Heredity and Evolution | Chapter Assessment | English | Grade 10

In an organism that is produced by sexual method of reproduction a character is influenced by:

• Maternal DNA

• Paternal DNA

• Both option 1 and option 2

• Neither option 1 nor option 2

Answer explanation

In a sexual reproduction, two organisms take part in reproduction and the genes of both partners are transferred equally in to the offspring. So in a organism that is produced by sexual method of reproduction a character is influenced by both maternal DNA and paternal DNA. Hence option 3 is the right answer.

Which of the following affects the process of speciation?

• Natural selection

• Genetic drift

• Geographical isolation

• All of these

Answer explanation

Natural selection, genetic drift and geographical isolation are the factors that affect speciation and lead to evolution. Hence option 4 is the right answer.

Which of the following statement is correct with respect to fossil dating?

• Time of fossil is determined on the basis of ratio of different isotopes of single element present in the fossil

• Time of fossil is determined on the basis of ratio of different elements present in the fossil

• Time of fossil is determined on the basis of ratio of carbon and oxygen present in the fossil

• Time of fossil is determined on the basis of ratio of carbon and nitrogen present in the fossil

Answer explanation

In the process of carbon dating the time of fossil is determined on the basis of ratio of different isotopes of single element present in the fossil.

The bones in forelimb of whale, cheetah, bat and man have the same structure because:

• They have the common ancestor

• One organism has given rise to another organism

• They perform the same function

• Both option 1 and option 3

Answer explanation

The bones in forelimb of whale, cheetah, bat and man have the same structure. These are homologous structures i.e. same basic structure but different purpose. This shows that they have a common ancestor. Hence option 1 is the right answer.

Some dinosaurs had feathers but they cannot fly but birds have feathers and they can fly. What does this imply?

• Birds have evolved from dinosaurs

• Dinosaurs have evolved from bird

• Feathers are homologous structure in both the organisms

• Feathers are analogous structure in both the organisms

Answer explanation

Some dinosaurs had feathers but they cannot fly but birds have feathers and they can fly. This means that birds have evolved from dinosaurs.

Which of the following statement is not correct?

• Frequency of genes in a population change over several generations and lead to evolution

• Heavy weight parents can have low weight offspring

• Organs that are similar in appearance and functions but different in basic structure and origin are analogous organs.

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

Answer explanation

Reduction in weight of organism because of starvation is not controlled genetically. Weight loss or weight depends on the internal factors e.g. any disease, as well as external factors .e.g. one can reduce weight through exercise. Hence statement in option 4 is not correct.

Which of the following are necessary for evolution by natural selection to take place?

• Population tend to grow faster than their food supplies

• Differences among individuals exist and lead to different numbers of successful offspring being produced

• Every individual should reproduce

• All of these

Answer explanation

For evolution of different species differences in the organism are important. By the process of natural selection useful differences/variations are selected and the non-useful differences/variations are deleted. The remaining population with useful differences/variations transmit their character to the offspring. So in evolution by natural selection: differences among individuals exist and lead to different numbers of successful offspring being produced.

In humans right handedness (R) is dominant over left handedness (r). What could be the genotype of parent if their child is left handed?

• Rr x RR

• RR x rr

• Rr x Rr

• None of these

Answer explanation

It is given that right handedness (R) is dominant over left handedness (r). Here both parents are right handed. Right handedness is dominant trait. So parents may have both dominant alleles 'RR' or one dominant and one recessive allele 'rr'. The left handedness is recessive trait and it will be expressed only when both alleles are of same type that is 'rr'. The child is left handed so its genotype is 'rr'. It means that child has received one 'r' from father and one 'r' from mother. Hence both parents should have 'r' gene in their genotype. So the probable genotype of both parents is 'Rr and 'Rr'. That is both parent are dihybrid. Hence option 3 is the right answer.

A dihybrid of garden pea plant having genotype 'RrYy' is crossed with homozygous recessive garden pea plant having genotype 'rryy'. What is the phenotypic ratio?

• 1 : 2 : 1

• 1 : 1 : 1 : 1

• 3 : 1

• 9 : 3 : 3 : 1

Answer explanation

The phenotypic ratio predicted for this cross is 1:1:1:1 as each of the four combinations of the two traits have equal chances of manifesting

Haemophilia and colour blindness both are X-linked diseases. A woman has one gene of haemophilia on one X chromosome and one gene of colour blindness on other X chromosome. The woman marries a man without any disorder. How will be the progeny?

• 50% heamophiliac daughters and 50% colour blind daughters

• 50% colour blind heamophiliac sons and 50% normal sons

• All daughters will be heamophiliac

• All daughter will be heamophiliac and all sons will be colour blind

Answer explanation

Haemophilia and colour blindness both are X-linked diseases. We know that human females have two X chromosomes and human male has one X chromosome and one Y chromosome. A women having gene of heamophilia on one X chromosome and gene of colour blindness on other X chromosome will have genotype: XhXc This women has married to the normal man. So the cross will be like this: Hence in the progeny 50% heamophiliac daughters and 50% colour blind daughters. Similarly there will be 50% heamophiliac sons and 50% colour blind sons. Hence option 1 is the right answer.