Multiple Choice Type
(Select the most appropriate option in each case)
The first scientist who proposed his theory for evolution was
- Lamarck ✓
The theory of Natural Selection was proposed by
- Darwin ✓
The organism studied for industrial melanism was a
- Moth ✓
Identify the pre-human ancestor.
- Ramapithecus ✓
- Neanderthal man
Short Answer Type
Why Neanderthal man and modern man belong to two distinct species?
Below are the characteristic differences between Neanderthal man and modern man as Neanderthal man and modern man exhibit different characteristics —
|Characteristics||Neanderthal man||Modern man|
|Cranial capacity||1450 cm3||1450 to 1600 cm3|
|Bipedalism||Absolute bipedalism||Perfect Bipedal locomotion|
|Size of canine teeth||small canines; heavier than that of modern man; presence of wisdom teeth||small canines; teeth closer to each other; wisdom teeth present|
|Forehead and brow ridges||Forehead low and slanting broad and flat; prominent eye brow ridges||Steep forehead; reduced brow ridges; flattened face|
|Development of Chin||Strong lower jaw with almost no chin||Prominent chin; snout disappeared|
|Hair on body||Reduced hair on the body||Highly reduced body hair.|
|Height & Posture||160 cm (about 5.5 ft), semi erect stooping posture||upto 190 cm; fully erect|
The range of cranial capacities in the following ancestral forms were
(b) Homo habilis
(c) Homo erectus
(e) Homo sapiens sapiens
(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.
Lamarck was the first scientist to propose his theory of use and disuse and inheritance of acquired characters to explain evolutionary process.
- Use and disuse — Parts of the body which are used extensively become larger and stronger, while those which are not used deteriorate.
- Inheritance of acquired characters — An organism could pass its modifications to its offspring.
Name any three vestigial organs found in humans.
Three vestigial organs found in humans are:
- Wisdom teeth
- Vermiform appendix
Give the scientific name of the organism which is cited as the classical example of 'natural selection'.
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.
(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:
(b) Vestigial organs
(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 those organs that have ceased to be of any use to the possessor but still persist generation after generation in a reduced form. In other words, vestigial organs are the remnants of features that served important functions in the organism's ancestors.
(c) Speciation — Origin of new species by gradual modification is called 'speciation'.
(a) Australopithecus and Cro-magnon (Chin)
(b) Australopithecus and Modern man (Body hair)
(c) Homo habilis and Homo sapiens sapiens (Posture)
(a) Difference between Australopithecus and Cro-magnon (Chin) —
|Lack of chin||Well-developed chin|
(b) Difference between Australopithecus and Modern man (Body hair) —
|Body covered with hair||Highly reduced body hair|
(c) Difference between Homo habilis and Homo sapiens (Posture) —
|Homo habilis||Homo sapiens|
|Bent kneed posture||Fully erect posture|
Differentiate between Lamarck's Theory and Darwin's Theory.
Main differences between the theories of Lamarck and Darwin —
|Lamarck's Theory||Darwin's Theory|
|Known as the theory of inheritance of acquired characters||Known as the theory of natural selection|
|Believes in the use and disuse of an organ. Parts used or changes acquired get transmitted to the next generation.||Believes that since variations exist in individuals, only the fittest survive in the struggle for existence.|
|New species evolve after a long period of time after many generations by acquiring new characters.||New species evolve due to accumulation of favourable variations over a long period of time.|
Explain four observable facts on which "Theory of Natural Selection" is based.
Charles Darwin's theory of Natural Selection is based on certain observable facts which are as follows:
- Overproduction — Overproduction is a driving force in natural selection, as it can lead to adaptation and variations in a species. Darwin argued that all species overproduce, since they have more offspring than can realistically reach reproductive age, based on the resources available. 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.
- Struggle for existence — According to Darwin, individuals multiply in a geometric ratio whereas space and food remain almost constant. Overproduction of organisms results in a struggle for existence among organisms. The struggle is to obtain food, space and mate.
- Variation — Progeny of the same parents are not exactly alike. Such differences are known as variations. The variations may be harmful or advantageous.
- 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.
Industrial melanism provides a good example of natural selection. Discuss.
Industrial melanism is a typical case of natural selection. It involves protective and adaptive coloration. A best example of this is shown by the peppered moth. These moths usually rest on the bark of the trees. 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.
Structured / Application / Skill Type
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.
Stage A → Australopithecus
Stage B → Homo sapiens sapiens (modern man)
(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 (modern man)
(c) Characteristic features of stage B (Homo sapiens sapiens):
- Bipedal locomotion with four reversed curves in the spine.
- Thoracic region flattened into a broad chest by flattening of sternum.
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.
(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:
- 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.
- Charles Darwin