CBSE Class 10 Science Reproduction Assignment Set 03

This second Class 10 Science assignment on Reproduction (chapter How Do Organisms Reproduce) has 23 questions arranged by marks, each with a step-by-step answer, a simple-words summary and a teacher's note. It covers sexual reproduction in flowering plants (pollination, fertilisation, seed and fruit formation) and the human male and female reproductive systems, with labelled diagrams of a flower and of pollen germination.

Very Short Answer Questions (1 Mark)

Question 1. If a woman is using copper-T, will it help in protecting her from sexually transmitted diseases?
Answer:
No. Copper-T only prevents implantation of the embryo in the uterus. It does not stop the contact and exchange of body fluids that spreads an STD, whereas a condom does.
In simple words: Copper-T prevents pregnancy but does not protect against STDs.

Teacher's Note:
1. Name the method that does protect: condom.
2. Copper-T is an IUCD.

Question 2. What are those organisms called which bear both the sex organs in the same individual? Give one example of such organisms.
Answer:
Such organisms are called hermaphrodites (bisexual organisms). An example is the earthworm (or leech).
In simple words: Hermaphrodites carry both male and female organs in one body.

Teacher's Note:
1. Name the term and one example.
2. Do not confuse with unisexual animals.

Question 3. List two functions of ovary of human female reproductive system.
Answer:
1. The ovary produces the eggs (ova), the female gametes.
2. It secretes the female sex hormones, oestrogen and progesterone.
In simple words: The ovary makes eggs and female hormones.

Teacher's Note:
1. Write one point on gametes and one on hormones.
2. Name the two hormones.

Question 4. List two unisexual flowers.
Answer:
Papaya and watermelon (also cucumber) bear unisexual flowers, each flower having either stamens or carpels.
In simple words: Papaya and watermelon have unisexual flowers.

Teacher's Note:
1. Hibiscus and mustard are bisexual, not unisexual.
2. Learn at least two examples.

Question 5. List two functions performed by testis in human beings.
Answer:
1. The testes produce the sperms (male gametes).
2. They secrete the male sex hormone, testosterone, which regulates sperm formation and brings about the changes seen in boys at puberty.
In simple words: The testes make sperms and the hormone testosterone.

Teacher's Note:
1. One point on gametes and one on hormone.
2. Testosterone causes secondary sexual characters.

Question 6. Differentiate between pollen grain and ovule.
Answer:
1. Pollen grain: produced in the anther; it contains the male gamete (male germ cell).
2. Ovule: present in the ovary of the carpel; it contains the female gamete (egg cell) and becomes the seed after fertilisation.
In simple words: Pollen carries the male cell; the ovule holds the egg.

Teacher's Note:
1. Mention where each is found.
2. Ovule becomes seed, ovary becomes fruit.

Question 7. Differentiate between germination and fertilisation.
Answer:
1. Germination: the development of the embryo in a seed into a seedling under suitable conditions.
2. Fertilisation: the fusion of the male gamete with the female gamete to form a zygote.
In simple words: Fertilisation makes the zygote; germination turns the seed into a seedling.

Teacher's Note:
1. Fertilisation comes first, germination later.
2. Give one line for each term.

Question 8. Why does the lining of uterus become thick and spongy during every month?
Answer:
Every month the ovary releases an egg and the uterus prepares for a possible pregnancy. Under the action of hormones the lining becomes thick, spongy and richly supplied with blood so that it can nourish an embryo if the egg is fertilised.
In simple words: The lining thickens each month to be ready to nourish an embryo.

Teacher's Note:
1. Link the thickening to a possible embryo.
2. If no fertilisation, the lining is shed as menstruation.

Question 9. Why is fertilisation not possible without pollination in plants?
Answer:
Pollination carries the pollen grains, which contain the male gametes, to the stigma. Without pollination the male gamete cannot reach the female gamete in the ovule, so fertilisation cannot take place.
In simple words: No pollen on the stigma means no male gamete reaches the egg.

Teacher's Note:
1. Pollination always comes before fertilisation.
2. Use the words pollen tube and male gamete.

Short Answer Questions I (2 Marks)

Question 10. How is the process of pollination different from fertilisation?
Answer:
1. Pollination is the transfer of pollen grains from the anther to the stigma. It takes place only in plants.
2. Fertilisation is the fusion of the male gamete with the female gamete to form a zygote. It takes place in all sexually reproducing organisms.
In simple words: Pollination moves pollen to the stigma; fertilisation joins the two gametes.

Teacher's Note:
1. One line each, starting with the definition.
2. Pollination comes before fertilisation.

Question 11. What is the role of the seminal vesicles and the prostate gland?
Answer:
1. Their secretions are added to the sperms along the path of the vas deferens, so the sperms are now in a fluid (semen), which makes their transport easier.
2. The fluid also provides nutrition to the sperms (the seminal vesicle secretion contains fructose), and the prostate secretion is alkaline.
In simple words: These glands give the sperms a fluid medium and food.

Teacher's Note:
1. Mention fluid medium and nutrition.
2. These are called accessory glands.

Question 12. List two preparations shown every month by the uterus in anticipation of pregnancy in the humans.
Answer:
1. The inner lining of the uterus becomes thick.
2. More blood vessels develop in the lining, to supply nourishment to a growing embryo.
In simple words: The uterus thickens its lining and increases its blood supply every month.

Teacher's Note:
1. Write both points.
2. If there is no pregnancy, the lining breaks down.

Question 13. Trace the path of sperms from where they are produced in human body to the exterior.
Answer:
Sperms are produced in the testes. They pass through the vas deferens, which joins the urethra coming from the urinary bladder. The urethra runs through the penis and opens to the outside. On the way the seminal vesicles and the prostate gland add their secretions.
In simple words: Testes, then vas deferens, then urethra, then out through the penis.

Teacher's Note:
1. Write the path in order, with arrows if you like.
2. Mention the glands that add secretions.

Question 14. What is the main difference between sperms and eggs of humans? Write the importance of this difference.
Answer:
1. Sperms are small and motile and carry either an X or a Y chromosome. Eggs are large, non-motile, store food and carry only an X chromosome.
2. Because the sperms are motile, they can swim to the egg for fertilisation. The X or Y chromosome of the sperm decides the sex of the child.
In simple words: Sperms are small swimmers; the egg is large and stationary.

Teacher's Note:
1. Mention motility and chromosomes.
2. Say what each difference does.

Question 15. The chromosomal number of the sexually producing parents and their offspring is the same. Justify this statement.
Answer:
1. In sexual reproduction the male and female gametes are formed by meiosis (reduction division), so each gamete contains half the number of chromosomes of the parent.
2. When the two gametes fuse at fertilisation, the original number of chromosomes is restored in the zygote, so the offspring has the same number as the parents (for example 23 + 23 = 46 in humans).
In simple words: Gametes carry half the chromosomes; fertilisation brings the full number back.

Teacher's Note:
1. Mention meiosis and fusion.
2. Use the human example of 23 and 46.

Short Answer Questions II (3 Marks)

Question 16. Differentiate between self pollination and cross pollination.
Answer:
1. Self-pollination: pollen is transferred from the anther to the stigma of the same flower (or another flower of the same plant). Cross-pollination: pollen is transferred to the stigma of a flower on a different plant of the same species.
2. Self-pollination occurs between genetically similar flowers; cross-pollination occurs between genetically different flowers.
3. Self-pollination gives little variation; cross-pollination brings more variation. Cross-pollination needs agents such as wind, water or animals.
In simple words: Self-pollination stays on one plant; cross-pollination goes between plants.

Teacher's Note:
1. Write at least three points.
2. Name the agents of cross-pollination.

Question 17. Mention the changes observed in flower after fertilisation.
Answer:
1. The zygote divides several times to form an embryo within the ovule.
2. The ovule develops a tough coat and is gradually converted into a seed.
3. The ovary grows rapidly and ripens to form a fruit.
4. The petals, sepals, stamens, style and stigma wither and fall off.
In simple words: After fertilisation the ovule becomes the seed and the ovary becomes the fruit.

Teacher's Note:
1. Write the changes in order.
2. Zygote becomes embryo inside the seed.

Question 18. How do sperms reach the female genital tract? Where do fertilisation and implantation of the embryo take place? For how long does the embryo remain attached to the uterine walls?
Answer:
1. The sperms are deposited in the vagina during copulation. They travel upwards through the cervix and uterus to the oviduct.
2. Fertilisation takes place in the oviduct (fallopian tube), giving a single-celled zygote. The zygote divides to form an embryo, which is implanted in the lining of the uterus.
3. The embryo stays attached to the uterine wall throughout the gestation period, which is about 40 weeks (nine months), until birth.
In simple words: Sperms swim up to the oviduct; the embryo settles in the uterus for about nine months.

Teacher's Note:
1. Name the site of fertilisation and of implantation.
2. Remember about 40 weeks for the gestation period.

Long Answer Questions (5 Marks)

Question 19. Explain what happens when: (a) Testosterone is released in males. (b) Pollen grains falls on the stigma of flowers. (c) Egg fuses with sperm cell. (d) Planaria is cut into many pieces. (e) Buds are formed on notches of the Bryophyllum leaf.
Answer:
(a) Sperm formation is stimulated and the changes of puberty appear in boys, such as thick hair on the face, pubic region and change in voice.
(b) A tube grows out of the pollen grain, travels through the style to the ovary and carries the male gamete to the female gamete.
(c) A zygote is formed, which is fertilisation.
(d) Each piece grows into a new Planaria (regeneration).
(e) The buds fall on the soil and grow into new plants (vegetative propagation).
In simple words: Each event leads to a result: puberty changes, pollen tube, zygote, new Planaria and new Bryophyllum plants.

Teacher's Note:
1. Answer each part in one or two lines.
2. Use the correct term for each process.

Question 20. (a) Draw a diagram showing germination of pollen on stigma of a flower and mark on it the following organs/parts: (i) Pollen grain (ii) Pollen tube (iii) Stigma (iv) Female germ cell. (b) State the significance of pollen tube. (c) Name the parts of flower that develop after fertilisation into (i) Seed (ii) Fruit.
Answer:
(a) See the labelled diagram below.

(b) The pollen tube grows from the pollen grain through the style and carries the male gamete (male germ cell) to the ovule, where it fuses with the female gamete for fertilisation.
(c) (i) The ovule develops into the seed. (ii) The ovary develops into the fruit.
In simple words: The pollen tube is a path that takes the male cell from the stigma to the egg.

Teacher's Note:
1. Label pollen grain, stigma, pollen tube, male germ cell, ovary and female germ cell.
2. Ovule becomes seed, ovary becomes fruit.

Question 21. (a) Draw a diagram of the longitudinal section of a flower and label on it sepal, petal, ovary and stigma. (b) Write the names of male and female reproductive parts of a flower.
Answer:
(a) See the labelled diagram below.

(b) The male reproductive part is the stamen (anther and filament), and the female reproductive part is the carpel (pistil), made of stigma, style and ovary.
In simple words: A flower has stamens (male) and a carpel (female) at the centre.

Teacher's Note:
1. Label sepal, petal, stigma, style, ovary, anther and filament.
2. Stamen is male and carpel is female.

Case Based Questions (4 Marks)

Question 22. The male reproductive system consists of portions which produce the germ-cells and other portions that deliver the germ-cells to the site of fertilisation. Testes are located outside the abdominal cavity in scrotum because sperm formation requires a lower temperature than normal body temperature. It also has a role of secretion of male sex hormone which brings changes in appearance seen in boys at the time of puberty. Vas deferens unites with a tube coming from urinary bladder. Urethra is a common passage for sperms and urine. Prostate gland and seminal vesicles add their secretions so that sperms are now in fluid. (i) Name the sex hormone associated with males. (a) Testosterone (b) Progesterone (c) Oestrogen (d) None of these. (ii) Which of the following statements is incorrect? (a) Sperms are present in a fluid (b) Fluid provides nutrition to sperms (c) Fluid makes easier transportation of sperms (d) Fluid helps to bind the sperms together. (iii) Testes are located outside the abdominal cavity in scrotum because (a) sperms formation requires higher temperature than body temperature (b) sperms formation requires lower temperature than body temperature (c) it is easier to transport sperms from the scrotum (d) None of these. (iv) Which of the following statements is incorrect? (a) Sperms and urine have a common passage from urethra. (b) Sperms have long tail that helps them to move forward. (c) Sperms contain genetic material. (d) Sperm formation requires 1-3 °C higher temperature than normal body temperature. (v) What is the nature of semen? (a) slightly acidic (b) neutral (c) slightly basic (d) strongly basic.
Answer:
(i) (a) Testosterone is the male sex hormone.
(ii) (d) "Fluid helps to bind the sperms together" is the incorrect statement. The fluid gives a medium, makes transport easier and provides nutrition.
(iii) (b) Sperm formation requires a lower temperature than the body temperature.
(iv) (d) "Sperm formation requires 1 to 3 °C higher temperature" is incorrect; it needs a lower temperature.
(v) (c) Semen is slightly basic (alkaline).
In simple words: The male reproductive system makes and carries sperms in a fluid medium, and the testes need a cooler place.

Teacher's Note:
1. Read the passage once, then underline the key words.
2. Remember the testes need lower than body temperature.

Question 23. Salman soaked a few seeds of Bengal gram (chana) and kept them overnight. Next morning, he drained the excess water and covered the seeds with a wet cloth. He then left the seeds for a day. After one day, he opened the seeds into two parts and carefully observed the different parts. (i) Which part of the flower develops into seed? (ii) Where does the energy required for germination of seeds come from? (iii) Which part of the seed emerges out the first? (iv) Define germination. (v) What are the necessary conditions for seed germination?
Answer:
(i) The ovule present in the ovary develops into the seed.
(ii) The cotyledons store food, which supplies the energy for germination.
(iii) The radicle (the future root) emerges first.
(iv) Germination is the process by which the embryo in a seed develops into a seedling under suitable conditions.
(v) Water, oxygen (air) and a suitable temperature.
In simple words: A seed germinates with water, air and warmth, using food stored in its cotyledons.

Teacher's Note:
1. The radicle comes out before the plumule.
2. Learn the three conditions of germination.