CBSE Class 10 Biology How do Organisms Reproduce MCQs Set 14

Answer: (b) Scion

Explanation:
1. The scion forms the shoot system that bears flowers and fruits.
2. So the fruit quality is of the scion's genotype.

Teacher's Note:
1. The stock provides roots and water.
2. Grafting is used to get good fruit varieties like mango.

Answer: (a) Axillary buds

Explanation:
1. A potato is a stem tuber and its eyes are the axillary buds in the axils of scale leaves.
2. Each eye can sprout into a new plant.

Teacher's Note:
1. This is vegetative propagation.
2. Potato pieces with eyes are planted.

Answer: (b) 3 + 2 + 3

Explanation:
1. The embryo sac has three antipodal cells at one end, two polar nuclei in the centre and three cells of the egg apparatus at the micropylar end.
2. This is the 3 + 2 + 3 arrangement.

Teacher's Note:
1. The egg apparatus has one egg and two synergids.
2. The embryo sac has seven cells and eight nuclei.

Answer: (c) The male gametophyte

Explanation:
1. A pollen grain is the male gametophyte formed from a microspore.
2. It produces the male gametes.

Teacher's Note:
1. The microspore mother cell divides to form pollen grains.
2. The pollen tube carries the male gametes.

Answer: (a) A male gamete fuses with a female gamete

Explanation:
1. Syngamy is the fusion of a male and a female gamete to form the zygote.
2. It is also called fertilisation.

Teacher's Note:
1. The pollen tube usually enters through the micropyle.
2. The zygote develops into the embryo.

Answer: (c) Antipodal, zygote, endosperm

Explanation:
1. Antipodal cells are haploid (n), the zygote is diploid (2n), and the endosperm is triploid (3n).
2. So option (c) is correct.

Teacher's Note:
1. Nucellus is diploid tissue of the ovule.
2. Primary endosperm nucleus arises from three nuclei.

Answer: (c) Autogamy

Explanation:
1. Transfer of pollen to the stigma of the same flower is self-pollination, or autogamy.
2. Geitonogamy is between flowers of the same plant.

Teacher's Note:
1. Allogamy is pollination between different plants.
2. Autogamy needs no pollinator.

Answer: (a) Proteins

Explanation:
1. The aleurone layer is the outer layer of the endosperm and is rich in proteins.
2. The rest of the endosperm stores starch.

Teacher's Note:
1. Aleurone also makes enzymes during germination.
2. It lies just below the seed coat.

Answer: (a) An embryo is formed without the fusion of the egg and the sperm

Explanation:
1. In parthenogenesis the egg develops into an embryo without fertilisation.
2. It is seen in honeybees (drones) and some lizards.

Teacher's Note:
1. 'Parthenos' means virgin.
2. It is a form of asexual reproduction.

Answer: (b) 3

Explanation:
1. Two polar nuclei and one male gamete nucleus fuse.
2. So three nuclei form the endosperm nucleus.

Teacher's Note:
1. This is called triple fusion.
2. The endosperm is triploid.

Answer: (a) Anemophily

Explanation:
1. Anemophily is wind pollination.
2. Hydrophily is by water, and entomophily by insects.

Teacher's Note:
1. Wind-pollinated flowers produce light pollen in large amounts.
2. Grasses are wind-pollinated.

Answer: (a) Leydig cells

Explanation:
1. Leydig (interstitial) cells of the testis secrete testosterone.
2. Sertoli cells nourish developing sperms.

Teacher's Note:
1. Testosterone is under the control of LH.
2. It causes male secondary sexual characters.

Answer: (c) Semen is without sperms

Explanation:
1. The vas deferens carries sperms from the epididymis to the urethra.
2. If cut, sperms cannot reach the semen, although they are still made.

Teacher's Note:
1. This is the vasectomy method of contraception.
2. The hormones remain normal.

Answer: (c) Epididymis, vas deferens, urethra, vas deferens

Explanation:
1. Sperms are stored in the epididymis, then pass through the vas deferens to the ejaculatory duct and the urethra.
2. In vasectomy the vas deferens is cut and tied.

Teacher's Note:
1. The urethra carries both semen and urine.
2. Sperms are made in the seminiferous tubules.

Answer: (a) LH

Explanation:
1. A sudden surge of luteinising hormone (LH) triggers the release of the egg.
2. FSH grows the follicle.

Teacher's Note:
1. Oestrogen rise starts the LH surge.
2. Progesterone maintains the uterine lining.

Answer: (c) Day 14

Explanation:
1. Ovulation takes place around the middle of the cycle, on day 14.
2. Menstruation occurs from day 1 to about day 5.

Teacher's Note:
1. The corpus luteum forms after ovulation.
2. The fertile period is around ovulation.

Answer: (b) 400

Explanation:
1. A woman releases one egg per month for about 35 to 40 years.
2. This is about 400 eggs.

Teacher's Note:
1. Millions of follicles are present at birth, but most degenerate.
2. Menopause ends ovulation.

Answer: (c) Fall in progesterone level

Explanation:
1. When the corpus luteum degenerates, progesterone falls.
2. The uterine lining can no longer be maintained and is shed.

Teacher's Note:
1. Menstruation lasts 3 to 5 days.
2. It happens if the egg is not fertilised.

Answer: (c) Menopause

Explanation:
1. Menopause is the permanent end of menstruation and ovulation.
2. Menarche is the first menstruation.

Teacher's Note:
1. It occurs around 45 to 50 years.
2. Oestrogen level falls at this time.

Answer: (b) (i), (ii), (iii) and (iv) are true

Explanation:
1. All four statements are correct.
2. The embryo gets food and oxygen from the mother through the placenta.

Teacher's Note:
1. After about eight weeks the embryo is called a foetus.
2. The placenta also removes wastes.

Answer: (b) Fallopian tube

Explanation:
1. The sperm meets the egg in the upper part of the fallopian tube (oviduct).
2. The zygote then moves to the uterus for implantation.

Teacher's Note:
1. Implantation occurs in the uterus.
2. Fertilisation in the human is internal.

Answer: (a) Copper-T

Explanation:
1. An intra-uterine contraceptive device is placed inside the uterus; Copper-T is one.
2. The diaphragm is a barrier method and oral pills are hormonal.

Teacher's Note:
1. Copper ions released are toxic to sperms.
2. It must be fitted by a doctor.

Answer: (b) Ovulation

Explanation:
1. The pills contain hormones that stop the release of eggs.
2. Without an egg, fertilisation cannot take place.

Teacher's Note:
1. They are taken in a regular course.
2. They do not protect against infections.

Answer: (b) To inhibit fertilisation

Explanation:
1. The copper ions in the device immobilise sperms and so prevent fertilisation.
2. It also makes the uterus unsuitable for implantation.

Teacher's Note:
1. It does not stop ovulation.
2. It can stay in place for years.

Answer: (a) Tubectomy

Explanation:
1. Tubectomy is the surgical method for women in which the fallopian tubes are cut and tied.
2. It blocks the path of the egg and the sperm.

Teacher's Note:
1. Vasectomy is the male method.
2. These are permanent methods.

Answer: (a) To inhibit ovulation

Explanation:
1. The hormones in pills keep the level high so that the pituitary does not release FSH and LH.
2. This inhibits ovulation.

Teacher's Note:
1. They may also thicken cervical mucus.
2. Sexual behaviour is not affected.