Q. Asexual reproduction takes place through budding in:

(a) Amoeba

(b) Yeast

(c) Plasmodium

(d) Leishmania

Ans. (b) Yeast

 Explanation :

Both asexual and sexual reproduction are possible for yeast. Budding is the process through which yeast multiply asexually.

Q. In human males, the testes lie in the scrotum, because it helps in the:

(a) process of mating

(b) formation of sperm

(c) Chloroplast

(d) all of the above

Ans. (b) formation of sperm

 Explanation :

Formation of germ cells or sperms takes place in the testes and it lies in the scrotum. In the scrotum (outside the abdominal cavity), the temperature is about 3°C lower than the temperature of the body. Testes lie in scrotum because the sperm formation requires a lower temperature than the normal body temperature.

Q. Which among the following is not function of testes at puberty?

(i) Formation of germ cells

(i) Formation of germ cells

(iii) Development of placenta

(iv) Secretion of estrogen

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (iii) and (iv)

(d) (i) and (iv)

Ans. (c) (iii) and (iv)

 Explanation :

Development of placenta and secretion of estrogen are related to female reproductive system, hence are not the function of testes at puberty.

Q. The correct sequence of organs in the male reproductive system for transport of sperms is

  • (a) testis → vas deferens → urethra
  • (b) testis → ureter → urethra
  • (c) testis → urethra → ureter
  • (d) testis → vas deferens → ureter

Ans. (a) testis → vas deferens → urethra

 Explanation :

Sperms formed in testis are delivered through the vas deferens which joins with another tube called urethra coming from the urinary bladder.

Q.During adolescence several changes occur in the human body. Mark one change associated with sexual maturity in boys.

  • (a) Loss of milk teeth
  • (b) Increase in height
  • (c) Weight gain
  • (d) Cracking of voice

Ans. (d) Cracking of voice

 Explanation :

Cracking of voice is associated with sexual maturity in boys which occurs during adolescence. Loss of milk teeth, height gain, and weight gain are all part of the natural growing process for both boys and girls as they become older.

Q. 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

Ans. (c) Vas deferens

 Explanation :

The ovaries, fallopian tubes, uterus, vagina, and external genitals make up the female reproductive system. Vas deferens is a male reproductive organ that connects the epididymis to the urethra and transports sperm from the testis to the urethra.

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

  • Ans. Vegetative propagation is practiced for growing some types of plants because:
  • 1. The plants which cannot produce seeds or produce non-viable seeds also can be easily propagated by this method.
  • 2. It is a ver y easy, quick and cheapest method of propagation.
  • 3. Seedless plants can be produced by vegetative propagation.
  • 4. Flowers and fruits are produced in very short time.
  • 5. Parental features are preserved.

Q. Why does menstruation occur in human females?

Ans. Menstruation occurs in human females when egg is not fertilised. Every month the ovary releases an egg and uterus prepares itself to receive the embryo. The wall of uterus gets thickened and they are richly supplied with blood which provides nutrition to the growing embryo from mother. If egg is not fertilised then there is no need of rich supply of blood and thick lining of uterine wall and egg also disintegrates thus egg along with blood and mucus comes out through vagina in the form of menstrual flow.

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

Ans. Due to recombination and crossing over in meiosis process during formation of gametes as well as during sexual reproduction the mixing up of male with female gametes produce some variations in the offsprings. These variations are necessary for survival of a particular species to the changing environment. If there would be no variations then there will be less chance of a particular species to get adapted to the changed environment and with course of time that particular species may extinct. Variations also lead to evolution of the species. Thus it is said that variation is beneficial to the species but not necessary for the individual.

Q. How are the methods of reproduction different in unicellular and multicellular organisms?

Ans. An unicellular organism has a single cell so there is no specific organ system for reproduction. They divide by the process of cell division. The different modes of reproduction in unicellular organism are binary fission, multiple fission, budding etc. But in multicellular organism there are specific tissues and organ system to carry out this process. There is formation of male and female gametes. It is a very complex process and normally takes more time as compared to unicellular organisms.

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

Ans. DNA copying is necessary as parents transmit their characters to offsprings through DNA. Due to this, the offsprings resemble in some of the features with their parents. But DNA copying also produces some variations in the offsprings that helps them to adapt to the changing environment.

Q. How does reproduction helps in providing stability to population of species?

  • Ans. There is a natural cycle of born and death, through reproduction the lost species can be replenished. Stability of a particular species is maintained by equalising birth and death ratios which is possible through reproduction. It ensures the survival of a particular species which might extinct if there is no reproduction process.

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

  • Ans. Complex organisms have highly and well developed tissue and organ system to perform a particular function. There is division of labour in the body of complex organisms. Their body is highly complicated and the tissue and organ system are highly differentiated and are made up of different kinds of cells. So, it is very difficult for complex organisms to give rise to new individuals through regeneration, which is seen in simple organisms like Hydra, Planaria etc.

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

  • Ans. An organism can be benefited if it reproduces through spores by following ways:
  • 1. Spores are covered with thick walls which protect them from adverse environmental conditions like drought, high temperature etc. So, they can survive even in these adverse conditions.
  • 2. They are ver y light, small and can be easily dispersed through wind, water, animals and on getting favourable conditions they germinate and give rise to new individuals.
  • 3. This mode of reproduction is simple and faster.
  • 4. Large number of spores are produced at one time within a sporangium.

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

  • Ans. Seminal vesicles and prostate glands are accessory reproductive organs. The secretion from seminal vesicles provides nourishment and motility to the sperms. Prostate glands secretion neutralises the acidic pH of vagina so that sperms can easily pass through vagina.

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

  • Ans.The embryo gets nourishment inside the mother’s body through a disc shaped structure called placenta. It connects embryo with mother’s blood. It supplies nutrients, oxygen to the growing embryo and removes carbon dioxide, wastes from embryo. Through this structure the blood of embryo comes in close contact with mother’s blood and by diffusion process exchange of nutrients occurs. The placenta is formed by interlocking of two sets of villi, which provide maximum surface area for absorption of nutrients and oxygen gas.

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

  • Ans.Changes seen in girls during puberty are:
  • 1. Appearance of thick hair in genital parts and under arm pits.
  • 2. Enlargement of breasts.
  • 3. Darkening of skin surrounding the nipples.
  • 4. Start of menstrual cycle.
  • 5. Oily skin and pimples.

Q. What are different methods of contraception?

Ans. The methods or devices used to prevent fertilisation and implantation are referred to as contraceptive methods. Some of the methods are:
  • 1. Barrier methods: Use of condoms in male and diaphragms in female prevents the entry of sperms into uterus.
  • 2. Chemical methods: Use of various hormonal pills prevents the release of egg from ovary. They cause a change in menstrual cycle thus delaying ovulation.
  • 3. IUCDs: Use of IUCDs devices like copper-T which is fitted inside uterus that prevents implantation of embryo into the wall of uterus.
  • 4. Surgical methods: Tubectomy is done in female where a small portion of oviducts are removed and ligated to prevent the entry of egg from ovaries. Vasectomy is done in males where a small portion of vas deferens is cut and ligated preventing passage of sperms.
  • 5. Natural methods: To avoid copulation around the time of ovulation.

Q. What could be the reasons for adopting contraceptive method?

Ans. The reasons for adopting contraceptive method are:

  • 1. Preventing unwanted pregnancies to control population growth.
  • 2. It protects from Sexually Transmitted Diseases like AIDS, Syphillis etc.
  • 3. Proper health of mother and child can be maintained by preventing frequent pregnancies.
  • 4. Sufficient gap between the offsprings, which ensures the proper health of the mother and child.

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

276

Q. How does binary fission differ from multiple fission?

Ans.
Binary fission Multiple fission
A single parent cell divides into two daughter cells. It results in production of many daughter cells.