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A newly married couple, Priya and Rohan, are planning to start a family. They are concerned about potential health risks and want to make informed decisions. They consult a doctor about various methods to prevent pregnancy. The doctor explains different contraceptive options, highlighting their mechanisms and potential side effects.(a) Rohan is considering a vasectomy. Explain the process of vasectomy and how it prevents pregnancy. [2 marks](b) Priya is considering using oral contraceptive pills. Explain how these pills work to prevent pregnancy and mention one potential side effect. [2 marks](c) They also discuss condoms. How do condoms act as a contraceptive method and what additional benefit do they offer? [2 marks](d) The doctor mentions that some methods involve placing a device in the uterus. Name one such device and explain its mode of action. 1mark
2
Assertion (A): Variations are essential for the long-term survival of a species, even if they are not beneficial for an individual in the short term.Reason (R): Variations provide a pool of genetic diversity that can help a species adapt to changing environmental conditions.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true. 1mark
3
A group of students collected water from a pond and observed a filamentous green alga under a microscope. They identified it as Spirogyra.(a) Describe the mode of reproduction observed in Spirogyra, explaining the process involved. [2 marks](b) What would happen if this Spirogyra filament matures and breaks into several smaller pieces? [1 mark](c) Explain why this mode of reproduction is considered asexual. 1mark
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A student observes a permanent slide of Amoeba. They notice that the organism is elongated and appears to be splitting into two.(a) Identify the process the Amoeba is undergoing. [1 mark](b) Explain the process in detail, mentioning the plane of division. [2 marks](c) How is this different from the reproductive process observed in Plasmodium? 2marks
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Assertion (A): Sexual reproduction leads to greater variations in the offspring compared to asexual reproduction.Reason (R): Sexual reproduction involves the fusion of gametes from two different individuals, combining genetic material.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true. 1mark
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Rohan is given a Bryophyllum plant and asked to demonstrate a method of vegetative propagation. He carefully removes a leaf and places it on moist soil.(a) Describe what happens next, leading to the formation of new plants. [2 marks](b) Name the type of reproduction demonstrated. [1 mark](c) Mention two advantages of this method of propagation. 2marks
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A scientist is studying the reproduction in Hydra. They observe small outgrowths on the body of the parent Hydra.(a) Identify the process of reproduction occurring in Hydra. [1 mark](b) Explain how this process leads to the formation of new individuals. [2 marks](c) What type of cells are primarily involved in this process? [1 mark](d) How does this differ from reproduction in Planaria when it is cut into pieces? 1mark
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Case Study: A small village observes a significant increase in the population of mosquitoes during the monsoon season. This leads to a surge in cases of malaria. The local health authorities are trying to understand the reproductive cycle of the Plasmodium parasite responsible for malaria.(a) Name the type of fission that occurs in Plasmodium. [1 mark](b) Explain the process of multiple fission as observed in Plasmodium. [2 marks](c) Why is understanding the reproductive cycle important for controlling malaria? 1mark
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Assertion (A): In flowering plants, the transfer of pollen from the anther to the stigma is essential for seed formation.Reason (R): Pollen grains contain the male gametes which fuse with the female gamete in the ovule to form a zygote.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true. 1mark
10
A teacher explains the male reproductive system to the students. They discuss the functions of different organs.(a) Where are the testes located in human males and why? [2 marks](b) Explain the role of the seminal vesicles and prostate gland in the process of sperm transport. [2 marks](c) What is the characteristic feature of sperms that aids in their movement? 1mark
11
A baker notices that a slice of bread left uncovered in a moist, dark place has developed fuzzy grey patches. He also observed yeast growing in a sugar solution in a test tube.(a) Identify the organism responsible for the fuzzy patches on the bread and explain its mode of reproduction. [2 marks](b) Name the process of reproduction observed in yeast in the sugar solution. [1 mark](c) Why does Rhizopus not grow on a dry slice of bread? 1mark
12
A student is learning about reproductive health. They are confused about the terms 'menstruation' and 'fertilisation'.(a) Explain the process of menstruation and state its approximate duration. [2 marks](b) Describe what happens when an egg is fertilised in the human female reproductive tract. [2 marks](c) What happens to the uterine lining if fertilisation does not occur? 1mark
13
Case Study: A farmer wants to cultivate banana plants that are resistant to a particular disease. He decides to use vegetative propagation.(a) Name the part of the banana plant typically used for propagation and explain the process. [2 marks](b) State two advantages of using this method for banana cultivation. [2 marks](c) Why is this method referred to as asexual reproduction? 1mark
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Assertion (A): Regeneration is a form of reproduction for organisms like Hydra.Reason (R): Specialized cells in Hydra proliferate and differentiate to form new individuals from body parts.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true. 1mark
15
A biology class is discussing the differences between sexual and asexual reproduction. They are asked to explain the significance of variations in the context of species survival.(a) Explain why variations are beneficial for the survival of a species. [2 marks](b) How does sexual reproduction contribute to generating more variations compared to asexual reproduction? [2 marks](c) Give an example of a type of asexual reproduction where variations are least likely to occur. 1mark
16
A student is observing a flower and identifies its different parts. They are asked to explain the events following pollination.(a) What is pollination? Differentiate between self-pollination and cross-pollination. [2 marks](b) Describe the process that occurs after a pollen grain lands on a suitable stigma. [2 marks](c) What changes occur in the ovary and ovule after fertilization? 1mark
17
Case Study: During adolescence, significant physical and hormonal changes occur in both boys and girls. These changes mark the onset of sexual maturity.(a) List three common changes observed in both boys and girls during puberty. [3 marks](b) Describe two changes that are specific to girls during puberty. 2marks
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Assertion (A): The process of reproduction is not essential for the survival of an individual organism.Reason (R): Reproduction ensures the continuation of species and provides genetic diversity through variations.(a) Both A and R are true and R is the correct explanation of A.(b) Both A and R are true but R is not the correct explanation of A.(c) A is true but R is false.(d) A is false but R is true. 1mark
19
A scientist is studying a unicellular organism that divides into many daughter cells simultaneously.(a) Identify this mode of reproduction. [1 mark](b) Name an organism that reproduces using this method and the disease it causes. [2 marks](c) How does this mode of reproduction differ from binary fission? 2marks
20
A group of students are discussing human reproductive health. They are concerned about sexually transmitted diseases (STDs) and unwanted pregnancies.(a) Name two bacterial STDs and one viral STD. [2 marks](b) Explain how the use of condoms can help in preventing the transmission of STDs. [1 mark](c) How can methods like IUDs (e.g., Copper-T) prevent pregnancy, and what is a potential side effect? 2marks
Answers
1
(a) Vasectomy is a surgical procedure in males where the vas deferens (tubes that carry sperm from the testes) are cut and tied or blocked. This prevents sperm from being ejaculated, thus preventing pregnancy.(b) Oral contraceptive pills contain hormones that prevent the ovaries from releasing eggs (ovulation) and also change the hormonal balance to prevent the uterine lining from thickening. A potential side effect can be hormonal imbalance leading to mood swings or irregular periods.(c) Condoms act as a physical barrier, preventing sperm from entering the vagina during sexual intercourse. They also help in protecting against the transmission of many sexually transmitted diseases.(d) An Intrauterine Device (IUD), such as the Copper-T, is placed inside the uterus. It prevents pregnancy by interfering with the movement of sperm, preventing fertilization, and making the uterine lining unsuitable for implantation.
2
(a) Both A and R are true and R is the correct explanation of A.
3
(a) Spirogyra reproduces asexually through fragmentation. The filament breaks into smaller pieces or fragments upon maturation, and each fragment grows into a new individual.(b) If the Spirogyra filament breaks into several smaller pieces, each piece will grow into a new Spirogyra filament, thus increasing the population.(c) This is asexual reproduction because it involves only one parent (the filament) and does not involve the formation or fusion of gametes.
4
(a) Binary fission.(b) In binary fission, the nucleus of the Amoeba first elongates and then divides into two. The cytoplasm also divides, leading to the formation of two daughter Amoebas. This division can occur in any plane.(c) Plasmodium reproduces by multiple fission, where the nucleus divides repeatedly to form many nuclei, followed by the division of the cytoplasm, resulting in the formation of many daughter cells simultaneously. Binary fission involves division into only two daughter cells.
5
(a) Both A and R are true and R is the correct explanation of A.
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(a) When a leaf of Bryophyllum is placed on moist soil, buds present on the leaf margins develop into new plants. These buds grow roots and shoots, eventually detaching from the leaf to become independent plants.(b) Vegetative propagation.(c) Two advantages are:i) Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.ii) This method can be used to propagate plants that have lost the capacity to produce seeds, like banana or rose.
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(a) Budding.(b) In budding, a bud develops as an outgrowth due to repeated cell division at a specific site on the parent Hydra. This bud grows into a tiny individual and eventually detaches from the parent body to become a new, independent Hydra.(c) Regenerative cells are primarily involved in the process of budding in Hydra, as they proliferate and contribute to the growth of the bud.(d) Budding in Hydra is the formation of a new individual from an outgrowth. Reproduction by regeneration in Planaria involves the growth of a complete organism from a fragment of the parent body when it is cut into pieces.
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(a) Multiple fission.(b) In multiple fission, the nucleus of Plasmodium divides multiple times to form several nuclei. Each nucleus then gets surrounded by a small amount of cytoplasm, forming numerous daughter cells (merozoites). These daughter cells are released when the parent cell ruptures.(c) Understanding the reproductive cycle of Plasmodium (which involves its transmission through mosquitoes) is crucial for developing strategies to interrupt its life cycle, such as controlling mosquito populations or preventing mosquito bites, thereby reducing malaria transmission.
9
(a) Both A and R are true and R is the correct explanation of A.
10
(a) The testes are located outside the abdominal cavity in the scrotum because sperm formation requires a temperature slightly lower than the normal body temperature.(b) The seminal vesicles and prostate gland add their secretions to the sperms. This fluid makes the transport of sperms easier and provides nutrition to them.(c) Sperms have a long tail that helps them move towards the female germ-cell.
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(a) The fuzzy patches on the bread are due to the growth of Rhizopus (bread mould). Rhizopus reproduces asexually through spore formation. The blob-like structures, sporangia, contain spores that are released and grow into new individuals.(b) Budding.(c) Rhizopus requires moisture to germinate and grow. A dry slice of bread does not provide the necessary moisture for the spores to develop into hyphae and grow.
12
(a) Menstruation is the process where the thickened lining of the uterus, which is richly supplied with blood vessels to nourish a potential embryo, breaks down and comes out through the vagina as blood and mucous. This happens roughly every month if fertilization does not occur. It usually lasts for about two to eight days.(b) If the egg is fertilised, it travels to the uterus and implants in the thickened uterine lining. The fertilised egg (zygote) begins to divide and develops into an embryo, which continues to grow and develop organs inside the uterus.(c) If fertilization does not occur, the thickened uterine lining is not needed and slowly breaks down, leading to menstruation.
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(a) Cormels or suckers, which are specialized underground stems, are typically used for propagating banana plants. These are planted in the soil and develop into new plants.(b) Two advantages are:i) Plants raised by vegetative propagation are genetically identical to the parent plant, ensuring desirable traits like disease resistance are maintained.ii) They bear flowers and fruits earlier compared to plants grown from seeds.(c) This is asexual reproduction because it involves only one parent plant and does not involve the fusion of gametes.
14
(a) Both A and R are true and R is the correct explanation of A.
15
(a) Variations are beneficial for the survival of a species because they provide genetic diversity. If the environment changes (e.g., temperature increase, disease outbreak), individuals with certain variations may be better adapted to survive and reproduce, thus ensuring the continuation of the species.(b) Sexual reproduction involves the combination of genetic material from two different parents. This mixing of genes leads to new combinations of traits (variations) in the offspring, thus generating greater diversity compared to asexual reproduction where offspring are largely genetically identical to the parent.(c) Binary fission, as seen in Amoeba or bacteria, is a mode of asexual reproduction where variations are least likely to occur as it primarily involves cell division with minimal changes in the DNA copy.
16
(a) Pollination is the transfer of pollen grains from the anther (male part) to the stigma (female part) of a flower.Self-pollination occurs when pollen is transferred from the anther to the stigma of the same flower or another flower on the same plant.Cross-pollination occurs when pollen is transferred from the anther of one flower to the stigma of a flower on a different plant of the same species.(b) After landing on a suitable stigma, the pollen grain germinates and grows a pollen tube. This tube grows down through the style and reaches the ovary, entering an ovule. The male gamete from the pollen grain then travels down the pollen tube to fuse with the female gamete (egg cell) inside the ovule. This process is called fertilisation.(c) After fertilization, the zygote within the ovule divides several times to form an embryo. The ovule develops a tough protective coat and matures into a seed. The ovary grows rapidly and ripens to form the fruit, enclosing the seed(s). Sepals often shrivel and fall off, but sometimes persist.
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(a) Three common changes observed in both boys and girls during puberty are:i) Growth of hair in new areas like armpits and genital areas.ii) Skin becoming oily and potential development of pimples.iii) Increased height and changes in body proportions.(b) Two changes specific to girls during puberty are:i) Increase in breast size and darkening of the nipples.ii) Onset of menstruation (menarche).
18
(a) Both A and R are true and R is the correct explanation of A.
19
(a) Multiple fission.(b) Plasmodium, the parasite that causes malaria.(c) In multiple fission, the nucleus divides repeatedly to form many nuclei, and then the cytoplasm divides, producing numerous daughter cells simultaneously. In binary fission, the nucleus and cytoplasm divide only once, producing two daughter cells.
20
(a) Two bacterial STDs: Gonorrhoea, Syphilis. One viral STD: Warts, HIV-AIDS.(b) Condoms act as a physical barrier that prevents semen (containing sperm) from entering the vagina. This barrier also prevents the direct contact of the penis with the vaginal or anal tissues, thus reducing the risk of transmission of viruses and bacteria that cause STDs.(c) IUDs like the Copper-T are placed in the uterus. They prevent pregnancy by releasing copper ions which are toxic to sperms, thus killing them or reducing their motility. They also cause inflammatory reactions in the uterus that prevent implantation. A potential side effect is irritation of the uterus, leading to pain or increased risk of infection.
