Concept explainers
Whale skeletons contain nonfunctional pelvic bones
- a. as a result of convergent evolution.
- b. due to catastrophism.
- c. because whales evolved from ancestors that had hind legs.
- d. because the bones might be needed for a future adaptation.
Introduction:
Evolution is a process of changes occurring in the heritable characters of living organisms over the period of time from generation to generation. In evolutionary studies, it is observed that some of the sequences from the genetic makeup of an early ancestor are reflected in their generation of related species. This proved that the genetic information is inherited from ancestors to their generations to pass the important traits or genes.
Answer to Problem 1MC
Correct answer:
Vestigial structures are those structures which lost functionality through time. They were evolved in ancestors to perform different functions but lost functionality in recent species. Pelvic bones in whales is an example of a vestigial structure that shows the evolution of four-legged ancestors to aquatic species with shrunken hind legs. The ancestors had fully functional pelvic bones which played important role in their terrestrial habitat but it lost functionality as whale evolved from terrestrial to aquatic habitats. Therefore, option (c) is correct.
Option (c) is given as “because whales evolved from ancestors that had hind legs”.
Explanation of Solution
Justify reason for the correct statement:
Whale skeleton contains nonfunctional pelvic bones as their ancestors who were land dwellers had hind legs. Hind legs were functional for land-dwelling ancestors but later with time as whales occupied aquatic habitats, the hind legs became nonfunctional. These structures which get nonfunctional through time due to change in habitats or due to reduced use of these structures are known as vestigial structures.
Hence, option (c) is correct.
Justify reasons for the incorrect statements:
Option (a) is given as “as a result of convergent evolution”.
Different species having similar adaptations or structures due to similar environmental conditions show convergent evolution. Whales do not have nonfunctional structures due to convergent evolution. Hence, it is a wrong answer.
Option (b) is given as “due to catastrophism”.
Catastrophism is the evolutionary change that occurs due to sudden environmental changes. Whales do not have nonfunctional structures due to catastrophism. Hence, it is a wrong answer.
Option (d) is given as “because the bones might be needed for a future adaptation”
Vestigial structures do not develop for the future needs or requirement in a species thus whales do not have nonfunctional structures for future adaptation. Hence, it is a wrong answer.
Hence, options (a), (b), and (d) are incorrect.
Vestigial structures are those structures that become nonfunctional due to loss of functionality or loss of its use. The ancestors of whales were land dwellers but as their species shifted to aquatic habitats their use of hind legs got reduced and became nonfunctional that is why whales have nonfunctional pelvic bones.
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Chapter 15 Solutions
Biology
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