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Overall similarity of
a. due to convergent evolution.
b. because of variation in rates of evolutionary change of different kinds of characters.
c. due to homoplasy.
d. All of the choices are correct.
Introduction:
The phylogeny explains the evolutionary history of a species. Systematics can be used to construct a phylogeny which is an evolutionary tree which depicts the relationship among different species by studying the similarities or differences among different species.
Answer to Problem 1U
Correct answer:
The basis of the phylogenetic tree is the evolutionary relationship represented between different lineages to determine the relationship among species. Thus, it is necessary to study the reasons relating to these similarities. The similarities usually arise due common ancestors. But there are other reasons also due to which the phenotypic similarities could arise even without any evolutionary relationship. The similarity could arise due to homoplasy, convergent evolution and due to the different rate of changes in various kinds of characters. Therefore option d. is correct.
Explanation of Solution
Reason for the correct statement:
Overall similarity in phenotypes of two different species could arise due to various reasons even when they do not share any evolutionary relationship. It may be due to changes in rate of evolutionary divergences occurring in different kind of characters as the evolutionary change in two different characters could be at the same time and could lead to similarities.
Also convergent evolution where species of different lineages show common functions even though they have different structures due to different ancestral lineages. Similarities may also arise due to derived set of characters, even by the species belonging to different ancestor lineages.
Option d. is given as “All of the choices are correct”.
As, “overall similarity of phenotypes may not always reflect evolutionary relationships due to convergent evolution, because of variation in rates of evolutionary change of different kinds of characters and due to homoplasy”, is the right answer.
Hence, option d. is correct.
Reasons for the incorrect statements:
Option a. is given as “due to convergent evolution”.
Similarities in phenotypes could arise due to the convergent evolution where different animals show common functions even though they have different structures due to different ancestral lineages. So, it is a wrong answer.
Option b. is given as “because of variation in rates of evolutionary change of different kinds of characters”.
Similarities in phenotypes of different species could arise due to the different rate of evolutionary changes in different type of characters as different species will independently evolve the same derived character. But “due to convergent evolution and due to homoplasy” are also correct. So, it is a wrong answer.
Option c. is given as “due to homoplasy”.
Homoplasy represents the set of characters that are shared by the species of different ancestor lineages. There is no evolutionary relationship between these species due to different ancestor lineage, but similarity in functions and structures leads to the overall similarity in the phenotypes. Other options “due to convergent evolution and because of variation in rates of evolutionary change of different kinds of characters” are also correct. So, it is a wrong answer.
Hence options a., b., and c. are incorrect.
The similarities in different lineages could arise due to homoplasy or due to the convergent evolution. Also, due to different rate of evolutionary divergences occurring in different kind of characters as the evolutionary change in two different characters could be at the same time and could lead to similarities.
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Chapter 23 Solutions
Biology
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