1A farmer is observing a Bryophyllum plant and notices small plantlets growing along the edges of its leaves. He wants to propagate this plant for his nursery.(a) What is the biological term for this mode of reproduction in Bryophyllum? [1 mark](b) Explain the process by which these plantlets grow into new, independent plants. [2 marks](c) Why would the farmer choose this method for mass propagation instead of growing from seeds, if Bryophyllum also produced seeds? 2marks
2A student is studying yeast under a microscope. They observe small outgrowths emerging from the parent cells.(a) Identify the process of reproduction being observed. [1 mark](b) Describe how this process leads to the formation of new individuals. [2 marks](c) The student notices that in a warm sugar solution, yeast reproduces much faster than in plain water. Explain the role of temperature and nutrients in this observation. 2marks
3Assertion (A): Asexual reproduction leads to the production of offspring that are genetically identical to the parent.Reason (R): Asexual reproduction involves mitosis, a type of cell division that produces two genetically identical daughter cells.(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. 1mark
4Observe the diagram of a flower and answer the questions.(Diagram of a longitudinal section of a flower showing stamen and pistil)(a) Identify the parts labelled X (anther) and Y (stigma). [1 mark](b) What is the role of part X in reproduction? [1 mark](c) What process is essential for the transfer of pollen from X to Y? [1 mark](d) If the stamens of a flower are removed before pollen is produced, and then pollen from another flower of the same species is dusted onto the stigma, what type of pollination would occur? 1mark
5A student is conducting an experiment to study pollination. They remove the stamens from a flower bud and cover it with a muslin bag. Later, they dust pollen from a different plant of the same species onto the stigma.(i) What is the purpose of removing the stamens? [1 mark](ii) What type of pollination is being demonstrated? [1 mark](iii) What would be the outcome if the flower were not covered with a muslin bag after dusting the pollen? 1mark
6During meiosis, homologous chromosomes separate. This process is crucial for sexual reproduction.(a) What is the primary outcome of meiosis in terms of chromosome number? [1 mark](b) How does this reduction in chromosome number contribute to maintaining the species' characteristic chromosome count in the offspring? [2 marks](c) Explain how the random segregation of chromosomes during meiosis leads to genetic variation. 2marks
7A scientist is studying the life cycle of a butterfly. They observe distinct stages of development from egg to adult.(a) Identify the type of metamorphosis seen in butterflies. [1 mark](b) Explain how this type of development differs from the direct development seen in some other animals. [2 marks](c) Why is this developmental process considered a part of sexual reproduction in animals? 1mark
8In many aquatic animals like fish and frogs, fertilization occurs outside the body.(a) Name this type of fertilization. [1 mark](b) Explain why these animals produce a large number of eggs. [2 marks](c) What are the potential disadvantages of this method of fertilization compared to internal fertilization? 1mark
9During the menstrual cycle, a woman's body prepares for a potential pregnancy.(a) Which organ in the female reproductive system undergoes changes in its lining? [1 mark](b) What is the purpose of the thickening of this lining? [1 mark](c) What happens to this lining if fertilization does not occur? 1mark
10A girl reaches puberty and starts experiencing menstruation.(a) What is the biological significance of menstruation? [1 mark](b) How is menstruation related to ovulation? [2 marks](c) Explain why menstruation stops during pregnancy. 2marks
11In human beings, the sex of the baby is determined by the father.(a) What are the sex chromosomes present in a human female and a human male? [1 mark](b) Explain how the combination of these chromosomes in the zygote determines the sex of the child. [2 marks](c) Why is prenatal sex determination often considered unethical? 1mark
12A student claims that a zygote formed after fertilization immediately attaches to the uterus wall.Critically examine this claim and state whether it is correct or not, providing at least two reasons for your answer. 3marks
13Case Study: Apple orchards in the lower Himalayan region are facing a decline in fruit yield due to climate change and a reduction in natural pollinators. A research group set up two experimental orchards: one relying on natural pollinators (Orchard A) and another incorporating beekeeping (Orchard B). They measured fruit setting and fruit drop.(i) What is the main hypothesis being tested in this experiment? [1 mark](ii) Identify the independent and dependent variables in this experiment. [2 marks](iii) Based on the scenario, what are the expected outcomes regarding fruit yield in Orchard B compared to Orchard A? Justify your answer. 2marks
14Assertion (A): Sexual reproduction in animals generally leads to more variations than asexual reproduction.Reason (R): Sexual reproduction involves the fusion of gametes from two different parents, leading to a new combination of genes.(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. 1mark
15A farmer is using vegetative propagation techniques like cuttings and grafting to grow a large number of plants quickly.(a) What is the advantage of using vegetative propagation for the farmer in terms of speed and genetic uniformity? [2 marks](b) Explain one significant disadvantage of relying solely on vegetative propagation for certain crops, especially in terms of disease resistance. 2marks
16In humans, the male reproductive system produces millions of sperm daily, while the female reproductive system typically releases one mature egg per month.(a) Explain the biological significance of this difference in gamete production. [2 marks](b) How does the structure of a sperm contribute to its function in fertilisation? 1mark
17A sexually transmitted infection (STI) is transmitted from an infected person to an uninfected person through close physical contact.(a) Name two examples of STIs. [1 mark](b) Explain why using condoms during sexual activity can help prevent the spread of STIs and unwanted pregnancies. 2marks
18A student observes a picture of a Rhizopus fungus growing on bread.(a) Identify the mode of reproduction typically seen in fungi like Rhizopus. [1 mark](b) Describe how this reproductive structure helps in the dispersal and germination of new individuals. [2 marks](c) Explain why keeping food in a refrigerator slows down the growth of such organisms. 1mark
19In flowering plants, the transfer of pollen from the anther to the stigma is crucial for reproduction.(a) Differentiate between self-pollination and cross-pollination. [2 marks](b) Describe two adaptations found in insect-pollinated flowers that help attract insects and facilitate pollen transfer. 2marks
20Case Study: A couple is unable to conceive. After medical evaluation, they are advised to undergo In-Vitro Fertilisation (IVF).(a) Briefly describe the process of IVF. [2 marks](b) What is the primary advantage of IVF for couples facing infertility? [1 mark](c) What ethical considerations might arise in discussions about IVF, particularly in the context of "test tube babies"? 2marks
Answers
1.(a) Vegetative propagation. [1 mark](b) The plantlets have roots and shoots, and can absorb nutrients and water from the soil. As they grow larger, they eventually detach from the leaf margin and establish themselves as independent plants. [2 marks](c) Vegetative propagation ensures that the new plants are genetically identical to the parent plant, preserving desirable traits. It is also often faster and more efficient for mass propagation than growing from seeds, especially for plants that may have slow seed germination or complex seed dispersal mechanisms. 2marks
2.
(a) Budding. [1 mark]
(b) A small outgrowth, called a bud, develops on the parent yeast cell. This bud grows and eventually detaches from the parent cell to become a new, independent yeast organism. [2 marks]
(c) Yeast, like other living organisms, require favourable environmental conditions for optimal growth and reproduction. Warm temperatures (around 25-35°C) are ideal for yeast activity. The sugar solution provides the necessary nutrients (food) for the yeast to respire and carry out its metabolic processes, thus leading to faster reproduction. [2 marks]
3(i) Both A and R are true, and R is the correct explanation of A. 1mark
4.
(a) X is the anther, and Y is the stigma. [1 mark]
(b) The anther produces pollen grains, which contain the male gametes. [1 mark]
(c) Pollination is the process of transfer of pollen grains from the anther to the stigma. [1 mark]
(d) Cross-pollination. [1 mark]
5.
(i) The purpose of removing the stamens is to prevent self-pollination, ensuring that any subsequent seed formation will be due to the introduced pollen. [1 mark]
(ii) This is an example of artificial cross-pollination. [1 mark]
(iii) If the flower were not covered, external agents like insects or wind could transfer pollen from other flowers (either self-pollination or cross-pollination with other plants) to the stigma, contaminating the results of the intended cross-pollination. [1 mark]
6.
(a) Meiosis reduces the chromosome number of a diploid parent cell by half, resulting in haploid daughter cells (gametes). [1 mark]
(b) When these haploid gametes (sperm and egg) fuse during fertilisation, they restore the diploid chromosome number characteristic of the species. This ensures that each generation has the correct number of chromosomes. [2 marks]
(c) During meiosis, homologous chromosomes pair up and then separate. Also, during prophase I, crossing over can occur between homologous chromosomes, exchanging genetic material. Furthermore, the random orientation of homologous chromosome pairs at the metaphase plate leads to different combinations of maternal and paternal chromosomes in the resulting gametes. This shuffling of genes creates unique combinations, leading to genetic variation among offspring. [2 marks]
7.
(a) Complete metamorphosis. [1 mark]
(b) Direct development involves the young ones resembling miniature adults, and they grow into adults without undergoing drastic changes in form. Complete metamorphosis, on the other hand, involves distinct larval and pupal stages with significant transformations in body structure, physiology, and behaviour. [2 marks]
(c) Butterflies reproduce sexually. The process involves the fusion of male and female gametes (sperm and egg) produced by the adult butterfly, which is the result of sexual reproduction. [1 mark]
8.
(a) External fertilization. [1 mark]
(b) These animals produce a large number of eggs because many eggs are lost due to environmental factors like water currents, predation by other animals, or failure to be fertilised. A high number of eggs increases the probability of some offspring surviving to maturity. [2 marks]
(c) The main disadvantages are: low survival rate of eggs and young ones due to exposure to the environment and predation, and dependence on water for fertilization, limiting their habitat. [1 mark]
9.
(a) The uterus. [1 mark]
(b) The thickening of the uterine lining is to prepare it for the implantation of a fertilised egg (zygote) and to provide nourishment for the developing embryo. [1 mark]
(c) If fertilization does not occur, the thickened uterine lining, along with blood vessels, breaks down and is shed from the body through the vagina. This process is called menstruation. [1 mark]
10.
(a) Menstruation is the shedding of the thickened uterine lining, along with some blood, when fertilization does not occur. It signifies that pregnancy has not begun. [1 mark]
(b) Ovulation is the release of a mature egg from the ovary, which typically occurs around the 14th day of a 28-day menstrual cycle. If the egg is not fertilised by sperm within about 24 hours of ovulation, the uterine lining begins to break down, leading to menstruation. Thus, menstruation follows ovulation when fertilization does not happen. [2 marks]
(c) During pregnancy, the uterine lining remains thick and well-supplied with blood vessels to nourish the developing embryo and fetus. Since the fertilized egg implants and develops, there is no need for the lining to shed, and thus menstruation stops. [2 marks]
11.
(a) Human females have XX sex chromosomes. Human males have XY sex chromosomes. [1 mark]
(b) The mother always contributes an X chromosome to her child. The father contributes either an X chromosome (resulting in XX, a female) or a Y chromosome (resulting in XY, a male). Therefore, the type of sperm that fertilises the egg determines the sex of the child. [2 marks]
(c) Prenatal sex determination can lead to sex-selective abortions, particularly of female fetuses, which can cause a significant imbalance in the sex ratio within society. This practice is considered unethical as it devalues one sex over the other. [1 mark]
12The claim that a zygote formed after fertilization immediately attaches to the uterus wall is incorrect.Reasons:
1After fertilization in the oviduct, the zygote undergoes several mitotic divisions while travelling towards the uterus. This journey typically takes several days.
2Implantation, which is the attachment of the developing embryo (blastocyst) to the uterine lining, occurs only after the zygote has developed into a blastocyst and reaches the uterus, usually about 6-10 days after fertilization. The uterus prepares itself for implantation, and the blastocyst actively burrows into the prepared lining. 3marks
13.
(i) The main hypothesis being tested is that the presence of beekeeping (managed pollinators) will lead to higher fruit yield (better fruit setting and reduced fruit drop) in apple orchards compared to relying solely on natural pollinators. [1 mark]
(ii) Independent variable: Type of pollination management (natural pollinators vs. beekeeping). Dependent variables: Fruit setting (number of fruits/fruit-bearing branches) and fruit drop (premature falling of developing fruits). [2 marks]
(iii) Orchard B (with beekeeping) is expected to have a higher yield of apples. This is because bees are effective pollinators, and introducing them ensures a sufficient number of pollinators, especially when natural pollinator populations are declining. Increased and effective pollination leads to better fruit setting and potentially less fruit drop, resulting in more apples. [2 marks]
14(i) Both A and R are true, and R is the correct explanation of A. 1mark
15.
(a) The advantage of using vegetative propagation is that it allows for the rapid production of a large number of plants. These plants are genetically identical to the parent, ensuring that desirable traits like yield, disease resistance (if present in the parent), or fruit quality are maintained consistently. [2 marks]
(b) A significant disadvantage is that if the parent plant is susceptible to a particular disease, all the vegetatively propagated offspring will also be susceptible to that same disease. This lack of genetic diversity makes them vulnerable to widespread outbreaks if the disease appears. [2 marks]
16.
(a) The vast difference in gamete production (millions of sperm vs. one egg) is an evolutionary strategy. For sperm, the sheer numbers increase the probability of one sperm reaching and fertilising the egg in the female reproductive tract. For the egg, being large and containing stored nutrients, it is a valuable resource, and producing too many would be metabolically costly and inefficient. The female system is geared towards protecting and nurturing a single, viable egg at a time. [2 marks]
(b) A sperm has a head containing the genetic material (nucleus) and an acrosome (containing enzymes) that helps it penetrate the egg's outer layers. It also has a long tail that whips back and forth, providing motility, which enables it to swim through the female reproductive tract to reach the egg. [1 mark]
17.
(a) Two examples of STIs are: Gonorrhoea, Syphilis, Herpes, HIV/AIDS, Genital Warts. [1 mark]
(b) Condoms act as a physical barrier that prevents sperm from entering the vagina and also prevents direct contact between the genitals, thus stopping the transmission of infectious agents (bacteria, viruses) present in semen, vaginal fluids, or on the skin. This dual action helps prevent both unwanted pregnancies and the spread of STIs. [2 marks]
18.
(a) Spore formation. [1 mark]
(b) Fungi like Rhizopus produce spores in sporangia (sac-like structures). These spores are lightweight and are easily dispersed by air currents. When they land on a suitable moist surface with adequate nutrients, they germinate and grow into new hyphae, forming a new fungal colony. [2 marks]
(c) Refrigeration significantly lowers the temperature, which slows down or stops the metabolic activities of fungi. This reduces their rate of growth and reproduction, thereby preserving the food for a longer period. [1 mark]
19.(a) Self-pollination: The transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant.Cross-pollination: The transfer of pollen grains from the anther of a flower on one plant to the stigma of a flower on another plant of the same species. [2 marks](b) Two adaptations of insect-pollinated flowers:
1Brightly coloured petals: To attract insects visually.
2Production of nectar and fragrance: To attract insects with scent and a food reward.
3Sticky or spiny pollen grains: To adhere to the insect's body.
4Sticky stigma: To receive pollen from the insect's body.(Any two of the above). 2marks
20.
(a) In Vitro Fertilisation (IVF) is a process where a woman's eggs are surgically removed from her ovaries and fertilised by sperm in a laboratory dish ("in vitro" means "in glass"). The fertilised egg (embryo) is then allowed to develop for a few days before being implanted into the woman's uterus. [2 marks]
(b) The primary advantage of IVF is that it provides a way for individuals or couples who are infertile, or face specific reproductive challenges (like blocked fallopian tubes), to have a biological child. [1 mark]
(c) Ethical considerations might include:
- The creation and disposal of surplus embryos.
- The potential for genetic selection or "designer babies."
- The financial cost and accessibility of the procedure.
- The moral and religious objections some people have to 'interfering' with natural conception.
- The emotional impact on children born through IVF if they learn about their conception. [2 marks]
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