BIOLOGY
12th Edition
ISBN: 9781260169614
Author: Raven
Publisher: RENT MCG
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Chapter 21, Problem 5S
The ancestor of horses was a small, many-toed animal that lived in forests, whereas today’s horses are large animals with a single hoof that live on open plains. A series of intermediate fossils illustrate how this transition has occurred, and for this reason, many old treatments of horse evolution portrayed it as a steady increase through time in body size accompanied by a steady decrease in toe number. Why is this interpretation incorrect?
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Changes in the traits of the fossils studied are consistent with what is expected to be favored by natural selection, given environmental changes during that time. Thus, from the late Miocene, modern horses evolved to have the following traits, consistent with grassland ecosystems becoming more common, EXCEPT for --
A. Formation of hooves and fused forelimb bones.
B. Teeth adapted for browsing rather than grazing..
C. A muscle and tendon system allowing for a springing motion in galloping.
D. Larger animals better designed for grazing.
The fossil record shows that the first mammals evolved 220 million years ago. The supercontinent Pangaea began to break apart 200 million years ago. On which continents would you predict that fossils of the first mammals will be found?
Because of selective forces, the dinosaurs were superbly adapted to their environments. After the dinosaurs became extinct, the small mammals that had been relatively unimportant animals in the background flourished and evolved into many new types, including the line that led to human beings. It is unlikely that these new types would have ever evolved had not the dinosaurs disappeared. If the extinction of the dinosaurs was caused by an extraterrestrial impact, did it matter how well they were adapted to their environment? What does this suggest about the starting cause in the evolutionary success of these new types of mammals?
Chapter 21 Solutions
BIOLOGY
Ch. 21.1 - Prob. 1LOCh. 21.1 - Prob. 2LOCh. 21.2 - Prob. 1LOCh. 21.2 - Distinguish between demonstrating that evolution...Ch. 21.3 - Contrast the processes of artificial and natural...Ch. 21.3 - Prob. 2LOCh. 21.4 - Prob. 1LOCh. 21.4 - Prob. 2LOCh. 21.4 - Prob. 3LOCh. 21.5 - Explain the evolutionary significance of...
Ch. 21.5 - Prob. 2LOCh. 21.6 - Prob. 1LOCh. 21.6 - Prob. 2LOCh. 21.7 - Characterize the criticisms of evolutionary theory...Ch. 21.7 - Prob. 2LOCh. 21 - Suppose that a male with a beak depth of 10 mm...Ch. 21 - Prob. 1IQCh. 21 - Prob. 2IQCh. 21 - Prob. 3IQCh. 21 - Why might the evolutionary line leading to...Ch. 21 - Artificial selection is different from natural...Ch. 21 - Gaps in the fossil record a. demonstrate our...Ch. 21 - The evolution of modern horses (Equus) is best...Ch. 21 - Homologous structures a. are structures in two or...Ch. 21 - Convergent evolution a. is an example of...Ch. 21 - Prob. 6UCh. 21 - The possession of fine fur in 5-month human...Ch. 21 - In Darwins finches, a. occurrence of wet and dry...Ch. 21 - Prob. 2ACh. 21 - Convergent evolution is often seen among species...Ch. 21 - What conditions are necessary for evolution by...Ch. 21 - Explain how data shown in figure 21.2a and b...Ch. 21 - Prob. 3SCh. 21 - Refer to figure 21.5, artificial selection in the...Ch. 21 - The ancestor of horses was a small, many-toed...
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- While the French biologist LaMarck was correct in proposing that evolution does occur, he believed that the long necks of giraffes evolved as generations of giraffes reached for ever higher leaves on the trees. Using these observations, LaMarck proposed the theory that evolution occurs due to the inheritance of characteristics acquired during an organism’s lifetime. From what you know about the scientific method, why is this incorrect?arrow_forwardSome advocates of the view that all organisms were created simultaneously by God argue that vestigial structures do not constitute evidence of evolution, because they show only that a divinely created structure can degenerate over time. According to this view, human tailbones are not evidence of evolution because they do not show that an adaptive improvement has occurred. Is this a valid argument?arrow_forwardHumans in the 21st century use their thumbs extensively to operate touchscreens on cellphones. Imagine a scenario, where the human population evolves to have more dexterous thumbs over the next 300 years. Which of the following is a Lamarckian explanation for this evolutionary change (and, therefore, would an incorrect evolutionary mechanism?) humans that develop more dexterity in their thumb over their lifetime due to frequent use of cellphones pass that ability to their children humans that were born with a mutation for more dexterous thumbs have more children thumb dexterity is a dominant traitarrow_forward
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