Chordates

If an animal has segments, bilateral symmetry, pharyngeal clefts, a post-anal tail, and deuterostomic development, it must be a member of the __________.

A __________ is a chordate but not a vertebrate.

Which of the following chordate characteristics contributes most to the formation of your ears?

Which of the following chordate characteristics contributes most to suspension-feeding devices in many invertebrate chordates?

Which of the following pairs is not a correct match?

Which of the following can be found in vertebrates but not in lancelets and tunicates?

A lamprey, a shark, a lizard, and a rabbit share all the following characteristics except __________.

Which of the following is among the earliest known vertebrates?

The operculum was an important adaptation for fish because it helps with __________.

Some sharks are viviparous, which means that __________.

A feature of bony fish not found in sharks is __________.

Which of the following organisms is most closely related to the ancestor of modern amphibians?

Which of the following sets of animals contains only gnathostomes?

The first vertebrates to live on land were __________.

Which of the following animals is an amphibian?

Habitat loss, the spread of a fungal disease, climate change, and pollution are causing severe population declines and extinction in __________.

Vertebrates and tunicates share a. jaws adapted for feeding. b. a high degree of cephalization. c. an endoskeleton that includes a skull. d. a notochord and a dorsal, hollow nerve cord.

True or false? Both echinoderms and vertebrates have endoskeletons. Explain.

True or false? Both echinoderms and vertebrates have endoskeletons. Explain.

Living vertebrates can be divided into two major clades. Select the appropriate pair. a. the chordates and the tetrapods b. the urochordates and the cephalochordates c. the cyclostomes and the gnathostomes d. the marsupials and the eutherians

What trait(s) characterize the vertebrates? a. vertebrae and a cranium b. jaws and a spinal cord c. bony endoskeleton d. notochord and post-anal tail

"In the chordate phylogenetic tree below, fill in the shared derived character that defines each clade. a. Notochord b. Vertebral column c. Jaws d. Bony skeleton e. Four limbs f. Amniotic egg g. Hairs"

What trait(s) characterize the vertebrates? a. vertebrae and a cranium b. jaws and a spinal cord c. bony endoskeleton d. notochord and post-anal tail

A lamprey, a shark, a lizard, and a rabbit share all the following characteristics except a. pharyngeal slits in the embryo or adult. b. vertebrae. c. hinged jaws. d. a dorsal, hollow nerve cord.

In Figure 34.25, which of the following is the sister taxon to the archosaurs? (A) synapsids (B) crocodilians (C) turtles (D) lepidosaurs

Which clade does not include humans? a. synapsids b. lobe-fins c. diapsids d. osteichthyans

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? Gene expression patterns can be used to test hypotheses based on morphology. For example, the regulatory gene Bapx1 is expressed in the hinge of the developing lower jaw in fishes and reptiles. Where would you predict Bapx1 expression to occur in mammals?

Why were the Tiktaalik fossils an exciting discovery for scientists studying tetrapod evolution? a. They are the earliest frog-like animal discovered to date. b. They show that tetrapods successfully colonized land much earlier than previously thought. c. They have a roughly equal combination of fishlike and tetrapod-like characteristics. d. They demonstrate conclusively that limbs evolved as lobe-fins dragged themselves from pond to pond during droughts.

Which of the following could be considered the most recent common ancestor of living tetrapods? a. a sturdy-finned, shallow-water lobe-fin whose appendages had skeletal supports similar to those of terrestrial vertebrates b. an armored, jawed placoderm with two pairs of appendages c. an early ray-finned fish that developed bony skeletal supports in its paired fins d. a salamander that had legs supported by a bony skeleton but moved with the side-to-side bending typical of fishes

To estimate the relative abundance of the major phyla, calculate how many named species of arthropods, mollusks, and nematode worms exist per named species of chordate (the phylum containing vertebrates, including humans; see Table 30.1). Do you think these calculations are likely to be underestimates or overestimates? Why?

EVOLUTION CONNECTION Living members of a vertebrate lineage can be very different from early members of the lineage, and evolutionary reversals (character losses) are common. Give examples that illustrate these observations, and explain their evolutionary causes.

There is some evidence that pharyngeal slits occur in certain species of echinoderms that appear early in the fossil record. If confirmed, what do these data suggest? a. Echinoderms are chordates. b. Pharyngeal slits were present in the earliest echinoderms and lost later. c. Some lineages of echinoderms are more closely related to chordates than others. d. Pharyngeal slits should not be used as a trait in phylogenetic analysis.

There is some evidence that pharyngeal slits occur in certain species of echinoderms that appear early in the fossil record. If confirmed, what do these data suggest? a. Echinoderms are chordates. b. Pharyngeal slits were present in the earliest echinoderms and lost later. c. Some lineages of echinoderms are more closely related to chordates than others. d. Pharyngeal slits should not be used as a trait in phylogenetic analysis.

Consider the evolution of protostomes and deuterostomes (this chapter): (1) Compare adaptations in protostomes and deuterostomes for living on land. (2) Recall that changes in the expression patterns of tool-kit genes in arthropods such as insects enabled a dramatic diversification of their segmented appendages and bodies. Design an experiment to test whether this concept applies to vertebrates.

Consider the evolution of protostomes and deuterostomes (this chapter): (1) Compare adaptations in protostomes and deuterostomes for living on land. (2) Recall that changes in the expression patterns of tool-kit genes in arthropods such as insects enabled a dramatic diversification of their segmented appendages and bodies. Design an experiment to test whether this concept applies to vertebrates.

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? Evolution often results in the co-option of a preexisting structure for a new use. Cite three examples from this chapter to support this statement. Evolution can also result in the loss of a trait. Cite three examples from this chapter.

Compare the adaptations of amphibians and reptiles for terrestrial life.

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? The illustration of the opossum skull shows that the ear bones are completely separated from the jawbone (as they are in all mammals). Pose a hypothesis to explain why this separation could be an adaptation that contributed to the radiation of mammals into diverse niches, including a nocturnal lifestyle.

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? How is the opossum related to you? Select True or False for each statement. T/F An opossum is an animal, but I am a human. T/F An opossum is a mammal, but I am a human. T/F An opossum is a marsupial, but I am a placental mammal. T/F The opossum and I are both tetrapods.

Birds and mammals are both endothermic, and both have four-chambered hearts. Most reptiles are ectothermic and have three-chambered hearts. Why don’t biologists group birds with mammals? Why do most biologists now consider birds to be reptiles?

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? Analyze the morphological data shown here and write a hypothesis to explain the origin of mammalian ear bones. (The cynodont shown is one of many extinct synapsid amniotes that lived early in the lineage that gave rise to mammals.)

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? How is the opossum related to you? Select True or False for each statement. T/F An opossum is an animal, but I am a human. T/F An opossum is a mammal, but I am a human. T/F An opossum is a marsupial, but I am a placental mammal. T/F The opossum and I are both tetrapods.

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? The illustration of the opossum skull shows that the ear bones are completely separated from the jawbone (as they are in all mammals). Pose a hypothesis to explain why this separation could be an adaptation that contributed to the radiation of mammals into diverse niches, including a nocturnal lifestyle.

Match each description on the left with the corresponding term on the right Closest relatives of chordates annelids nematodes sponges arthropods flatworms cnidarians molluscs echinoderms chordates

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? Gene expression patterns can be used to test hypotheses based on morphology. For example, the regulatory gene Bapx1 is expressed in the hinge of the developing lower jaw in fishes and reptiles. Where would you predict Bapx1 expression to occur in mammals?

A good scientific hypothesis is based on existing evidence and leads to testable predictions. What hypothesis did the paleontologists who discovered Tiktaalik test? What evidence did they use to predict where they would find fossils of transitional forms?

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? Researchers studied mice embryos as a model organism to determine whether the cells of the ear bones originated from the same embryonic cells as the cells that form the jaw in other vertebrates. Why would the researchers use mice instead of humans? Do the results from mice tell you something about your own ears? Why or why not?

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? Evolution often results in the co-option of a preexisting structure for a new use. Cite three examples from this chapter to support this statement. Evolution can also result in the loss of a trait. Cite three examples from this chapter.

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from? Analyze the morphological data shown here and write a hypothesis to explain the origin of mammalian ear bones. (The cynodont shown is one of many extinct synapsid amniotes that lived early in the lineage that gave rise to mammals.)

The size and shape of the vertebrate skull can reveal a great deal about an animal’s lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don’t. Where did ear bones come from?

A marine biologist has dredged up an unknown animal from the seafloor. Describe some of the characteristics that could be used to determine the animal phylum to which the creature should be assigned.

The adaptation that freed vertebrates from water for reproduction and allowed them to radiate into diverse terrestrial environments was the __________.

Which of the following characteristics is not shared by extant birds and extant reptiles?

The opossum is an example of a(n) __________ mammal.

All mammals __________.

Which of the following is an archosaur group?

Unlike eutherians, both monotremes and marsupials a. lack nipples. b. have some embryonic development outside the uterus. c. lay eggs. d. are found in Australia and Africa.

What two major lineages make up the living Amniota?

What two major lineages make up the living Amniota?

Which statement is true about endothermy in mammals and birds? a. They both inherited this trait from a common ancestor. b. Birds are more closely related to mammals than to reptiles. c. Endothermy arose independently in these two lineages. d. Birds are reptiles and all reptiles are ectothermic.

Which statement is true about endothermy in mammals and birds? a. They both inherited this trait from a common ancestor. b. Birds are more closely related to mammals than to reptiles. c. Endothermy arose independently in these two lineages. d. Birds are reptiles and all reptiles are ectothermic.

Compare amniotic eggs to placentas.

Compare amniotic eggs to placentas.

Analysis of DNA from a variety of sources has led most researchers to agree that __________.

What was the earliest hominin to have an enlarged brain (relative to body size)?

__________ arose very early in hominid evolution; __________ evolved more recently.

Which of the following correctly lists probable ancestors of modern humans from the earliest to the most recent?

Which of the following traits distinguishes hominins from other apes?

Included among the extant groups of apes are __________.

All species of New World monkeys are __________.

Humans and lorises share many traits that probably evolved in our early primate ancestors; one such trait is __________.

Primates are distinguished from other mammals by __________.

Draw a phylogeny of major populations of modern humans that would reject the out-of-Africa hypothesis.

In the primate phylogenetic tree below, fill in groups (a)–(e). Of the groups, which are anthropoids and which are apes? a. b. c. d. e.

Genetic diversity in living human populations is highest in Africa and decreases as a function of distance traveled by the human migration that left Africa many millennia ago. Draw a graph to show this trend. (Hint: What is the independent variable? What is the dependent variable? What kind of graph is appropriate for this kind of data? Add a label where you would expect to find a data point for the Yanomamö tribe of the Amazon rain forest in South America. Why is it important to use indigenous people for this study?

Most species of hominins are known only from Africa. Which species have been found in other parts of the world as well? a. early Homo—H. habilis and H. ergaster b. H. erectus, H. neanderthalensis, and H. floresiensis c. gracile australopithecines d. robust australopithecines

As hominins diverged from other primates, which of the following appeared first? a. reduced jawbones b. an enlarged brain c. the making of stone tools d. bipedal locomotion

Fossils suggest that the first major trait distinguishing hominins from other primates was a. a larger brain. b. erect posture. c. forward-facing eyes with depth perception. d. tool making.

Which of the following correctly lists possible ancestors of humans from the oldest to the most recent? a. Homo erectus, Australopithecus, Homo habilis b. Australopithecus, Homo habilis, Homo erectus c. Australopithecus, Homo erectus, Homo habilis d. Homo ergaster, Homo erectus, Homo neanderthalensis

Which of these is not a member of the anthropoids? a. chimpanzee b. tarsier c. human d. New World monkey

Humans possess which of the following traits? Select True or False for each trait. T/F triploblasty T/F parthenogenesis T/F viviparity T/F metamorphosis

Studies of DNA support which of the following? a. Members of the group called australopiths were the first to migrate from Africa. b. Homo sapiens originated in Africa. c. Sahelanthropus was the earliest hominin. d. Chimpanzees are more similar to gorillas and orangutans than to humans.

Draw a phylogeny of major populations of modern humans that would reject the out-of-Africa hypothesis.

The earliest members of the genus Homo a. had a larger brain compared to other hominins. b. probably hunted dinosaurs. c. lived about 4 million years ago. d. were the first hominins to be bipedal.

Humans possess which of the following traits? Select True or False for each trait. T/F triploblasty T/F parthenogenesis T/F viviparity T/F metamorphosis

Genetic diversity in living human populations is highest in Africa and decreases as a function of distance traveled by the human migration that left Africa many millennia ago. Draw a graph to show this trend. (Hint: What is the independent variable? What is the dependent variable? What kind of graph is appropriate for this kind of data? Add a label where you would expect to find a data point for the Yanomamö tribe of the Amazon rain forest in South America. Why is it important to use indigenous people for this study?

One of the misconceptions about human evolution is expressed in the question “If chimpanzees were our ancestors, then why do chimpanzees still exist?” Use Figure 19.10A to explain the answer.

What adaptations inherited from our primate ancestors enable humans to make and use tools?

Summarize the hypotheses that explain variation in human skin color as adaptations to variation in UV radiation.

Explain some of the reasons why the human species has been able to expand in number and distribution to a greater extent than most other animals.

Anthropologists are interested in locating areas in Africa where fossils 4–8 million years old might be found. Why?

SCIENTIFIC THINKING By measuring the fossil remains of Homo floresiensis, scientists have estimated its weight to be around 32.5 kg and its brain volume to be roughly 420 cm3. Plot these values on the graph in Figure 19.13A. Which hominin has the most similar relationship of brain volume to body mass? Does this information support the hypothesis that H. floresiensis is a dwarf form of H. erectus, or an alternative hypothesis? Explain.