bio 204 midterm 3 part 2 (4-6)
There are multiple causes for amphibian population crashes and species extinctions - what are these? One cause is particularly problematic - what is this problem?
"Standard" problems: 1. Habitat destruction 2. Over-exploitation Other Factors: 1. Introduced species (mountain yellow-legged frogs impacted by introduced trout in CA) 2. Climate change, including increased UV-B radiation 3. Water pollutants 4. Emerging infectious diseases => chytrid fungus *Rapid Spread of Chytrid Fungus in Central America (problematic problem)
Why is insect pollination so important to humanity??
- => essentially all terrestrial ecosystems would collapse without this interaction; this includes Agroecosystems One of the most important Ecosystem Services on Earth
Outline the timeline of diversification for Arthropods, including 1) time of origin in the fossil record, and 2) general timing of terrestrial invasions.
-"the earliest fossils are from the Cambrian explosion (535-525 million years ago), indicating that the arthropods are at least that old."(700) Along with arthropods, the fossil record of the Cambrian explosion contains many species of lobopods, a group from which arthropods may have evolved. - Arthropods = first animals to invade land, ~ 420 MYA (lecture) -arthropod fossils from several continents indicate that by 410 million years ago, millipedes, centipedes, spiders, and a variety of wingless insects all had colonized the land
Why is Acanthostega an important fossil tetrapod - i.e., what does this fossil tell us about tetrapod evolution?
-Acanthostega: a "fish with fingers!" -Key to limb bones
What are the two primary groups of living tetrapods?
-Amphibians -Amniotes (reptiles, birds, mammals)
What are the four major groups of living arthropods, and the habitats in which each group can be found?
-Chelicerata, Pycnogonids & horseshoe crabs are marine, arachnids are terrestrial -Myriapoda, all are terrestrial; centipedes (chilopoda), millipedes (diplopoda) -Crustacea, thrive in a broad range of marine, fresh-water, and terrestrial environments; barnacles, lobsters and crabs. -Hexapoda, "insects live in almost every terrestrial habitat and in fresh water, and flying insects fill the air."
The ray-finned fish epidermis has multiple functions - what are these??
-Epidermal glands secrete "mucous" -Reduces drag; provides protection from pathogens -Nearly "watertight" - barrier to water gain/loss
Did gnathostome lungs evolve on land, or in aquatic habitats? What is the evolutionary fate of lungs in some Ray-finned fishes? How do these animals thus respire?
-First evolved in fishes -Most ray-fins possess a swim bladder (*Derived from lungs) ==> aids in maintaining position in water column -These fish use various organs - including modified swim bladders, modified stomachs, and modified intestines - to breathe air. -A fish's swim bladder manipulates neutral buoyancy by controlling the amount of air in the swim bladder, allowing it to swim at different depths
Why are modern coelocanths considered "living fossils"? What are general characteristics of "living fossils"?
-Fossils in same lineage range from 400-75 MYA, representing 125 different species!! -"This survivor from the age of dinosaurs has body parts found in no other living creature" - Scientists thought the coelacanth died out 66 million years ago, because it vanishes from the fossil record then. But in 1938 a live coelacanth was hauled up in a fisherman's nets off South Africa. Since then, another surviving species has turned up in Indonesia. What is a "living fossil"?? -A living (extant) species representing a group that was previously more diverse, and has a well-known fossil record -Typically exhibit slow rates of morphological evolution => living species surprisingly similar in morphology to fossil species -Other examples: Lungfish, Japanese Giant Salamander...
Explain how the countercurrent exchange mechanism allows fish to extract oxygen from the water as it flows over their gills.
-In the gills, oxygen diffuses from an area of high concentration, the water, into an area of lower concentration, the fish's bloodstream. -oxygen-rich water and oxygen-deficient blood flow in opposite directions, resulting in continuous oxygen diffusion. This is because even though the oxygen concentration may decrease, the amount of oxygen in the water is always slightly greater than that in the blood, allowing diffusion to continue, and equilibrium to be avoided. In this case, the maximum amount of oxygen that can enter the blood is 90%, much greater than the amount which entered via concurrent exchange which would be 50%. -There is an adaptation that fish have to maximize the flow of oxygen into the blood called countercurrent exchange. This is when the water flowing over the lamellae is in the opposite direction as the blood flowing through the capillaries. In this way, the concentration of oxygen in the blood as it moves through the capillaries is always lower than the water,
Why are gnathostomes successful?
-Jaws (& Teeth) - grasp, manipulate, shear food objects => New food resources become available -Unpaired + paired fins => better, faster, more maneuverable swimmers
Jaws evolved from which structures in more early-diverging Vertebrates? What is the evidence for this homology?
-Jaws evolved from anterior pharyngeal arches of early-diverging vertebrates Evidence for Gill Rod <> Jaw Homology: 1) Position on body (positional homology) 2) Both structures derived during development from neural crest cells 3) Nerve distribution to associated muscles is similar
Insect wings are not appendages, explain. How does this differ from the condition seen in other animals with powered flight?
-NOT appendages - cuticular extensions of dorsal thorax => unlike flying vertebrates, do NOT forfeit functionality of appendages to fly!!!
What are neural crest cells? What are important cell derivatives of neural crest cells? Also use an example from an adult vertebrate.
-Neural Crest cells: population of multipotent, migratory developmental cells arising from top margin of neural tube -neural crest: in vertebrates, a region located along the sides of the neural tube where it pinches off from the ectoderm. Neural crest cells migrate to various parts of the embryo and form pigments cells in the skin and parts of the skull, teeth, adrenal glands, and peripheral nervous system. Ex. Facial Cartilage & Bone
How are placoid scales related to teeth in Chondrichthyes? How do shark teeth differ from the teeth of other Gnathostomes?
-Placoid Scales: mineralized dermal tissues, tooth-like scales -Chondrichthyes(shark) teeth form from skin as whorls => rest ON jawbone -Placoid scales develop into teeth for Chondrichthyes, not part of the jaw while in other gnathostomes teeth are embedded into the jawbone
Amphibians are either "tied to water" (i.e., must have water to complete part of their lifecycle), or found in moist terrestrial habitats. What aspects of amphibian biology impose these constraints?
-SKIN - Thin permeable skin lacking scales - permeable to respiratory gases (many taxa with cutaneous respiration) -Thin, permeable skin implies dessication(extreme dryness) in dry habitats -Amphibians generally rely heavily on their moist skin for gas exchange with the environment. Some terrestrial species lack lungs and breathe exclusively through their skin and oval cavity (book) -EGGS - covered with a jelly-like substance, no protective shell -eggs lack a shell and dehydrate quickly in dry air
Where are spider silk proteins produced, and how do these silks exit the spider body??
-Spider Silks are Produced in Abdominal Silk Glands => produced as liquid proteins -silk passes through the spinnerets and exits through the spigots which are mobile, finger-like protrusions and the resulting silk emerges as a solid.
How do lungfish breathe? When during vertebrate evolution did lungs evolve (i.e., at the base of which clade, where on the vertebrate tree)?
-breathe using both Gill & Lung Respiration -have lungs that are derived from the swim bladder, an organ used for buoyancy in most bony fishes. -coelacanths? During siluria time period
What does complete metamorphosis mean? What are the lifestages of an insect with complete metamorphosis?
-complete metamorphosis: the transformation of a larva into an adult that looks very different, and often functions very differently in its environment, than the larva. -Insects with complete metamorphosis have larval stages specialized for eating and growing that are known by such names as caterpillar, maggot, or grub. The larval stage looks entirely different from the adult stage, which is specialized for dispersal and reproduction. Metamorphosis from the larval stage to the adult occurs during a pupal stage. Egg >> larva >> pupa >> adult stages
Why can't shark populations quickly rebound after over-harvesting - at least three reasons?
-don't reproduce fast enough. They are biennial, meaning they reproduce every other year. -gestation periods are long, taking anywhere between 9 months and 2 years depending on the species -small litter sizes -mature at a much later age than other aquatic animals, which also inhibits their ability to reproduce, making them more vulnerable to over-harvesting and extinction
In an experimental setting, how could one rule out contact chemoreception and vision as a means of prey detection, leaving electroreception as the most obvious mechanism of detection?
-experiments indicate that when the shark was able to detect an electrical signal, it used that to locate the fish-and it was also capable of homing on a chemical signal when no electrical signal was present. This dual system allows sharks to find both living and dead food items. (slide 31 for more info)
Describe and define the function of the lateral line system
-lateral line system: organs that form a row along each side of the body and are sensitive to vibrations in the surrounding water -for mechanoreception (detecting low frequency vibrations in water) => e.g., water movements caused by struggling fish -extremely sensitive hair cells that respond to water displacement
What does the word gnathostome mean?
-means "jaw mouth" and therefore refers to vertebrates with jaws
Define ecdysis?
-the process of shedding the old exoskeleton (book) -periodic molting for growth (lecture)
The cuticular exoskeleton of arthropods (including insects) retains water, is light, flexible & supportive. Chitinous cuticle is also used to build important body structures - give three examples
-wings -membranes for hearing -cuticular structures for producing sound -cuticular lenses
What are 5 reasons for the success (i.e., diversity) of Insects?
1) Complex senses of vision: hearing, olfaction, touch, etc.. 2) Possess wings (only invert animals with wings) 3) co-Diversification with plants (e.g., pollination, plant-feeding) 4) Most diverse groups (but NOT all insects) with Complete Metamorphosis: Egg >> larva >> pupa >> adult stages 5) Many are Parasites
Recall the four key chordate characters. These characters evolve into different structures with different functions in derived chordates - give an example using the pharyngeal gill slits
1) Dorsal, hollow nerve cord ==> Spinal cord plus brain 2) Notochord -Fibrous, supportive rod extending length of body beneath dorsal nerve cord -reduced in most Vertebrates (e.g., remnant intervertebral discs in adult humans) 3) Pharyngeal slits or clefts -Allow water to bypass digestive tract -Suspension-feeding devices in invertebrate chordates -respiration in aquatic Vertebrates (gills) ==> jaws in jawed Vertebrates 4) Muscular, post-anal tail
Genes are often duplicated in genomes (i.e., a single gene gives rises to two "daughter" genes through duplication of a chromosome or part of a chromosome). What are the three possible fates of such duplicated genes?
1) Lose functionality (pseudogene), go "extinct" 2) Neofunctionalization - evolve a "new function" different from ancestral gene 3) Subfunctionalization - two "daughter" genes each take on part of function of "mother" gene
What are two ecological implications of complete metamorphosis??
1) Major morphological change implies major ecological difference between lifestages (= reduced competition among lifestages) 2) Pupal stage can evade harsh seasonal conditions, populations can rapidly respond to resource availability
Name 4 major anatomical changes that occur in the transition from tadpole to adult frog?
1) loss of gills 2) formation of limbs 3) loss of tail 4) change of digestive system
Many biologists claim that arthropods are the most successful animal lineage. What are 3 measures of "evolutionary success" for Arthropods
1)Ecological Diversity - in essentially all habitats >> aquatic + dominant life form on land & in the air 2)Numerically Dominant Metazoans - some estimates suggest a billion, billion individuals 3)Species Diversity - 2/3rd of all described animals; ~1 million species described
What are some of the ecological reasons that tetrapods may have invaded land?
1. Unexploited food resources on land (lots of APODS!) 2. VERY little competition on land (no other BIG animals) 3. LOTS of competition, MANY predators in water 4. Terrible fear of Dunkleosteus
What are two keys adaptations for predation seen in spiders?
2 "Keys" to Spider Predation & Success: Silks, Venoms
Describe and define the function of the Ampullae of Lorenzini
Ampullae of Lorenzini (Sensitive electroreceptors): any of an array of electroreceptors in the head of sharks, skates, and rays capable of detecting weak electrical signals produced by muscular activity in other creatures. (dictionary.com) -Detecting Electrical Discharge = electroreception -Seawater conducts electricity well -Sharks & rays detect electrical fields that accompany muscle contractions of prey items!! -Can also use electroreceptors to detect small differences in water temperature => used for navigation (water currents), finding prey that prefer certain water temperatures, etc...
LECTURE 6 REVIEW QUESTIONS
BONY FISHES, MOVING TO LAND
LECTURE 5 REVIEW QUESTIONS
CHORDATES
Vertebrates are said to be morphologically disparate - what does this mean?
Concept of Morphological Disparity - Great variation in morphological form despite relatively limited species diversity - contrast this with, for example, beetles => HUGE number of species, limited diversity in form
LECTURE 4 REVIEW QUESTIONS
ECDYSOZOA & ARTHROPODS
Tetrapods ultimately evolved to be land animals. What characters already possessed by tetrapod ancestors facilitated this transition to land?
Key Tetrapod Features "in place" which facilitated Terrestrial Invasion: I. Bony Endoskeleton => system of body support in a non-supportive environment II. Lungs (*gills don't work on land!) - primitive feature for Bony-fishes (Osteichthyes) III. Pectoral & pelvic girdles, with associated limbs + terminal phalanges => obviously important in land-based locomotion
Pollination is a so-called +/+ ecological interaction - what is benefit to insects from this interaction?
Mutualism - both parties benefit, evolve co-dependence -plants receive fertilization services, insects rewarded with nutrient-rich nectars & pollen
Why is the mass production of spider silks (for human use) difficult? How are researchers overcoming this hurdle??
Technical hurdles: -Spiders are predators!! -liquid protein to solid silken fiber transition difficult to replicate -Primary Solution - Recombinant Spider Silks
Draw a "standard" salamander lifecycle. California tiger salamander populations are in decline - describe one terrestrial threat, and two aquatic threats
Terrestrial: -extirpation of ground squirrels -urbanization -agricultural conversion -roads or other barriers -habitat fragmentation -genetic isolation Aquatic: -destruction of wetlands -agricultural conversion -environmental pollution -introduced species such as bullfrogs, crayfish, and mosquitofish -drought Standard life cycle: -adult migration and breeding -eggs hatch after 2-4 weeks -aquatic larval stage, metamorphosis is triggered by drying of pond -juvenile migration and estivation -adult estivation
When did tetrapod terrestrial invasions occur? Were tetrapods the first animals onto land?
Tetrapod Transition to Land: -Fossils suggest late Devonian invasions (360-380 MYA) -Plants and other animals (apods) already on land
What are the functions of spider silks - i.e., how do spiders use their silks??
The Many Functions of Spider Silks: -Egg sacs, Nests -Silks used in dispersal by immature spiders ("ballooning") -Burrow Protection (e.g., trapdoors) - antifungal properties, concealment, mechanical protection from predators and soil pathogens -"Spider webs" - silken constructs used to detect, capture & hold, wrap prey (mostly insects)
What are some primary characters of Chondrichthyes?
•Well developed paired fins and toothed jaws •Counter-current gill respiration (posterior pharyngeal arches retain gas exchange function) •Placoid scales •Mostly cartilaginous endoskeleton •Large, oily livers aid in buoyancy (*lack swim bladders)
