Answer:

A farmer prefers asexual reproduction when they want to produce:

• Genetically identical plants with desired traits (e.g., high yield, disease resistance).
• Plants quickly and uniformly.
• Propagate plants that do not produce viable seeds.

A farmer prefers sexual reproduction when they want:

• Genetic variation in offspring.
• To develop new varieties with improved characteristics.
• Seeds that can be stored and used for future planting.

Answer:

Complex animals and flowering plants use sexual reproduction because:

• It creates genetic variation, helping species adapt to changing environments.
• It allows for evolution over generations.
• They have specialised reproductive organs for sexual reproduction.

Simple organisms like yeast and hydra use asexual reproduction because:

• It is fast and efficient in favourable conditions.
• They can produce large numbers of offspring quickly.
• It does not require a mate, saving energy and time.

Answer:

The process about to happen next is fertilisation. The pollen tube carries the male gamete down through the style to the ovary, where it fuses with the egg cell to form a zygote.

Answer:

Calotropis (madar) and dandelion seeds have hair-like structures that help them float in the air. They are adapted for wind dispersal.

Answer:

This is cross-pollination. The pollen from one variety is transferred to the stigma of another variety of the same species.

Answer:

Animals with external fertilisation produce more eggs because:

• Eggs are released into the environment where many are destroyed by predators, water currents, or environmental factors.
• Producing more eggs increases the chances that at least some will be fertilised and survive.

Answer:

Internal fertilisation provides more protection to gametes because:

• Fertilisation occurs inside the female body, protecting gametes from external threats.
• The developing embryo is protected inside the mother or inside a shelled egg.
• Young ones have a higher chance of survival.

Answer:

Ravi is entering puberty (adolescence). These are physical changes caused by hormones during the transition from childhood to adulthood.

Answer:

Rina's next period is most likely on 2nd April.

Calculation: 5th March + 28 days = 2nd April (assuming March has 31 days).

Answer:

A human zygote has 46 chromosomes (23 pairs). It receives 23 chromosomes from the sperm (father) and 23 from the egg (mother).

Answer:

Condoms (male or female) are protective devices that can be used during sexual activity to reduce the spread of Sexually Transmitted Infections (STIs).

Answer:

If a couple uses oral contraceptive pills but not condoms, the risk of Sexually Transmitted Infections (STIs) remains because:

• Oral pills only prevent pregnancy by altering hormone levels.
• They do not provide a barrier against bacteria or viruses that cause STIs.

Answer:

Advantages:

• Human babies receive extensive care and learning from adults.
• They develop complex social and cognitive skills.
• Parental care ensures higher survival rates.

Disadvantages:

• Parents must invest a lot of time, energy, and resources.
• Fewer offspring can be produced over a lifetime.
• Increased vulnerability during early years if caregivers are not present.

Answer:

The correct option is (ii) Cross-pollination.

Explanation: Since the anthers were removed (emasculation), self-pollination was prevented. Pollen from another plant of the same species was used, ensuring cross-pollination.

Answer:

Correct order: (iii) → (i) → (ii) → (iv)

Pollination → Pollen germination on stigma → Fertilisation → Formation of zygote

Answer:

The correct option is (iv) A is false, but R is true.

Explanation: The zygote does not immediately attach to the uterus wall – it travels to the uterus and implants after several days. The uterus wall is prepared to receive the zygote only after ovulation, not always.

Answer:

Asexual reproduction produces genetically identical offspring because:

• It involves only one parent.
• The offspring are produced by mitosis, which produces daughter cells with the same number of chromosomes as the parent.
• There is no fusion of gametes from two parents.

Answer:

The menstrual cycle stops during pregnancy because:

• Once fertilisation occurs and the embryo implants in the uterus, the uterine lining is maintained to support the developing foetus.
• Hormones produced during pregnancy prevent the shedding of the uterine lining.
• Menstruation would remove the lining and the embryo, so it stops to protect the pregnancy.

Answer:

Night-blooming flowers are white or light in colour because:

• They are pollinated by nocturnal pollinators like moths and bats.
• White or light flowers are more visible in low light conditions.
• They often have a strong fragrance to attract pollinators at night.

Answer:

Vegetatively propagated plants are more vulnerable to diseases because:

• They are genetically identical (clones) – if one plant is susceptible to a disease, all are.
• There is no genetic variation to help plants resist new diseases.
• Sexually reproduced plants have genetic diversity, increasing the chance that some plants will be resistant.

Answer:

If all flowers were only capable of self-pollination:

• Genetic diversity would decrease over generations.
• Offspring would be genetically identical or very similar to the parent.
• The population would become more vulnerable to diseases and environmental changes.
• New traits would not be introduced, limiting the ability to adapt.

Answer:

Suitable methods:

• Vegetative propagation – cutting, grafting, layering.
• Tissue culture – growing plants from small tissue samples.

Why effective:

• They produce genetically identical plants quickly.
• They require only one parent.
• They are faster than sexual reproduction and do not require seeds.

Answer:

(i) Hypotheses that can be tested:

• Pollen germination is highest at a specific sugar concentration.
• Higher sugar concentrations may inhibit pollen germination.
• Optimal sugar concentration is required for pollen tube growth.

(ii) Parameters to keep the same:

• Type of pollen grains used.
• Temperature.
• Amount of pollen on each slide.
• Time allowed for germination.
• Type of sugar used.

Answer:

Tomato: Self-pollination – stamens cover the stigma, so pollen can fall directly onto the stigma of the same flower.

Wheat: Wind pollination – flowers open after pollination, pollen is light and carried by wind.

Papaya: Cross-pollination – male and female flowers are on different plants, so pollination must occur between plants.

Answer:

(i) Hypotheses:

• Beekeeping (mixed farming) increases apple fruit yield.
• Natural pollinators are insufficient for optimal apple production.
• Beekeeping reduces fruit drop and increases fruit setting.

(ii) Parameters:

• Fruit setting percentage.
• Fruit drop percentage.
• Type of pollination (natural vs beekeeping).
• Location and environmental conditions.

(iii) Comparison:

• Place B (with beekeeping) likely shows higher fruit setting and lower fruit drop compared to Place A.
• Beekeeping ensures more effective pollination and higher yields.

(iv) Inference:

• Beekeeping improves apple yield.
• Declining natural pollinator populations affect agriculture.
• Mixed farming (beekeeping + apple cultivation) is a sustainable solution.

Answer:

The claim is not always correct.

Reasons:

• The menstrual cycle varies from 21 to 35 days in different women – not everyone has a 28-day cycle.
• Ovulation typically occurs about 14 days before the next period begins, not always on day 14.
• Stress, health conditions, and lifestyle can affect the timing of ovulation.

Answer:

This is a research/project activity.

Why save indigenous seeds:

• Indigenous seeds are adapted to local climate and soil conditions.
• They have natural pest resistance and require fewer chemical inputs.
• They help maintain genetic diversity in crops.
• They are climate-resilient and important for food security.

Answer:

This is a research/report activity.

IVF (In-vitro Fertilisation):

• Uses: Helps couples with infertility, genetic disorders, and for fertility preservation.
• Drawbacks: Expensive, not always successful, ethical concerns, multiple pregnancies.

Answer:

This is a field survey activity.

Points to cover:

• Crops grown through vegetative propagation.
• Crops grown using seeds.
• Indigenous vs hybrid varieties.
• Indigenous vs hybrid breeds of farm animals.

Answer:

This is a field observation activity.

Key observations:

• Identify pollinators (bees, butterflies, wind, water).
• Record which plants they visit.
• Understand reasons for declining pollinator populations.

Answer:

This is a practical kitchen activity.

Expected observations:

• L.S.: Shows internal structure – seed arrangement, placenta, fruit wall.
• T.S.: Shows cross-section – number of chambers (locules), seed attachment.
• Seed attachment: Seeds are attached to the placenta (ovary wall).

Link: The ovary develops into the fruit, and ovules develop into seeds.

Answer:

This is a thought-provoking question.

Unicellular organisms do not age in the same way as multicellular organisms because:

• They reproduce by binary fission or budding, creating new individuals.
• The parent cell essentially divides into two new cells, leaving no 'old' individual.
• Aging is associated with deterioration of tissues and organs, which unicellular organisms lack.
• However, over many generations, mutations can accumulate, affecting the population.