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Ch. 32 - Deuterostome Animals
All textbooksFreeman 8th EditionCh. 32 - Deuterostome AnimalsProblem 16
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Chapter 31, Problem 16

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.

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Hi everyone. Here's our next question. Mexican tetra is also known as the blind cave fish. It is a freshwater fish of the family cherish the day. Why do some cave living fish like mexican Tetra lose their eyes? Let's look to our answer choices, Choice A says to help them hide from their predators. Well that wouldn't be our answer. Having not having eyes. This doesn't give them any advantage in camouflage um or any other way to hide from their predators. Choice B says because of their diet. Well, there isn't any lack that causes them to lose their eyes um but rather because the eyes are necessary in that dark environment. So I see says because of the lack of nutrients needed for eye development. Again, not an answer there, it's not that they're lacking anything in their diet um that causes that it's not a defect in them. Just again, they don't need eyes in their dark environment. So finally we're at choice D because of the absence of light and this is our correct answer in that absence of light. Um Eyesight is not a useful adaptation. So the genes that are usually used for eye development can be reassigned to features more useful for their life and caves. We'll see you in the next video
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Textbook Question

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.

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Textbook Question

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?

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Textbook Question

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?

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