NCERT Solutions for Class 10 Science Chapter 8 Heredity

CBSE Class 10 Science Chapter 8 Exercise Questions

So, basically in this section, we will see the NCERT In Text Questions. In-text questions are one of the most important parts of understanding the topics. Students must go through this One of the concepts of heredity

Topic 8.1, Page Number 129

Q. 1. If trait A exists in 10% of a population of an asexually reproducing species and trait B exists in 60% of the same population, which trait is likely to have arisen earlier?

Answer:

Trait B is more likely to have arisen earlier because it has a higher percentage of the population and in asexual reproduction, traits are carried over to the next generation with minimal changes in the traits.

For example, all the sugarcanes in the field that reproduce asexually, have almost similar characteristics, however, the animals and humans which reproduce sexually, have more chances of traits in the next generation.

Q. 2. How does the creation of variations in a species promote survival?

Answer:

Variation in our characteristics occurs due to sexual reproduction and inaccurate copying of DNA. The varied characteristics that fit for survival pass on to the next generation more easily and the characteristics that are not favourable for survival will vanish after some generation.

Favourable variations help a species to adapt to changes in its environment and they promote the survival of a species.

Class 10 Heredity Solutions: Topic 8.2 Solutions, Page Number 133

Q. 1. How do Mendel’s experiments show that traits may be dominant or recessive?

Answer:

Mendel conducted many experiments by crossing the Tall plants and Short plants. he found that the trait Tall which appears in the first generation also appeared in the second generation with 75 % in number. and the trait short appeared in the second generation by 25% in number. Hence he concluded that trait Tall is Dominant and the trait Short is recessive.

in other words:

Tall + Tall = Tall

Tall + Short = Tall

Short + Tall = Tall

Short + Short = Short

As we can see there are 3 out of 4 Tall in the Next Generation. Hence it is a dominant trait.

Hence by this experiment, he showed that traits can be Dominant or Recessive.

Q. 2. How do Mendel’s experiments show that traits are inherited independently?

Answer:

In Mandel's one of the experiments, he crossed the Pure breeding Tall plants having round seed with Short plants having wrinkled seed. here he found some of the new traits like Tall plants having wrinkled seeds and Short plants having round seeds.

Tall and Round + Short and Wrinkled = Tall and Round + Tall and Wrinkled +Short and Wrinkled + Short and Round

( Previous Trait) (New Trait) (Previous Trait ) (New Trait)

Those new traits would not have been there if traits were inherently dependent.

Hence he concluded that traits are inherited independently

Q. 3. A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?

Answer:

No, This information is not sufficient to conclude any trait is dominant or recessive. this is because we don't know the blood group of all offspring.

The given blood group A can be AA or AO, so we can't really draw any conclusion from it.

Q. 4. How is the sex of the child determined in human beings?

Answer:

Half the male gametes have X-chromosomes and the other half have Y-chromosomes human male has one X-chromosome and one Y-chromosome. In other words, The human male has one X chromosome and one Y chromosome On the other hand, all-female gametes have only X chromosomes. If a sperm carrying a Y-chromosome fertilizes an ovum then the child born will be a boy.

On the other hand, if a sperm carrying X-chromosomes fertilizes an ovum then the child born will be a girl.

X + X = Girl

X + Y = Boy.

Q. 1. A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic makeup of the tall parent can be depicted as

(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw

Answer:

As half the progenies are short, this implies that the parent plant also will have a collection of short genes. Also since all progenies bore violet flowers, the violet color is dominant over white.

Hence TtWW might be the correct answer.

Q. 2. An example of homologous organs is

(a) our arm and a dog’s fore-leg.
(b) our teeth and an elephant’s tusks.
(c) potato and runners of grass.
(d) all of the above.

Answer:

Homologous organs have the same origin but different functions. all the given options have the same origin and hence correct option is d.

Q. 3. In evolutionary terms, we have more in common with

(a) a Chinese school-boy.
(b) a chimpanzee.
(c) a spider.
(d) a bacterium.

Answer:

We are human beings like a Chinese boy. Thus, option (a) is correct.

Both human and Chinese boy are of the same ancestry and belongs to Homo Sapiens.

Q. 4. A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?

Answer:

For considering a trait as dominant or recessive, we need the information of a minimum of 3 generations.

If the grandparent, parent and the children. all have light-coloured eyes, then we can conclude that light-eye colour is a dominant trait.

Class 10 Science Ch 8 Question Answer:

Q. 5. How are the areas of study – evolution and classification – interlinked?

Answer:

Classification involves grouping organisms into a formal system based on similarities and differences. Two species are more closely related if they have more characteristics in common and if two species are closely related then it means they have a more recent common ancestor.

We classify organisms according to their characteristics which is similar to the things we analyze in evaluation. Hence both areas of study are interlinked.

Q. 6. Explain the terms analogous and homologous organs with examples.

Answer:

Analogous organs: Those organs which have different basic structures but have a similar appearance and perform similar functions are called analogous organs. Example - wings of bird and insect.

Homologous organs: Those organs which have the same basic structure but different functions are called homologous organs. Example: forelimb of humans and forelimb of lizard.

Q. 7. Outline a project which aims to find the dominant coat colour in dogs.

Answer:

(i) Select two varieties of dogs one with white coat color, the other with black coat color.

(ii) Crossbreed them taking a male dog from one variety and bitch (female dog) from the other variety.

(iii) Observe the colour of the offspring of the F1 generation.

(iv) Now, bring about breeding among the organisms of the F1 generation.

(v) Observe the coat colour of organisms (pups) of F2 generation and note the variations in coat colour.

(vi) Draw conclusions based on your study.

One of the probable inheritance patterns may be as given below.

Phenotypic ratio = 3: 1,

Black coat colour (3): White coat colour (1)

Q. 8. Explain the importance of fossils in deciding evolutionary relationships.

Answer:

Fossils provide us with evidence about many things:

1) The organisms that lived long ago in the past.

2) Connecting links between two groups. for example, the feather in some dinosaurs means that birds are very closely related to reptiles.

3)The development of any particular species by evaluation.

4) The period of the organisms.

5) Simple to complex body design journey.

Q. 9. What evidence do we have for the origin of life from inanimate matter?

Answer:

The evidence for the origin of life from inanimate matter was provided through an experiment, conducted in 1953, by Stanley L. Miller and Harold C. Urey.

In the experiment, they assembled an atmosphere containing molecules like ammonia, methane and hydrogen sulfide, but no oxygen, over water. This was similar to the atmosphere that was thought to exist on the early earth. This was maintained at a temperature just below 100°C and sparks were passed through the mixture of gases to simulate lightning.

At the end of a week, 15% of the carbon from methane, had been converted to simple compounds of carbon including amino acids which make up protein molecules and support life in the basic form.

Thus, this experiment suggests that life on Earth arose fresh.

Q. 10. Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?

Answer:

Sexual reproduction causes more viable variations due to the following reasons:

1)Error in the copying of DNA, which is not highly significant.

2) Random segregation of paternal and maternal chromosomes at the time of gamete formation.

3)Exchange of genetic material between homologous chromosomes during the formation of gametes.

4) Accumulation of variations occurred due to sexual reproduction over generation after generation and selection by nature created wide diversity.

In the case of asexual reproduction, only very small changes due to inaccuracies in DNA copying pass on to the progeny. Thus, offspring of asexual reproduction are more or less genetically similar to their parents. So, it can be concluded that evolution in sexually reproducing organisms proceeds at a faster pace than in asexually reproducing organisms.

Q. 11. How is the equal genetic contribution of male and female parents ensured in the progeny?

Answer:

The inheritance of equal parent chromosomes ensures equal genetic contribution within the relative of male and female folk. There are 23 pairs of chromosomes. There is no pairing of all human chromosomes. The primary twenty-two trials are called autosomes out of those twenty-three pairs, and the remaining one pair is also thought to be sex chromosomes drawn as X and Y. Females have an ideal trial of 2 X sex chromosomes and males have an inappropriate trial of I X and I Y chromosome.
During the replication process, the male germ cell (haploid) fuses with the feminine gamete (haploid) resulting in the formation of the diploid fertilized ovum as the fertilization method takes place. Within the relative, the fertilized ovum receives the associated degree of equal contribution from the oldsters of genetic material. Of the comparatively twenty-three pairs of chromosomes, the parent contributes twenty-two autosomes and one X or sex chromosome, whereas the feminine parent contributes twenty-two autosomes and one chromosome.

Q. 12. Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?

Answer:

It is not always true. The variations that confer an advantage to an individual organism are definitely of more survival value because natural selection prefers these variations. But there are several other variations which, though do not provide an advantage to the organism in if present condition, survive and are inherited by the next generations. Such non-advantageous variations may become advantageous in future when the environmental conditions change.

For example, at this stage of evolution, The art, and music skills that we acquire don't give us any survival benefit but are still called a good quality trait or variation.