NOVA LA3S The Evolution Lab MISSION 2 small step: There have been a number of dr

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NOVA LA3S The Evolution Lab MISSION 2 small step: There have been a number of dramatic transitions over the history of life. After a few billion years of nothing but single-celled organisms, mutlticellular lite developed. Organisms evolved tissues and organs. Plants developed skeletons And, of course spores, flowers, and seeds. Animals developed complex neurological systems and external and internal , bacteria evolved novel methods to live just about everywhere on Earth. One of those great transitions is the subject of this level. Have you ever heard of an animal called Tiktaalik? How about Acanthostega? They are but two o ite from water to land. Answer questions 6-9 below before you move on to the next level, "Origin of whales." t the many remarkable fossils we have that document the transition of animal 6. For an animal that lives in shallow water, what is the advantage of having eyes on the top of its head? We know that Tiktaalik is more closely related to Acanthostega than it is to Eusthenopteron because Tiktaalik and Acanthostega: 7. a. b. c. d. Both lacked digits Both lacked strong forearms Both had a humerus, radius, and ulna Both had eyes on the top of their heads 8. Ichthyostega is a 370-million-year-old fossil from Greenland. ichthyostega had digits, eyes on the top of its head, and strong, armlike bones. It also had no gills and a reduced tail-traits it had in common with Tulerpeton. Acanthostega, Eusthenopteron, and Tiktaalik all had gills and full tails Use the abbreviations provided to draw a phylogenetic tree that includes Ichthyostega. A = Acanthostega D digits IIchthyostega Tu Tulerpeton Ti= Tiktaalik eyes on top of a flat head G/T loss of gills and a reduced tail s = strong, armlike bones Animals commonly called reptiles, amphiblans, birds, and mammals are all tetrapods-a term that means "four feet." The transition from water to land is fascinating to scientists in part because it's our history-the transition documents the evolution of tetrapods, and humans are tetrapods Tetrapods form a clade. Which of the following is true of tetrapods? 9. a. Tetrapods are more complex than non-tetrapods. b. Tetrapods are more evolved than non-tetrapods. c. Tetrapods are more closely related to each other than to non-tetrapods d. All of the above PBS LearsingMedia

Explanation / Answer

ANS 6) Advantages of having eyes on the top of the head for an animal that lives in shallow water is that because the eyes are on top of their head they can see above the water while the rest of their body is hidden under water and they can focus easily on their prey.

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ANS 7) Tikaalik and Acanthostega

d) both had eyes on top of their head.

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ANS 9) Which of the following is a true tetrapod:

d) All of the above

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