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

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

What two major lineages make up the living Amniota?

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. Australopithecus afarensis

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.

Which of the following nested monophyletic groups are correctly organized from largest (most inclusive) to smallest (least inclusive), showing your place in the tree of life?

a. Deuterostomes>Chordates>Vertebrates>Mammals

b. Animals>Mammals>Vertebrates>Primates

c. Chordates>Primates>Mammals>Hominins

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

Consider the evolution of protostomes and deuterostomes (this chapter):

Compare adaptations in protostomes and deuterostomes for living on land.

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.

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?

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

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.

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?

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.