TS Inter 2nd Year Zoology Study Material Chapter 7 Organic Evolution

Telangana TSBIE TS Inter 2nd Year Zoology Study Material 7th Lesson Organic Evolution Textbook Questions and Answers.

TS Inter 2nd Year Zoology Study Material 7th Lesson Organic Evolution

Very Short Answer Type Questions

Question 1.
What are panspermia?
According to Cosmozoic theory or Panspermia, life might have existed all over the universe in the form of resistant spores called cosmozoa or panspermia. They might have reached the earth accidentally.

Question 2.
Define prebiotic soup. Who coined this term?
The molecules of ammonia, hydrocarbons and water underwent condensation, oxidation, reduction and polymerisation due to energy sources to produce complex molecules like sugars, amino acids, fatty acids, purines, pyramidines and later nucleosides and nucleotides. All these reactions occurred in the ocean, which was described as the hot dilute soup or prebiotic soup by Haldane.

Question 3.
How did eukaryotes evolve?
Eukaryotes evolved probably by two processes, a) Prokaryotes lived in the ancestral eukaryotes symbiotically and evolved into organelles such as mitochondria and plastids. b) The endomembrane system of eukaryotes might have evolved by the infolding of plasma membrane of the ancestral prokaryotes.

Question 4.
What are the components of the mixture used by Urey & Miller in their experiments to simulate the primitive atmosphere?
The components used by Urey and Miller for their simulation experiment are water vapour, methane, ammonia and hydrogen.

Question 5.
Mention the names of any four connecting links that you have studied.
The four connecting links are :

  1. Eusthenopteron between fishes and amphibians.
  2. Seymouria between amphibians and reptiles.
  3. Archaeopteryx between reptiles and birds.
  4. Cynognathus between reptiles and mammals.

TS Inter 2nd Year Zoology Study Material Chapter 7 Organic Evolution

Question 6.
Define Biogenetic Law, giving an example. [March 2020]
Biogenetic law or Theory of recapitulation was proposed by Ernst Haeckel. It states that Ontogeny repeats phylogeny which means the developmental history of an organism repeats the evolutionary history of its ancestor, e.g. : Tad pole larva of frog resembles fish both externally and internally. It possesses a tail, gills and 2 chambered heart like that of a fish. Later is metamorphoses into adult frog.

Question 7.
Define atavism with an example. [March 2020]
Sudden appearance of some vestigial organs in a better developed condition as in the case of the tailed human baby is called atavism. .

Question 8.
Cite two examples to disprove Lamarck’s inheritance of acquired characters.

  1. Well developed muscles of athletes are not inherited to their children.
  2. Making perforations to pinna for wearing ornaments has been in practice in India for the past several centuries. However no girl child is born with ready made perforations in their pinna.

Question 9.
Who influenced Darwin much in formulating the idea of Natural Selection?

  1. Thomas Malthus (An essay on the principles of populations)
  2. Sir Charles Lyell (Principles of Geology)
  3. Alfred Russel Wallace (On the tendency of varieties to depart from original types)

Question 10.
What is common between Darwinism and Lamarckism?
Lamarckism is the first scientific assumption that recognised the “adoption to the environment as a primary product of evolution. Darwinism also says that during struggle for existence, the organisms with beneficial variations alone will survive.

Question 11.
What is meant by genetic load? Give an example.
The existence of deleterious genes within the populations is called genetic load, e.g.: Gene for sickle cell anaemia, (homozygenes individuals for sickle cell gene (Hbs Hbs) usually die early due to anaemia. Those heterozygous (HbA Hbs) can live reasonably healthy and exhibit resistance to malaria. So this disadvantageous gene is carried).

TS Inter 2nd Year Zoology Study Material Chapter 7 Organic Evolution

Question 12.
Distinguish between allopatric and sympatric speciations.

  1. If speciation takes place due to geographical isolation, it is called allopatric speciation.
  2. If speciation takes place in the organisms which live in the same habitat, capable of interbreeding, but do not interbreed due to some isolation mechanisms is called sympatric speciation.

Question 13.
Mention the scientific names of ape like and man like earlier primates. Which man like primate first used hides to cover the bodies?

  1. Ape like earlier primate – Dryopthecus Man like earlier primate – Ramapithecus
  2. Man like primate first used hides to cover their bodies is Homoneanderthalensis.

Short Answer Type Questions

Question 1.
Distinguish between homologous and analogous organs. [Mar. 18, 17; May 17 (A.P); Mar. 15 (A.P & T.S) May/June; Mar. 14]
Homologous organs :
The organs which have similar structure and origin but not necessarily the same function are called homologous organs. The evolutionary pattern that describes the occurrence of similarity in origin and internal structure is called homology. Such organs show adaptive radiation, hence ‘divergent evolution’, e.g. the appendages of vertebrates such as the flippers of whale, wings of bat, forelimbs of horse, paw of cat and hand of man, have a common pattern in arrangement of bones eventhough their external form and function may vary to suit their mode of life. It explains that all vertebrates might have had a common ancestor.

Analogous organs :
The organs which have dissimilar structure and origin but perform the same function are called analogous organs. Analogous organs suggest ‘convergent evolution’, e.g. wings of a butterfly and wings of a bird.

Question 2.
Write a short note on the theory of mutations. [Mar. ’15 (A.P.); May/June ’14]
Mutation theory :
It was proposed by Hugo de Vries, a Dutch botanist who coined the term ‘mutation’. Mutations are sudden, random inheritable changes that occur in organisms. He found four different forms in Oenothera lamarckiana (commonly called ‘evening primrose’) such as O. brevistylis-smaW style, O. levifolia-smooth leaves. O. gigas- the giant form, O. nanella- the dwarf form (mutant varieties). T.H. Morgan studied the inheritance pattern of mutations in Drosophila melanogaster. Darwin called mutations (large variations) sports of nature or saltations, whereas Bateson called them discontinuous variations.

Salient Features of Mutation theory:

  1. Mutations occur from time to time in naturally breeding populations.
  2. They are discontinuous and are not accumulated over generations.
  3. They are full-fledged, and so there are no ‘intermediate forms’.
  4. They are subjected to Natural Selection.

TS Inter 2nd Year Zoology Study Material Chapter 7 Organic Evolution

Question 3.
Explain Darwin’s theory of Natural Selection with industrial melanism as an experimental proof. [Mar. ’18, 17; May ’17 (A.P.); Mar. ’15 (T.S.) Mar. ’14)]
Experimental verification of Natural Selection – Industrial melanism :
An important practical proof for the operation of Natural Selection is the classical case of industrial melanism, exhibited by peppered moth – Biston betularia. These moths were available in two colours, grey and black. Prior to industrial revolution, the grey moths were abundant. During the industrial revolution, the black forms were more and the grey forms were less in the industrial cities like Birmingham. Biologists proposed that with the industrial revolution, more soot was released due to the burning of coal, which resulted in the darkening of the barks of trees.

Grey moths on the dark bark were easily identified and predated more by birds. Hence the number of grey moths decreased and that of the black moths increased in the population. It means Nature offered ‘positive selection’ pressure to the black (melanic) forms. Bernard Kettlewell, a British ecologist, tested this hypothesis experimentally. He collected both the grey and the black forms of Biston betularia for his experiment.

He released them in two sets of equal numbers; one set in Birmingham, a polluted urban area, and the other set in Dorset, an unpolluted rural area. After a few days he recaptured them. Of those moths recaptured from Birmingham, there were more black forms. Among those recaptured from Dorset there were more grey forms. The reason for such a difference is: the melanic forms could not be easily spotted by predator birds as their body colour merged with the dark colour of the bark of trees in Birmingham area. In the rural areas (Dorset) the grey forms had better survival chance as their body colour merged with the light coloured surroundings. This explains the differential survival of the moths due to Natural Selection. It will be interesting to know that there was a reversal in the selection process after the introduction of pollution check laws in the urban areas.

Question 4.
Discuss the role of different patterns of selections in evolution.
Selection is a process by which the organisms that are physically. Physiologically and behaviourally better adapted to the environment, survive and reproduce. Selection is an operative process. Selections are 3 types.
a) Stabilising or Centripetal selection :
It is the selective elimination of phenotypically extreme individuals from the two ends of the phenotypic distribution and preserving those that are in the mean of the phenotypic distribution.

b) Directional selection :
It operates in response to gradual changes in environmental conditions. Directional selection works by constantly removing individuals from one end of the phenotypic distribution.

c) Disruptive or Centrifugal selection :
It is a rarest form of selection and is very important in bringing about evolutionary change. As a result of increased competition, selection pressure acting within the population may push the phenotypes away from the population mean towards the ends of the population. This can split the population into two or more sub-population called species populations. Each population may give rise to a new species. It is also called as adaptive radiation.

Question 5.
Write a short note on Neo-Darwinism. [March 2020]
Modern synthetic theory of Evolution or Neo-Darwinism :
Weismann’s germplasm theory, de Vries’ mutation theory and Mendel’s laws of inheritance helped a lot in understanding the origin and inheritance of variations. The scientists such as Huxley, Haeckel, Simpson, etc., supported Darwinism. Later Fisher, Sewall Wright, Mayr explained Natural Selection in the light of post-Darwinian discoveries (Synthetic theory / Genetical theory / Neo-Darwinism). According to this theory, five basic factors are involved in the process of organic evolution. They are (i) Gene mutations, (ii) Chromosomal mutations, (iii) Genetic recombinations, (iv) Natural Selection and (v) Reproductive isolation.

i) Gene mutations :
Changes in the structure of a gene (DNA molecule).are called gene mutations or point mutations. They alter the phenotypic characters of the individuals. Thus, gene mutations tend to produce ‘variations’ in the offspring.

ii) Chromosomal mutations :
Changes in the structure of chromosomes (due to deletion, addition, duplication, inversion or translocation) are called chromosomal mutations. They also bring about variations in the phenotype of organisms which lead to the occurrence of variations in the offspring.

iii) Genetic recombinations :
Recombinations of genes due to crossing over during meiosis are also responsible for bringing about genetic variability among the individuals of the same species, thus, contributing to the occurrence of heritable variations.

iv) Natural Selection :
Natural selection does not produce any genetic changes but once genetic changes occurred, it favours some genetic changes while rejecting others. Hence it is considered the driving force of evolution.

v) Reproductive isolation :
The absence of gene exchange between populations is called the reproductive isolation. It plays a great role in giving rise to new species and preserving the species integrity.

Question 6.
In a population of 100 rabbits which is in Hardy-Weinberg equilibrium, 24 are homozygous long-eared. Short ears are recessive to Along ears. There are only two alleles for this gene. Find out the frequency of recessive allele in the population.
Number of rabbits in the population with H.W. equilibrium = 100
Number of dominant homozygous long eared rabbits = 24
Frequency of homozygous dominant long eared rabbits, p² = \(\frac{1}{100}\) × 24 = 0.24
Frequency of dominant allele, p = 0.49
Frequency of recessive allele, q = 1 – 0.49 = 0.51

TS Inter 2nd Year Zoology Study Material Chapter 7 Organic Evolution

Question 7.
What is meant by genetic drift? Explain genetic drift citing the example of Founder Effect. [March 2019]
TS Inter 2nd Year Zoology Study Material Chapter 7 Organic Evolution 1
Genetic Drift :
The change in the frequency of a gene that occurs merely by chance and not by selection, in small populations, is called genetic drift or Sewall Wright effect. Suppose, for a gene with two alleles, the frequency of a particular allele is 1% (q = 0.01), the probability of losing that allele by chance from the small population is more. The end result is either Fixation (p or q = 1) or Loss (p or q = 0) of that allele. The probability of reaching the end point depends on the size of the population. Genetic drift tends to reduce the amount of genetic variation within the population mainly by removing the alleles with low frequencies. It can be exemplified by the Founder Effect and Bottleneck Effect.

Founder effect :
If a small group of individuals from a population start a new colony in an isolated region, those individuals are called the founders of the new population. The allelic frequencies of their descendants are similar to those of the founders rather than to their ancestral parent population, e.g. presence of O+ ve blood group in nearly 100% of the Red-lndians. It means the forefathers of the Red Indian tribe were predominantly O+ ve and they isolated themselves reproductively from other populations.
TS Inter 2nd Year Zoology Study Material Chapter 7 Organic Evolution 2

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