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NCERT Solutions Class 10 Science Chapter 8 how do organisms reproduce? - topmarksapp.com

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How do Organisms Reproduce?

NCERT Solution

NCERT Exercise

1. Asexual reproduction takes place through budding in

(a) Amoeba

(b) Yeast

(c) Plasmodium

(d) Leishmania

(b) Yeast

2. Which of the following is not a part of the female reproductive system in human beings?

(a) Ovary

(b) Uterus

(c) Vas deferens

(d) Fallopian tube

(c) Vas deferens

3. The anther contains

(a) Sepals

(b) Ovules

(c) Pistil

(d) Pollen grains

(d) Pollen grains

4. What are the advantages of sexual reproduction over asexual reproduction?

  • Because of lower number of offspring there is a better. chance of survival.
  • The offspring has the characters of both the parents.
  • Adaption to environmental changes is easy for the offspring.
  • It also improves the health of humans.

5. What are the functions performed by the testis in human beings?

The functions performed by the testis in human beings are:

  • The production of sperm cells.

  • Production of the male sex hormone, testosterone.

  • Production of male hormone known as androgens.

6. Why does menstruation occurs?

Menstruation is the process in which blood and mucous flows out through vagina. This process happens every month. Every month an egg is released from one of the ovaries. During this time, uterus prepares itself for fertilized egg. Some changes occurs at this point of time like the inner lining of the uterus gets thickened. Now the inner lining is supplied with sufficient amount of blood for the embryo. But the fertilization of egg doesn’t takes place because there is no interaction between the egg and the sperms. So when the egg doesn’t get fertilized, the uterine membrane ruptures. Through which bleeding starts along with mucous from vagina. 

7. Draw a labelled diagram of the longitudinal section of a flower.

8. What are the different methods of contraception?

Methods used to prevent the pregnancy in women  is contraception. 

Different methods of contraception are:

  • Barrier method: In this method fertilization of ovum and sperm are prevented by using barriers like condoms, diaphragms, cervical cap and contraceptive sponge.
  • Oral Contraceptives: Oral and vaginal pills are used to prevent the release of eggs. This pills consist of small dose of hormones that prevent the release of eggs. 
  • Surgical methods: Sperm transfer can be blocked through vasectomy  and tubectomy. Placing contraceptive devices like loop or Copper T in uterus prevents pregnancy.
  • Natural methods: By avoiding the sextual contact from day 10th to 17th of menstruation cycle.  

9. How are the modes for reproduction different in unicellular and multicellular organisms?

10. How does reproduction help in providing stability to populations of species?

Reproduction helps in providing stability to the population of species. It is possible by producing new individuals of the same species from existing organisms. Reproduction also maintains the continuity of species. Stability is maintained by keep a check of rate of births and rate of deaths.

11. What could be the reason for adopting contraceptive methods?

Following are the reasons for adopting contraceptive methods:

  • To control population
  • To avoid unplanned pregnancy
  • To avoid transfer of sexually transmitted diseases.

Intext Exercise

Pg. No. 128

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

DNA is the genetic material found in chromosomes, present in nucleus of cells. It is responsible for carrying information for the next generation. It also helps in producing organisms of its type. Copying of DNA is the basic event of reproduction. DNA copying is important to inheriting the traits of the parents. Any variations in DNA copying will give rise to origin of new species.

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

The reason why the variation is beneficial to the species than individuals is because sometimes the climatic changes have a drastic effect on the species, which makes their survival difficult. For examples, if the temperature of the water body increases, then there might be certain species of microorganisms which might die. This may result in disturbance in the environment. So, variation is beneficial to species and not for the individuals.

Pg. No. 133

1. How does binary fission differ from multiple fission?

Binary fission is the process in which when a single cell is divided into two equal halves. Examples are bacteria and amoeba.

Multiple fission is the process in which a single cell divides into multiple daughter cells at the same time. Ex:  algae and sporozoans. 

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

  • Reproduction is through spores which is simple and fast. 
  • Number of spores produced in one sporangium would be large.
  • The protective layer around the spores help them to overcome the unfavorable environmental condition.
  • Spores are carried by wind to faraway places.

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

Regeneration is the process in which formation of new organisms from it’s body part happens. In complex organisms all these organ systems are interconnected and work in full coordination. They can regenerate a few of their lost body parts like skin, blood, muscles, etc. but they are not able to give rise to new individuals through regeneration. Regeneration is possible for  simple organisms that have simple  body designs like planaria, hydra etc.

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

  • It is a simple and less time consuming process to grow a plant. 
  • Plants parts can be used for the purpose of reproduction.
  • Those plants lost it ability for the sexual reproduction( through seeds) can be reproduced through this method.
  • A good quantity of plants can be maintained. 

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

DNA carries genetic information. It is necessary to for the offspring to get similar DNA’s as in parents to produce its own kind. It through the process of DNA Replication offspring get similar DNA’s as in parents.

Pg. No. 140

1. How is the process of pollination different from fertilization?

During pollination transfer of pollen grains from anther to stigma takes place. This process requires various pollinators like air, water and some insects. If pollination is successful then it results in fertilization. 

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

Seminal vesicles prostate gland produce secretions that provides lubrication for sperms and helps in easy transportation of sperms. Seminal vesicles and the prostate gland provides nutrients in the form of fructose, calcium and some enzymes.

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

  • Hair growth in genital area, underarms, face, hands and legs.
  • The size of the breast increases and skin around breast darkens.
  • Beginning of menstrual cycle.
  • The size of uterus and ovary increases.

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

Placenta which is a special tissue embedded in the uterine wall. It helps the embryo get oxygen and glucose from mother’s tissue.

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

Contact of body fluids is not stopped by using Copper- T. So women cannot protect her from sexually transmitted diseases by using Copper- T.