Biology

Two pea plants one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds produce F1 progeny that have round, yellow (RrYy) seeds. When F1 plants are selfed, the F2 progeny will have a new combination of characters. Choose the new combination from the following
(i)Round, yellow

(ii) Round, green

(iii) Wrinkled, yellow

(iv) Wrinkled, green

a)(i) and (ii)

b)(i) and (iv)

c)(ii) and (iii)

d)(i )and (iii)

Solution: The cross between the F2 progeny of the same plant is - Hence, the correct answer is (c) (ii) and (iii).

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32. In the context of conservation of natural resources, explain the terms reduce, recycle and reuse. From among the materials that we use in daily life, identify two materials for each category.

Solution – explanation of the terms with examples – Reduce – when the use of the material or substance is lowered . For eg. Electricity , petroleum Recycle – when the used material is converted into...

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27. In a village in Karnataka, people started cultivating crops all around a lake which was always filled with water. They added fertilisers to their field in order to enhance the yield. Soon they discovered that the waterbody was completely covered with green floating plants and fishes started dying in large numbers.

Analyse the situation and give reasons for excessive growth of plants and death of fish in the lake. Solution – the fertilizers used for irrigation had spread into the lake water . The chemicals...

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13. In our country, there are attempts to increase the height of several existing dams like Tehri and Almati, dams across Narmada. Choose the correct statements among the following that are a consequence of raising the height of dams

(i) Terrestrial flora and fauna of the area is destroyed completely (ii) Dislocation of people and domestic animals living in the area (iii) Valuable agricultural land may be permanently lost (iv)...

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5. The pH of water sample collected from a river was found to be acidic in the range of 3.5 – 4.5, on the banks of the river were several factories that were discharging effluents into the river. The effluents of which one of the following factories is the most likely cause for lowering the pH of river water?

(a) Soap and detergent factory (b) Lead battery manufacturing factory (c) Plastic cup manufacturing factory (d) Alcohol distillery Correct option – (  d ) Explanation – alcohol distillery is...

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Some dinosaurs had feathers although they could not fly but birds have feathers that help them to fly. In the context of evolution, this means that
a) reptiles have evolved from birds

b) there is no evolutionary connection between reptiles and birds

c) feathers are homologous structures in both the organisms

d) birds have evolved from reptiles

Solution: Dinosaurs had feathers, but they couldn't fly. The feathers were later developed for flight by birds. Dinosaurs were reptiles, which indicates that birds descended from them. So, the...

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Select the statements that describe characteristics of genes
(i) genes are a specific sequence of bases in a DNA molecule

(ii) a gene does not code for proteins

(iii) in individuals of a given species, a specific gene is located on a particular chromosome

(iv) each chromosome has only one gene

a) (i) and (ii)

b) (i) and (iii)

c) (i) and (iv)

d) (ii) and (iv)

Solution: Since genes code for specific proteins, statement ii) is incorrect. Because chromosomes can have any number of genes, Statement 4 is incorrect. Hence, the correct answer is (b) (i) and (iii)

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According to the evolutionary theory, the formation of a new species is generally due to
a)sudden creation by nature

b)accumulation of variations over several generations

c)clones formed during asexual reproduction

d)movement of individuals from one habitat to another

Solution: Several generations of DNA variation result in the formation of new species. Since there are no gametes involved in asexual reproduction, there will be no variety. Individual movement...

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Which of the following statements is not true with respect to variation?
a)All variations in a species have an equal chance of survival

b)Change in genetic composition results in variation
c)Selection of variants by environmental factors forms the basis of evolutionary processes.

d)Variation is minimum in asexual reproduction

Solution: Since only useful variation has a chance of surviving, statement a) is incorrect. To survive, nature selects the most adaptable variant. This is Darwin’s theory of Natural selection. So,...

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If the fossil of an organism is found in the deeper layers of earth, then we can predict that
a)the extinction of organism has occurred recently

b)the extinction of organism has occurred thousands of years ago

c)the fossil position in the layers of earth is not related to its time of extinction

d)time of extinction cannot be determined

Solution: Deep in the soil, older fossils can be unearthed. As a result, option b) is the correct response. So, the answer is (b) the extinction of organisms has occurred thousands of years ago.

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Select the correct statement
a)Tendril of a pea plant and phylloclade of Opuntia are homologous

b)Tendril of a pea plant and phylloclade of Opuntia are analogous

c)Wings of birds and limbs of lizards are analogous

d)Wings of birds and wings of bat are homologous

Solution: Due to similar design and origin, a pea plant's tendon and an Opuntia phylloclade are homologous. So, the correct answer is (a) Tendril of a pea plant and phylloclade of Opuntia are...

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New species may be formed if
(i)DNA undergoes significant changes in germ cells

(ii) chromosome number changes in the gamete

(iii) there is no change in the genetic material

(iv) mating does not take place

a)(i) and (ii)

b)(i) and (iii)

c)(ii), (iii) and (iv)

d)(i), (ii) and (iii)

Solution: Evolution will not occur until the genetic material changes and alters. As a result, the evolution of new species necessitates changes in genetic material and chromosome variety. So, the...

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Select the incorrect statement
a)Frequency of certain genes in a population change over several generations resulting in evolution

b)Reduction in weight of the organism due to starvation is genetically controlled

c)Low weight parents can have heavyweight progeny

d)Traits which are not inherited over generations do not cause evolution

Solution: Option b) is incorrect because weight loss and growth are influenced by external causes rather than hereditary factors. So, the correct answer is (b) Reduction in weight of the organism...

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Which of the following statement is incorrect?
i)For every hormone, there is a gene.

ii)For every protein, there is a gene.

iii)For the production of every enzyme, there is a gene.

iv)For every molecule of fat, there is a gene

Solution: Option d is incorrect since every protein, enzyme, and hormone is regulated by a specific gene, whereas fats are not controlled by a gene. So, the correct answer is (d) for every molecule...

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A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because
i)tallness is the dominant trait

ii)shortness is the dominant trait

iii)tallness is the recessive trait

iv)height of pea plant is not governed by gene β€˜T’ or β€˜t’

Solution:  Only dominant traits are expressed in the first progeny of a monohybrid cross. So, the correct answer is (a) tallness is the dominant trait.

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From the internet, gather information about the chromosome numbers of five animals and five plants. Correlate the number with the size of the organism and answer the following questions.
(a) Do larger organisms have more number of chromosomes/cells?

(b) Can organism with fewer chromosomes reproduce more easily than organisms with more number of chromosomes?

(c) More the number of chromosomes/cells greater is the DNA content. Justify.

Soln: AnimalsChromosome numbersPlantsChromosome numbersMan46Corn20Cat38Cotton52Horse64Garden pea14Rabbit44Mango40Elephant56Onion16 1. The number of chromosomes has nothing to do with the size of the...

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The correct sequence of organs in the male reproductive system for transport of sperms is
(a) testis β†’ vas deferens β†’ urethra

(b) testis β†’ ureter β†’ urethra

(c) testis β†’ urethra β†’ ureter

(d) testis β†’ vas deferens β†’ ureter

Soln: The tube that joins the testes to the urethra is known as the Vas deferens. The vas deferens is a coiled conduit that transports sperm from the epididymis to the urethra and ejaculatory duct....

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Which among the following is not the function of testes at puberty?
(i) formation of germ cells

(ii) secretion of testosterone

(iii) development of placenta

(iv) secretion of estrogen

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (iii) and (iv)

(d) (i) and (iv)

Soln: Gonads have two functions: hormone production and gamete production. Testes produce sperm and testosterone in males. The testis is a male reproductive organ but estrogen is produced in...

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Offspring formed as a result of sexual reproduction exhibit more variations because
(a) sexual reproduction is a lengthy process

(b) genetic material comes from two parents of the same species

(c) genetic material comes from two parents of different species

(d) genetic material comes from many parents

Soln: A zygote is formed when a male gamete fertilised the female gamete in case of sexual reproduction, to make new progeny. Offspring have more variants as a result of the...

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Which of the following statements are true for sexual reproduction in flowering plants?
(i) It requires two types of gametes

(ii) Fertilisation is a compulsory event

(iii) It always results in the formation of zygote

(iv) Offspring formed are clones

(a) (i) and (iv)

(b) (i), (ii) and (iv)

(c) (i), (ii) and (iii)

(d) (i), (ii) and (iv)

Soln: Sexual reproduction is a process that involves two parents and produces two types of gametes, male and female. During fertilisation, the gametes combine to produce the zygote. This is a...

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Which of the following statements are true for unisexual flowers?
(i) They possess both stamen and pistil

(ii) They possess either stamen or pistil

(iii) They exhibit cross-pollination

(iv) Unisexual flowers possessing only stamens cannot produce fruits

(a) (i) and (iv)

(b) (ii), (iii) and (iv)

(c) (iii) and (iv)

(d) (i), (iii) and (iv)

Soln: Unisexual flowers bear only male or female flowers, never both at the same time. As there is just one sex, cross-fertilization occurs, in which gametes are produced by two separate plants....

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Which of the following statements are true for flowers?
(i) Flowers are always bisexual

(ii) They are the sexual reproductive organs

(iii) They are produced in all groups of plants

(iv) After fertilisation, they give rise to fruits

(a) (i) and (iv)

(b) (ii) and (iii)

(c) (i) and (iii)

(d) (ii) and (iv)

Soln: Answer is (d) (ii) and (iv) Flowering plants, often known as Angiosperms, bear flowers as a feature. They are not produced by other plants such as Bryophytes, Pteridophytes, and...

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Length of pollen tube depends on the distance between
(a) pollen grain and the upper surface of the stigma

(b) pollen grain on the upper surface of stigma and ovule

(c) pollen grain in anther and upper surface of stigma

(d) upper surface of stigma and lower part of style

Soln: The pollen grain is placed on the flower's stigma. If the pollen grain and the stigma are compatible, the pollen grain germinates on the stigma, taking advantage of the moisture and nutrients...

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Factors responsible for the rapid spread of bread mould on slices of bread are
(i) a large number of spores

(ii) availability of moisture and nutrients in bread

(iii) presence of tubular branched hyphae

(iv) formation of round shaped sporangia

(a) (i) and (iii)

(b) (ii) and (iv)

(c) (i) and (ii)

(d) (iii) and (iv)

Soln: A large number of spores ensures that even in difficult conditions, a few spores survive. The bread's moisture and nutrients give the perfect habitat for the spore to develop into mould. So,...

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The number of chromosomes in parents and offsprings of a particular species remains constant due to
(a) doubling of chromosomes after zygote formation

(b) halving of chromosomes during gamete formation

(c) doubling of chromosomes after gamete formation

(d) halving of chromosomes after gamete formation

Soln: During the formation of gametes, the number of chromosomes in the parents is halved and when these gametes fuse with the other gamete during fertilization, they restore the normal number of...

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The correct sequence of reproductive stages seen in flowering plants is
(a) gametes, zygote, embryo, seedling

(b) zygote, gametes, embryo, seedling

(c) seedling, embryo, zygote, gametes

(d) gametes, embryo, zygote, seedling

Soln: In sexually reproducing flowers the male (pollen grains) need to meet the female gamete (ovule). So, for the fusion of the male and female gamete, the pollen grains must reach the stigma, and...

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In Spirogyra, asexual reproduction takes place by
(a) breaking up of filaments into smaller bits

(b) division of a cell into two cells

(c) division of a cell into many cells

(d) formation of young cells from older cells.

Soln: Spirogyra reproduces by the process of fragmentation which is a type of asexual reproduction. It breaks up the filaments into smaller pieces upon maturation and these pieces are known as...

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