Heredity And Evolution Long Answer Questions

Question 1. The genotype of green-stemmed tomato plants is denoted as GG and that of purple-stemmed tomato plants as gg. When these two are crossed:

1. What colour of stem would you expect in their F, progeny?
2. Give the percentage of purple-stemmed plants if F, plants are self-pollinated.
3. In what ratio would you find the genotypes GG and Gg in the F2 progeny?

Answer:

1. Green (as G denote the tes dominant gene and is expressed in all plants of F₁ generation).
2. 25% in F₂ generation raised by self-pollinated F₁ plants.
3. GG-25% Gg-50% Ththe the us, ratio s 1: 2 in F₂ progeny.

Question 2. While playing near a sugarcane field, Mohan noticed that the players were almost similar to one another. At the same time, he noticed the mango trees in the next plot of land which are not similar to one another. Mohan’s brother told Mohan that sugarcane reproduces asexually, hence there is little variation, Mango reproduces sexually, hence there is a larger variation.

Read and Learn More Class 10 Science Solutions

1. Why can sugarcane not reproduce sexually?
2. Can mango reproduce asexually?
3. If a person wants to have a flower garden, what type of plants should he grow?

Answer:

1. Because they do to bear flowers.
2. Yes, by grafting and layering.
3. Since the flower garden will be ornamental the person should plant saplings which are obtained from the same parent asexually. This will give a uniform look to his garden.

Question 3. How do Mendel’s experiments show that the:

1. Traits may be dominant or recessive.
2. Traits are inherited independently?

Answer:

1. When Mendel cross-pollinated pure tall pea plants with pure dwarf pea plants, only tall plants were obtained in the F₁ generation. On self-pollinating the F₁ progeny, both tall and dwarf plants appeared in the F₂ generation in the ratio of 3: 1. Appearance of tall character in both the F₁ and F₂ progenies shows that it is a dominant character. The absence of a dwarf character in the F₁ generation and its reappearance in F₂ shows that dwarfness is the recessive character.
2. When Mendel conducted a dihybrid cross having two sets of characters, he obtained only one set of parental characters in the F₁ generation whereas in the F₂ generation, he obtained both sets of parental characters, now recombined in the ratio of 9:3:3:1.

The appearance of new recombinants in the F₂ generation along with parental type shows that traits are inherited independently.

Question 4.

1. By carrying out experiments with two different traits in pea plants, what did Mendelndal conclude regarding inheritance?
2. Given below is the experiment carried outMendelndal to the udy inheritance of two traits, height and shape of seeds in plantslant. Write appropriate traits in the boxes marked a, b, c, d and

Answer:

1. Mendel concluded after carrying out experiments with two different traits in pea plants that traits are independently inherited, i.e., the inheritance of a pair of factors is independent of the other pair of factors.
2. 1. Dwarf, Round
   2. Tr, Tr (Tall, Wrinkled)
   3. tR, tR (Dwarf, Round)
   4. F₁ generation: TrtR (All tall and round seeds)
   5. [F₂ generation: Tall and Round (TTRR), Tall and Wrinkled (Tr Tr), Dwarf and Round (tt RR), Dwarf and Wrinkled (tt rr)]

Question 5. What are fossils? How are they formed? Describe in brief two methods of determining the age of fossils. State any one role of fossils in the study of the process of evolution.
Answer:

Fossils are preserved remains or impressions of pre-historic organisms in the different strata of the earth’s crust.

Or

Fossils are dead remains of animals and plants from the rom remote past.

Fossils are formed when dead organisms are not completely decomposed. The organisms may get trapped in the resins of the tree, lava of volcanoes or hot mud which, when hardened, retains the animals’ parts thus forming fossils. Two methods of determining the age of fossils are as follows:

1. Relative method- By estimating the age of the layer of earth’s crust where the fossil is found. Fossils near the surface are recent and those in the deeper layers are more The radiocarbon dating method detects the ratios of different isotopes of carbon in the fossils.

Fossils help in determining the connecting links between various groups and their origin from their primitive ones, e.g., Archaeopteryx.

Question 6. Give differences between:

1. Heredity and variations.
2. Dominant and recessive traits.
3. Natural and artificial selection.

Answer:

1. Heredity: It is the transmission of characters from parents to the next generation.
   1. Variations: The changes that occur in the DNA of an organism because of mutations, or by chance.
2. Dominant: The trait which expresses itself even in the presence of contrast. It appears in all the progenies in the F₁ generation.
   1. Recessive: The trait which can express itself only in condition. It does not appear in the F₁ generation.
3. Natural Selection: It is the gradual natural process by which any biological traits become either more or less common in a population, for example maple, a beetlesetle eaten up by a crow, leading to an increase in the population of grbeetlesetle.
   1. Artificial Selection: It is the artificial mechanism of selecting the breeds having desirable characteristics to bring about major changes in plants and animaFor example, different vegetables are generated from wild varieties of cabbage.

Question 7.

1. Why do we say that homozygous plants produce pure progeny?
2. Define heterozygous.
3. Explain how the process of speciation takes place.

Answer:

1. Because of the presence of the same set of genes.
2. Having different pairs of genes.
3. 1. Natural selection.
   2. Geographical isolation, Reproductive isolation.
   3. Genetic drift.
   4. Accumulated variaticausesing changes in the DNA of germ cells to an extent, such as a change in the number of chromosomes. Due to this, the germ cells of the two groups cannot be there. This results in the emergence of a new species.

Question 8.

1. What is geographical isolation?
2. Illustrate ate formation of a species with the help of an example where individuals are very different from each other and one capable of reproduction among themselves.

Answer:

1. Geographical isolation is the isolation of the population by physical barriers such as stretches of water or mountain ranges.
2. There is a population of red beetles living in a mountain area covered with green bushes. Various sub-populations in the large population exist in the neighbourhood. Individuals of a sub-population reproduce sexually among themselves and numerous variations accumulate in these sub-populations of red beetles.

There may be some reproduction among these sub-populations. If a beetle from one sub-population strays on another’s area and some individuals from one sub-population may be carried by predators to the areaanotherther sub-population, then random reproduction takes place. It may leadthe the to migration of genes from one sub-populationanotherther.

If the sub-populations are isolated due to the presenceriversiver between them:

1. Variation will accumulate in isolasub-populationstiThroughoutdgenerationstion, the sub-populations would get very different from each other due to the processes of genetic drift and natural selection and they will not be able to reproduce themselves.

Question 9. Work out which trait would be considered dominant and which one recessive in the given figure

Answer:

1. In a cross between coloured flowered and white flowered plants ts, the F1 generation has all coloured flowered plants. So, the coloured flowered trait is dominant the ver white flowered trait did not express in the F, generation but appears in the F2 generation. So, itaa the recessive trait.

Question 10. Name any five vegetables generated from a common ancestor through artificial selection rather than natural selection. , Also mention the features for which each vegetable is selected.
Answer:

Some of the vegetables generated from a common ancestor, wild cabbage, through artificial selection rather than natural selection, are:

• Cabbies’ age selected fa rom short distance between leaves.
• Broccwas oli selected from arrested flower development and thick stem. Cauliflowers were selected for sterile flowers forming a large flower.
• Kohlrwas abi was selected for a swollen edible stem.
• Kwas ale selected for large leaves.

Question 11. A tall pea plant bearing violet flowers is crossed with a short pea plant bearing white flowers. Work out the F₁ and F₂ generations. Give F₂ ratio.
Answer:

Question 12. Given below is the experiment carried out by Mendel to study the inheritance of two traits in grapes pea:

1. What does A, B, C, D, E, F and G represent in these boxes?
2. State the objective for which Mendel performed this experiment.

Answer:

1. A = gamete of round green (RY) plant

B = gamete of wrinkled (ry)

C = F₁ generational-roundound yellow)

D= 9, E = 3, F = 3, G = 1

2. To show the independent inheritance of traits or to prove the ove law of independent assortment.

Question 13. Does geographical isolation of individuals of a species lead to the formation of a new species? Provide a suitable explanation.
Answer:

Yes, geographical isolation gradually leads to genetic drift. This may impose limitations on the sexual reproduction of the separated population. Slowly the separated individuals will reproduce among themselves and generate new variations.

Continuous accumulation of those variations through a few generations may ultimately lead to the formation of a new species.

Question 14. Bacteria have a simpler body plan when compared with human beings. Does it mean that human beings are more evolved than bacteria? Provide a suitable explanation.
Answer:

This is a debatable issue. the  If appearance of complexity is concurrent with evolution, then human beings are certainly more evolved than bacteria. But if we take the totality of life characteristics into account, then it is hard to label eitorganismisms as evolved.

Question 15. All the human races like Africans, Asians, Europeans, Americans and others might have evolved from a common ancestor. Provide a piece of evidence in support of this view.
Answer:

• All humans are a single species irrespective of their race. All of them have a common body plan, structure physiology and metabolism etc. The earliest member of the species, Homo sapiens, can be traced there.
• All the above evidence could lead the the to result that Africans, Asians, Europeans, Americans and others might have evolved from a common ancestor.

Question 16. Differentiate between inherited and acquired characters. Give one example for each type.
Answer:

• Characters that are passed on from parents to offspring are inherited characters g., the colour of s and the ds, colour of eyes.
• Characters appearing in an individual’s lifetime but which cannot be transmitted to the next generation are acquired characters e.g., obese body, loss of a finger in an accident.

Question 17. Give reasons why acquired characters are not inherited.
Answer:

Acquired characters do not produce changes in the DNA of germ cells, so they cannot be inherited. Only those characters which have a gene for them can be inherited.

Question 18. Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.
Answer:

We see immense diversity in size, form, structure and morphological features in the living world. But at the molecular level, these diverse types of organisms exhibit unbelievable similarity. For instance, basic biomolecules like DNA, RNA, carbohydrates, proteins, etc., exhibit remarkable similarity in all organisms.

Question 19. In the following crosses write the characteristics of the progeny

Answer:

1. Round, yellow
2. Round, yellow Round, green Wrinkled, green Wrinkled, yellow
3. Wrinkled, green
4. Round, yellow

Question 20. In question 9, what are the combinations of characters in the F₁ progeny? What are their ratios?
Answer:

1. Round Yellow – 9
2. Wrinkled yellow – 3
3. Round Green – 3
4. Wrinkled green – 1 9:3:3:1

Question 21. How is the study of fossils considered significant?
Answer:

The fossil study is considered significant because a broad historical sequence of biological evolution can be built The phylogeny of man, horse and elephant has been worked out.

1. Habits and behaviour of extinct species can be inferred.
2. Reliable information on ancient environments and climate can be obtained.
3. Fossils provide direct evidence of past life.
4. The provides convincing proof of organic evolution.

Question 22. Suggest with reason, which of the following are homologous and which are analogous organs

1. Scalesfishshes and Shell of mollusc
2. The trunk of an elephant and the hand of a Chimpanzee
3. The wing of a bird and the wing of a bat
4. The nails of a human being and the claw of a cat
5. Ginger and sweet potato.

Answer:

1. Fish Scales and Mollshellshell are analogous structures because both are protected but differ in origin trunkrunk of the elephant the and hand of a Chimpanzee are analogous structures because both are prehensile in functioning but differ in origin (The elephant trunk is an extension of the proboscis) and the structure winging of a bat and wing of a bird are analogous structures, both are similar in functioning but differ in origin nails of hubeingseing and claw of cat are homologous structures because these are similar in origin a differ in functioning.
2. Ginger and Sweet potato are structures although these are storage structures. Because ginger is a stem modification while sweet potato is a root modification.