Question

i) a) Explain in brief - Lamarck’s principle of ‘use or disuse of organs’.
b) Give two examples.
c) What are ‘acquired characters'?

ii) a) Why some living organisms have to perform anaerobic respiration?
b) Give examples of such living organisms.
c) What are the two steps of anaerobic respiration?

iii) If frog population in paddy fields declines all of a sudden,
a) What will be the effect on paddy crop?
b) Number of which consumers will decline and which will increase?
c) Name the Indian states where paddy is cultivated on a large scale.

iv) a) What is clean technology ?
b) Why is it essential to ban plastic bags?

vii) Explain in brief - D.N.A. Fingerprinting. Give two examples where this technique is used.


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Answer 1

Lamarckism – Theory of Inheritance of Acquired Characters!

Lamarckism is the first theory of evolution, which was proposed by Jean Baptiste de Lamarck (1744-1829), a French biologist. Although the outline of the theory was brought to notice in 1801, his famous book “Philosophic Zoologique” was published in 1809, in which he discussed his theory in detail.



The theory of inheritance of acquired characters states that modifications which the organism acquires in adaptation to the environments which it meets during its lifetime are automatically handed down to its descendants, and so become part of heredity. His evolutionary ideas can be discussed in brief as follows:

1. Internal forces of life tend to increase the size of the organism:

New structures appear be­cause of an “inner want” of the organism, i.e., the internal forces of life tend to increase continu­ously the size of an organism and its component parts.

2. Direct environmental effect over living organisms:

The organs of an animal became modified in appropriate fashion in direct response to a changing environment.

3. Use of disuse:


The various organs became greatly improved through use or reduced to vestiges through disuse.

4. Inheritance of acquired characteristics:

Such bodily modifications, in some manner, could be transferred and impressed on the germ cells to affect future generation. Thus, inheritance was viewed by Lamarck simply as the direct transmission of those superficial bodily changes that arose within the life time of the individual owing to use or disuse (Volpe, 1985).

Examples in support of Lamarckism:

Lamarck explained his theory by giving the following examples:

(i) Giraffe:

The ancestors of giraffe were bearing a small neck and fore-limbs and were like horses. But as they were living in places with no surface vegetation, they had to stretch their neck and fore-limbs to take the leaves for food, which resulted in the slight elongation of these parts. Whatever they acquired in one generation was transmitted to the next generation with the result that a race of long necked and long fore-limbed animals was developed.

(ii) Aquatic birds:

Aquatic birds like ducks have been evolved from the terrestrial ancestors. Since they had to go to water due to lack of food, etc., some structures like web between the toes developed in them, so that they could live in water easily. The wings were not used for flying as they were not needed, and later on they got reduced.

(iii) Flat fishes:

(Deep sea fishes) present at the bottom of sea where there is no sunlight, led an inactive life, lying on one side of the body. The eye of that side (lying towards bottom) migrated towards upper side and, thus both eyes are on one side of the body.

(iv) The whales lost their hind-limbs as a consequence of the inherited effect of disuse.

(v) The wading birds (e.g., Jacana) developed its long legs through generations of sustained stretch­ing to keep the body above the water level.

Lamarckian theory was simple and it had some appeal, as it provided a way in which changes in organisms could come about. It was the first completely comprehensive mechanistic theory that was offered. Furthermore, it was the theory that lent itself to predictions and, therefore to testing.



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Answer 2

a) i) if an individual uses a particle organ will become stronger and if it is not used the organ will weaken . The stronger and weaker organ will then be inherited by the offspring .overtime the organ of these individuals be modified due to their use of disuse. If an organ is disused it may disappear in future generation .

We do not agree with the model of use and disuse of proposed by Lamarck because it suggest that the modification of the organism acquires in the lifetime can be passed along to its offspring .

ii)he is states that the long neck of the giraffe evolved as a cumulative product of many ancestral generation stretching higher and higher .