MODULE 5

Based on the phylogeny shown in Figure 34.25, identify the sister group for (a) reptiles, (b) squamates, and (c) the clade that includes crocodilians and birds.

(a) synapsids, (b) tuataras, (c) turtles

For each major group think about

- a familiar example -what is the general body plan? (what kind of symmetry, head? , tissue layers, body cavity, legs? - how does it eat? -how does it move? -how does it reproduce?

What are some examples of crustaceans?

- chelicerates -myriapods -hexapods - crustaceans (largely aquatic invertebrates) -crabs, lobster, crayfish, krill, barnacles

Choanoflagellates

- colonial choanoflagellates the sister group to all other animals - these are protists, not fully multicellular organims. But they share many features with animals.

What are some examples of hexapods?

-chelicerates -myriapods -hexapods (the insects) - most successful of all arthropods 1.Beetles 2.Flies 3.Bees, wasps, ants 4.Butterflies, moths

What is the basic process of embryonic development?

1. After fertilization, the zygote undergoes rapid cell division in a process called cleavage 2. Cleave results in the formation of a hollow, multicellular "ball" of cells called a blastula 3. The blastula will tuck into itself and undergo gastrulation 4. Gastrulation forms a gastrula

What are some characteristics of echinoderms?

1.Thin epidermis 2.Endoskeleton 3.Water vascular system 4.Tube feet 5.Bilateral symmetry as larvae

when did the first animals arise roughly

600 million years ago

Compare three aspects of the early development of a snail (a mollusc) and a human (a chordate).

A snail has a spiral and determinate cleavage pattern; a human has radial, indeterminate cleavage. In a snail, the coelomic cavity is formed by splitting of mesoderm masses; in a human, the coelom forms from folds of archenteron. In a snail, the mouth forms from the blastopore; in a human, the anus develops from the blastopore.

Explain how the molluscan foot in gastropods and the excurrent siphon in cephalopods represent examples of descent with modification

All molluscs have inherited a foot from their common ancestor. However, in different groups of molluscs, the structure of the foot has been modified over time by natural selection. In gastropods, the foot is used as a holdfast or to move slowly on the substrate. In cephalopods, the foot has been modified into part of the tentacles and into an excurrent siphon, through which water is propelled (resulting in movement in the opposite direction).

What are some characteristics of mollusks?

All of them have a soft body and a hard shell (can be internal or external) Body plan with 3 parts: 1.Muscular foot for movement 2.Visceral mass containing organs 3.Mantle: a fold of tissue that goes over the visceral mass that produces the shell

Amphibians require water for reproduction; their bodies can lose water rapidly through their moist, highly permeable skin; and amphibian eggs do not have a shell and hence are vulnerable to desiccation.

Amphibians require water for reproduction; their bodies can lose water rapidly through their moist, highly permeable skin; and amphibian eggs do not have a shell and hence are vulnerable to desiccation.

When approximately did animals first evolve? What protist are they most similar to?

Animals first evolved about half a billion years ago Most similar to choanoflagellates •Have a cell body, a color, and a flagellum

Describe how animals that lack a body cavity exchange materials without an internal transport system.

Animals that lack a body cavity tend to have thin, flat bodies. Such animals don't require an internal transport system: With bodies that are only a few cells thick, the exchange of nutrients, gases, and wastes can occur across the entire body surface.

Describe key adaptations of aquatic gnathostomes.

Aquatic gnathostomes have jaws (an adaptation for feeding) and paired fins and a tail (adaptations for swimming). Aquatic gnathostomes also typically have streamlined bodies for efficient swimming and swim bladders or other mechanisms (such as oil storage in sharks) for buoyancy.

Explain why birds are considered reptiles.

Birds are descended from theropod dinosaurs, and dinosaurs are nested within the archosaur lineage, one of the two main reptile lineages. Thus, the other living archosaur reptiles, the crocodilians, are more closely related to birds than they are to non-archosaur reptiles such as lizards. As a result, birds are considered reptiles. (Note that if reptiles were defined as excluding birds, the reptiles would not form a clade; instead, the reptiles would be a paraphyletic group.)

Identify four avian adaptations for flight.

Birds have weight-saving modifications, including the absence of teeth, a urinary bladder, and a second ovary in females. The wings and feathers are adaptations that facilitate flight, as do efficient respiratory and circulatory systems that support a high metabolic rate.

Use the cnidarian life cycle diagram in Figure 33.7 to determine the ploidy of a feeding polyp and of a medusa.

Both a feeding polyp and a medusa are diploid, as indicated by the pink arrow in the diagram.The medusa stage produces haploid gametes.

What is the difference between protostomes and deuterostomes?

Both are bilaterians Protostomes: Blastopore becomes mouth Deuterostomes: Blastopore becomes anus

What derived characters do sharks and tuna share? What features distinguish tuna from sharks?

Both are gnathostomes and have jaws, four clusters of Hox genes, enlarged forebrains, and lateral line systems. Shark skeletons consist mainly of cartilage, whereas tuna have bony skeletons. Sharks also have a spiral valve. Tuna have an operculum and a swim bladder, as well as flexible rays supporting their fins.

The insect Drosophila melanogaster and the nematode Caenorhabditis elegans are prominent model organisms. Are these species the most appropriate invertebrates for making inferences about humans and other vertebrates? Explain.

Both insects and nematodes are members of Ecdysozoa, one of the three major clades of bilaterians. Therefore, a characteristic shared by Drosophila and Caenorhabditis may be informative for other members of their clade—but not necessarily for members of Deuterostomia. Instead, Figure 33.2 suggests that a species withinEchinodermata or Chordata might be a more appropriate invertebrate modelorganism from which to draw inferences about humans and other vertebrates.

Compare and contrast the polyp and medusa forms of cnidarians.

Both the polyp and the medusa are composed of an outer epidermis and an inner gastrodermis separated by a gelatinous layer, the mesoglea. The polyp is a cylindrical form that adheres to the substrate by its aboral end; the medusa is a flattened, mouth-down form that moves freely in the water.

What are some characteristics of cnidarians? What makes them different from sponges/other animals?

Cnidarians are the first animals to have true tissues. They are diploblastic, meaning their gastrula has two layers: an ectoderm and an endoderm.

Describe the evidence that cnidarians share a more recent common ancestor with other animals than with sponges.

Cnidarians possess tissues, while sponges do not. Also unlike sponges, cnidarians exhibit body symmetry, though it is radial and not bilateral as in most other animal phyla.

Identify the shared features of early fossil vertebrates.

Conodonts, among the earliest vertebrates in the fossil record, were very abundant for 300 million years. While jawless, their well-developed teeth provide early signs of bone formation. Other species of jawless vertebrates developed arm or on the outside of their bodies, which probably helped protect them from predators. Like lampreys, these species had paired fins for locomotion and an inner ear with semicircular canals that provided a sense of balance. There were many species of these armored jawless vertebrates, but they all became extinct by the close of the Devonian period, 359 million years ago.

What are some characteristics of arthropods?

Cuticle: An exoskeleton made of protein/chitin that covers the entire body of an arthropod •Provides protection and points of attachment for muscle/appendages •Prevents water loss/dessication •This enabled arthropods to be some of the first animals to walk on land Open circulatory system: Heart pumps hemolymph into a cavity surrounding tissues and organs Arthropods also have eyes, olfactory sensors, and antennae.

What is the difference between diploblastic and triploblastic organisms?

Diploblastic: two cell layers in gastrula (ectoderm and endoderm) •Includes cnidarians Triploblastic: three cell layers in gastrula (ectoderm, mesoderm, and endoderm) •Includes bilaterians

How do sea star tube feet attach to substrates?

Each tube foot consists of an ampulla and a podium. When the ampulla squeezes, it forces water into the podium, which causes the podium to expand and contact the substrate. Adhesive chemicals are then secreted from the base of the podium, thereby attaching the podium to the substrate.

You've read that echinoderms and chordates are closely related and have evolved independently for over 500 million years. Explain how both of these statements can be correct.

Echinoderms and chordates are both members of Deuterostomia, one of the three main clades of bilaterian animals. As such, chordates (including humans) are more closely related to echinoderms than we are to animals in any of the other phyla covered in this chapter. Nevertheless, echinoderms and chordates have evolved independently for over 500 million years. This statement does not contradict the close relationship of echinoderms and chordates, but it does make clear that"close" is a relative term indicating that these two phyla are more closely related to each other than either is to animal phyla not in Deuterostomia.

Describe how the features and diversity of echinoderms illustrate the unity of life, the diversity of life, and the match between organisms and their environments

Echinoderms include species with a wide range of body forms. However, even echinoderms that look very different from one another, such as sea stars and sea cucumbers, share characteristics unique to their phylum, including a water vascular system and tube feet. The differences between echinoderm species illustrate the diversity of life, while the characteristics they share illustrate the unity of life. The match between organisms and their environments can be seen in such echinoderm features as the eversible stomachs of sea stars (enabling them to digest prey that are larger than their mouth) and the complex, jaw-like structure that sea urchins use to eat seaweed.

Many new animal body plans emerged during and after the Cambrian explosion. In contrast, cnidarians today retain the same diploblastic, radial body plan found in cnidarians 560 million years ago. Are cnidarians therefore less successful or less "highly evolved" than other animal groups? Explain. (See Concepts 25.3 and 25.6.)

Evolution is not goal oriented; hence, it would not be correct to argue that cnidarians are not "highly evolved"simply because their form had changed relatively little over the past 560 million years. Instead, the fact that cnidarians have persisted for hundreds of millions of years indicates that the cnidarian body plan is a highly successful one.

Identify at least five derived traits of primates.

Hands and feet adapted for grasping, flat nails, large brain, forward-looking eyes on a flat face, parental care, and movable big toe and thumb

Identify some characters that distinguish hominins from other apes.

Hominins are a clade within the ape clade that includes humans and all species more closely related to humans than to other apes. The derived characters of hominins include bipedal locomotion and relatively larger brains.

Suggest key roles that mineralized bone might have played in early vertebrates.

In armored jawless vertebrates, bone served as external armor that may have provided protection from predators. Some species also had mineralized mouthparts, which could be used for either predation or scavenging.

Evaluate whether the origin of cell-to-cell attachment proteins in animals illustrates descent with modification

In descent with modification, an organism shares characteristics with its ancestors (due to their shared ancestry), yet it also differs from its ancestors (because organisms accumulate differences over time as they adapt to their surroundings). As an example, consider the evolution of animal cadherin proteins, a key step in the origin of multicellular animals. These proteins illustrate both of these aspects of descent with modification: Animal cadherin proteins share many protein domains with a cadherin-like protein found in their choanoflagellate ancestors, yet they also have a unique "CCD" domain that is not found in choanoflagellates.

Provide an example in which different features of organisms in the hominin evolutionary lineage evolved at different rates.

In hominins, bipedal locomotion evolved long before large brain size. Homo ergaster, for example, was fully upright, bipedal, and as tall as modern humans, but its brain was significantly smaller than that of modern humans.

You are a chordate, yet you lack most of the main derived characters of chordates. Explain.

In humans, these characters are present only in the embryo. The notochord becomes disks between the vertebrae; the dorsal, hollow nerve cord develops into the brain and spinal cord; the pharyngeal clefts develop into various adult structures, and the tail is almost completely lost.

Summarize the main stages of animal development. What family of control genes plays a major role?

In most animals, the zygote undergoes cleavage, which leads to the formation of a blastula. Next, in gastrulation, one end of the embryo folds inward, producing layers of embryonic tissue. As the cells of these layers differentiate, a wide variety of animal forms are produced. Despite the diversity of animal forms, animal development is controlled by a similar set of Hox genes across a broad range of taxa.

What are gnathostomes? What are some characteristics of gnathostomes?

Includes: •Chondrichthyans (sharks, rays, and skates) •Osteichthyans(mineralized skeleton) •Tetrapods(four legs, life on land) Characteristics: •Jaws that can be used to grip and slice food •Skeletal rods that support gills (in some organisms) •Enhanced hox genes •Enhanced forebrain (enhanced smell and vision

Describe likely features of the common ancestor of chordates. Explain your answer.

Lancelets are the most basal group of living chordates, and as adults they have key derived characters of chordates. This suggests that the chordate common ancestor may have resembled a lancelet in having an anterior end with a mouth along with the following four derived characters: a notochord; a dorsal, hollow nerve cord; pharyngeal slits or clefts; and a muscular, post-anal tail.

Develop a hypothesis to explain why the diversity of mammals increased in the Cenozoic. Your explanation should consider mammalian adaptations as well as factors such as mass extinctions and continental drift

Mammals are endothermic, enabling them to live in a wide range of habitats. Milk provides young with a balanced set of nutrients, and hair and a layer of fat under the skin help mammals retain heat. Mammals have differentiated teeth, enabling them to eat many different kinds of food. Mammals also have relatively large brains, and many species are capable learners. Following the mass extinction at the end of the Cretaceous period, the absence of large terrestrial dinosaurs may have opened many new ecological niches to mammals, promoting an adaptive radiation. Continental drift also isolated many groups of mammals from one another, promoting the formation of many new species.

Describe the origin and early evolution of mammals.

Mammals are members of a group of amniotes called synapsids. Early (nonmammalian) synapsids laid eggs and had a sprawling gait. Fossil evidence shows that mammalian features arose gradually over a period of more than 100 million years. For example, the jaw was modified over time in nonmammalian synapsids, eventually coming to resemble that of a mammal. By 180 million years ago, the first mammals had appeared. There were many species of early mammals, but most of them were small, and they were not abundant or dominant members of their community. Mammals did not rise to ecological dominance until after the extinction of the dinosaurs.

Scientists think that amphibian populations may provide an early warning system of environmental problems. What features of amphibians might make them particularly sensitive to environmental problems?

Many amphibians spend part of their life cycle in aquatic environments and part on land. Thus, they may be exposed to a wide range of environmental problems, including water and air pollution and the loss or degradation of aquatic and/or terrestrial habitats. In addition, amphibians have highly permeable skin, providing relatively little protection from external conditions, and their eggs do not have a protective shell.

In case you are asked about this...

Monophyletic: A group of organisms that includes an ancestral species and all of its descendants Paraphyletic: A group of organisms that includes an ancestral species and some of its descendants Polyphyletic: A group of organisms that do not share a common ancestor

Contrast monotremes, marsupials, and eutherians in terms of how they bear young.

Monotremes lay eggs. Marsupials give birth to very small live young that attach to a nipple in the mother's pouch, where they complete development. Eutherians give birth to more developed live young.

Evaluate this claim: Ignoring the details of their specific anatomy, worms, humans, and most other triploblasts have a shape analogous to that of a doughnut.

Most triploblasts have two openings to their digestive tract, a mouth and an anus. As such, their bodies have a structure that is analogous to that of a doughnut: The digestive tract (the hole of the doughnut) runs from the mouth to the anus and is surrounded by various tissues (the solid part of the doughnut). The doughnut analogy is most obvious at early stages of development (see Figure 32.10c).

How do nematode and annelid body plans differ?

Nematodes lack body segments and a coelom; annelids have both.

What are some features of annelids?

Parapodia: Bristles made of chitin that are used for locomotion Most annelids have a closed circulatory system, a coelom, and a nervous system.

How are differences in the anatomy of lampreys and conodonts reflected in each animal's feeding method?

Parasitic lampreys have a round, rasping mouth, which they use to attach to fish. Non-parasitic lampreys feed only as larvae; these larvae resemble lancelets and like them, are suspension feeders. Conodonts had two sets of mineralized dental elements, which may have been used to impale prey and cut it into smaller pieces.

What are the two life stages of cnidarians? How do cnidarians reproduce?

Two stages: polyp and medusa

What are chondrichthyans?

Sharks, skates, and rays •Have cartilaginous skeletons •Suspension feeders •Efficient predators: acute sight and smell, able to detect changes in electric fields to find prey

Some amphibians never leave the water, whereas others can survive in relatively dry terrestrial environments. Contrast the adaptations that facilitate these two lifestyles.

Some fully aquatic species are paedomorphic, retaining larval features for life in water as adults. Species that live in dry environments may avoid dehydration by burrowing or living under moist leaves, and they protect their eggs with foam nests, viviparity, and other adaptations.

What are sponges? How do they eat?

Sponges are multicellular organisms without any true tissues Food particles in water will flow through the pores of a sponge. From there, the choanocyte of the sponge will use phagocytosis to uptake and digest the food particles.

In several different animal lineages, organisms with a head first appeared around 530 million years ago. Does this finding constitute proof that having a head is favored by natural selection? Explain.

Such a finding suggests that early organisms with a head were favored by natural selection in several different evolutionary lineages. However, while a logical argument can be made that having a head was advantageous, fossils alone do not constitute proof.

Explain how tapeworms can survive without a body cavity, a mouth, a digestive system, or an excretory system.

Tapeworms can absorb food from their environment and release ammonia into their environment through their body surface because their body is very flat, due in part to the lack of a body cavity.

Describe the origin of tetrapods and identify some of their key derived traits.

Tetrapods are thought to have originated about 365 million years ago when the fins of some lobe-fins evolved into the limbs of tetrapods. In addition to their four limbs with digits—a key derived trait for which the group is named—other derived traits of tetrapods include a neck (consisting of vertebrae that separate the head from the rest of the body) and a pelvic girdle that is fused to the backbone.

Describe three key amniote adaptations for life on land.

The amniotic egg provides protection to the embryo and allows the embryo to develop on land, eliminating the necessity of a watery environment for reproduction. Another key adaptation is rib cage ventilation, which improves the efficiency of air intake and may have allowed early amniotes to dispense with breathing through their skin. Finally, not breathing through their skin allowed amniotes to develop relatively impermeable skin, thereby conserving water.

Describe two adaptations that have enabled insects to thrive on land.

The arthropod exoskeleton, which had already evolved in the ocean, allows terrestrial species to retain water and support their bodies on land. Wings allow insects to disperse quickly to new habitats and to find food and mates. The tracheal system allows for efficient gas exchange despite the presence of an exoskeleton.

WHAT IF? Some molecular evidence suggests that the sister group of animals is not the choanoflagellates, but rather a group of parasitic protists, Mesomycetozoa. Given that the separasites lack collar cells, can this hypothesis be correct? Explain.

The collar cells of sponges bear a striking resemblance to a choanoflagellate cell. This suggests that the last common ancestor of animals and their protist sister group may have resembled a choanoflagellate. Nevertheless, mesomycetozoans could still be the sister group of animals. If this is the case, the lack of collar cells in mesomycetozoans would indicate that over time their structure evolved in ways that caused it to no longer resemble a choanoflagellate cell. It is also possible that choanoflagellates and sponges share similar looking collar cells as a result of convergent evolution.

Describe how sponges feed.

The flagella of choanocytes draw water through their collars, which trap food particles. The particles are engulfed by phagocytosis and digested, either by choanocytes or by amoebocytes.

Based on fossil evidence, summarize how key hominin features have changed over time.

The fossil record shows that from 4.5 to 2.5 million years ago, a wide range of hominin species walked upright but had relatively small brain sizes. About 2.5 million years ago, the first members of genus Homo emerged. These species used tools and had larger brains than those of earlier hominins. Fossil evidence indicates that multiple members of our genus were alive at any given point in time. Furthermore, until about 1.3 million years ago, these various Homo species also coexisted with members of earlier hominin lineages, such as Paranthropus. The different hominins alive at the same periods of time varied in body size, body shape, brain size, dental morphology, and the capacity for tool use. Ultimately, except for Homo sapiens, all of these species became extinct. Overall, human evolution can be viewed as an evolutionary tree with many branches—the only surviving lineage of which is our own.

Identify the four derived characters that all chordates have at some point during their life.

The four characters are a notochord; a dorsal, hollow nerve chord; pharyngeal slits or clefts; and a muscular, post-anal tail.

WHAT IF? What animal characteristics would be needed by an imaginary plant that could chase, capture, and digest its prey—yet could also extract nutrients from soil and conduct photosynthesis?

The imaginary plant would require tissues composed of cells that were analogous to the muscle and nerve cells found in animals: "Muscle" tissue would be necessary for the plant to chase prey, and "nerve" tissue would be required for the plant to coordinate its movements when chasing prey. To digest captured prey, the plant would need to either secrete enzymes into one or more digestive cavities (which could be modified leaves, as in a Venus flytrap) or secrete enzymes outside of its body and feed by absorption. To extract nutrients from the soil—yet be able to chase prey—the plant would need something other than fixed roots, perhaps retractable "roots" or a way to ingest soil. To conduct photosynthesis, the plant would require chloroplasts. Overall, such an imaginary plant would be very similar to an animal that had chloroplasts and retractable roots.

Annelid anatomy can be described as "a tube within a tube."Explain.

The inner tube is the alimentary canal, which runs the length of the body. The outer tube is the body wall. The two tubes are separated by the coelom.

How would the appearance of organisms with jaws have altered ecological interactions? Provide supporting evidence.

The origin of jaws altered how fossil gnathostomes obtained food, which in turn had large effects on ecological interactions. Predators could use their jaws to grab prey or remove chunks of flesh, stimulating the evolution of increasingly sophisticated means of defense in prey species. Evidence for these changes can be found in the fossil record, which includes fossils of 10-m-long predators with remarkably powerful jaws, as well as lineages of well-defended prey species whose bodies were covered by armored plates.

Based on the phylogeny in Figure 32.11 and the information in Figure 25.11, evaluate this statement: "The Cambrian explosion actually consists of three explosions, not one."

The phylogeny in Figure 32.11 indicates that molluscs are members of Lophotrochozoa, one of the three main groups of bilaterians (the others being Deuterostomia and Ecdysozoa). As seen in Figure 25.11, the fossil record shows that molluscs were present tens of millions of years before the Cambrian explosion. Thus, long before the Cambrian explosion, the lophotrochozoan clade had formed and was evolving independently of the evolutionary lineages leading to Deuterostomia and Ecdysozoa. Based on the phylogeny in Figure 32.11, we can also conclude that the lineages leading to Deuterostomia and Ecdysozoa were independent of one another before the Cambrian explosion. Since the lineages leading to the three main clades of bilaterians were evolving independently of one another prior to the Cambrian explosion, that explosion could be viewed as consisting of three "explosions," not one.

What main characteristic do echinoderms and chordates have in common?

They are deuterostomes •Echinoderms is the last true group of invertebrates •Chordates have both vertebrates and invertebrates

What are some characteristics of chordates?

They have bilateral symmetry and are coelomates. They are also segmented. 1.Notochord -a cartilaginous "spine" 2.Dorsal hollow nerve cord 3.Pharyngeal slits 4.Muscular post-anal tail Invertebrate chordates are lancelets and tunicates.

Animal Diversity and Body Plans

Think about: -symmetry -development -body cavity (coelom) -tissue systems -segmentation -external appendages

Suppose ctenophores are basal metazoans and sponges are the sister group of all remaining animals. Under this hypothesis, redraw Figure 32.11 and discuss whether animals with tissues would form a clade.

Under the hypothesis that ctenophores are basal metazoans, sponges (which lack tissues) would be nested within a clade whose other members all have tissues. As a result, a group composed of animals with tissues would not form a clade.

Some genetic studies suggest that the most recent common ancestor of Homo sapiens that lived outside of Africa left Africa about 50,000 years ago. Compare this date with the dates of fossils given in the text. Can both the genetic results and the dates ascribed to the fossils be correct? Explain.

Yes, both can be correct. Homo sapiens may have established populations outside of Africa as early as 180,00 years ago, as indicated by the fossil record. However, those populations may have left few or no descendants today. Instead, all living humans may have descended from Africans that spread from Africa roughly 50,000 years ago, as indicated by genetic data.

Imagine that we could replay the history of life. Is it possible that a group of vertebrates that colonized land could have arisen from aquatic gnathostomes other than the lobe-fins? Explain.

Yes, that could have happened. The paired appendages of aquatic gnathostomes other than the lobe-fins could have served as a starting point for the evolution of limbs. The colonization of land by aquatic gnathostomes other than the lobe-fins might have been facilitated in lineages that possessed lungs, as that would have enabled those organisms to breathe air.

Are snakes tetrapods? Explain.

Yes. Although snakes lack limbs, they descended from lizards with legs. Some snakes retain vestigial pelvic and leg bones, providing evidence of their descent from an ancestor with legs.

MAKE CONNECTIONS Historically, annelids and arthropods were viewed as closely related because both have body segmentation. Yet DNA sequence data indicate that annelids belong to one clade (Lophotrochozoa) and arthropods to another (Ecdysozoa). Could traditional and molecular hypotheses be tested by studying the Hox genes that control body segmentation (see Concept 21.6)? Explain.

Yes. Under the traditional hypothesis, we would expect body segmentation to be controlled by similar Hox genes in annelids and arthropods.However, if annelids are in Lophotrochozoa and arthropods are in Ecdysozoa (as current evidence suggests), body segmentation may have evolved independently in these two groups. In such a case, we might expect that different Hox genes would control the development of body segmentation in the two clades.

Based on the phylogenetic tree in Figure 34.2, predict which vertebrate groups should have lungs or lung derivatives. Explain

You would expect the vertebrate groups Actinopterygii, Actinistia, Dipnoi, Amphibia, Reptilia, and Mammalia to have lungs or lung derivatives. All of these groups originate to the right of (evolved after) the hatch mark indicating the appearance of this derived character in their lineage.

What are some examples of myriapods?

chelicerates myriapods earliest terrestrial animals mandibles for eating centipedes and millipedes

What are some examples of chelicerates?

chelicerates: claw like feeding appendages scorpion, dust mites, web building spider

Tissue Layers

endoderm mesoderm ectoderm most animals have a central body cavity (coelom)

What are some characteristics of amphibians?

•Can be aquatic or terrestrial •Lungs and moist skin that functions in gas exchange •Eggs lack a rigid shell •Fertilization is external in most species

What are some derived characters of amniotes?

•Egg reduced dependence on water for reproduction •Egg shells of reptiles prevent desiccation •Most mammals lost their eggshell, and the embryo develops within the mother's body •Egg has four membranes: •Amnion: Fluid-filled sac that surrounds and cushions the embryo

What are some derived characteristics of tetrapods?

•Four limbs and feet with digits •A neck which enables head movement •Fusion of pelvic bone to the backbone •Absence of gills (except in aquatic species) •Ears

What are some characteristics of hagfishes?

•Jawless •Reduced vertebrae •Cartilaginous skull •Eyes, ears, a small brain, and nasal opening •Slime glands

What are some characteristics of lampreys?

•Jawless •Reduced vertebrae •Notochord •Cartilaginous skeleton •Inhabit freshwater and marine environments •Parasites latch onto host fish and feed off their blood/tissue

What are some shared derived characters of mammals?

•Mammary glands that produce milk •Hair and fat layer for insulation •Kidneys •Endothermic •Extensive parental care •Teeth modified for shearing, crushing, and grinding

What are osteichthyans?

•Ray-finned fishes •Lobe-finned fishes

What are some shared derived characters of reptiles?

•Shells are made of keratin, prevents desiccation •Lay eggs on land •Ectothermic (except for birds)

What are some derived characters of birds that allows them to fly?

•Wings, feathers •No urinary bladder •Small gonads (female birds only have one ovary) •Toothless mouths •Air-filled bones