Human Evolution

A is False and R is True.

Explanation
"Survival of the fittest" is a concept associated with Darwin's theory of natural selection, not Lamarck's theory. Lamarck's theory is based on the idea that characteristics acquired during an organism's lifetime can be passed on to its offspring.
Lamarck used the example of the giraffe's neck to illustrate his principle of 'use and disuse,' suggesting that giraffes stretched their necks to reach higher leaves, and this trait was then passed on to their offspring.

A is True and R is False.

Explanation
Vermiform appendix is a small and narrow worm-like tubular structure, projecting from the blind part of the colon. It is a vestigial organ in humans having no function.

Both A and R are True.

Explanation
Natural selection is the differential survival and reproduction of individuals due to differences in their phenotypes (observable traits). It is a crucial mechanism of evolution, leading to changes in inheritable traits within populations over generations.

(a) Evolution — Evolution is a slow and continuous process whereby complex forms of life have emerged from simpler forms through millions of years.

(b) Vestigial organs — Vestigial organs are remnants of once-functional structures in the organism's ancestors that have lost their original purpose through evolution in the present-day species.

(c) Speciation — Origin of new species by gradual modification is called 'speciation'.

(d) Bipedalism — Walking straight on hind limbs and freeing of forelimbs from ground is called bipedalism.

(e) Natural selection — Natural selection is the process by which certain heritable traits become more or less common in a population over generations based on their impact on an organism's survival and reproduction in a specific environment.

(a) Difference between Australopithecus and Cro-magnon (Chin) —

(b) Difference between Australopithecus and Modern man (Body hair) —

(c) Difference between Homo habilis and Homo sapiens (Posture) —

Main differences between the theories of Lamarck and Darwin —

Caecum

Reason — Caecum is not a vestigial organ as it absorbs fluid and salt from the digested food.

Smoke

Reason — Earlier the light colour winged moths outnumbered dark winged moths as they could escape the predators but after industrialisation the dark winged moths were able to escape the predators while light colour winged moths were preyed upon. Therefore, the smoke acted as selective agent.

Lamarck

Reason — Lamarck was the first scientist to propose his theory of evolution.

Theory of inheritance of acquired characters

Reason — According to the theory of inheritance of acquired characters organisms can pass on traits acquired during their lifetime to their offspring.

Natural selection

Reason — Charles Darwin explained the origin of species using the idea of natural selection.

Use and disuse

Reason — Use and disuse was discussed by Lamarck.

Cro-magnon

Reason — Cro-magnon came just before the modern man.

Darwin

Reason — Darwin is known as father of evolution because his theory of evolution by natural selection became the foundation of modern evolution studies.

Peppered moth

Reason — Peppered moth showed natural selection of dark winged moths after industrial revolution.

Darwin

Reason — "The Origin of Species" was written by Charles Darwin.

Four postulates of Darwin's theory were:

1. Overproduction : more offsprings are produced than can survive
2. Struggle for existence
3. Variation : Individuals within a species show variation
4. Survival of the fittest

(a) Australopithecus → 450 to 600 cm³

(b) Homo habilis → 680 to 735 cm³

(c) Homo erectus → 800 to 1125 cm³

(d) Cro-magnon → 1450 to 1600 cm³

(e) Homo sapiens sapiens → 1450 to 1600 cm³

Lamarck was the first scientist to propose his theory of use and disuse and inheritance of acquired characters to explain evolutionary process.

1. Use and disuse — Parts of the body which are used extensively become larger and stronger, while those which are not used deteriorate.
2. Inheritance of acquired characters — An organism could pass its modifications to its offspring.

Three vestigial organs found in humans are:

1. Wisdom teeth
2. Vermiform appendix
3. Pinna

Biston betularia is a classical example of 'Natural Selection'.

(a) The fossil history of humans is fragmentary.

(b) The first remarkable human fossil was that of Homo habilis.

(c) Evolution is an ever continuing process.

Stage A → Australopithecus

Stage B → Homo sapiens sapiens (modern man)

(a) Contrasting characters between Australopithecus and Homo sapiens sapiens :

(b) Stages of human evolution in their correct sequence:

Australopithecus → Homo habilis → Homo erectus → Neanderthal man → Cro-Magnon man → Homo sapiens sapiens (modern man)

(c) Characteristic features of stage B (Homo sapiens sapiens):

1. Bipedal locomotion with four reversed curves in the spine.
2. Thoracic region flattened into a broad chest by flattening of sternum.

(a) Industrial Melanism

(b) Common name — Peppered moth

Scientific name — Biston betularia

(c) Biston betularia, this moth with its light coloured wings dotted with spots blended well with the lichens growing on the houses and tree trunks on which it rested. After the Industrial Revolution, pollution resulted in a decline in the growth of lichens. The tree bark got exposed due to the absence of lichens. As a result, dark-coloured moths now got an advantage of a dark background, were camouflaged and survived, while the light-coloured moths were easily picked by predators. This showed that in a mixed population, those moths which could adapt to the changing environment after the Industrial Revolution survived and increased in number, while the ones which could not adapt were slowly wiped out from the population.

(d) The theory explaining Industrial Melanism and the name of the scientist who gave it is given below:

1. Natural selection — During the struggle for existence, only those individuals which have advantageous variations survive while the ones which lack these variations are wiped out. Nature selects only those variations which are suitable for existence. This process is called natural selection.
2. Charles Darwin

(a) The figure depicts evolution in Giraffe due to extensive use of neck and forelimbs.

(b) The area where giraffe fed on grasses, fell short of its ground level vegetation and therefore they had to stretch their neck and forelimbs to reach leaves of trees.

(c) Lamarck's theory of inheritance of acquired characters

(d) Lamarck

(e) According to this theory, variations are seen in organisms due to less or overuse of organs. These variations are passed on to the offsprings. After many generation these variations become permanent feature of the organism.