Q1: Define reproduction. Why is it important for living organisms?
Ans: Reproduction is a biological process by which living beings produce new individuals of their own kind. It is important because it ensures the continuity of life on Earth and the transfer of genetic information from one generation to the next.
Q2: What is vegetative propagation? Give two examples.
Ans: Vegetative propagation is a method of asexual reproduction in plants where new plants arise from the vegetative parts (growing parts) of a plant. Examples include potato and ginger, which sprout new plants from their fleshy underground stems without producing seeds.
Q3: What is budding? Name one organism that reproduces by budding.
Ans: Budding is a type of asexual reproduction in which repeated cell division at a specific site on the parent body produces a small outgrowth called a bud, which enlarges and separates from the parent to live independently. Hydra is an organism that reproduces by budding.
Q4: What are spores? How do they help in reproduction?
Ans: Spores are tiny, lightweight, usually single-celled structures produced in huge numbers (millions from one mould colony) in a sac-like structure. They float easily through air currents and, on finding moisture and nutrients, germinate quickly into a new individual. Fungi like Rhizopus reproduce by spore formation.
Q5: Why are offspring produced by asexual reproduction called clones?
Ans: In asexual reproduction, the central process is mitosis, which produces daughter cells having the same number of chromosomes as the parent cell. Because of this, the offspring are genetically identical to the parent and are called clones.
Q6: What is meiosis and why is it necessary for sexual reproduction?
Ans: Meiosis is a special type of cell division in which the chromosome number of a parent (diploid) cell is reduced to half (haploid) in daughter cells called gametes. It is necessary for sexual reproduction because if gametes were not haploid, the chromosome number would double in every generation.
Q7: How many chromosomes do human body cells have? How many chromosomes does a human gamete have?
Ans: Human body cells have chromosomes (23 pairs). During meiosis, the chromosome number is halved, so each human gamete (sperm or egg) has chromosomes.
Q8: Name the male and female reproductive parts of a flower and state the function of each.
Ans: The stamen is the male reproductive part – it consists of a filament and an anther which produces pollen grains containing male gametes. The pistil is the female reproductive part – it consists of the stigma, style, and ovary, where the ovary contains ovules each having an egg cell (female gamete).
Q9: Define pollination. Distinguish between self-pollination and cross-pollination.
Ans: Pollination is the transfer of pollen grains from the anther to the stigma of a flower. When pollen is transferred to the stigma of the same flower or another flower on the same plant, it is called self-pollination. When pollen is transferred from the anther of one plant to the stigma of a flower of another plant of the same type, it is called cross-pollination.
Q10: What is fertilisation in plants? What is the fertilised egg called?
Ans: Fertilisation in plants is the fusion of the male gamete (from the pollen tube) with the egg cell in the ovule. The fertilised egg is called a zygote, which later develops into an embryo. After fertilisation, the ovule develops into a seed and the ovary develops into a fruit.
Q11: Name any three agents of pollination and give one example plant for each.
Ans: (i) Wind – wheat, maize, and rice have light pollen grains and feathery stigmas for wind pollination.
(ii) Water – aquatic plants like Vallisneria and Hydrilla are pollinated by water currents.
iii) Insects (bees, butterflies) – sunflower, hibiscus, and marigold are pollinated by insects and have brightly coloured, fragrant flowers that produce nectar.
Q12: What is external fertilisation? Give one example.
Ans: External fertilisation is the method in which the fusion of male and female gametes takes place outside the body of the female. It is seen in many aquatic animals such as frogs and most fish, where the female releases eggs into water and the male releases sperm over the eggs.
Q13: What is gametogenesis? Where does it take place in humans?
Ans: The process of formation of gametes (sperm and eggs) is called gametogenesis. It takes place in the testes (in males) and the ovaries (in females), and involves meiosis, which reduces the chromosome number from 46 to 23 in the resulting gametes.
Q14: What is the function of the testes in the male reproductive system?
Ans: The testes produce sperm (male gametes) and also produce hormones that control sperm production and cause the physical changes in boys during puberty. The testes are located in the scrotum, which keeps them slightly cooler than normal body temperature – a condition necessary for sperm formation.
Q15: What is ovulation? When does it typically occur in the menstrual cycle?
Ans: Ovulation is the process in which a mature egg is released from one of the ovaries. It typically occurs around day 14 of the menstrual cycle. After ovulation, the egg travels from the ovary to the oviduct (fallopian tube).
Q16: What is menstruation? How long does it typically last?
Ans: When an egg is not fertilised, the thick inner lining of the uterus (which had prepared to receive a zygote) is no longer needed and sheds along with some blood through the vagina. This process is called menstruation or a period, and it usually lasts 3 to 7 days.
Q17: What is a zygote in humans and how does it develop into a foetus?
Ans: When a sperm fuses with an egg in the oviduct, the fertilised egg is called a zygote. The zygote undergoes mitotic divisions while travelling to the uterus and implants in the uterine lining. It develops into an embryo and from about the ninth week is called a foetus, which continues to grow until birth.
Q18: Into how many trimesters is human pregnancy divided? How long does pregnancy last?
Ans: Human pregnancy lasts about nine months and is divided into three stages called trimesters. In the first trimester, major organs start forming; in the second, the foetus grows bigger and stronger; and in the third trimester, the baby grows rapidly and gets ready for life outside the womb.
Q19: What are Sexually Transmitted Infections (STIs)? Name any three.
Ans: Sexually Transmitted Infections (STIs) are infections that can be transmitted from an infected person to an uninfected person through sexual activity. Examples include gonorrhoea, syphilis, and HIV (which can eventually lead to AIDS). Using condoms can help prevent their transmission.
Q20: Name any two contraceptive methods used to prevent unwanted pregnancy and briefly explain how each works.
Ans: (i) Condoms – these are barrier methods that physically prevent sperm from reaching the egg; they also help prevent the spread of STIs.
(ii) Intra-Uterine Devices (IUDs) such as Copper-T – these are placed inside the uterus to prevent pregnancy, though they may sometimes irritate the uterus.
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