Long answer -Class 10 -Science-Biology-Chapter 7: How Do Organisms Reproduce

Class 10 -Science- Long Short answer  -Biology-Chapter 7: How Do Organisms Reproduce

Q1. Give reasons why a woman should avoid frequent pregnancies. Explain the following methods of contraception giving one example of each.

(i) Barrier method

(ii) Chemical method

Ans:

Pregnancy is a very complex process. It includes a the very long period of around 9-10 months. A woman has to suffer a lot of hormonal changes during this period and also her inner body needs recovery after one pregnancy because it has undergone a lot of wear and tear during fetal development and mostly during labor.

According to doctors, there should be a gap of 3 years between subsequent pregnancies. In order to prevent unwanted pregnancy, Contraceptives should be used.

i) Barrier method includes preventing the entry of sperms inside the vagina, so that it cannot fertilize the egg. This includes the use of condoms which are available for both males and females. cervical caps, IUD’S are some examples of barrier method.

ii) Chemical methods involve using chemicals in order to either kill the sperms or making the surroundings inhospitable for them. These mostly contain acids or some salts such as lactic acid, or potassium permanganate. E.g. – Tablets (unwanted 72), jellies, creams and pastes.

Q2. Answer the following:

a. How is zygote formed?

b. State the function of placenta in the mother’s body.

c. At what interval the egg is formed in human female ovary?

d. Name two STDs caused by bacterial infection.

e. Why is prenatal sex determination prohibited?

Ans : a. Zygote is formed by the fusion of male and female gamete.

b. Placenta is a special tissue through which the developing embryo/foetus gets nutrition from mother’s blood. It also transports wastes of the embryo into mother’s blood. c. Ovulation releases mature ovum from ‘ the ovary. It happens once during a menstrual cycle that is for roughly 28 days. d. STDs caused by bacterial infection are Gonorrhoea and Syphilis. e. Prenatal sex determination is misused and it may be the reason for female foeticide.

 Q3. Explain what happens when: a. Testosterone is released in males.

 b. Pollen grain falls on the stigma of the flower.

 c. Egg fuses with sperm cell.

 d. Planaria is cut into many pieces.

e. Buds are formed on the notches of the Bryophyllum leaf.

Ans : 

a. (i) Formation of sperms, change in appearance.

(ii) Thick hair growth on the face and voice begin to crack.

b. A tube grows out of the pollen grain and travel through the style to reach the ovary.

c. Zygote is formed (fertilization).

d. Each piece grows into a complete organism.

e. Buds may fall on the soil and develop into new plants.

Q4. Define the following processes:

a. Fertilization

b. Menstruation 

c. Binary fission

d. Vegetative propagation  

e. Regeneration

Ans : a. The fusion of male gamete with female gamete is known as fertilization.

b. Menstruation cycle takes place every month when egg is not fertilized. It lasts for about two to eight days and during this cycle the lining of uterus slowly breaks and comes out through the vagina as blood and mucus.

c. Binary fission is the splitting of nucleus into two daughter cells which can take place in any plane. It can be observed in Amoeba.

d. When vegetative part of a plant like the root, stem or leaves develops into new plant under appropriate conditions, it is known as vegetative propagation.

e. When body of an organism cuts into any number of pieces and each piece grows into a complete