CBSE Class 10 Science How do Organisms Reproduce MCQs Set 14

Answer: (b) it keeps the body design of the species similar across generations. Copying DNA passes the blueprint for body design to the next generation.

Teacher's Note:
1. Copying is never perfectly accurate, which gives rise to small variations.
2. These variations help species survive changes in the environment.

Answer: (a) binary fission. Amoeba divides into two daughter cells after the nucleus divides; this is binary fission.

Teacher's Note:
1. Plasmodium divides into many daughter cells, which is multiple fission.
2. Amoeba splits in any plane, unlike Leishmania.

Answer: (b) it has a whip-like structure at one end. The flagellum at one end gives the cell a definite orientation for division.

Teacher's Note:
1. Amoeba, with no fixed shape, can divide in any plane.
2. Leishmania cannot.

Answer: (b) fragmentation. The filament breaks into pieces and each piece grows into a new filament.

Teacher's Note:
1. Fragmentation works only for simple organisms with undifferentiated cells.
2. Complex animals cannot do this.

Answer: (b) budding. A bud grows out as a small outgrowth, develops into a tiny Hydra and then detaches.

Teacher's Note:
1. Buds contain cells from regenerative regions.
2. Yeast also reproduces by budding.

Answer: (b) sporangia containing spores. Rhizopus reproduces by spores formed inside sporangia on upright hyphae.

Teacher's Note:
1. Spores have thick walls that protect them in harsh conditions.
2. They germinate when they find moisture and food.

Answer: (a) regeneration. Specialised cells divide and form all needed cell types to rebuild a whole organism.

Teacher's Note:
1. Regeneration is not the same as reproduction in most organisms.
2. Planaria is the standard example.

Answer: (a) leaf notches. Buds in the notches of the leaf margin fall on the soil and grow into new plants.

Teacher's Note:
1. This is vegetative propagation.
2. It is used for growing plants without seeds.

Answer: (b) Rose. Rose is propagated using stem cuttings (and grafting).

Teacher's Note:
1. Banana, sugarcane and jasmine are other examples.
2. Plants raised this way are genetically identical to the parent.

Answer: (b) the plants bear flowers and fruits earlier. Vegetative propagation raises plants that flower and fruit earlier than those grown from seeds, and keeps parental traits.

Teacher's Note:
1. It is useful for plants like banana and orange that rarely produce viable seeds.
2. The offspring are clones.

Answer: (b) grow new plants from a few cells in a nutrient medium. A small piece of tissue is grown in a sterile nutrient medium to form a callus and then whole plants.

Teacher's Note:
1. It is commonly used for ornamental plants.
2. It gives many identical plants quickly.

Answer: (b) Stamen. The stamen has an anther that produces pollen grains.

Teacher's Note:
1. The carpel is the female part with stigma, style and ovary.
2. A flower with both is bisexual.

Answer: (b) pollination. Pollination is the transfer of pollen to the stigma, by wind, water or animals.

Teacher's Note:
1. Fertilisation happens later, when male and female gametes fuse.
2. Pollination only brings them close.

Answer: (b) fruit. The ovary ripens into the fruit and the ovules become seeds.

Teacher's Note:
1. The zygote becomes the embryo within the seed.
2. The other floral parts usually wither.

Answer: (b) germination. Germination is the development of a seedling from the embryo under suitable conditions.

Teacher's Note:
1. Water, air and warmth are needed.
2. The seed stores food in the cotyledons.

Answer: (a) from stigma through the style to the ovule. The pollen tube carries male gametes through the style to the ovule.

Teacher's Note:
1. Fertilisation then occurs inside the ovule.
2. This makes the tube the link between pollination and fertilisation.

Answer: (b) testes. The testes make sperms in the seminiferous tubules.

Teacher's Note:
1. The testes also produce testosterone.
2. They lie in the scrotum, where the temperature is lower.

Answer: (a) sperm formation needs a temperature lower than body temperature. Sperm production needs a temperature slightly lower than the normal body temperature.

Teacher's Note:
1. This is why the scrotum is outside the body cavity.
2. It acts as a natural temperature regulator.

Answer: (b) oviduct (fallopian tube). The sperm meets the egg in the oviduct and the zygote forms there.

Teacher's Note:
1. The zygote then moves to the uterus, where it implants.
2. The ovary only releases the egg.

Answer: (b) wall of the uterus. The developing embryo embeds in the thick, spongy lining of the uterus.

Teacher's Note:
1. The lining is prepared each month for this purpose.
2. If there is no pregnancy, it breaks down.

Answer: (a) placenta. The placenta has villi that transfer oxygen and nutrients to the embryo and remove wastes.

Teacher's Note:
1. It is a disc-like tissue embedded in the uterine wall.
2. It links the mother and the embryo.

Answer: (b) breaks down and is released as menstrual flow. The lining breaks down and leaves with blood and mucus through the vagina as menstruation.

Teacher's Note:
1. The cycle repeats about every 28 days.
2. Menstruation lasts for around two to eight days.

Answer: (b) Breast development and start of menstruation. Breast development and the start of menstruation are female changes at puberty.

Teacher's Note:
1. Facial hair and voice change are changes in boys.
2. Puberty is controlled by sex hormones.

Answer: (c) condom. A condom blocks sperms and also stops infections passing between partners.

Teacher's Note:
1. Oral pills change hormonal balance, and Copper-T prevents implantation.
2. Neither protects against infection.

Answer: (b) Syphilis. Syphilis (like gonorrhoea, HIV-AIDS and warts) spreads through sexual contact.

Teacher's Note:
1. Malaria, cholera and typhoid spread by vectors, food or water.
2. Prevention includes barrier methods.

Answer: (a) vasectomy and tubectomy. Vasectomy blocks the vas deferens in males, and tubectomy blocks the fallopian tubes in females.

Teacher's Note:
1. Both methods stop the egg and sperm from meeting.
2. They are meant for permanent control.