CLS Aipmt 17 18 XII Zoo Study Package 4 SET 1 Chapter 4

Chapter

4

Evolution Solutions SECTION - A School/Board Exam. Type Questions Very Short Answer Type Questions : 1.

Which theory of origin of life says that the life on earth came from outerspace?

Sol. Theory of Panspermia/Cosmic/Cosmozoan theory. 2.

Name the sail ship in which Darwin travelled.

Sol. H.M.S. Beagle. 3.

Give one example of analogy in plants.

Sol. Sweet potato and potato. 4.

Do placental mammals in Australia also show adaptive radiation like marsupials? Give the answer in yes or no.

Sol. Yes. 5.

What is the essence of Darwinian theory about evolution?

Sol. Natural selection. 6.

Name one biologist famous for his work on populations.

Sol. Thomas Malthus. 7.

How do mutations arise in a population?

Sol. Mutations arise suddenly in a population. 8.

If q is the frequency of occurrence of an allele A, then what is the probability of individuals with genotype AA?

Sol. q2. 9.

Progymnosperms originated in which period?

Sol. Turtles, Tortoises and Crocodiles. Devonian. 10. The fossils discovered in Java belonged to which ancestor of man? Sol. Homo erectus. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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Short Answer Type Questions : 11. Name the gases used by Miller in his experiment and which theory was more or less accepted by his experiment. Sol. Miller used CH4, H2, NH3 and water vapour at 800°C in a closed flask in his experiment. The theory of chemical evolution of life; as proposed by Oparin and Haldane, was more or less accepted by his experiment. 12. Explain why do we say that when we see stars we apparently are peeping into the past? Sol. This is because we can only see an object when the light emitted by it reaches our eyes. Now stars are trillions of kilometres away from us and hence, the light emitted by them would have started its journey millions of years back. That is why it is said that when we see stars we apparently are peeping into the past. 13. How the concept of ‘common ancestor’ was explained/concluded by Darwin? Sol. While on his sea voyage, Darwin observed that various living forms share similarities in their structure and behaviour among themselves and also with the life forms that have extinct from earth millions of years ago. Darwin concluded that similarities among unrelated organisms can only arise when they are descended from common ancestors. Hence, like this the concept of ‘common ancestor’ came into his mind. 14. Which characteristics are selected by the nature? Sol. Those characteristics which enable some organisms to survive better than others in various natural conditions including food scarcity, harsh climatic conditions etc; are selected by the nature. 15. What do you mean by the term palaeontology? Sol. Paleontology studies the history of past life on earth through fossils. Fossils are the paleontological evidences of evolution. Fossils are the pressured remains of those life-forms that have become extinct millions of years ago from earth. 16. How can you say that homology indicates common ancestry? Sol. As we know the homologous organs are anatomically similar but due to adaptations to different habitats, they developed different functions according to the need. Hence, the similar structures having common origin, diverged to adapt different habitats. Hence, it shows that homology indicates common ancestry. 17. Why did predators spot the white-winged moths more than dark-winged moths after industrialisation set in? Sol. It easy for a predator bird to spot a moth against a contrasting background. The smoke and soots deposited on the tree trunks caused the darkening of latter. Hence, it was easy for the predators to spot white-winged moths against the dark background of trunks of trees after industrialisation set in. 18. How Darwin came to the conclusion of adaptive radiation in Galapagos Islands? Sol. In Galapagos Islands, Darwin observed an amazing diversity of creatures and his special attention went to some small black birds. He realised that these birds were of many varieties with different beaks and feeding habits but still they shared similarities. Hence, he concluded that these all birds arose from a common ancestor which was seed-eater and various varieties arose from a common ancestor through adaptive radiation. 19. When ‘more than one’ adaptive radiation occurs in an isolated geographical area, how can it be called convergent evolution? Exemplify. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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Sol. This can be exemplified by the placental mammals and marsupials, inhabiting the Australia island. We know that Australian marsupials show adaptive radiation and placental mammals of Australia also show adaptive radiation. Some of placental mammals evolved into varieties that appear similar to marsupials. For example lemur is a placental mammal which appears similar to spotted cuscus which is a marsupial. Hence, two different types of mammals converged towards similarity due to living in the similar habitats. 20. Describe two interpretations of work of Thomas Malthus on populations. Sol. (i) He said that the size of a population nearly remains stable except for some seasonal fluctuations. (ii) He also mentioned that no two individuals in any population are exactly alike. The members of a population vary in their characteristics even though superficially they look similar. 21. To what factor the rate of appearance of new life forms is linked? Sol. The rate of appearance of new life forms is linked to the life span or life cycle of the organism. For example, the bacteria have very short life spans that is why they become millions of individuals even in the duration of hours. So a new variant population takes time of only some days to develop in them. While in organisms having years of life spans, a variant takes millions of years to arise. 22. According to Hugo de Vries, what causes speciation? Sol. According to Hugo deVries, mutations cause speciation. He came to this conclusion while studying evening primrose. He said that mutations arise suddenly in a population and inherited mutations suddenly bring changes in the already existing population which leads to a new species formation over few generations. 23. What does the disturbance in Hardy-Weinberg equilibrium indicate? Sol. The disturbance in Hardy-Weinberg equilibrium indicates that there is any change in the frequencies of alleles in the population which indicates occurrence of evolution in that population. 24. What is the effect on the peak of the distribution curve when nature poses disruptive effect on traits of a character? Explain with a diagram.

Number of individuals with phenotype

Sol. When nature poses disruptive effect, it means it selects the individuals at both the ends of the curve and this results in the formation of two peaks in the curve.

Two peak form

Distribution curve 25. Give two characteristic features of mammals and also tell what were the first mammals on earth? Sol. (i) Mammals are viviparous which means they do not lay eggs outside (with few exceptions) rather they directly give birth to their young ones and protect them until they are born and even after that. (ii) Mammals are more intelligent in sensing the danger than other animals. The first mammals on the earth were like shrews. Actually the first mammals were egg laying, Ornithorhynchus. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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26. About how many years ago the dinosaurs disappeared from the earth? Also name the biggest dinosaur with its height. Sol. About 65 mya, dinosaurs suddenly disappeared from the earth. The biggest dinosaur was Tyrannosaurus rex which was about 20 feet in height. It had huge fearsome dagger-like teeth. 27. Which animals are thought to be the ancestors of first amphibians and first reptiles respectively? Sol. Lobefins, the fishes with stout and strong fins are thought to be evolved into first amphibians and the amphibians are thought to be evolved into first reptiles. 28. Who are modern Homo sapiens? When and where did they arise on earth? Sol. Today’s man is the modern Homo sapiens. They arose during ice age between 75,000–10,000 years ago. They arose in Africa and moved across continents and developed into distinct races that we can see today. 29. Which fossils lead to the belief that about 3–4 mya, man-like primates walked in eastern Africa? Sol. Few fossils of man-like bones were discovered in Ethiopia and Tanzania, the east African countries. When these fossils were studied, they revealed that about 3-4 mya, man-like primates walked in eastern Africa. 30. If the skulls of adult modern human being, baby chimpanzee and adult chimpanzee are compared then what do you observe and what does it indicate? Sol. We observe that the skull of baby chimpanzee is more like adult human skull than adult chimpanzee skull. Long Answer Type Questions : 31. (i) Explain Big Bang theory. (ii) When did life appear according to this theory? Sol. (i) The Big Bang theory was proposed to explain the origin of universe. According to this theory, the origin of universe took place due to a single huge explosion in the space due to which the various galaxies were formed in it. Its various postulates were : (a) The earth formed about 4.5 billion years back. (b) There was no atmosphere on early earth. (c) Water vapour, methane, carbon dioxide and ammonia were released from the molten mass which came out of earth due to volcanic eruptions. (d) The UV rays broke up water into Hydrogen and Oxygen. (e) The ozone layer formed from oxygen slowly (f) Water vapour condensed fell down as rain, to fill the depressions and form oceans. (ii) Life appeared on earth almost 4 billion years back. 32. Discuss the theory of spontaneous generation of life in brief and also tell why this theory was dismissed? Sol. The theory of spontaneous generation says that life originated on the earth from decaying and rotting matter like straw, mud etc. The proponents of this theory said that even the mud could give rise to life forms like frogs. The material which is undergoing decay can also give rise to houseflies, mosquitoes etc. This theory was dismissed because there was no scientific basis of its hypothesis. Many of the scientists opposed this idea that how could mud give rise to life forms? Many scientists disproved it experimentally and Louis Pasteur was one of them who through an experiment using yeast demonstrated that no life can arise from killed yeast. It is only the pre-existing life that can give rise to new life ahead. 33. Who gave the experimental proof of Oparin-Haldane theory? Explain diagrammatically. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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Sol. Hint : Miller’s experiment. 34. (i) Which conclusions of Alfred Wallace were similar to that of Darwin? Discuss. (ii) How can you say that the geological history of earth closely correlates with the biological history of earth? Sol. (i) Alfred Wallace was a naturalist who worked in the Malay Archepelago, a chain of islands. He also came to the similar conclusion of ‘natural selection’ about which Darwin talked during his sea voyage round the world. Wallace also observed that some individuals can better adapt to their environment than others and those that better adapt, they survive and are selected by the nature. The credit for such a selection was given to the variations in the characteristics of those individuals. (ii) The biological history of earth means the history that depicts which and when an organism evolved on the earth, and when it got extinct, what are its close relatives, etc. whereas the geological history is the history of various epochs, periods and eras of the earth which are used to study the age of earth. It was observed that various existing organisms share their ancestors either in recent history or in the distant history and how closely they are related, that can be interpreted by knowing the period or era in which their common ancestors existed. More closely related organisms will share ancestors in recent history and less closely related organisms will share ancestors in distant history. Different aged rock sediments contain fossils of different life forms who probably died during the formation of a particular segment. A study of fossils in different sedimentary layers indicates the geological period in which they existed. 35. (i) How can you say that fossils represent the extinct organisms? (ii) How are the ages of fossils calculated? Sol. (i) Fossils are the preserved remains of hard parts of life-forms found in rocks. When an organism dies, sometimes its body parts especially the hard parts like bones, teeth, etc. do not decompose and get preserved in the rocks. It is a well known fact now that many organisms keep on evolving on one side and keep on getting extinct on the other side. Those that became extinct millions of years ago (like dinosaurs) got buried in those rocks that were forming during their extinctions. Hence fossils represent the extinct organisms. (iI) There are two methods of finding the age of fossils : (a) Relative dating : By digging the earth and then in the order of finding the fossils, their relative ages are calculated. One which is found earlier is thought to be younger than the one which is found in the deeper layers. (b) Radioactive dating or absolute dating : This method is employed for accurately calculating the age of fossils with the help of radioactive isotopes. 36. (i) What are homologous structures? (ii) Give examples. (iii) Homologous structures are the result of which type of evolution? Sol. (i) The structures which perform different functions in different organisms but share similarity in their anatomy are called homologous structures. (ii) Examples are (a) Forelimbs of whales, bats, cheetah and human. (b) Vertebrate hearts or brains (c) Thorn of Bougainvillea and tendril of Cucurbita (ii) They are the result of divergent evolution. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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37. (i) What do you mean by the ‘biochemical similarities’? (ii) What do you infer by the presence of biochemical similarities? Sol. (i) Biochemical similarities refer to the similarities in the proteins and genes. The proteins and genes are present at the subcellular level, i.e., they are the components of cells. Even different looking organisms can have similarities in their genes (the segments of chromosomes) and proteins present in their cells. (ii) These similarities point towards the ‘common ancestry’. It is because if the proteins and genes performing a given function are found to be similar in two organisms, it shows that these two organisms share common ancestor in their history. If the similarities are more, they are more related and if less, then they are less related but related. 38. Anthropogenic actions can lead to speciation. Explain this with suitable examples. Sol. Hint : Antibiotic resistance in bacteria and herbicides, pesticides resistant varieties. 39. Study the figure given below and answer the following questions.

(i) Which animals are depicted in the given figure? (ii) What phenomenon they are representing? (iii) How can you say that these are the result of that phenomenon? Sol. (i) Given figure depicts the Australian marsupials all of which evolved on the Australian island continent. (ii) They are representing the phenomenon of adaptive radiation. (iii) These all marsupials are different from each other in their habitats and modes of living. All are the different species. But they all evolved from the single ancestral stock representing that they have radiated in an isolated geographical area from the single species. Hence, it is said that they are the result of adaptive radiation. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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40. Study the picture given below and answer.

(i) Which animals are depicted on the left and right side of the picture respectively? (ii) How are they related to one another? (iii) Their relation points towards which phenomenon? Sol. (i) On the left side of the picture, placental mammals are shown and on the right side, marsupials are shown. (Both present on the Australian island). (ii) Mammals on the left side are placental, i.e., they show true placenta formation during pregnancy unlike the marsupials on the right side. The placental mammals appear similar to the marsupials depicted adjacent to them. These two types of mammals not only ‘appear’ similar but also they have similar modes of living. For example, flying squirrel is a placental mammal which appears similar to flying phalanger which is a marsupial. (iii) Their similarities in appearances and modes of living show that they are the result of convergent evolution. Because due to living in the same habitat, they developed similarities in their structures and modes of living. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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41. (i) What were the views of Lamarck about evolution of life forms? (ii) What are the two key concepts of Darwinian theory of evolution? Sol. (i) Lamarck had the following views about evolution of life forms. He said that the ‘use and disuse of any organ’ is the driving force for the evolution. He gave the examples of giraffes and said that present day giraffe has so long neck because its ancestors used to stretch their necks while eating the leaves of tall trees. Hence, as they stretched, it become more elongated. Second main view was that the characters acquired by an organism during its life time pass on to its offsprings. He said that the ancestors of giraffes passed on their acquired character of elongated necks to their succeeding generations. (ii) (a) Branching descent (b) Natural selection. 42. Elaborate the three types of natural selection. Sol. Hint :

(1) Stabilising selection (2) Directional selection (3) Disruptive selection

43. (i) How can genetic recombination lead to evolution? (ii) Which factor should be coupled to heritable variations to give rise to new population? Sol. (i) Genetic recombination occurs during gametogenesis (gamete formation). We know that sperm and ova are the male and female gametes, respectively and their process of formation are called spermatogenesis and oogenesis, respectively. During the meiosis (taking place in gametogenesis), crossing over of chromosomes takes place which exchanges the genes between homologous chromosomes. This results in new combinations of genes that can lead to variations that are inherited to next generation and if these inherited variations are selected by the nature, it can lead to evolution. (ii) Enhanced reproductive success should be coupled to heritable variations to result in the speciation. 44. (i) First amphibians were ancestors of which animals? (ii) Are first amphibians still living on the earth? (iii) Around what time jawless fish evolved on earth? (iv) For nearly 200 million years, which animals dominated on earth? Sol. (i) First amphibians were the ancestors of modern day frogs and salamanders. (ii) No, there is no specimen of first amphibians left with us. They have extinct from earth. (iiI) Jawless fish evolved around 350 mya. (iv) Reptiles of different shapes and sizes dominated on earth for nearly 200 million years. 45. (i) Compare the cranial capacities of Homo habilis, Homo erectus, Neanderthal man and Homo sapiens. (ii) Can we say that the development of human brain and language appears to be an example of ‘parallel evolution’? If yes then why and vice versa. Sol. (i) Homo habilis was the first human-like being on the earth and it had a cranial capacity around 650–800cc. Homo erectus had a comparatively larger brain of around 900cc capacity. The Neanderthal man had a very large cranial capacity of about 1400cc but was not more intelligent as today’s man. Homo sapiens also has cranial capacity of about 1300–1600cc. Modern Homo sapiens, i.e., today’s man is the most intelligent and creative creature on the earth. (ii) Yes, the development of human brain and language can be cited as the example of parallel evolution. This is because as the human brain size grew from 400–500cc to present time 1300–1600cc capacity, its language and ability to communicate using speech developed accordingly. This is due to the well-developed ‘speech areas’ present in cerebral cortex. Modern man is best able to exress his feelings and communicate which made many developments in the world possible. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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SECTION - B Model Test Paper Very Short Answer Type Questions : 1.

Name a galaxy having its solar system.

Sol. Milky way galaxy. 2.

What was the ultimate fitness according to Charles Darwin?

Sol. Reproductive fitness, i.e., ability to produce more progeny than others. 3.

Name any two extinct animals.

Sol. Stegosaurus and Archaeopteryx. 4.

Give an example of evolution by natural selection.

Sol. Industrial melanism. 5.

Where did Darwin observe the adaptive radiation of small black birds?

Sol. Galapagos Islands. 6.

Define saltation.

Sol. Saltation means single step large mutation. 7.

Which animals took over the earth when reptiles came down in number?

Sol. Mammals. 8.

Mention the dietary preference of Australopithecines.

Sol. Fruits. They were frugivorous. Short Answer Type Questions : 9.

Universe is comprised of huge clusters of galaxies. Explain the Origin of Universe.

Sol. Huge clusters of galaxies comprise the universe. A galaxy is defined as a massive, gravitationally bound system of stars and planets having clouds of gas and dust. 10. Give two examples of convergent evolution. Sol. (1) Analogous structures/potato and sweet potato (2) More than one adaptive radiation in an isolated geographical area/Lemur and Spotted cuscus. 11. How can you say that lichens can be used as industrial pollution indicators? Sol. Lichens can be used as industrial pollution indicators because they do not grow in the areas that are polluted. So whether an area is polluted or not, it can be predicted by the presence or absence of lichens in that area. 12. Define fitness. How is it related to natural selection? Sol. Fitness is the end result of the ability to adapt and get selected by nature. The organisms who are better fit in an environment than others, leave more progeny, therefore will survive more and hence are selected by the nature. 13. What is Founder effect? Sol. Founder effect is a special case of genetic drift which is oberved when a section of population drifted from the original population forms a new population itself rather than merging in the other population. The drifted individuals become founders and this effect is called founder’s effect. 14. Define (i) Gene pool (ii) Gene flow. Sol. (i) Gene pool is the complete set of total genes and their alleles in a population. (ii) Gene flow is the transfer of alleles or genes from one population to another but only when it happens multiple times. 15. Discuss two effects of continental drift on evolution of mammals. Sol. (1) Due to continental drift, when South America joined North America, the South American mammals were overridden by the North American mammals. (2) Pouched mammals of Australia survived because of lack of competition from any other mammal. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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Short Answer Type Questions : 16. Give three evidences of evolution. Sol. (1) Fossils – the paleontological evidences. (2) Homologous and analogous structures. (3) Artificial breeding of plants and animals, done by man. 17. Discuss how homology is accounted for by the idea of branching descent? Sol. Branching descent means many species arising from common ancestor species in the way as if they are the branches of ancestral species. As more descending takes place, branching continues. Similarly the homology also indicates common ancestry as the branching descent does. Hence we can say that homology can be justified by the idea of branching descent. 18. What do understand by ‘non-cellular forms of life’? When did first non-cellular forms of life originated on earth? Sol. Non-cellular forms of life means those forms of life which exist on earth without a cellular structure. It means they are the life forms but still having no cellular structure. First non-cellular forms of life originated about 3 billion years back. They would have been giant molecules, e.g., RNA, Protein, Polysaccharides, etc. It is clear that these molecules are not the cells but the parts of cell i.e., the non-cellular forms of life. 19. What were the three connotations of theory of special creation. Why this theory was strongly challenged during nineteenth century? Sol. (1) Earth is about 4000 years old. (2) All living organisms were created in the same form in which they are existing today. (3) The biodiversity was always the same since creation and will be same in the future also. This theory was strongly challenged because all of its ideas had no scientific proof. Moreover its connotations were not acceptable to majority of biologists that how biodiversity can remain same if new organisms keep on evolving and old ones keep on extincting. 20. Give the pictorial representation of three types of natural selection. Sol. Peak gets higher and narrower

Number of individuals with phenotype

(a)

Phenotypes favoured by natural selection

Medium-sized individuals are favoured

Peak shifts in one direction

(b)

Two peaks form

(c)

Fig.: Diagrammatic representation of the operation of natural selection on different traits : (a) Stabilising (b) Directional and (c) Disruptive Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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21. Discuss in brief the evolution of reptiles on earth. Sol. The reptiles evolved from the amphibians. Early reptiles have become extinct from earth but their modern day descendents like turtles, tortoises, crocodiles, etc. are existing on the earth. For nearly 200 million years after they evolved, the reptiles dominated on earth. About 200 mya, some of these reptiles went back to the water to evolve into fish-like reptiles. The land reptiles were dinosaurs, largest of which was Tyrannosaurus rex. The dinosaurs got extinct suddenly about 65 mya. Long Answer Type Questions : 22. Study the figure given below and answer the questions following it.

1

2

3

4

(i) Write down your observations on the varieties seen in the Darwin’s finches shown above. (ii) How did Darwin explain the existence of different varieties of finches on Galapagos Islands? Or

(a)

(b)

(i) Write your observations on the figure depicted above. (ii) What was the explanation put forth for this observation? Sol. Hints : (i) Different shapes of beaks and their feeding habits. (ii) Adaptive radiation of finches. Or Hints : (i) Effect of industrialisation on the number of moths. (ii) Explanation, the predators will spot the moth against a contrasting background. 23. (i) What do you understand by genetic equilibrium? (ii) How gene migration affects the Hardy-Weinberg equilibrium? Or (i) Discuss in brief about Dryopithecus, Ramapithecus and Australopithecines. (ii) How Neanderthal man is related to modern Homo sapiens? Give the time of existence on earth and cranial capacity of the Neanderthal man. Sol. (i) Genetic equilibrium means that gene pool of a population remains constant and the frequencies of occurrence of its various alleles are stable. This equilibrium points towards the stability of allelic frequencies in a population until and unless this equilibrium is not disturbed by any kind of evolutionary force. For example, in a diploid organism, if p is the frequency of allele A, then the probability of appearance of A on both the chromosomes is p2. It is expected value. But when frequency of this allele A measured is found to be different from p2, it indicates disturbance in the genetic equilibrium which points towards the evolution. Aakash Educational Services Pvt. Ltd. Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456

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(ii) Gene migration is one of the ‘evolutionary force’ that tends to affect the Hardy-Weinberg equilibrium (or genetic equilibrium). When a segment of population migrates from one population to another, it results in the ‘transfer’ of genes from old to new one, resulting in addition of new alleles/genes in the new population and vice versa, therefore, disturbing the genetic equilibrium. Or (i) Dryopithecus : Ancestor of modern day apes as it was more ape-like. It existed 15 mya on earth. It had semierect posture. It used to eat soft fruits and leaves. It used to live mainly on trees. They were more ape like. Ramapithecus : It was more man-like and lived on the tree tops but also walked on the grounds. Its jaws and teeth were like that of humans. They used to eat hard nuts and seeds. They were more man like. Dryopithecus and Ramapithecus : were hairy and walked like gorillas and chimpanzees. Australopithecus : It had erect posture and had human as well as ape characters. (ii) The Neanderthal man is the ancestor of modern Homo sapiens. It lived in near east and central Asia between 1,00,000–40,000 years back and had a brain size of 1400cc.







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