1. (a) Gametes
2. (b) Menstrual cycle (menstruation)

1. (a) Oviduct
2. (b) Implantation

1. (i) The ratio of chromosome number between egg and its zygote is 1:2. An egg is a female gamete with a haploid number of chromosomes. During fertilisation, it fuses with a male gamete (also haploid) to form a zygote with a diploid number of chromosomes.
2. (ii) Sperms and eggs are genetically different in the nature of the sex chromosome. The sperm contains either X or Y-chromosome, whereas an egg will always have an X-chromosome.

1. Barrier method: In this method, fertilisation of the ovum and sperm is prevented with the help of barriers such as a condom.
2. Implants and surgical methods: Contraceptive devices such as a loop and copper-T rod are placed in the uterus to prevent pregnancy. Surgical methods such as vasectomy (blocking of the vas deferens in males) and tubectomy (blocking of fallopian tubes in females) can also be used to block gamete transfer.

1. The four whorls of a flower are: (i) Calyx, (ii) Corolla, (iii) Androecium, and (iv) Gynoecium.

1. Characters of the plants can be preserved through successive generations.
2. Seedless plants can be grown through vegetative reproduction.
3. By cutting and grafting methods, flowers and fruits can be grown in a shorter time duration.
4. It is a cheaper, easier and more rapid method of plant propagation.

1. Pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma.

1. Significance: Pollination is essential for fertilisation and seed formation, allowing plants to produce offspring for the next generation.

1. (i) Spores are formed in sporangia. Non-flagellated, non-motile spores are called aplanospores, and flagellated, motile spores are called zoospores.
2. (ii) Sweet potato is an example of a plant where modified tuberous roots can be propagated vegetatively when planted in soil.

1. Gametes are a prerequisite for sexual reproduction. Both sperm and ova unite to form a zygote, which further develops and forms an embryo that becomes a baby.

1. (a) On maturation, sporangia release spores which germinate into new mycelium under moist conditions.
2. (b) When a mature Spirogyra filament attains considerable length, its filaments break into smaller pieces or fragments, and each fragment gives rise to a new filament (fragmentation).

1. The slide showing budding in yeast would show one nucleus in the parent cell body and another one in the bud.
2. The slide showing binary fission in Amoeba would show two nuclei in the centrally constricted organism.

Five stages of binary fission in Amoeba: (a) Parent cell, (b) Nucleus lengthens, (c) Nucleus divides into two parts, (d) Cytoplasm divides, (e) Two smaller Amoebae produced

1. Yes, parental identity is lost in the binary fission of Amoeba.
2. Binary fission is an asexual mode of reproduction in Amoeba where a single parent cell divides into two daughter cells, and each daughter cell receives a copy of genetic material — hence the original parent cell no longer exists as a distinct entity.

1. The process is called "budding" and it is observed in Yeast.
2. Budding — The parent (yeast) cell produces a small protuberance that grows to form a bud. First, karyokinesis takes place (the nucleus of the parent cell divides), then the daughter nucleus moves into the daughter cell, and the process continues to form a chain of buds.

1. Germinating seeds are taken in the experiment as they are living cells and carry out respiration, releasing CO₂ gas which is absorbed by KOH solution, thus creating a vacuum in the flask due to which water in the bend tube is pulled up.
2. If the seeds are boiled, the cells would be killed, and then no gas would be released.

1. (a) True.
2. (b) True.
3. (c) True.

1. The probability of a male child being born is 50% and a female child being born is 50% in human beings.
2. This is because the sperm carries either an X or Y chromosome (in equal proportion), while the egg always carries an X chromosome. If the sperm carrying X fuses with the egg, the child is female (XX); if the sperm carrying Y fuses with the egg, the child is male (XY).

Advantages

1. Allows more time for brain development and learning.
2. Helps in acquiring complex skills, language, and social behaviour.
3. Leads to better care and protection from parents.

Disadvantages

1. Requires long-term parental care and resources.
2. Higher risk if proper care is not provided.
3. Slower independence compared to other animals.

1. In frogs, the egg contains a limited amount of yolk that only supports the embryo's development up to the larval stage. After hatching, the larva becomes independent and feeds on external food sources.
2. In contrast, birds produce eggs with a large amount of yolk, which provides complete nourishment for the embryo until it fully develops.
3. The young bird hatches in a more developed and active state, ready to begin life outside the egg.

1. Vegetative propagation is an asexual method of plant reproduction that occurs through leaves, roots, and stems. This can occur through fragmentation and regeneration of specific vegetative parts of plants.

Two methods

1. Grafting
2. Cutting

Advantages

1. It is a quicker, cheaper and easier method of plant propagation.
2. It makes possible the production of seedless varieties such as banana, orange, jasmine, etc.

1. (a) Self-pollination is the transfer of pollen grains from anther to stigma of the same flower. Cross-pollination is the transfer of pollen grains from the anther of one flower to the stigma of another flower.
2. (b) Petals attract insects for pollination. After fertilisation, they dry and fall off.
3. (c) Fertilisation is the fusion of male and female gametes to form a zygote. After fertilisation, the ovule develops into a seed, and the ovary develops into a fruit.

OR

1. Future shoot: Plumule. Future root: Radicle. Cotyledon: Stores food for the developing embryo.

1. (i) Leishmania — Binary fission; Plasmodium — Multiple fission.
2. (ii) Sexual reproduction leads to more variations, which are useful for ensuring the survival of a species.
3. (iii)a. Sugar solution provides nutrients for growth and multiplication, whereas water does not.
4. (iii)b. Moisture is required for the growth of Rhizopus, which a dry slice of bread lacks.

OR

1. The filamentous structures are Spirogyra. They multiply by fragmentation — the Spirogyra filament simply breaks up into smaller pieces upon maturation, and each piece grows into a new individual.

1. (i) Hypotheses: Use of beekeeping (managed pollinators) increases pollination efficiency; increased pollination leads to higher fruit setting and lower fruit drop; decline in natural pollinators reduces apple yield.
2. (ii) Independent variable: Type of pollination (natural vs beekeeping). Dependent variables: Fruit setting, Fruit drop. Controlled variables: Type of apple plants, soil, climate, irrigation practices.
3. (iii) Place A (natural pollinators): Lower fruit setting, higher fruit drop, overall lower yield. Place B (with beekeeping): Higher fruit setting, lower fruit drop, overall higher yield.

OR

1. The data shows that beekeeping improves pollination, leading to better fruit formation and reduced fruit loss. Therefore, managed pollination increases apple yield significantly.

1. (i) External fertilisation is the process where fertilisation occurs outside the body, usually in water, when sperm is released over eggs.
2. (ii) Internal fertilisation is seen in reptiles, birds, and mammals, where fertilisation occurs inside the female body.
3. (iii) Aquatic animals produce many eggs because survival chances are low. Many eggs are lost due to predators or environmental conditions, so producing more increases the chance that some will survive.

OR

1. External fertilisation occurs outside the body with many eggs and a low survival rate. Internal fertilisation occurs inside the female body with fewer offspring but higher survival due to protection and care.

1. (a) Sexual propagation uses the seed. Asexual propagation uses roots/stem/leaves.
2. (b) (i) Flower: Rose/Jasmine. (ii) Fruit: Grapes/Orange/Banana.
3. (c) Two advantages of vegetative propagation:

1. Production of genetically similar plants.
2. Propagated plants bear fruits and vegetables earlier than those produced from seeds.

OR

1. Put small pieces of potato containing notches or "eyes"/buds in moist cotton for a few days and observe. The notches or buds will give rise to fresh green shoots and roots.

(a) Parts

1. (i) Ovary — production of eggs.
2. (ii) Oviduct/Fallopian tube — site of fertilization.
3. (iii) Uterus — site of implantation.
4. (iv) Vagina/Vaginal passage — entry of the sperms.

(b) Changes in uterus

1. (i) After implantation, the zygote starts dividing in the uterus. The thickened uterine lining, richly supplied with blood vessels, nourishes the developing embryo. A placenta develops, which provides oxygen and food to the embryo and removes waste substances.
2. (ii) If an egg does not get fertilized, the uterine lining slowly breaks down and comes out as blood and mucous along with the unfertilised egg (menstruation).

(a) Categories of contraception

1. Barrier method: Physical barriers like condoms (worn over penis), diaphragm (used by females), cervical cap, and copper-T (an IUCD) are used.
2. Chemical method: Spermicidal applications by women, vaginal pills, or oral contraceptive pills (OCPs) are used. OCPs alter hormonal levels in the female body and are not meant for males.
3. Surgical method: Portion of vas deferens in males (vasectomy) or portion of fallopian tube in females (tubectomy) is cut or ligated, stopping the release of gametes.

(b) Why prenatal sex determination is prohibited

1. Selective Medical Termination of Pregnancy (MTP) of female foetuses using amniocentesis is the main reason behind the declining female-male sex ratio in our country. This is because many sections of our society considered the girl child as a burden. That is why the Government of India prohibited prenatal sex determination by law.

Benefits in the long run

1. Generating awareness about girls being equal helping hands in the family income.
2. Banning prenatal sex determination tests.
3. Banning certain ill practices in our society like the dowry system.

(c) Infections from unsafe sex

1. Bacterial diseases: (i) Gonorrhoea, (ii) Syphilis.
2. Viral diseases: (i) Warts, (ii) HIV-AIDS.

1. (i) Puberty is the period of life when the production of germ cells, i.e. ova (female) and sperm (male), starts in the body. This period of sexual maturation is called puberty.

(ii) Functions of male reproductive parts

1. Testes: Paired, oval-shaped male sex glands. Consist of seminiferous tubules, where sperms are produced. Produce the male sex hormone testosterone.
2. Seminal Vesicles: Fluid and nutrients combine with sperm to form semen — a milky, viscous fluid containing fructose, proteins and other chemicals for nourishing and stimulating sperms.
3. Vas deferens: Also known as sperm duct; connects testes for the passage of semen.
4. Urethra: Common passage for both sperms and urine, but never carries both at the same time.

1. (iii) Testes are located outside the abdominal cavity in the scrotum because sperm formation requires a lower temperature than normal body temperature.
2. (iv) Sperms are tiny bodies that consist mainly of genetic material and a long tail that helps them move towards the female germ-cell.

1. (i) The ovary contains ovules, and each ovule has an egg cell.
2. (ii) The stamen produces pollen grains, which are yellowish in colour.
3. (iii) A unisexual flower contains either stamens or carpels, whereas a bisexual flower contains both stamens and carpels.
4. (iv) When a pollen grain falls on the stigma of the carpel, it bursts open and grows into a pollen tube, which moves downwards through the style towards the female gamete in the ovary.
5. (v) The tip of the pollen tube bursts open and the male gamete comes out, combining with the nucleus of the female gamete present in the ovule to form a fertilised egg called a zygote.

(a) Asexual reproduction in Amoeba

1. In Amoeba, asexual reproduction occurs by fission (binary and multiple). The nucleus first divides into two daughter nuclei by mitosis, then the body along with cytoplasm constricts from the middle, which gradually deepens and eventually divides into two individual parts, each with one nucleus. Thus, two daughter Amoebae develop from one — this is called binary fission.
2. In multiple fission, the nucleus repeatedly divides to form a large number of nuclei, which reach the periphery. Later, cytoplasm gathers around each nucleus to form a daughter Amoeba. Several individuals (equal to the number of nuclei) develop from a single Amoeba.

(b) Sexual reproduction in plants

1. The male reproductive organ 'stamen' makes the male gametes.
2. The female reproductive organ 'carpel' makes the female gametes.
3. The male gametes fertilise the female gametes.
4. The fertilised ovules grow and become seeds.
5. The seeds produce new plants under favourable conditions like presence of water, warmth, air, light, etc.