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प्रश्न
Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.
उत्तर
All living organisms existing on earth show immense diversity in size, form, structure and morphological features but at the molecular level, these organisms exhibit unbelievable similarity. For instance, these organisms are made up of the basic biomolecules like DNA, RNA, carbohydrates, proteins etc. which show remarkable similarity in all of them. DNA in all organisms is made up of same units (nucleotides) and has the same double-helical structure. So, evolution has exhibited a greater stability of molecular structure when compared with morphological structures.
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संबंधित प्रश्न
Study the following statements:-
I. Wings of birds and wings of bats are homologous organs.
II. Wings of birds and wings of insects are modified forelimbs.
III. Wings of birds and wings of insects are analogous organs.
IV. Wings of birds and forelimbs of horse are homologous organs.
The correct statements are
(A) I and II
(B) II and III
(C) III and IV
(D) I and IV
Which of the following pairs of two vegetables represent the correct homologous structures?
(A) Sweet potato and potato
(B) Sweet potato and tomato
(C) Carrot and potato
(D) Radish and carrot
There are five animals A, B, C, D and E. The animal A uses its modified forelimbs for flying. The animal B uses its forelimbs for running whereas the animal C uses its forelimbs for grasping. The animal D can live on land as well as in water and uses its forelimbs to prop up the front end of its body when at rest. The animal E which respires by using spiracles and tracheae uses wings for flying but its wings are analogous to the modified forelimbs of animal A.
(a) What could the animals A, B, C, D and E be?
(b) Why are the forelimbs of animals A, B, C, D called homologous organs?
(c) What does the existence of homologous organs in animals A, B, C and D tell us about their ancestors ?
(d) Why are the modified forelimbs of animal A and the wings of animal E called analogous organs?
(e) State whether animals A and E have a common ancestor or not.
X, Y, and Z are three animals. The animal X can fly but animal Y can only run on ground or walls. The forelimbs of animals X and Y have the same basic design but they are used for different purposes such as flying and running respectively. The animal Z became extinct an long time ago. The study of fossils of Z tells us that it had some features like those of X and some like those of Y. In fact, Z is said to form a connecting link in the evolutionary chain of X and Y.
(a) What could the animals X, Y and Z be?
(b) What name is given to the forelimbs like those of X and Y which have the same basic design but different functions?
(c) Name one feature in which Z resembled X.
(d) Name one feature in which Z resembled Y.
(e) Which is the correct evolutionary chain involving X, Y and Z : X → Z → Y or Y → Z → X?
Answer the following question:
What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor? Justify your answer.
Similarities in the initial stages indicate the _______ evidence.
Observe the given images and answer the following questions.
- Which evolutionary evidence does it indicate?
- What does it prove?
- State another example of evolutionary evidence.
Explain any five types of evidence that support the theory of evolution.
Select vestigial organs from the following.
Analogous organs arise due to ______.
