper, with digestive, circulatory, excretory and reproductive organs. Loose term for remaining body parts.

Practice question: chitin

Found in fungi, crustaceans, and insects.

Holometabolous (complete) metamorphosis

Four life stages: egg --> larva --> pupa --> adult. Major reorganization at pupal stage. Larva free to develop very different (specialized) morphology for feeding, unencumbered by adult appendages. Adults specialize on dispersal and reproduction.

Cnidarian clades

Four major clades: Anthozoa (sea anemones, corals, sea pens). Hydrozoa (hydrozoans). Scyphozoa (sea jellies). Cubozoa (cube or box jellies).

Clades of Mollusca

Four major clades: chitons, gastropods, bivalves, cephalopods. Fifth one may be considered: Monoplacophora (small group). Was known only from Paleozoic fossils until a live specimen was found in 1952.

Examples: Insects with complete metamorphosis

Four orders of insects with complete meta.

Ascomycota fruiting bodies

Fruiting bodies of Ascomycota have a variety of shapes, including edible fungi like morels and truffles.

Net diversification

Function of the speciation rate and extinction rate. The fossil record helps us determine how much extinction has an influence on net diversification. When you see a clade with lots of species, it either has a higher speciation rate or lower extinction rate.

Body plan: fungi

Fungi are often recognized by mushroom structures, but this is only one stage of their life cycle, and most of them are microscopic.

Phylogeny: fungi

Fungi are part of Opisthokonts, a group of eukaryotes defined by having a single, posterior flagellum. Fungi have two important characteristics: absorptive heterotrophy and chitin. Insects, which are animals, have chitin, but not in their cell walls.

The origins of fungi

Fungi probably evolved from a unicellular protist with a flagellum. The common ancestor of fungi and animals may have been similar to today's choanoflagellates. The Opisthokonts clade is formed by choanoflagellates, fungi and animals. Opisthokont = behind + pole (to push a boat). Animals have flagella in the form of sperm.

Division in fungi

Fungi reproduce asexually by fragmentation, budding, or producing spores. Budding, which is a method of asexual reproduction, occurs in most yeasts and in some filamentous fungi. Budding is to fungi as binary fission is to bacteria.

Characteristics of fungi

Fungi spend most of their lives as active foragers; many (but not all) are saprobes that feed off of dead or decaying organic material. In a single leaf of a plant, you may find 100-120 different species of fungi. Fungi are often found in moist and humid environments due to their susceptibility to desiccation. Fungi can be decomposers, parasites, predators, or mutualists Fungi are important plant pathogens, especially in moist environments. Some make no fruiting bodies.

Glomeromycota

Glomeromycota form arbuscular mycorrhizae with plants; the hyphae penetrate plant cells. Myko = fungus Rhiz = root Enable plants to colonize land. We don't know anything about their sexual reproduction. Benefits to plants: Protection from root pathogens Increased longevity of fine roots Protection from heavy metals in soil Linkages between plants (common mycorrhizal network)

Placozoans

Group of tiny marine animals having a simple asymmetrical body and a small genome; considered an ancient lineage. Diploblastic. Only two described species. No mouth, gut, or nervous system.

Hypotheses about early metazoan phylogeny

H1: Porifera-sister (traditional view): The porifera (sponges) are sister to the other animals. Sponges are simple. Based on morphology alone, this would make sense. Note: placozoans are incredibly derived. Review: You can resolve three way polytomies three ways. H2: Ctenophora-sister (more recent view): DNA sequence data supports the idea that ctenophores are sister to all animals. Radical idea, but it is a hypothesis. Ward: "The two hypotheses (H1, Porifera-sister; and H2, Ctenophora-sister) lead to different expectations about what might have been the original (ancestral) metazoan characteristics, with respect to diploblasty (i.e., a gut), muscles, and nerves. With H2 those characteristics could be ancestral, with H1 they likely arose later, because Porifera do not exhibit these features."

Phylogeny: vertebrates

Hagfishes and lampreys. Some studies suggest they might be sister taxa. Vertebrae may have been secondarily lost in hagfishes. Vertebrae could be at the base of the tree. Still being debated.

Table of features of Metazoa

Heterotrophy was present well before the MRCA of Metazoa. All opisthokonts are heterotrophic. It is not a synapomorphy.

Arthropoda: Hexapods

Hexapods are the most diverse subgroup of arthropods. Just three insect orders contribute half of all described animal species! 1/4 of all animal species are beetles.

Practice question: flightlessness

How do you get DNA from extinct birds? These are recent extinctions. We can scrape out the center of bones and get DNA out of it. We can sequence the DNA. We did the same thing with Neanderthals. Fossil bones that aren't too old can be used to extract DNA.

Annelid movement

Hydrostatic skeleton: fluid-filled cavity surrounded by muscles. 1. Contraction of circular muscles --> elongation of body segments. 2. Contraction of longitudinal muscles --> shortening of body segments. Setae anchor segments in substrate before step #2. Compartmentalized coelom means that action can be localized. Alternating waves of contraction move down body. Hydrostatic skeleton: fluid-filled cavity surrounded by muscles. Fluid is essentially incompressible, so action by antagonistic muscles changes shape of the cavity, causing movement; or maintains body support under hydrostatic pressure. Long explanation: The circular muscles contract. They are squeezed. That elongates the worn. The longitudinal muscles contract and and decrease the elongation and push the worm forward. The setae act like anchors and add resistance. They prevent the worm from moving backwards. They determine the direction of the movement.

Hyphae characteristics

Hyphae cell walls have chitin. Hyphae with incomplete cross walls are septate (branching divisions). Hyphae without septa are coenocytic (don't contain divisions). In this way, structures can divide similar to dichotomous branching in plants. Advantages of hyphae: Contain a high surface area to volume ratio. Hyphae are in direct contact with the environment. Allow for efficient absorptive nutrition. Disadvantages of hyphae: Susceptible to desiccation. To counter this, fungi are often found in moist and humid environments.

Triploblastic development

Illustrates the formation of a complete gut and a body cavity/coelom. Blastopore: opening in the developing gut. The fate of the blastopore differs among two major groups of Bilateria (protostomes and deuterostomes). Blastopore is only found in organisms that undergo gastrulation. Ctenophores, cnidarians, and Bilateria have a blastopore. Sponges don't. Gastrulation: the inward movement of cells from the outside of the blastula into the interior (vagination). Creates an embryonic gut. Characteristics during early development is a good representation of a given organism, as opposed to characteristics when the organism is older. This makes classification easier. Following the formation of the endoderm and ectoderm, a mesoderm (in pink) develops in between them. Having the mesoderm provides the Incompressibility of the fluids within the cavity. It develops in different places that vary based on what organism it is. The blastocoel is the fluid filled cavity of the blastula. The coelom is an internal fluid filled cavity. If it is present, it forms within the mesoderm. The coelom displaces much of the blastocoel. It is not present in all groups. Coelom: fluid-filled body cavity surrounded by mesoderm. Provides a hydrostatic skeleton. Mesoderm: source of most organs and organ systems.

Innovation: dikaryon state

In dikarya, the dikaryon life stage (n+n) is expanded. There are two distinct haploid nuclei inside one cell or hyphae

Functional importance of the coelom

In the case of some more simplistic animals such as worms, the coelom can act like a skeletal structure for the animal, allowing it to move and retain its shape. In more complex organisms such as humans, a coelom acts as the area where your organs are allowed to grow, develop, and work. A coelom can absorb shock or provide a hydrostatic skeleton.

Practice question: mutualism

In the image, the green portion is the photosynthetic organism. The fungi cover and protect it.

Oscula vs. siphons

In tunicates, they bring water in through the incurrent siphon. Pharyngeal gill slits are modified to make a basket. This basket functions as a filter structure. Waste products and filtered water pass out of the excurrent siphon. Oscula are the openings of the cavity of sponges. Ostea are small openings that water gets sucked into. Choanocytes grab food particles. The osculum is a relatively narrow opening. High pressure and lots of velocity. Water shoots out of the osculum. This ensures that the sponge doesn't filter the same way over and over again. The osculum is specifically a sponge term. Siphons is more of a general term. It would be incorrect to call the siphons of tunicates oscula.

Cnidarian guts

Incomplete gut: single opening (serving as mouth and anus) leads to gastrovascular cavity (place where food processing occurs).

Innovation: decoupling plasmogamy and karyogamy

Innovation: fusing the cell, but not fusing the nuclei. Plasmogamy: fusion of cells. Karyogamy: fusion of nuclei. Karyogamy takes time to occur in fungi. Name origins: Plasma (i.e., plasma membrane) Karyo (i.e. eukaryote = nucleus) Gamos: greek for marriage.

Insect evolution

Insect orders (major clades) arose in Permian (260 mya) or earlier. Angiosperms likely originated ~140-200 mya. Thus, coevolution with flowering plants had an effect on diversification within insect orders, not on the origin of major clades. Insects came before flowering plants.

Arthropoda: tagmata

Insects have three major body parts. These aren't segments. Each of these parts has multiple segments. It is about combining segments for a particular function. Degree of cephalization and tagmosis is a spectrum.

Additional notes

It is better to think of cephalization as an evolutionary tendency of Bilateria, associated functionally with bilateral symmetry. Bilateral symmetry is not a synapomorphy of Bilateria. Echinoderms can control the rigidity of their endoskeleton neuronally, but muscles are also involved in movement. For example, contraction of muscles around the ampullae of the tube feet can cause retraction and extension of the suckers. Amniotes are better adapted to life on land (especially in dry environments), but amphibians still have the key tetrapod traits of articulated limbs (for walking on land) and, in most species, lungs (to extract oxygen from air). Swim bladders occur in ray-finned fish and coelacanths. The swim bladder has become modified as a lung in lungfish and tetrapods. Gastropods are an example of a secondarily asymmetrical mollusk (because of torsion of the visceral mass).

Amniote innovations

Key innovations to exploit terrestrial environment: Impermeable skin. Impermeable skin contains carotene and is often covered by hair, feathers, or scales. Less chance of losing water. Efficient kidneys. More efficient kidneys means that nitrogenous wastes can be voided with the use of less water. Amniote egg (with shell and membranes that resist desiccation underneath the shell). Most animals have dispensed with the shell, but still keep the membranes. The membranes can be used to form the placenta.

Practice question: lampreys and lancelets

Lampreys are superficially similar to lancelets. They have no bone and no jaws; the larvae are mud-dwelling filter feeders. Can't be an ancestral similarity within vertebrates because lancelets are not vertebrates. Lancelets are the sister group of all other chordates.

Lancelets (cephalochordates)

Lancelets (or amphioxus); small filter-feeding marine animals. Segmented body muscles. Viewed as a model for what the first chordate looked like. Old name: Amphioxus. Show all of the four chordate features in the adult form.

Land snails and love darts

Land snails are monoecious (hermaphrodites) - exchange sperm. Often preceded by elaborate courtship ritual, including piercing with "love darts." Land snails are gastropods, but they are monoecious. Mating pair of land snails each give each other packets of sperm. Darts made of chiton or calcium carbonate. Love darts contain chemicals that facilitate the fertilization of the egg by the sperm. Just like the spicules of sponges are useful to tell apart sponges, love darts can be used by taxonomists to distinguish snail species.

Ray-finned fish (Actinopterygii)

Largest clade of bony fish (~30,000 species). Very diverse feeding habits. Most common type of fish that you might see. Especially diverse in coral reefs. Example: Cichlid fish.

Ascomycota (sac fungi)

Largest group of fungi (2/3 species). Creates a diagnostic spore structure, ascus with 8 spores in a sac. Variety of fruiting bodies, many cup-like. Many yeasts and molds are ascomycetes. Yeasts reproduce through budding if they can. There are at least 1500 species of yeast.

Attine ants

Leafcutter ants have been cultivating for 50 million years. Ants evolved at least three different agricultural systems in the past 30 million years. The ants cut vegetation and feed it to smaller worker ants. The worker ants clean them and chew them down. The fungus breaks down the toxins and the leaves. The ants eat the remains. The ants need the fungus as a means to acquire food. The fungus cannot live without the ants. A mature colony of ants can eat as much as a cow. When queens leave their nests, they carry a small piece of fungus to the next nest/colony.

Examples of convergence: evolution of snake-like reptiles

Lepidosaurs. Lizards and lizard like things.

Lichen

Lichen: fungus and photobiont. An organism made of a fungus and either algae or autotrophic bacteria (cyanobacteria) that live together in a mutualistic relationship. Survive harsh environments. ~30,000 species. Fungi give water and nutrients to their hosts in return for photosynthates. Cyanobacteria can fix nitrogen and give it to the fungus. Composed of two parts: a mycobiont (which is the fungus that forms the lichen body) and a photobiont (which is green algae and/or cyanobacteria that perform photosynthesis). Photobiont: ~100 species of green algae and cyanobacteria are known to form lichens. 85% of lichens just with green algae. 10% of lichens just with cyanobacteria. 5% of lichens with both green algae and cyanobacteria Nearly all lichen forming fungi are obligately dependent on their photobiont. Nearly all photobionts are not obligately dependent on the lichen symbiosis.

Cnidarian life cycle

Life cycle: typically involves alternation between an asexual polyp stage and a sexual medusa stage. Similar to alternation of generations in land plants. But there are many variations on this theme. In some cnidarians one or the other stage has been lost (e.g., corals and sea anemones have no medusa stage). Free swimming medusa. Separate sexes (dioecious). Male and females release gametes into the water. Fertilization occurs in the water. The only haploid stage is the gametes. Zygote develops into a ciliated larva called a planula larva. It can settle on a surface and develop into a polyp. When the polyp is mature, if can produce more medusae asexually by producing a series of flat plate like structures that are clones of itself. They then develop into mature medusae. Polyp is the second body plan in the life cycle. Summary: Free-swimming medusae release sperm and eggs. Zygote develops into a ciliated larva (planula). Larva settles and develops into a polyp. Mature polyps produce (and release) medusae asexually.

Brittle stars (Ophiuroidea)

Long slender arms (multi-branched in basket stars). Locomotion by arm movement. Abundant but secretive (light-avoiding).

Origins of white fungi

Lots of carbon deposits in the carboniferous period. This is when the white rot fungi appeared.

Life cycle of a sea squirt (tunicate)

Main type of tunicate. Another group of chordates called larvaceans, in which adults retain larvae like characteristics (called paedomorphosis). Urochordates are the group that these organisms occupy. Paedomorphosis: retention of larval traits in adults.

Evolution of jaws

Major innovation. Gill arches at the anterior end of the animal became modified as bony jaws.

Army ants

Mass foraging, nomadic ants with specialized queens (egg-laying machines). Subgroup of ants that are nomadic. So successful at feeding that they deplete their food sources and have to move to a different area.. Colonies can contain up to 20 million workers. Prey upon invertebrates and occasionally small vertebrates. "Keystone species": because of (1) intensity of predation and (2) a diverse fauna of dependent organisms (e.g., antbirds). Ant birds live in and around army ants swarms. As army ants move through the forest, they flush up insects. Birds swoop in and eat insects that the army ants don't see or leave behind.

Practice question: arachnids

Means that arachnids either colonized the land more than once, or the horsetail crabs could have gone back to the ocean.

Schizocoely vs. enterocoely

Mesoderm can start to displace the blastocoel. Schizocoely: schizo means split. Bands of mesoderm split and create a cavity. Found in protostomes. Enterocoely: mesoderm develops from the outpocketing of the gut wall. Process is responsible for the creation of the coelom in deuterostomes. True coelom: entirely surrounded by mesoderm tissue. A reduced coelom is a true coelom. Pseudocoelom: partially surrounded by mesoderm and endoderm.

Advantages of triploblasty

Mesoderm provides the basis for most of the organs in animals. Enables a more complex morphology and greater flexibility.

Metabolism

Metabolism in fungi is diverse, but few species are capable of utilizing simple or very complex substrates. Fungi are capable of consuming complex substances, with some being able to consume lignin. Even if a substance is complex, and the fungi use lots of energy and enzymes to break it down, the fungi gets a lot out of it. It's also a cost benefit analysis. Organic material (towards the extremes) is very hard to degrade. Big investments have to be made for little energy to be accessed.

Microsporidia

Microscopic protozoans that cause disease in insects. No mitochondria. Obligate intracellular parasites. Mitosomes are the remnants of mitochondria. We still don't know what they are entirely. They don't have DNA like mitochondria, nor do they have a means to generate energy.

Mites and ticks

Mites and ticks are vectors of diseases that affect humans. Lyme's disease is spread through ticks. Mites include serious plant pests. Tiny.

Molds

Molds are ascomycetes that rarely undergo sexual reproduction in their life cycle (asexual instead). Spores are produced asexually outside of a sporangium.

Cnidarians: monecious and dioecious organisms

Monoecious (one house) organisms: single individual produces both sperm and eggs. Dioecious (two houses) organisms: sperm and eggs produced by different individuals; separate males and females. Examples: Sea jellies and hydrozoans: usually dioecious. Corals and sea anemones (anthozoa): either monoecious or dioecious Cube jellies (have eyes in some species): dioecious (some "copulate"). Copulate: Rather than releasing the sperms and the eggs in the water (fertilization occurs in water), some males present a packet of sperm to the female.

Ants

Most diverse and abundant group of social insects (30,000+ species). Have colonized almost all terrestrial habitats Some ant queens have been recorded to live for 30-40 years. Natural selection has extended longevity. By comparison, most adult insects tend to only live a few weeks.

Mollusks and segmentation.

Most mollusks lack segmentation. Monoplacophorans have some serially repeated body parts, so do chitons (plates on top are segmented) to some degree. Hypothesis: originally mollusks were segmented, but for some reason segmentation was lost in major groups.

Hyphae vs. spores

Most of the morphological variation in fungi are fruiting bodies; hyphae and spores do not look that different from one another. The difference is that hyphae are septated.

Chytrids

Mostly aquatic fungi with flagellated zoospores that represent an early-diverging fungal lineage. They were the first fungi. Many chytrids are parasitic. Flagellated spores and gametes allow them to spread more readily in aquatic and marine habitats. Contributing to a global die off of amphibians. Chytrids infect frogs. Around the world, 700 frog species have disappeared because of this fungus. Disease started because people were transporting frogs in South Africa. Frog eggs were being harvested for pregnancy tests. Chytrids are the only group of fungi that retain swimming spores. They are implicated in global amphibian decline. Mainly parasites that live in water. They didn't need to lose their flagellum, as it helps them move around.

Molluscan reproduction

Mostly dioecious (separate sexes), some species monoecious (same individual produces both kinds of gametes). Fertilization mostly external in chitons and bivalves (gametes are released into the water), internal in gastropods and cephalopods (packets of sperm are taken into the body of a partner).

Protostomes

Mouth first. Blastopore becomes mouth. Anus forms secondarily. Protostome characteristics: Mesoderm forms near lip of blastopore Coelom (if present) is formed by the splitting of the mesoderm.

Deuterostomes

Mouth second. Blastopore becomes anus. Mouth forms secondarily.

Characteristics of Metazoa

Multicellular organisms, with cell specialization, communication (nutrient exchange) and interdependency. They don't just live in colonies; there is a division of labor, interdependence, communication, etc. They cannot live alone. Heterotrophs (require organic compounds as food). Food is taken into the gut. First type of digestion occurs extracellularly (inside the gut), which is often followed by intracellular digestion. Diplontic life cycle. Distinctive male gametes: spermatozoa. Unique development: zygote --> blastula --> gastrula). Distinctive cell junctions (septate junctions) unique to metazoans. Metazoans have cell junctions called gap junctions or septate junctions. In sponges, digestion is strictly intracellular. They don't have a gut. Collagen (a fibrous protein) and proteoglycans (polysaccharide-linked proteins) are found in the extracellular matrix. These classes of proteins lie in between cells. Not all of them are synapomorphies.

Uses of sponges

Natural products from sponges have potential pharmacological uses. Examples: anti-inflammatory, antitumor, antibiotic, antihistamines, and more.

Arthropoda: reproduction

Nearly all arthropods are dioecious. Mollusks have both monecious and dioecious groups. Annelids have variation. We don't see variation like that in Arthropods. Fertilization usually internal. Sperm are taken into the female's body. Development often involves larval stage (but some taxa have direct development). Direct development: the embryo develops into a miniature adult. Complex metamorphosis in some insects and crustaceans. Multiple, distinct stages.

Predator fungi

Nematophagous fungi are soil dwelling fungi that form rings with their hyphae. These rings catch nematodes, and the hyphae proceed to attack, invade, and digest the nematodes.

Mycotoxins

Neurotoxins produced by fungi. Mycotoxins are secreted by fungi and may have important impacts on human health; either through secondary infection or chronic exposure. Mycotoxins are the most potent biological carcinogens that we know of.

Sea urchins (Echinoidea)

No arms, but usually long spines. Ossicles (skeletal plates) fit together into a test. Omnivores, important as grazers of algae. Can be common in surface waters. When they die, the test washes up on the shore. Importance: Decline in sea urchin has resulted in the overgrowth of algae near corals. Destruction of coral reefs.

Lampreys

No bone, no jaws. Sucker-like mouth and rasping teeth. As adults, they are blood sucking parasites. Sucker like mouth. Larvae are not parasitic; they are filter feeders living in the mud. Similar to lancelets in this way.

Ectomycorrhizae vs. endomycorrhizae

No, ectomycorrhizae and mycorrhizae are not synonymous terms. The term mycorrhizae encompasses two major groups of Glomeromycota: (1) Ectomycorrhizae - this group do not penetrate the plant cell when forming a mutualistic interaction with the plant host (Ecto = outside), and (2) Endomycorrhizae - this group penetrate the plant cell with forming a mutualistic interaction with the plant host (Endo = inside).

Review: characteristics of Metazoa

Not all of these features are synapomorphies. Not all of them arose in the MRCA of the group.

Practice question: diplontic life cycle

Note: gametes are the only haploid stage.

Practice question: What do you think is the most meaningful measure of evolutionary success?

Note: this question is talking about entire clades, not specific animals. Notes for A: Ecological dominance can be had one day and lost the next day. Longevity shows a greater evolutionary success. We think of evolution as a long term process. If you're going to be dominant or have a lot of species, you require some staying power. Notes for B: Ecological dominance implies better fitness. Greater ability to propagate genes is fitness. Notes for C: Lots of species means more diversity and putting your eggs in different baskets. If we used longevity, it is an unfair competition. For example, sponges have been around for a lot longer than humans. The Bilateria is younger. Produced more species. They have diversified more. They are more ecologically dominant. Number of species is associated with dominance. Argument against C: the number of species could be transitory (not permanent). A species could have been prevalent many years ago, and now be almost extinct. Does that mean that they didn't have evolutionary success?

Arthropoda: Hexapods

Numerous beneficial and harmful species. Bees pollinate plants for us. Silkworms provide silk. Ladybugs eat pests. Numerous species spread diseases (mosquitos) or compete for our resources, like plants.

Importance of fungi

Nutrient cycling: Break down dead organic material as decomposers. Food: Economically important in terms of food. People lose their money due to food waste prompted by fungi. Fungi are common in our diet and form essential parts of food such as cheese and bread. Truffles are fungi. Fermented beverages: Fermented beverages and sauces use specific strains of yeast, a unicellular fungus. Beer and wine: Used in the creation of beer and wine. Sulfite is added to kill off natural fungi and create wine that is based on a single fungus of interest. Meat substitutes: Fungi are used as synthetic meat substitutes. Mycoproteins originally discovered in a soil sample in England. Recreational drugs: Few fungi are toxic to humans and other animals. Some are hallucinogens. Medicines: Many fungi have important medical applications, including the biosynthesis of antibiotics, statins, steroids, and birth control. Statins improve heart health by lowering cholesterol levels. Their components are created by fungi. Example: Lipitor is a biosynthetic statin. Biofuels: Gas contains at least 10% ethanol. Ethanol is produced by the fermentation of yeasts. Corn and sugarcane can be used to make ethanol. If corn is used, an enzyme has to be used to break down starch for fermentation to take place. Dyes: Native Americans collected lichens to make dyes. Industrial: Because fungi are absorptive heterotrophs, they are useful "factories" for the biosynthesis of drugs, enzymes, acids, and alcohols. Fungi do the digestion for humans. Fungi have already evolved to secrete enzymes out of the cell. The product is made outside of cell, instead of humans having to remove the products intracellular (like in Bacteria), which requires resources.

Zygomycota fungi (a.k.a. conjugating fungi) life cycle

Occurs in bread. Long explanation: Spores are formed and released. If conditions aren't great, a partner is needed. In terms of hyphae, the negative and positive types are just to differentiate between two partners. They are of the same species, but are different. The hyphae release chemicals that attract each other to one another. They start getting closer and closer. At the tips of the hyphae, they start to form gametangia. All of the nuclei become concentrated in that area. When they touch, they fuse. Plasmogamy occurs. The zygosporangium is a structure that has all of the nuclei, but the nuclei aren't fused yet. A zygospore is formed. It can live in an environment for quite some time; it is very tolerant. The nuclei eventually fuse. They undergo meiosis. They make the sporangiophore, and the cycle occurs all over again. The dikaryon stage is for a short period of time.

What is the advantage of undergoing plasmogamy instead of fusing right away?

Once a fungus finds a partner, they keep that partner for a long time. When conditions change, they fuse their nuclei. It is very hard to find a mate in the soil.

Practice question: flightlessness

Once birds lose the ability to fly, they generally never re-evolve flight. Some of the similarities in anatomy must have been due to convergent evolution.

Subterranean fungi

One problem being underground is that it is harder for dispersal to occur. The spores don't extend far away. Fungi with subterranean fruiting bodies are largely dispersed by animals. Some fungi have a pheromone called androstenol. Humans have it in their urine and saliva. This pheromone attracts organisms like pigs, which aids in dispersal.

Pharyngeal slits

Openings between the pharynx and the exterior. Associated with filter feeding or respiration.

Phylogeny: chordates

Ostracoderms and placoderms are extinct groups of bony fish.

Ctenophores (comb jellies)

Other names: comb jellies and sea walnuts. About 250 species. Extensive mesoglea. All aquatic (mostly marine, with a few freshwater). Contain eight rows of bands of cilia and move by beating their cilia. Capture small plankton with two tentacles that discharge adhesive material (tentacles then bring food to mouth). Enigmatic group whose placement in the metazoan phylogeny has been controversial. Cnidarians also have radial symmetry and diploblastic development, which lead some people to place them close together in the phylogeny (this is now considered incorrect). Complete gut. One way gut (contain both a mouth and anus). Like cnidarians, they contain a network of nerves (not like a brain). Nerve nets. Some ctenophores engulf other ctenophores. "Tissue - lack organs. Ctenophora have radial symmetry and 2 germ layers. Lack cephalization, body cavity, or segmentation. Reproduce sexually or asexually about 100 species. Sticky tentacles collect prey, largest organism to use cilia for locomotion." Summary: Radial symmetry. Diploblastic development. Complete gut. Nervous system (nerve net). Lack cephalization. Simple musculature.

Unidirectional flow of food and water

Pacu: seed-eating piranha. Feeding in fishes: efficient unidirectional flow. Water goes in the mouth, out the pharyngeal slits. Variation in the jaws and muscles around the jaws. They are efficient feeders because of a unidirectional flow of water and food into the mouth. Water exits out the phalangeal slits.

Echinodermata symmetry

Pentaradial symmetry around oral/aboral axis; no head. Similar to cnidarians and ctenophores in this way. Symmetry must have evolved independently. Echinoderm larvae are bilaterally symmetrical. Secondary character because pentaradial symmetry evolved after bilateral symmetry, then bilateral symmetry evolved again. Secondary character. Larvae of echinoderms are bilaterally symmetrical. Zygote --> Cleavage --> Blastula --> Gastrulation --> Gastrula --> Bilateral larva --> Radially symmetrical adult. Primary bilateral symmetry: bilateral symmetry is part of the ancestral condition. Secondary bilateral symmetry: went back to bilateral symmetry. Sand dollars and sea cucumbers show a degree of bilateral symmetry as adults.

Pharyngeal slits

Pharyngeal slits are openings in the pharynx (the region just posterior to the mouth) that extend to the outside environment. In organisms that live in aquatic environments, pharyngeal slits allow for the exit of water that enters the mouth during feeding. Some invertebrate chordates use the pharyngeal slits to filter food out of the water that enters the mouth. In vertebrate fishes, the pharyngeal slits develop into gill arches, the bony or cartilaginous gill supports. In most terrestrial animals, including mammals and birds, pharyngeal slits are present only during embryonic development. In these animals, the pharyngeal slits develop into the jaw and inner ear bones.

Pilobolus cannonball fungi

Pilobolus cannonball fungi have one of the fastest biological mechanisms known. The yellow structure is the spore. There is a container full of water. As light gets in and and the container gets hot, it fires. The water pressure becomes seven atmospheres. Light is focused by the sporangium and water pressure builds to 7atm. Each spore can travel up to 6 ft at over 20,000G.

Annelid reproduction

Polychaetes: usually dioecious (separate sexes), with external fertilization and trochophore larva. Others (Clitellata): monoecious (hermaphrodites), with internal fertilization and direct development (no trochophore larva). What develops from the zygote is a miniature form of the adult. Asexual reproduction: regeneration from body fragments. Both polychaetes and clitellata are capable of asexual repro.

Mammals: Marsupials

Pouched mammals. Short gestation period for their young. Young have to stay in the mom's pouch for awhile. Marsupials evolved in isolation on Australia for ~40 million years - they convergently evolved similar body forms to those of eutherians elsewhere.

Leeches

Predators and blood-sucking ectoparasites. Lack setae; have anterior and posterior suckers for attaching to prey. Anticoagulants: blood flows better and doesn't clot. Vasodilator: blood flows more freely. It is less painful for the animal and better for the leech, too. Leeches can be used to clean up wounds. Often don't carry diseases. Leeches can be terrestrial. They wave their body in hopes of attaching to a host. They detect CO2 and heat. Leeches love rain. Can be marine, terrestrial, or freshwater. Like oligochaetes, they have a clitellum. All leeches are hermaphrodites

Annelida heads

Presegmental head and postsegmental terminal part (pygidium ).

Primary and secondary metabolites

Primary metabolites: Produced during active cell growth. Adding a substrate or food for the organism. The organism starts to grow. As the food is consumed and the cells grow, a product is formed (primary metabolite). Involved in core processes. Always present, important for life. Respiration, etc. Secondary metabolites: Produced near the onset of the stationary phase. The fungus grows and doesn't produce anything. The conditions soon become inappropriate for growth. Once these inappropriate conditions are created, a product starts to be produced (secondary metabolite). Cells won't die immediately if they stop being produced. Defense, signaling molecules to attract mates, etc. Example: When the cells slow down their growth, antibiotics can be produced. Why do they do this? Maybe they create antibiotics to kill the competitors around them so that they have more resources to themselves.

Flatworms (Platyhelminthes)

Primitive worms which lack a coelom and have a simple digestive tract with a single opening. Include the following: Free-living flatworms (i.e. the genus of Planaria). Aquatic predators that eat small organisms. Flukes. Tapeworms. Flukes and tapeworms are parasitic and often cycle from vertebrate to vertebrate.

Phylogeny: Hexapoda

Primitively winged insects are incapable of folding wings over body.

Ostracoderms

Probably filter feeders and scavengers. Radiated in Silurian and Devonian (~400 mya).

Protostome vs. deuterostome development

Protostome characteristics: Mesoderm forms near lip of blastopore Coelom (if present) is formed by the splitting of the mesoderm. Deuterostome characteristics: Mesoderm and coelom form from outpocketing of gut wall.

Pseudocoelom

Pseudocoelom develops in some protostomes. Instead of the mesoderm creating a new internal cavity (coelom). In pseudo, the mesoderm continues to develop, but the blastocoel stays. The coelom has endoderm on one side and mesoderm on the other side. Usually, the coelom is surrounded by two walls of the mesoderm. Nematodes (roundworms) have a pseudocoelom.

Phylogeny: vertebrates

Red: Terrestrial with secondarily aquatic species (= the tetrapods). Blue: Aquatic only. A major transition from water to land (and back again). Tetrapods: amphibians, reptiles, and mammals. Coelacanths and lungfishes are smaller groups. Coelacanths are a rare group, as are the lungfishes. Red dot is the transition of water to land. Some tetrapods have gone back to water, like whales. Lobe-finned fishes: Pectoral and pelvic fins modified as robust structures borne on a lobe-like stalk. Transition was faciliatetd by the lobed fins. We still see lobe finned fishes in the coelacanths and lungfishes. The limbs of tetrapods evolved from lobe fins. Swim bladder: Present in ray finned fishes. Helps fish maintain buoyancy. Got modified into a sac that served the function of a lung. Colonization of land involved: Use of lungs (modified from the swim bladder). Modification of lobed fins to become limbs.

Amphibians

Require moist environments. Lose water rapidly through skin. Early stages often require water. Amphibians are sister to amniotes. Three major clades: (A) Caecilians (limbless); (B) Frogs and toads (tailless); and (C, D) Salamanders (tailed). Caecilians look like a tiny snake or earthworm. Not very common, mostly tropical. Second group is frogs and toads. Most successful of living groups today. Third group: salamanders are still tailed. Can be toxic. Amphibian decline: Many amphibian populations have suffered recent declines. Pathogenic chytrid fungus has been implicated in some cases—but considerable uncertainty about cause(s) of decline. Decline could also be caused by habitat degradation.

Hagfishes

Scavengers on dead animal carcasses. No bone, jaws, or vertebrae. Tongue with rasping teeth. Can tie themselves in knot for greater leverage when tearing food from prey. Marine. Possible that they had vertebrae and lost them. Produce copious amounts of slime. Most organisms don't eat them.

Tunicates (urochordates)

Sea squirts (ascidians) and relatives. Sea squirts are bag-like, with enlarged perforated pharynx for filter-feeding. Incurrent siphon for bringing water in and an excurrent siphon for releasing water. Tunicate larvae show all of the four characteristics. Pharyngeal slits is the only persistent feature in adults.

Body plan: Annelida

Segments marked externally (rings) and internally (septa). Body structures repeated in each segment (e.g., setae, nephridia). Each segment with paired appendages (parapodia that are only found in polychaetes) body wall with inner longitudinal and outer circular muscles. Parapodia is a synapomorphy of Annelids, even though not all Annelids show that feature. Synapomorphies can be lost over time.

Disadvantages of sexual reproduction

Sexual reproduction is thought to have some disadvantages, such as slower reproduction, fewer offspring and high energy expenditure, in comparison to asexual reproduction. As I mentioned in class, if environmental conditions are perfect, there is no reason for sexual reproduction to occurs for fungi.

Chitons (Polyplacophora)

Shelly mollusks with segmentation. Dorsoventrally flattened. Multiple shell plates. Multiple gills.

Sac fungi (Ascomycota) life cycle

Similar to the Basidiomycota life cycle. Spores are released. They germinate and mate in the same way. They go through plasmogamy. The plasmogamy stage is much faster than the Basidiomycota life cycle. As soon as they form the ascoma (the fruiting structure that looks like a cup), the fruiting structure gives rise to an ascus. They fuse. Meiosis occurs, then spores are formed. Mitosis occurs, creating eight daughter cells in the ascus structure. Reproduction is mainly asexual. Ascomycota fruiting structures have a haploid and dikaryotic hyphae mixture.

Dikaryon features (similarities and differences between Ascomycota and Basidiomycota)

Similarities between Ascomycota and Basidiomycota: 1) Spore formation happens by karyogamy followed by meiosis. 2) Life cycle with 3 stages: haploid, dikaryotic and diploid. 3) Hyphae are never diploid (2n); they are either haploid (n) or dikaryotic (n + n). Differences between Ascomycota and Basidiomycota: 1) Duration spent in dikaryon stage varies: short lived in Asco, months or years in Basidio. 2) Reproduction mainly asexual in Asco, reproduction mainly sexual in Basidio.

Practice question: Arthropod morphology

Similarities observed between myriapods and hexapods probably represent convergent adaptations to life on land. Crustaceans are mostly aquatic.

Coevolution between insects and flowering plants

Similarly, clades of phytophagous (plant-feeding) insects have been compared to sister taxa that are not plant feeders. For example, latex-and resin-bearing plants have more species, on average, than sister taxa without these features. On average, plant-feeding insects are more species-rich than sister taxa that do not feed on plants (predators or scavengers). Reason: specialization and more niches. Explanation: If you're feeding on plants, you can specialize to a greater degree. Can specialize on a specific plant. You can also specialize on different parts of the plant, not just the species of plant.

Pie chart: sponges

Size is proportional to the species diversity of the group. Sponges are not diploblasts. They do not have gastrulation. Ctenophores and cnidarians are diploblasts.

Practice question continued: why aren't pharyngeal slits synapomorphies

Slits are found in the hemichordates. Slits are found in the original features of deuterostomes. They can't be a synapomorphy of chordates because slits arose before chordates evolved. Example: Schizocoely (splitting the bands of the mesoderm) can't be a synapomorphy of lophotrochozoans because it arose earlier in protostomes.

Choanoflagellates

Small group of aquatic protists, unicellular or colonial. Collar cell: ovoid in shape, with a collar of microvilli (tentacles) surrounding the single flagellum. Movement of flagellum --> (1) locomotion and (2) feeding (bacteria trapped on collar). There is a single flagellum surrounded by microvilli. Movement of the flagellum brings water across the microvilli. Small food particles are captured and taken into the cell by phagocytosis. Clusters of cells can live together, but there isn't a division of labor. No complex system of communication or dependency from one cell to another.

Sea cucumbers (Holothuroidea)

Soft-bodied and slug-like (ossicles much reduced). Greatly elongated oral/aboral axis, secondarily bilateral. Grazers, suspension feeders.

Examples: Hemipteroids (true bugs and allies)

Some Hemiptera are predatory. Most are plant-feeders.

Bath sponges

Some demosponges have spongin (complex network of collagen) but no spicules: these have long been harvested for use as bath sponges. They have been largely replaced by synthetic sponges and luffa.

Sea slugs (Nudibranchs) and cnidarians

Some feed on cnidarians, despite their stinging tentacles. Plumed sea slugs feed primarily on sea anemones and hydroids. They have elongated protrusions, called cerata, on their back Sea slugs ingest the nematocysts and transport them undischarged to the tips of the cerata (they are placed in sacs that open to outside). The nematocysts are then used by the sea slug for its own defense. They steal the defensive mechanism of cnidarians to protect themselves.

Communication between plants

Some studies suggest that two different plants can communicate to each other through hyphae. Plants can tell each other to produce chemicals in the presence of a herbivore.

Why is predation so low in sponges?

Sponges are often dominant organisms in marine benthic environments, and experience limited predation. (1) Sponge spicules provide a physical deterrent. Hard spicules get stuck in predators mouths, for example. (2) Sponges have potent biochemical defenses (biotoxins). (3) They use antimicrobial agents to prevent infection by microbes. They produce antibiotic compounds. They reduce the probability of infection by microbes. (4) They employ chemical warfare (chemical repellants) against organisms that compete for space with them. When they land in one place, they are sessile. They produce chemicals that inhibit the settling of other organisms in the environment around them.

Ergosterol vs. cholesterol

Steroid-type protein found in the cell membrane of fungi; similar in configuration to adrenal hormones and testosterone. Similar to cholesterol in humans. Cholesterol and ergosterol are important because they help maintain the structure of the cell membrane, granting it the ability to bend and resist forces. If you want to kill a fungus, you can get rid of its ergosterol.

Cephalopods

Subgroup of the mollusks. Examples: nautiluses, squids, octopuses, cuttlefish, etc. Characteristics: Most advanced of all of the mollusks. Lots of sensory capabilities. Wholly marine; actively mobile predators. Largest and smartest invertebrates. Foot modified as tentacles and a siphon. Nautilus with shell, in others shell is internal (squid, cuttlefish) or lost (octopus). Most of them don't have shells. They have other ways to protect themselves (partially through mobility). Locomotion by jet propulsion: siphon expels water from mantle cavity. Siphon is used to bring water into the mantle cavity. When the water is expelled from the cavity, it provides a jet propulsion that moves the animal through the water. They have two eyes.

Easy substrates

Substances that are easily consumed and broken down. Examples: fruit, flesh, leaves, cotton, and paper.

Phylogeny: Insects with complete metamorphosis

Such organisms tend to be successful organisms.

Mycorrhizae

Symbiotic relationship between the mycelium of a fungus and the roots of certain plants. Plant provides sugars (photosynthates) to the fungus. 98% of plants on Earth are dependent on fungi. Fungal partner provides water, nutrients, and minerals through their massive surface area. Enzymes and DNA need phosphorous. Fungi give phosphorous to plants.

Symbiotic relationships in sponges

Symbiotic relationships are common. Mutualism: Cyanobacteria or algae living in sponge mesohyl, exchanging nutrients. Commensalism: Other marine organisms inhabiting sponges, using them for shelter (facilitated by porous nature). Obligate inhabitants: Shrimp (Spongicola). A male-female pair of shrimp enters the sponge when they are young, and later become trapped in the glass-like case when they grow too large to leave.

Tetrapod limbs

Tetrapod limbs are modified fins. Fossils from the Devonian period. Lobe finned fish to a fossil with intermediate characteristics. Pectoral fins are equivalent to arms. Pelvic fins became legs.

Practice question: turtles

The degree of relatedness is based on when they last shared a common ancestor. Turtle and crocs last shared a common ancestor at the split between turtles and archosaurs. Birds and turtles and turtles and crocs are equally related. Don't be fooled by adjacency.

Biology of clownfish (gender roles)

The dominant individual is the female. She mates with subdominant males. When the female dies, one of the subdominant males turns into the dominant female.

How did insect wings evolve?

The gene that governs the development of the dorsal appendages of a crustacean is the same gene that governs wings. A gene that evolved in the development of dorsal appendages is the same gene that arose in fruit flies.

Examples of Basidiomycota

The gills are the black part.

Mutualisms between clownfish and sea anemones

The mucus of the clownfish contains chemicals that deter firing of the nematocysts. Benefits to clownfish: Protection from enemies (safe nest site). Food left-overs. Benefits to sea anemone: Defense against potential predators and parasites. Nutrients from clownfish excrement.

Practice question: notochord

The notochord provides skeletal support, gives the phylum its name, and develops into the vertebral column in vertebrates. The dorsal hollow nerve cord develops into the central nervous system: the brain and spine. Pharyngeal slits are openings in the pharynx that develop into gill arches in bony fish and into the jaw and inner ear in terrestrial animals. The post-anal tail is a skeletal extension of the posterior end of the body, being absent in humans and apes, although present during embryonic development.

Chytrids life cycle

The only fungi that have flagella. Both their spores and gametes swim using flagella. The female gamete is bigger than the male gamete. Spores are called zoospores. Most exhibit alternation of generations. Reproduction: If the conditions are perfect, chytrids prefer to reproduce asexually. If conditions become poor, they need to increase the diversity of their genes to ensure that at least one daughter cell survives. They find partners to exchange and recombine genes. Long explanation: Sporangia releases zoospores. They grow into a multicellular haploid structure. The male and female gametangia are then formed. They release gametes. Gametes fuse. As they fuse, they fuse the cell and the karyon (they fuse the nuclei together). A zygote is formed. Meiosis occurs and more spores are released. The cycle continues. "The process of fertilization is both plasmogamy and karyogamy happening together. You stated correctly that this is what happens for Chytrids as the female (n) and male (n) gametes fuse as soon as they find each other to form a zygote (2n). No dikaryon stage is observed for this fungal group."

Old phylogeny: turtles

The position of the turtles has been controversial until now. This is the older view, which is based on morphology and fossil evidence. Example: cranial head. Molecular data conflicts with this placement.

Ascus

The products of meiosis (ascospores) are borne in a sac (ascus). The fleshy fruiting bodies of the fungus consist of both dikaryotic and haploid hyphae.

Phylogeny: fungi

The relationships among fungi are not well understood; several polytomies remain and many species await discovery. Six main groups.

Phylogeny: opisthokonts

The sister group of animals is the choanoflagellates.

How do sponge sperm reach the egg?

The sperm have to enter another sponge and to be captured by the choanocyte, and transported to a receptive oocyte. They need to cross the cellular barrier of choanocytes; enter the mesohyl; locate the egg; and fertilize it. This rather impressive feat initially involves sperm capture by choanocytes and enclosure in an intracellular vesicle (much like the formation of a food vacuole during feeding). The choanocyte then loses its collar and flagellum and migrates through the mesohyl as an ameboid cell, transporting the sperm to the oocyte. The sperm aren't treated as food. They are transported to the oocyte. Choanocytes no doubt regularly consume the unlucky sperm of different species of sponges. But, by some as yet undiscovered recognition mechanism, they respond with a remarkably different behavior to sperm of their own kind. Sperm of other kinds of species are treated as food.

Antibiotics and fungi

There are few fungal antibiotics because humans and fungi are very similar. It is hard to target the fungi specifically. For example, fungal antibiotics have to affect chitin production or ergosterol.

Arthropod phylogeny

There are morphological characters to support the "classic view" that hexapods and myriapods are sister taxa. For example, they share tracheae (air tubes) and appendage structures not seen in crustaceans.

Molluscan development

There isn't always a larval stage. It is called a trochophore larva. That can develop into a veliger larva (no need to know name of this), and then it finally develops into an animal mollusk. Often: trochophore larva --> veliger larva --> adult. Direct development in some mollusks. This means no intermediate larval stages.

Snakes

They are a monophyletic group. Evolved once from a lizard like ancestor.

What was the function of pro-wings (before flight)?

This argues that pro-wings arose from gill-like structures in a larval aquatic stage, that were retained and modified in adults for other purposes. E.g., thermoregulation (basking in sun), gliding in the air, or sailing along the water surface. Thermoregulation: flaps that allowed insect to heat up as they emerged from the water. Could have been used for gliding but not flying. Allowed aquatic insects to sail around water surface as they emerged as adults. The wings then became large enough to allow flight. Some insects live in water as immatures and then became terrestrial. Insect lineage that developed wings was one that had aquatic larvae and terrestrial adults. Modification of gill like structures in larvae became wings in adult. Implies that lineage had at least an aquatic larval stage.

Insect reproduction

This highly fecund termite queen can lay 30,000 eggs/day and live for ~15 years. Queen is surrounded by workers. The massive part is just her abdomen full of ovaries.

Phylogeny: echinodermata

This shows secondary bilateral symmetry. It went back to being bilateral. Originally, there was a change in the adults to radial symmetry at the base of the tree. Two of the groups reverted to bilateral symmetry.

Sheep liver fluke (Dicrocoelium)

Three hosts: sheep, snail, and ant. Cycles from sheep to snail to ant. Explanation: The eggs of the fluke enter the digestive track of the sheep, and are present in the feces of the sheep. The snail eats the feces. The snail is then infected by the fluke eggs. The snails leave slime. The slime contains some of the flukes. Ants eat the snail slime. When the ant gets fluke larvae inside of it, its behavior changes. Some of the larvae migrate to the brain of the ant. Instead of going back to the colony, the ant climbs to the top of vegetation. The ant climbs on the stem, and it increases the chances of the ant being eaten by sheep (which graze). The cycle continues.

Phylogeny: mammals

Three major clades of mammals: (1) prototherians (echidna, duck-billed platypus), (2) marsupials, and (3) eutherians.

Hemimetabolous (incomplete) metamorphosis

Three stages: egg --> nymph --> adult. Nymph similar in structure to adult (but with wing pads only). Nymphs constrained to resemble adult morphology to some degree. Encumbered with appendages, wing pads, etc.

Hexapoda: body plan

Three tagmata: head, thorax and abdomen. One pair of antennae (two pairs in other crustaceans). Three pairs of legs (located on the thorax).

Review: mollusks and segmentation

Traditional view was that wormy creatures were succeeded by mollusks that had a shell (i.e. monoplacophora and polyplacophora). Some segmentation in these groups. Gastropods, bivalves, and cephalopods are not segmented. The classic view is different. Wormy creatures and chitons were sisters. The monoplacophora and cephalopods were sisters. The segmented groups weren't close ancestors. One explanation is convergent evolution.

Phylogeny: deuterostomes

Trends in vertebrate evolution: Increased cephalization. Increased agility of movement. New feeding modes (especially predation). "Physiological upgrading."

Phylogeny: triploblasty and diploblasty

Triploblasty is a further derivation of the diploblastic state. Diploblasty arose deep in the tree. Not all of the descendants are diploblasts. A bunch of them are triploblasts. Cnidarians and ctenophores are the main diploblasts. Blastocoel is called the mesoglea in cnidarians.

Truffles

Truffles are from underground. Why do these organisms decide to bury themselves in the soil and not show up as a mushroom? Answer: they are more protected from predators. They can access nutrients from the soil. It prevents desiccation, as they have access to more moisture. Truffles are enclosed fruiting bodies. Enclosed fruiting bodies (truffles, puffballs) have also evolved multiple times within Basidiomycota and Ascomycota.

Club fungi (Basidiomycota) life cycle

Two different spores. Reproduction: If the conditions are perfect, no sexual reproduction occurs. If conditions are poor, partners are required. Mycelial hyphae get together. Plasmogamy occurs. A mycelium is dikaryotic. The zygospore is just one cell. The mycelium doesn't involve the fusion of nuclei. The dikaryotic mycelium can last quite a long time (i.e. more than a century). They don't fuse their nuclei. If you open a basidioma (fruiting structure), you see gills. They develop into the basidium. The nuclei eventually fuse. They go through meiosis. Results in four basidiospores. Those spores are released into the environment. A single mushroom can produce 1 trillion spores. This fungi can produce a ton of spores. Reproduction is mainly sexual.

Phylogeny: protostomes

Two major clades: Ecdysozoa and Lophotrochozoans.

Freshwater clams

Type of bivalve. Southeastern United States is a center of diversity (30% of world's species). Many species are threatened by pollution. Life cycle includes a larval stage (glochidium) parasite on fish. Glochidia are sometimes bunched together by the parent clam and then released. In a few species, the bunching of larvae is a form of a structure that looks like a fish. Mantle edge of some clams mimics small minnow: predatory fish get a mouthful of glochidia instead of a meal Early stages of mussels are parasitic on fish. By mimicking a minnow, the parasite increases the chances of transferring to a fish host.

Cone snails

Type of gastropod. Shoot harpoon-like radula (laden with toxin) at prey.

Yeast

Unicellular fungus. Not a monophyletic group. Yeasts are easy to culture, grow fast, can be maintained for long periods of time, and are inexpensive. Used on a daily basis by humans. Yeasts live in liquid or moist environments and absorb nutrients directly across cell surfaces. Can undergo sexual reproduction, but prefer not to.

Amphioxus song takeaways

Vertebrates did not evolve from a lancelet. They evolved from the common ancestor of those two things. Vertebrates came from the common ancestor of Amphioxus and vertebrates. Similarly, humans did not evolve from chimps. Humans and chimps share a common ancestor. Doesn't mean we evolved from chimps. MRCA of lancelets and humans probably looked a lot more like lancelets than humans. Lancelets have evolved much less than vertebrates. Fossil evidence supports this idea.

Aquiferous systems of sponges

Water flows continuously into numerous incurrent pores (ostea), traverses internal chambers, and exits out of one or more excurrent pores (oscula); propelled by movement of flagella of many choanocytes. Travels through the internal parts of the sponge. Water exits through the oscula. The water's movement is caused by the movement of the flagella. System varies in complexity among different kinds of sponges. No need to memorize the names of each kind of system.

Phylogeny importance: Pseudogymnoascus destructans

We were able to understand this disease better with phylogeny. It is common with bats in Europe. They have developed resistance to the fungus. Migration of bats to North America introduced the fungus to nonresistant populations.

Carboniferous Period

When ferns and amphibians were dominant and coal deposits formed. Lycophytes and early conifers were abundant. Lycophytes used to be big and tall. Fungi started to feed on them.

White rot fungi

White rot fungi break down cellulose, hemicellulose, and lignin. Common in all types of trees. White fungi evolved when there was a lot of lignin on the ground. We know this because of phylogenies. We don't know how lignin is broken down. We do know that the fungi developed an enzyme to do so. They blast the carbon ring apart. They use laccase oxidase to break it down, instead of carrying a bunch of genes to break it down, which costs energy and is inefficient. It produces laccase oxidase, an enzyme capable of degrading phenolic substances. Evolution of a lignin-degrading peroxidase was one of the main determinants of diversification among fungi.

Sea slugs (Nudibranchs)

Why are they brightly colored? Warning coloration to predators, as many species are toxic.

How did insect wings evolve?

Wings could have evolved from three structures (three hypotheses): Top of thorax. Side of thorax. Dorsal leg appendages. Best supported by evidence. Comparative gene expression studies suggest that wings arose from dorsal appendages at the base of the legs. In crustaceans the dorsal appendages are used for respiration.

Fungal invasion of host tissues

With respect to plants, fungi can invade stomata guard cells. They anchor themselves inside the plant.

Cellulose, hemicellulose, and lignin

Wood is composed largely of cellulose, hemicellulose, and lignin; all of which are difficult to break down. Cellulose < Hemicellulose < Lignin. Cellulose: Cellulose is made of lots of sugars. It is difficult to break down because there are beta 1, 4 glycosidic bonds. Starch has one alpha glycosidic bond. Starch is easy to break down. Cellulose is hard to break down. Hemicellulose: Hemicellulose have a similar structure to cellulose. However, side chains are incorporated. Cellulose has to be hard in order to stand the pressure of the tree. Hemicellulose has the very same structure. Side chain chemicals are attached. In order for an organism to take in the glucose, they have to remove all of the colorful side chains. You are still getting the same amount of energy, even despite the extra energy required. This is disadvantageous. Lignin: Contains lots of rings and side chains. The most difficult plant component to break down.

Zygomycota

Zygomycota are aseptate fungi, the most common is Rhizopus, which causes bread mold.

Animal development

Zygote --> Blastula --> Gastrula Blastocoel: an internal fluid filled cavity. A blastula occurs in all animals. Some of the cells on the outside of the blastula migrate into the interior of the blastula. This is gastrulation. Results in some cells being exterior (ectoderm) and interior (endoderm). Two cell layers: endoderm and ectoderm. Animals with two cell layers are called diploblastic. Gastrulation: formation of cell layers by invagination (in-pocketing) of blastula to form gastrula. It is the formation of the embryonic gut. Diploblastic animals: two cell layers formed, ectoderm and endoderm. Triploblastic animals: three cell layers formed: the ectoderm, endoderm, and mesoderm. The mesoderm forms in between the ectoderm and endoderm.