Human Evolution

Which of the following is not a vestigial organ ?

1. Vermiform appendix
2. Caecum
3. Wisdom teeth
4. Ear pinna

Answer

Caecum

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

The selective agent that was responsible for causing the change in peppered moth was :

1. Lichens
2. Humans
3. Birds
4. Smoke

Answer

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.

The first scientist who proposed his theory for evolution was ;

1. Darwin
2. Lamarck
3. Mendel
4. Wallace

Answer

Lamarck

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

The theory proposed by Lamarck is :

1. Autogenesis theory
2. Germplasm theory
3. Theory of inheritance of acquired characters
4. Theory of abiogenesis

Answer

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.

Charles Darwin explained the origin of species through:

1. Mutation
2. Natural selection
3. Acquired characters
4. Hybridization

Answer

Natural selection

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

Which one of the following was not explained by Darwinism?

1. Natural selection
2. Struggle for existence
3. Use and disuse
4. Survival of the fittest

Answer

Use and disuse

Reason — Use and disuse was discussed by Lamarck.

Which of the following human ancestral stages came just before the modern man ?

1. Cro-magnon
2. Ramapithecus
3. Homo habilis
4. Neanderthal man

Answer

Cro-magnon

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

The scientist who is regarded as the "Father of Evolution" is :

1. Mendel
2. Walther Flemming
3. Darwin
4. Lamarck

Answer

Darwin

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

Industrial melanism was highlighted by :

1. Polar bear
2. Butterfly
3. Peppered moth
4. Bear

Answer

Peppered moth

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

The famous book “The Origin of Species” was written by :

1. Carl Linnaeus
2. Darwin
3. Lamarck
4. Mendel

Answer

Darwin

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

Mention four postulates of Darwin's theory.

Answer

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

The range of cranial capacities in the following ancestral forms were

(a) Australopithecus

(b) Homo habilis

(c) Homo erectus

(d) Cro-magnon

(e) Homo sapiens sapiens

Answer

(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

Mention the two principles through which Lamarck explained his ideas.

Answer

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.

Name any three vestigial organs found in humans.

Answer

Three vestigial organs found in humans are:

1. Wisdom teeth
2. Vermiform appendix
3. Pinna

Give the scientific name of the organism which is cited as the classical example of 'natural selection'.

Answer

Biston betularia is a classical example of 'natural selection'.

Tick mark (√) the correct option in the following statements.

(a) The fossil history of humans is complete/fragmentary.

(b) The first remarkable human fossil was that of H. habilis/H.africanus.

(c) Evolution is an ever continuing/promptly ending process.

Answer

(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.

Define the following terms:

(a) Evolution

(b) Vestigial organs

(c) Speciation

(d) Bipedalism

(e) Natural selection

Answer

(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.

Distinguish between:

(a) Australopithecus and Cro-magnon (Chin)

(b) Australopithecus and Modern man (Body hair)

(c) Homo habilis and Homo sapiens sapiens (Posture)

Answer

(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) —

Differentiate between Lamarck's Theory and Darwin's Theory.

Answer

Main differences between the theories of Lamarck and Darwin —

Given below are two figures (A and B) representing the two stages of evolution of human beings.

Answer the following:

(a) Mention any two contrasting characters between the two stages.

(b) Write all the stages of human evolution in their correct sequence.

(c) State any two characteristic features of stage B.

Answer

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.

Given below are two figures (A and B) showing a phenomenon that was first observed in Manchester before and after the year 1850.

Answer the following.

(a) What name has been given to this phenomenon?

(b) Give the common name and the scientific name of the insect involved in this phenomenon.

(c) Briefly mention why the changes shown in the two figures appeared.

(d) The following phenomenon provides a classical explanation of a scientific theory given by a certain scientist.

(i) Name and explain the said theory.

(ii) Give the name of the scientist who gave this theory.

Answer

(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

Observe the figure given below and answer the questions that follow:

(a) What is the figure depicting ?

(b) What was the reason that the giraffe stretched their neck and forelimbs ?

(c) What is the name of the theory that is being depicted in the figure ?

(d) Who explained the theory ?

(e) What is the conclusion of this theory ?

Answer

(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.