9. Heredity and Evolution Class 10 science Solutions English Medium-Text-book Questions

Text-book Questions

Page no. 143

Q1. If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?

Ans: The trait which was presented in previous generation will remain same under asexual reproduction, but there shall be some differences. Similarly, the trait which exists in more percentage, it must be presented in before. So trait B which exists in 60 % probably it likely to have arisen earlier.  

Q2. How does the creation of variations in a species promote survival?

Ans: The species receive variation from their parents, while some variations are special in them, however which makes them special in nature. Different individuals in a species due to these differences may get advantages. Their survival will be fixed by nature to have accordingly variations. 

Page no. 147

Q1. How do Mendel’s experiments show that traits may be dominant or recessive?

Ans: According to Mendal's experiments, He selected two traits of pea which was tall pea plants and other was short pea plants as parents plants. In F₁ generation all plants were tall, but in second generation called F₂ three forth of pea plants were tall and one third were short. Both TT and Tt plants were tall while tt plants were only short, this experiments show that both traits were inherited but T trait for tallness was dominant and t trait for shortness was recessive. 

Q2. How do Mendel’s experiments show that traits are inherited
independently?

Ans: In Mendal's experiments show that all plants were tall in F₁ generation. No one was short, while parents were taken both tall and short plants of traits. Surprisingly, There were one third plants were short. This shows that traits are inherited independently.

Q3. 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?

Ans: Blood group O is dominant. The trait which appears is dominant in two trait blood group A and O. 

Q4. How is the sex of the child determined in human beings?

Ans: Sex chromosomes determines the sex in human being, in which there is only one pair sex chromosomes in human being. The males have XY chromosomes and the females have XX chromosomes. All children get X chromosome from their mother. So that is clear mother is no responsible for boy or girl. But Only Y chromosome of father determines sex of baby that will be boy or girl. A child who inherits an X chromosome from her father will be a girl, and one who inherits a Y chromosome from him will be a boy.

Page no. 150

Q1. What are the different ways in which individuals with a particular trait may increase in a population?

Ans: 

(i) Using sexual reproduction which provide large numbers of variation. 

(ii) However changing in colour prevent species like beetals. 

(iii) Small species may be victims, so there is great possibility to survive a large species. 

Q2. Why are traits acquired during the life-time of an individual not inherited?

Ans: Dominant traits transfer from one generation to other generation by DNA. An individual do not use sexual reproduction. So This has no special reproductive cells to reproduce. Hence, the trait transfer to DNA through reproductive cells. So there is no chance to inherit aquired trait over generation. Therefore the experiences of an individual during its lifetime cannot
be passed on to its progeny.  

Q3. Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?

Ans: Any individual evolutes when this produces changes. Changes bring variations and variations are responsible for their survival. But tiger have no made so much changes in their species. This causes small number of tigers a cause of worry from the point of view of genetics. 

Page no. 151 

Q1. What factors could lead to the rise of a new species?

Ans: (i) Genetic drift and natural selection affect the variations and they become too much differ.  

(ii) Changing in Chromosomes causes the germ cells of the two groups cannot fuse with each other.. 

(iii) Changing in DNA . 

Q2. Will geographical isolation be a major factor in the speciation of a selfpollinating plant species? Why or why not?

Ans: Physical features are affected by geographical separation. And variation among them may be another reason for species emergence, but the main reason is their change during DNA replication. In self-pollinated species, there is very little chance of new changes or variations occurring in new generations.

Q3. Will geographical isolation be a major factor in the speciation of an
organism that reproduces asexually? Why or why not? 

Ans: Organisms produced in asexual reproduction are almost identical to each other and there is very little difference between them. Variations in this process occur only during DNA replication and these variations are very rare. Geographical separation can be a major factor in the emergence of species because due to this, the organisms that survive in the new environment generate new ones inside themselves.

Page no. 156

Q1. Give an example of characteristics being used to determine how close
two species are in evolutionary terms.

Ans: Examples of Evolutionary Relationship Determination of Two Species:- Like birds, reptiles and water-land animals, mammals also have four legs. Even if their infrastructure has been transformed to perform different tasks on one. In this way, we can understand these relations only by homologous features.

Q2. Can the wing of a butterfly and the wing of a bat be considered
homologous organs? Why or why not?

Ans: No, they are called homologous parts not social. The structure of the wings of a butterfly and a bat is different. They are not the same in origin and die.

Butterfly wings do not have ears while bats have them.

Q3. What are fossils? What do they tell us about the process of evolution?

Ans: Remains of dead animals, marks on rocks or molds and body impressions of those who were alive thousands of years ago. Such preserved remains are called fossils. These fossils tell us many things about the process of bio-evolution such as which fossils are new and which are old, which species have become extinct. These fossil evolutions can also determine the characteristics of various forms and classes that sometimes describe them.

Page no. 158 

Q1. Why are human beings who look so different from each other in terms
of size, colour and looks said to belong to the same species?

Ans: All humans are members of the same species. For example, DNA with excavation, scheduling and fossil studies. Determination of sequence gives knowledge of different stages of human being. Human ancestors originated from Africa. The ancestors from Africa spread to different regions and some remained there. Thus virtual species have no biological basis.

Q2. In evolutionary terms, can we say which among bacteria, spiders, fish
and chimpanzees have a ‘better’ body design? Why or why not?

Ans: The ancestors of both humans and chimpanzees were the same. Chimpanzee can perform its activities like humans. But due to the excessive complexity, there are also flaws in the physical design from the point of view of development, but still bacteria are better than spiders and fish.Answer: The ancestors of both humans and chimpanzees were the same. Chimpanzee can perform its activities like humans. But due to the excessive complexity, there are also flaws in the physical design from the point of view of development, but still bacteria are better than spiders and fish.