NCERT Solution for Class 10 Science Chapter 9
Heredity and Evolution
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Intext Questions
Page No-156
Questions No-1
Give an example of characteristics being used to determine how close two species are in evolutionary terms.
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The presence of feathers in dinosaurs and birds indicates that they are evolutionarily
related. Dinosaurs had feathers not for flying but instead these feathers provided
insulation to these warm-blooded animals. However, the feathers in birds are used for
flight. This proves that reptiles and birds are closely related and that the evolution of wings
started in reptiles.
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Let us take the example of humans and apes. Both of them have similar body design. Body hair and mammary glands are present in both the animals. Hence, these two animals are closely related in evolutionary term. Now take some common characters between a fish and a man. Vertebral column, brain box and jaws are present in both of them. But fish and man look entirely different from each other. Hence, they are not very closely related in evolutionary term; rather are like distant relatives.
Analysis of the organ structure in fossils allows us to make estimates of how far evolutionary relationships go, e.g,. presence of feathers in some fossil dinosaurs indicates that birds are closely related to reptiles.