Study Important Questions for Class 10 Science Chapter 7 – How do Organisms Reproduce

 

Study Important Questions for Class 10 Science Chapter 7 – How do Organisms Reproduce

Short Answer Question (2 Marks)

1. Define reproduction. Why is it important?

Ans: Reproduction is the process of producing new organisms of the same kind. It is important to increase the population of individuals and maintain continuity of life. Without reproduction organisms become extinct.

2. What is callus?

Ans: In artificial vegetative propagation, an isolated plant structure called ex plants is cultivated in a glass container under aseptic conditions with proper nutrient medium. The ex plants become identical masses of cells called callus.

3. What happens if the mature ovum is not fertilized in a female? Name the process.

Ans: If mature ovum is not fertilized in a female it gets released into fallopian tubes. This process is known as menstruation.

4. Give two examples each of IUD and STD.

Ans: Examples of IUCD are Copper–T and loops. Examples of STD are Syphilis and gonorrhea.

5. What do you understand by self-pollination & cross pollination? Give examples of each.

Ans: In self pollination the pollen is transferred from the stamen to the stigma in the same flower. Examples of self pollination are wheat, rice etc.

In cross pollination pollen is transferred from one flower to another. The pollen is transferred through wind, water or animals. Examples of cross pollination are plums, blackberries etc.

6 List two important functions of gonads.

Ans: Two important functions of gonads are production of gametes in male and female and production of sex hormones.

7. What is the function of the cowper's gland and prostate gland?

Ans: Function of Cowper’s glands is the secretion of a white, viscous and alkaline secretion lubricant.

Function of Prostate gland is to keep the sperm active and mobile.

8. List various reproductive parts of the flower.

Ans: Reproductive organs of flower are sepals, petals, stamens and pistils.

Stamen is the male reproductive part also known as androecium.

Pistil is the female reproductive part and made up of three parts named ovary, style and stigma. Pistils are also known as carpel and collectively known as gynoecium.

9 How does a human foetus derive nutrition?

Ans: A special disc-like structure is made between the embryo and the uterus wall called placenta. It is a link between the mother and the foetus. This disc remains embedded within the uterine wall. It has villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides an outsized area for the transfer of nutrients mother to foetus.

10 Why does menstruation occur?

Ans: When the egg is not fertilized and the uterus has not received a fertilized egg, the lining becomes thick. The thick and soft inner lining of the uterus along with the blood vessels and the dead egg comes out of the vagina in the form of blood. This cycle is known as menstruation.

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

Ans: An organism is benefited if it reproduces through spores as spores are enclosed by thick walls that protect them until they come into contact with appropriate moist surface and can begin to grow.

12 Blueprints of body design are stored in the DNA. Why?

Ans: The chromosomes present within the nucleus of a cell contain information for inheritance of features from parents to child in the form of DNA molecules. DNA is the information basis for creating proteins. Thus, blueprints of the body design are stored in the DNA.

13 What causes joining up of stock and scion in the grafting technique of vegetative propagation in plants? Define the terms stock and scion. Name one positive trait each of the plant contributing scion and stock should have.

Ans: The combining of the vascular tissues of the scion and stock causes joining of the two parts in grafting technique of vegetative propagation in plants. The plant contributing root stock should be ready to keep the plant more immune to diseases and pests that are soil borne. The plant contributing scion should be ready to produce flowers and fruits quicker than those plants which are planted through seeds. Any desirable trait which is required in the offspring is the positive trait. For Example - large number of fruit production.

14 Name the surgical methods of birth control in human males and females respectively.

Ans: Surgical methods of birth control in male are Castration and Vasectomy. In castration testes are removed from the body of a male. In vasectomy small pieces of both the vas deferens are cut and removed.

Surgical methods of birth control in females are ovariectomy, tubectomy and laparoscopy. In ovariectomy, ovaries are removed from the body. In tubectomy small pieces of both the fallopian tubes are removed and in laparoscopy fallopian tubes are blocked with the help of an instrument named laparoscope.

15 What is grafting? Why is it used in horticulture practices?

Ans: Grafting is a method in which a plant stem is attached to another rooted plant. The cutting of the stem which is grafted on the other plant is scion and the rooted plant on which the cutting is grafted is called stock. The scion and stock are placed on each other such that there is no gap between them. The cambium action takes place between them and they get merged. Grafting is used in plants such as banana, orange, rose and jasmine because they lose the capacity to produce seeds.

16 What is the importance of DNA copying in reproduction?

Ans: DNA copying in reproduction is the basic event. DNA contains information for the inheritance of features from parents to children. DNA present in the nucleus of cells is the information source for creating protein. If information is changed, altered proteins will be made that lead to different body designs.

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

Ans: Variations are useful for the existence of species in different environment conditions. If a population of reproducing organisms were suited to a specific niche and if the niche is drastically altered the population might be exhausted. However, some differences are present and some species will survive. Thus, variation is beneficial to species but not for the individual.

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

Ans: A special disc-like structure is made between the embryo and the uterus wall called placenta. It is a link between the mother and the foetus. The embryo gets nutrition from the mother’s body with the help of placenta. This disc remains embedded within the uterine wall and has villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides an outsized area for glucose and oxygen to transfer the mother to the embryo and waste products from embryo to mother.

Long Answer Questions (5 Marks)

1. Describe triple fusion in plants? Where does it occur? Draw a neat and clean well labeled diagram to support your answer.

Ans: After pollination, the pollen grains germinate within the stigma by producing plant parts. This plant part is made from the inner wall of the pollen grain. It penetrates the stigma and passes through the design and enters the ovule through a gap called male gamete it releases two male gametes within the embryo sac. One male gamete fuses with egg cells and second fuses with two polar nuclei. The fusion of 1 male gamete with the egg cells is named syngamy. The fusion of the second male gamete with two polar nuclei is called triple fusion. This process occurs in the ovary.

What are the different methods of contraception?

Ans: Different methods of contraception are barrier method, chemical method and surgical method.

• Barrier method – In this method, a device used to stop the entry of sperms in the female genital tract. Condom, Diaphragm, Cervical caps and Copper-T are used in this method.

• Chemical method – In this method certain drugs (containing hormones) are used by the females. These drugs are available in the form of pills. There are two types of pills generally used for preventing pregnancies i.e oral pills and vaginal pills or creams.

• Surgical method – In this method small part of vas deferens in male is cut and removed. It is known as vasectomy. In females the oviduct of the female is removed, it is known as tubectomy.

How are spores produced in sporangia of Rhizopus?

Ans: Spores are thread-like structures that developed above the hyphae of the bread mould (Rhizopus). The tiny blob-on-a-stick structures known as sporangia contain cells, or spores, that can eventually develop into new Rhizopus individuals. In each sporangium, a nucleus divides a number of times generating a large number of nuclei.

Nuclei surrounded by a little cytoplasm are covered by thick walls that protect them until they come into contact with another moist surface and can begin to grow. The wall of sporangium breaks to release the spores in air.

What are the advantages of vegetative propagation?

Ans: Advantages of vegetative propagation are as follows:

• It is a speedy, inexpensive and easy method of reproduction of multiple numbers of plants.

• Plants produced are genetically identical plants (clones) that have similar characteristics to the parent.

• Plants rose by vegetative propagation earlier produce fruits and flowers and have superior quality fruits or flowers.

• Disease free plants can be produced by vegetative propagation.

Very Short Answer Questions (1 Mark)

1. In vegetative reproduction, the new individuals are genetically –

1. Similar

2. Dissimilar

3. Abnormal

4. None of these

Ans: a) Similar

2. When an organism breaks into a number of parts and each part develop into an individual, it is called –

1. Budding

2. Binary fission

3. Regeneration

4. Spore formation

Ans: c) Regeneration

3. In Female, fertilization of ovum takes place in

1. Vagina

2. Ovary

3. Uterus

4. Fallopian tubes

Ans: d) Fallopian tubes

4. Define parthenogenesis.

Ans: Parthenogenesis is the process of development of an organism from an unfertilized egg.

5. How many male gametes are produced by pollen grains?

Ans: Two gametes are produced by pollen grains.

6. During grafting, the portion of plant that is grafted is called –

1. Stock

2. Scion

3. Stalk

4. Stem

Ans: b) Scion

7. Which part of the flower forms the fruit?

1. Whole flower

2. Only stamens and carpel

3. Only ovary

4. Only carpel

Ans: c) Only ovary

8. Anemophily is the pollination by –

1. Birds

2. Rain

3. Insects

4. Wind

Ans: d) Wind

9. What is syngamy?

Ans: Fusion of male gamete with the egg cell is called syngamy.

10. Name the structure through which pollen tubes enter the ovule.

Ans: Pollen tubes enter the ovule through stigma.

11. A common feature of reproduction in Amoeba, spirogyra and yeast is that –

1. Asexual reproduction occurs after sexual reproduction

2. Asexual reproduction occurs before sexual reproduction

3. Asexual reproduction does not involve gametes

4. Asexual reproduction involves only one parent

Ans: d) Asexual reproduction involves only one parent.

12. The normal duration of menstrual cycle is

1. 7 – 8 days

2. 13 – 15 days

3. 3 – 4 days

4. 28 days

Ans: d) 28 days

13. Which of the following is an IUCD?

1. Copper – T

2. Diaphragm

3. Oral pills

4. Tubectomy

Ans: a) Copper – T

14. What is parturition?

Ans: Parturition is the process of birth of a fully developed fetus in completion of gestation.

15. What is puberty?

Ans: Puberty is the process of physical changes when the reproductive system is functionally active or starts producing ova or sperm.

16. Fertilization in plants occurs in the –

1. Embryo sac

2. Style

3. Pollen tube

4. Stigma

Ans: a) Embryo sac

17. Characters that are transmitted from parents to offspring during reproduction show

1. Only similarities with parents

2. Only variations with parents

3. Neither similarities nor variations

4. Both similarities and variations with parents

Ans: d) Both similarities and variations with parents

18. Which among the following diseases is not sexually transmitted?

1. Syphilis

2. Gonorrhea

3. HIV – AIDS

4. Hepatitis

Ans: d) Hepatitis

19. What is tubectomy?

Ans: Tubectomy is the permanent method of contraception in women by removal of a section of fallopian tube.

20. Name the causative organism of AIDS?

Ans: The causative organism of AIDS is HIV – Human Immunodeficiency virus.