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Q1. Whose theory was put to test by Miller and Urey and what was the theory? How did their experiment give due to abiotic origin of life on Earth? 

Solution

Urey and Miller tested the theory of Oparin and Haldane, which states that life originated on the Earth through physiochemical processes of atoms combining to form molecules which in turn react to produce inorganic and organic compounds. Urey and Miller created the similar environment in laboratory using glass apparatus and tubes. They took methane, ammonia, hydrogen and water vapour and supplied electron charge using cathode in a closed flask of 75,000V. After a week, it was observed that a number of complex organic molecules have originated such as sugar, nitrogen base and amino acids.

Q2. What are the key concepts of Darwinian theory of evolution?

Solution

Key concepts of Darwinian theory of evolution are- (i) Branching descent (ii) Natural selection

Q3. (a) What is gene migration? (b) Name the phenomenon by which dark coloured moth originated from grey coloured moth 

Solution

(a) When a section of population migrates, it results in addition of new genes or alleles to one population and their loss to another population. This is called gene migration. (b) The phenomenon by which dark coloured moth originated from grey coloured moth is called industrial melanism.

Q4. Define reproductive isolation. Give its significance.

Solution

Reproductive isolation is the inability of interbreeding of even related groups of animals due to presence of some isolating mechanism. Its significance is that it helps in evolutionary divergence.

Q5. Are the thorns of Bougainvillea and tendrils of Cucurbita homologous or analogous? What type of evolution has brought such a similarity in them? 

Solution

The thorns of Bougainvillea and tendrils of Cucurbita are homologous organs. Divergent evolution has brought a similarity in them.

Q6. State the significance of Coelocanth in evolution. 

Solution

Coelocanth is a connecting link between bony fishes and amphibians.

Q7. Name the period of geological history when lycopod flourished.

Solution

Lycopod were seen in the Jurassic period of Mesozoic Era.

Q8. What is theory of spontaneous generation? Name the scientists who dismissed it.

Solution

Theory of spontaneous generation states that living organisms originated abiogenetically from non-living materials at once. This theory was dismissed by Francisco Redi, Lazzaro Spallanzani and Louis Pasteur.

Q9. Write a short note on Homo erectus.

Solution

Homo erectus evolved about 1.7 million years ago from Homo habilis. It occurred in Java, China and Europe. There were three forms of erect man- Homo erectus erectus (Java-ape man), Homo erectus pekinensis (Peking man) and Homo erectus heidelbergensis (Heidelberg man).

Q10. Among Ramapithecus, Australopithecous and Homo habilis, who probably did not eat meat?

Solution

Homo habilis were not carnivorous.

Q11. What do you understand by differential reproduction and reproductive isolation? In what context are these terms used?

Solution

The phenomenon in which all organisms who reach reproductive stage reproduce with varying degree of success, some reproduce more offspring and some reproduce only few is called differential reproduction. The phenomenon in which the individual belonging to same species reproduce among themselves to maintain the integrity of species is called reproductive isolation. Differential reproduction and reproductive isolation are used in reference to natural selection.

Q12. How do we compute the age of a fossil?

Solution

We can compute the age of fossil by following methods such as radiocarbon dating, uranium lead-method, potassium-argon method and electro spin resonance method.

Q13. Life originated from earth's inorganic atmosphere in past but not today. Suggest two reasons. 

Solution

(i) Presence of oxygen (ii) Existence of living organism

Q14. (a)Define natural selection. (b)Differentiate between vestigial organs and atavistic organs. (c)How do Darwin's finches illustrate adaptive radiation?

Solution

(a) The process whereby organisms better adapted to their environment tend to survive and produce more offspring is called natural selection. (b) Vestigial organs are non-functional organs in an organism but were functional in ancestors .Example- Vermiform appendix of man but atavistic organs are those vestigial organs which have become functional. Example- A baby born with a tail. (c) Darwin’s finches are a group of small sized black birds which were first noticed by Darwin on the Galapagos Island. David Lack reported that these finches evolved from a common ancestral type of South American mainland but radiated to different geographical areas and adapted differently in their feeding habits so developing different types of beaks.

Q15. Explain how homologous organs support the theory of organic evolution. 

Solution

The forelimbs of some animals have similar anatomical structure. They possess humerus, radius, ulna, carpals, metacarpals and phalanges in their forelimbs. For example, forelimbs of man, whales, bats, cheetah indicates that they have common ancestors which supports organic evolution.

Q16. Among Dryopithecus and Ramapithecus, which one was more man-like?

Solution

First man-like hominid was Ramapithecus.

Q17. List the two theories of origin of life. 

Solution

(i) Theory of Chemical Evolution (ii) Theory of Abiogenesis

Q18. Mention how is mutation theory of Hugo de Vries different from Darwin's theory of natural selection. 

Solution

According to Hugo de Vries, new species arise due to single step large mutation whereas according to Darwin, evolution occurs gradually by the method of natural selection.

Q19. Write the similarity between the wing of a butterfly and the wing of a bat. What do you infer from the above with reference to evolution? 

Solution

Wings of a bird and a bat perform the same function of flying despite of their structural dissimilarity. This infers that they are analogous organs.

Q20. List the postulates of Neo-Darwinism.

Solution

The four factors that is present in Neo- Darwinism are- genetic variations, natural selection, speciation and reproductive isolation.

Q21. Define homologous organ. Give one example of an organ homologous to hand of man.

Solution

The organs with same structural design and development origin but differing in their functions are called homologous organs. The forelimb of human being is homologous to forelimbs of whales and bats.

Q22. What are the key concepts of Darwinian theory of evolution? 

Solution

(i) Survival of the fittest (ii) Natural selection

Q23.  What is meant by abiotic synthesis? Who proposed the idea and who supported it experimentally? 

Solution

Abiotic synthesis means origin of life from non-living constituents, i.e. chemical evolution of life state that diverse organic molecules were synthesized from inorganic constituents. This idea was proposed by Oparin and Haldane. It was experimentally proved by Urey and Miller.

Q24. Are flippers of penguin and dolphin homologous or analogous? What type of evolution has brought such a similarity in them? 

Solution

Flippers of penguin and dolphin are analogous organs. Convergent evolution is a similarity in them.

Q25. What is speciation? Name two mechanisms of speciation.

Solution

Origin of new species from a pre-existing species is called speciation. Two mechanisms of speciation are- (i) Gradual speciation (ii) Abrupt speciation

Q26. Define natural selection.

Solution

The process by which plants and animals that can adapt to changes in their environment and are able to survive and reproduce is called natural selection. 

Q27. Name the common ancestor of the great apes and man

Solution

Dryopithecus and Ramapithecus are the common ancestor of great apes and man.

Q28. Name the scientist who disproved spontaneous generation theory. 

Solution

Louis Pasteur disproved spontaneous generation theory. 

Q29. Name any two vertebrate body parts that are homologous to human forelimbs.

Solution

Wings of birds and forelimbs of horse are homologous to human forelimbs.

Q30. What does Hardy-Weinberg equation p2 + 2pq + q2 = 1 convey? 

Solution

Hardy- Weinberg equation conveys genetic equilibrium i.e. sum total of all allelic frequencies is 1.

Q31. What is the significance of Archaeopteryx in the study of organic evolution? 

Solution

Archaeopteryx is a connecting link between reptiles and birds. It shows features of both birds and reptiles giving evidence that birds have evolved from reptiles.

Q32. Why Australopithecus is called African ape-man?

Solution

The fossils of Australopithecus were discovered from the rocks of late Pliocene period in South Africa. It had a number of apes like characters such as small cranial size, long canines etc but was bipedal like man.

Q33. According to Hardy- Weinberg's principle, the allele frequency of a population remains constant. How do you interpret the change of frequency of alleles in a population? 

Solution

Change of frequency of allele in a population will result in natural selection leading to the evolution.

Q34. Define genetic drift. 

Solution

A sudden change in gene frequency by chance alone rather than by natural selection is called genetic drift.

Q35. What causes speciation according to Hugo de Vries? 

Solution

Mutation causes speciation.

Q36. Discuss the role of reproductive isolation in evolution.

Solution

Reproductive isolation refers to the mechanisms which check the populations of two different species from interbreeding. The populations with different genotypes must be isolated so that differences may accumulate to the level of speciation. It also leads to the origin of new species by accumulation of genetic variations in a population which lets evolution to occur.

Q37. (a) Name the primates that lived about 15 million years ago. List their characteristic features. (b) (i) Where was the first man-like animal found?       (ii) Write the order in which Neanderthals, Homo habilis and Homo erectus appeared on earth. State the brain capacity of each one of them.     (iii) When did modern Homo sapiens appear on this planet? 

Solution

(a) Primates were Dryopithecus and Ramapithecus that lived 15 million years ago. Their characteristics features were-  (i) They were hairy and walked like gorillas and chimpanzees.  (ii) Ramapithecus was more man-like.  (iii) Dryopithecus was more ape-like. (b) (i)First man-like animal was found in Ethiopia and Tanzania.  (ii) The order of appearance from earliest to the latest is Homo habilis, Homo erectus and Neanderthals.  The brain capacity of Homo habilis is 650-800 cubic centimeters, Homo erectus is 900 cubic centimeters and Neanderthals is 1400 cubic centimeters.  (iii) Modern Homo sapiens appeared between 75,000- 10,000 years ago.

Q38. Give a biological term for single step large mutation.

Solution

Single step large mutation is called as saltation.

Q39. What are the various components of human evolution? Give one example. 

Solution

During human evolution, ancestral human types had undergone a number of remarkable changes in their brain size, skeletal features, and dietary preference. For example, Australopithecus had a brain capacity of 450 cubic centimeters and was chinless. It was primarily fruit-feeder but also hunted with stones.

Q40. (i)Who proposed the theory of origin of life? (ii)What were the conditions prevailing about 3.6 billion years ago, to create life on primitive earth?

Solution

(i)Oparin and Haldane proposed the theory of origin of life. (ii)On the primitive earth there was no atmosphere. The volcanic eruption and molten mass released water vapour, methane, carbon dioxide and ammonia which formed earth’s atmosphere. Huge amount of energy was liberated from lightning and UV-rays as there was no ozone layer.