Chapter 14 : Human Evolution - Selina Solutions for Class 10 Biology ICSE

Biology is one of the crucial subjects in ICSE Class 10. ICSE Class 10 Biology speaks about the cell as the basic unit of life, genes, and evolution and deals with how living organisms interact with the environment, including the behavior of living beings. TopperLearning is one of the premier online platforms which helps students of ICSE Class 10 to study various concepts in Biology.

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Chapter 14 - Human Evolution Excercise Ex. 1

Question 1

The first scientist who proposed his theory for evolution was

(a) Darwin

(b) Mendel

(c) Lamarck

(d) Wallace

Solution 1

(c) Lamarck

Question 2

The theory of Natural Selection was proposed by

(a) Mendel

(b) Lamarck

(c) Wallace

(d) Darwin

Solution 2

(d) Darwin

Question 3

The organism studied for industrial melanism was a

(a) Butterfly

(b) Moth

(c) Honeybee

(d) Cockroach

Solution 3

(b) Moth

Question 4

Identify the pre-human ancestor.

(a) Ramapithecus

(b) Australopithecus

(c) Neanderthal man

(d) Cro-Magnon

Solution 4

(a) Ramapithecus

Question 5

Why Neanderthal man and modern man belong to two distinct species?

Solution 5

Neanderthal man and modern man exhibit different characteristics, and hence, they are considered two distinct species. Below are the characteristic differences between Neanderthal man and modern man:

Characteristics

Neanderthal man

Modern man

Locomotion

Absolute bipedalism

Bipedal locomotion

Head and forehead

Large head, broad, flat and sloping forehead

Upright head, skull on the top of the vertebral column, steep forehead

Brow ridges

Prominent brow ridges

Reduced brow ridges

Chin

No chin

Well developed and prominent chin

Hair on body

Less hair on the body

Prominent hair on limbs

Cranial capacity

1450 cm3

1450 to 1600 cm3

 

Question 6

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

Solution 6

Ancestral forms

Cranial capacities

(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

 

Question 7

Mention the two principles through which Lamarck explained his ideas.

Solution 7

(a) Use and disuse:

Parts of the body which are used extensively become larger and stronger, while those which are not used deteriorate.

 

(b) Inheritance of acquired characters:

An organism could pass its modifications to its offspring.

Question 8

Name any three vestigial organs found in humans.

Solution 8

Three vestigial organs found in humans are wisdom teeth, vermiform appendix and pinna.

Question 9

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

Solution 9

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

Question 10

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.

Solution 10

(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. 

Question 11

Briefly discuss the Theory of Natural Selection as given by Darwin.

Solution 11

Charles Darwin proposed the idea of natural selection. Darwinism or Theory of Natural Selection is based on some facts:

(i) Overproduction:

  • All organisms have the capacity to reproduce at a very high rate.
  • However, organisms cannot survive by reproduction alone.
  • Due to lack of food and space, offspring soon begin to die.
  • Some are eaten by predators, while some get destroyed due to adverse environmental conditions.

(ii) Struggle for existence:

  • Overproduction of organisms results in a struggle for existence among organisms.
  • The struggle is to obtain food, space and mate.

 (iii) Variation:

  • Progeny of the same parents are not exactly alike. Such differences are known as variations. The variations may be harmful or advantageous.

(iv) Survival of fittest:

  • In the struggle for existence, organisms that develop new favourable characteristics will survive in the long run. This idea is called 'Survival of the fittest'.
  • Organisms which survive will transmit favourable characters to their offspring.
  • These characters get accumulated and give rise to new species.

 

Question 12

Industrial melanism provides a good example of natural selection. Discuss.

Solution 12
  • The best example is industrial melanism showing the effect of industrial pollution on the moth population on a nearby tree.
  • Before industrialisation, light-coloured lichen used to grow on trees and moth predators could not spot white moths easily, while dark moths were lesser in the moth population. However, due to industrial pollution, lichens could not grow on trees and it became difficult for predators to spot dark moths on the dark background of the stem bark, and thus, the population of white moths became less than that of dark moths.
  • This process is termed industrial melanism. Before industrialisation, white moths were better adapted towards nature, but after industrialisation, dark-coloured moths were more fit towards the changed environmental conditions.
Question 13

How would you justify that Australopithecus was a human ancestor?

Solution 13

Australopithecus averaged about 120 cm tall, and the cranial capacity ranged from 450-600 cm3. It had a low forehead, protruding face, lack of chin and low brain capacity. Teeth resembled man because the dental arc was a smoothly rounded parabola, and a simian gap was absent which justifies a human ancestor.  

Question 14

Name the six ancestral forms in their correct sequence through which modern man has evolved.

Solution 14

Correct sequence through which modern man evolved:

1. Australopithecus

2. Homo habilis

3. Homo erectus

4. Neanderthal man

5. Cro-Magnon

6. Homo sapiens

Question 15

Briefly discuss Lamarckian Theory of Inheritance citing an appropriate example.

Solution 15
  • According to the theory of inheritance of acquired characters, 'the changes in structure or function of any organ acquired during the life-time of an individual in response to changes in the surrounding environment are inherited by offspring and keep on adding over a period of time'. 
  • This theory states that characters are acquired by animals in two ways:

- Effects of environment

- Use and disuse of body parts

  • For example, the long neck of giraffe is explained by Lamarck on the same principle. Giraffe, which lived in the dry and arid deserts of Africa, tried to reach the foliage high up on the trees to eat them as there was no vegetation on the ground. In the process, its neck and forelegs got stretched a bit and this was inherited by the next generation. Then, in the next generation, the same efforts continued. Gradually, through many successive generations, we got a giraffe having a long neck and long forelegs.
Question 16

Explain the occurrence of vestigial organs on the basis of Lamarck's theory of use and disuse.

Solution 16

Organs which are found in reduced or rudimentary condition and do not perform any function in the possessor are called vestigial organs or non-functional organs. They help in understanding the history of evolution and continuity of life.

 

1. Wisdom teeth: They are the last molars which appear last at the age of 17-20 years.

 

2. Vermiform appendix: It projects from the blind end of the caecum and is a functionless organ in humans. It is helpful in herbivorous mammals.

 

3. Pinna: It is the lobe-like part of the external ear which humans cannot move as in other mammals. As it is poorly developed, it is a vestigial organ.

Question 17

Given alongside 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.

Solution 17

Stage A: Australopithecus

Stage B: Homo sapiens sapiens

 

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

Characters

Australopithecus 

Homo sapiens sapiens 

Cranial capacity

450 to 600 cm3

1450 to 1600 cm3

Development of chin

Lack of chin, prognathous face

Prominent chin, snout disappeared

 

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

Australopithecus ® Homo habilis ® Homo erectus ® Neanderthal man ® Cro-Magnon man ® Homo sapiens sapiens

 

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

 Bipedal locomotion with four reversed curves in the spine

 Forehead steep, reduced brow ridges

Question 18

Given alongside 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.

Solution 18

(a) Industrial melanism

 

(b) Common name: Peppered moth

Scientific name: Biston betularia

 

(c) Reasons for changes in the two figures:

 Before the Industrial Revolution, a thick growth of white-coloured lichen covered the trees. As a result, the light-coloured moths were camouflaged and survived under this cover, while the dark-coloured moths were easily spotted by predators.

 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) (i) 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.

(ii) Charles Darwin

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