NCERT Solution for Class 10 Science Chapter 9
Heredity and Evolution
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Exercises Questions
Page No-159
Questions No-6
Explain the terms analogous and homologous organs with examples.
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Homologous organs are similar in origin (or are embryologically similar) but perform
different functions. For example, the forelimbs of humans and the wings of birds look
different externally but their skeletal structure is similar. It means that their origin is
similar (as wings in birds are modifications of forearm) but functions are different – the
wings help in flight whereas human forearm helps in various activities.
Analogous organs, on the other hand, have different origin but perform similar functions.
For example, the wings of a bird and a bat are similar in function but this similarity does
not mean that these animals are more closely related. If we carefully look at these
structures, then we will find that the wings of a bat are just the folds of skin that are
stretched between its fingers whereas the wings of birds are present all along the arm.
Therefore, these organs are analogous organs.
Homologus organs are those organs which have the same basic structural design and origin but have different functions.
For Example: The forelimbs of humans and the wings of birds look different externally but their skeletal structure is similar.
Analogus organs are those organs which have the different basic structural design and origin but have similar functions.
For Example: The wings of birds and insects.
Homologous Organs: Organs which have common design but serve different functions in different animals are called homologous organs. For example; the forelimbs of all tetrapods are composed of humerus, radio-ulna, tarsals and metatarsals. Yet, the forelimbs of frogs are adapted to a jumping movement, those of birds are used for flying and those of humans are used for handling tools. This shows that frogs, birds and humans have evolved from a common ancestor.
Analogous Organs: Organs which have different design but serve a common function in different animals are called analogous organs. Wings of birds and wings of bat are good examples of a pair of analogous organs. Wings of birds are composed of all the bones of forelimb and are covered with feathers. Wings of bats are mainly composed of the digital bones and a thin membrane covering the structure. Yet wings in both the organisms are used for flying.