1Revise, Reflect, Refine13 questions
Q.1A flower’s anthers are removed before it matures. Later, pollen from another plant of the same species is dusted onto its stigma and seeds are produced. Which process has been ensured here? (i) Self-pollination (ii) Cross-pollination (iii) Fertilisation (iv) Tissue culturev
Answer:(ii) Cross-pollination.
Q.2Arrange the following stages of sexual reproduction in plants in the correct order: (i) Pollen germination on stigma (ii) Fertilisation (iii) Pollination (iv) Formation of zygotev
Answer:Correct sequence: (iii), (i), (ii), (iv).
Q.3Assertion (A): The zygote formed after fertilisation immediately attaches to the uterus wall. Reason (R): The uterus wall is always prepared to receive the zygote. (i) Both A and R are true, and R is the correct explanation of A. (ii) Both A and R are true, but R is not the correct explanation of A. (iii) A is true, but R is false. (iv) A is false, but R is true.v
Answer:(iv) A is false, but R is true.
Q.4Why does asexual reproduction produce offsprings that are genetically identical to the parent?v
Answer:Asexual reproduction involves one parent and mitotic division without gamete fusion or recombination, so offspring inherit the same genetic material as the parent except for rare mutations.
Q.5Explain why the menstrual cycle stops during pregnancy.v
Answer:During pregnancy, hormones maintain the uterine lining and prevent ovulation and menstruation. The lining is not shed because it supports the developing embryo.
Q.6Why are flowers that bloom at night white or light in colour as compared to flowers that bloom during the day?v
Answer:Night-blooming flowers are often white or pale so they are visible in low light to night pollinators such as moths. Many also produce fragrance to attract pollinators.
Q.7Why do vegetatively propagated plants tend to be more vulnerable to diseases than sexually reproduced plants?v
Answer:Vegetatively propagated plants are clones. If the parent is susceptible to a disease, all clones may be susceptible, whereas sexual reproduction creates variation and may produce resistant individuals.
Q.8If all flowers in a type of plant were only capable of self-pollination, how would it affect the genetic diversity over several generations? Explain.v
Answer:Repeated self-pollination would reduce genetic diversity over generations, increase homozygosity, and make the population less adaptable to changing conditions or disease.
Q.9A farmer wants to produce a large number of genetically identical plants quickly. Suggest suitable reproduction methods and explain why they are effective.v
Answer:Use vegetative propagation such as cuttings, grafting, layering or tissue culture. These methods rapidly produce many genetically identical plants and preserve desirable traits of the parent.
Q.10Suresh prepares slides with pollen grains in different sugar concentrations (0%, 2.5%, 5%, 7.5%, 10%) to study the germination of pollen. (i) What are the different hypotheses which can be tested using this set-up? (ii) What parameters should be kept the same in this set-up?v
Answer:Hypotheses: pollen germination depends on sugar concentration and has an optimum concentration. Constants should include pollen source, temperature, time, solution volume, slide method, number of pollen grains and observation method.
Q.11Look at the picture given below and think in line with the given prompts and find out which type(s) of pollination might have been followed in these flowers — Tomato Wheat Papaya Stamens cover the stigma. Flowers open Male and female flowers after pollination. are often borne on different papaya trees.v
Answer:Tomato—self pollination; wheat—self pollination; papaya—cross pollination.
Q.12In the lower Himalayan region of northern India, apples are an important cash crop that contribute significantly to farmer’s livelihoods. The fruit yield in apple cultivation is declining continuously, associated with climate change and a significant decline in the population of natural pollinators. A researcher-farmer group set up two experimental apple orchards at two distinct locations: Places A and B. In apple orchards at Place A, they allowed natural pollinators to pollinate the flowers of the apple. In apple orchards at Place B, they applied mixed farming techniques of beekeeping. Along with honey, the farmer yielded apples. The yield of apples is depicted in Fig. 11.24, in terms of fruit setting (number of fruits/the total number of corresponding fruit-bearing branches) and cent fruit drop (premature falling of developing fruits) in the two types of experimental placesPer of apple orchards. (i) What are the hypotheses the researcher- farmers group has thought of for this investigation? (ii) What are the different parameters in the experiment? (iii) Compare and analyse the data of two experimental orchards Places A and B, in terms of high yields of apple fruits. (iv) Based on your analysis, what do you infer from the data?v
Answer:The hypothesis is that beekeeping increases pollination and apple yield. Parameters include pollination method, fruit setting, fruit drop, orchard location and environmental conditions. Orchards with beekeeping should show higher fruit set and lower fruit drop, supporting the inference that managed pollinators improve yield and farmer income.
Q.13A student claims, “In humans, ovulation always happens on day 14 of the menstrual cycle”. Critically examine this claim and state whether the claim is correct or not. Give at least two reasons for your answer.v
Answer:The claim is not always correct. Day 14 is an approximation for a typical 28-day cycle; cycle length varies among people and between cycles, and stress, health, age and hormones can shift ovulation.