NCERT Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce?

Topic 8.1 Do organisms create exact copies of themselves:

Q. 1. What is the importance of DNA copying in reproduction?

Answer:

Importance of DNA copying in reproduction-

1. It keeps the characteristics of the parent species
2. the characteristics and features are transferred to their progeny
3. It produces variation in an organism which is the basis of the evolution of new species

Q. 2. Why is variation beneficial to the species but not necessarily for the individual?

Answer:

Variations are beneficial for the survival of the species. Populations of organisms fill well-defined places in the ecosystem, using their ability to reproduce. However, these places can change because of reasons beyond the control of the organisms and could even wipe out the entire population. However, if some variations were to be present in a few individuals in these populations, there would be some chance for them to survive.

For example - If there were a population of bacteria living in temperate waters and suppose the water temperature was to be increased by global warming. Most of these bacteria would die, but the few heat resistant variants would survive and grow further. Variation is thus useful for the survival of species over time.

How do Organisms Reproduce Class 10 Topic 8.2 Modes of Reproduction Used by Single Organisms:

Q. 1. How does binary fission differ from multiple fission?

Answer:

Difference between binary fission and multiple fission-

Q. 2. How will an organism be benefited if it reproduces through spores?

Answer:

An organism is benefited if it reproduces through spores because spores are surrounded by a thick layer and due to this they can be protected in adverse conditions. In favourable condition, these spores continue to grow again.

In this way, they can manage to survive in unfavourable condition.

Q. 3. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Answer:

Simple organisms like Hydra and Planaria can produce a new individual through the process of regeneration. However, In a complex multicellular organism have an organ-system level of organisation. Each organ systems of their body work together as an interconnected unit.

They have a high degree of organisation in their body. So, they cant be reproduced from their cut body parts by the regeneration process.

Q. 4. Why is vegetative propagation practised for growing some types of plants?

Answer:

Vegetative propagation- This method is used for growing certain types of plant which usually does not give any seed or produce non-viable seeds.

It is also used for plants growing which bears the superior traits because they produce genetically identical plants.

Q. 5. Why is DNA copying an essential part of the process of reproduction?

Answer:

DNA copying is an essential part of the process of reproduction so that the characteristics of the parent species are transmitted to it's down the line (offspring) and at the same time some variation also produced in the offspring.

This changes in the DNA provides an organism with the capability to survive in the changing condition.

NCERT solutions class 10 science chapter 8 how do organisms reproduce topic 8.3 Sexual reproduction:

Q. 1. How is the process of pollination different from fertilisation?

Answer:

Difference between pollination and the fertilization-

Pollination is the transfer of pollen grains from another stamen to the stigma of a capel. It takes place by certain pollinating agents such as air, water, birds and some insects etc.

On the other hand, fertilisation occurs when the male and female gametes fuse. It occurs inside the ovule and leads to the zygote formation.

Q. 2. What is the role of the seminal vesicles and the prostate gland?

Answer:

The role of the seminal vesicles and the prostate gland-

(i) Both secrets fluids which forms a part of the semen. The fluid of seminal vesical form 60% of the semen and the rest are from the prostate glands. It makes the path smooth through which sperm travels.

(ii) This fluid protects the sperm from the acid present in the urethra

(iii). Also, they can provide nutrition to the sperm in the form of calcium, fructose and some enzymes.

Q. 3. What are the changes seen in girls at the time of puberty?

Answer:

At the age of puberty, The following changes occur in girls-

1. Mammary glands develop and enlarge.
2. Hair grows under armpits and pubic region.
3. Fallopian tube, uterus and vagina enlarge
4. Menstruation starts
5. Ovaries start to release eggs.

Q. 4. How does the embryo get nourishment inside the mother’s body?

Answer:

Inside the mother's body embryo gets nourishment from the mother's blood. There is a structure called placenta, it contains villi.

This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.

Q. 5. If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?

Answer:

No, Copper-T is a contraceptive method which prevents the formation of zygote inside the uterus.

It cannot prevent a woman from Sexually Transmitted Diseases.