DNA is the blueprint for making proteins. A change in DNA leads to different proteins being made, which ultimately results in an altered body design.

Source: Chapter 7, Section 7.1

The examiner expects you to establish the DNA → protein → body design chain in one line. The key idea from the passage is: DNA directs protein synthesis; changed DNA = different proteins = changed body design. Avoid writing more than one sentence for a 1-mark question.

When a variation arises in a new DNA copy during cell division, there are two possible outcomes:

1. The cell dies — if the variation is so drastic that the new DNA copy cannot work with the inherited cellular apparatus.
2. The cell survives — if the variation is minor, the cell continues to live, being subtly different from the original.

Source: Chapter 7, Section 7.1

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The examiner expects both outcomes stated clearly — death (drastic variation) and survival (minor variation). The key phrase "subtle difference" signals understanding that surviving variants are similar but not identical. Avoid over-explaining; one crisp line per outcome is enough for 2 marks.

Variation during reproduction is beneficial to a species because it improves the chances of survival when environmental conditions change. However, most individual organisms possessing a variation may not benefit from it — in fact, they may be at a disadvantage in existing conditions.

Example: In a population of bacteria living in temperate water, if global warming raises the water temperature, most bacteria will die. Only those few individuals with a heat-resistant variation will survive and reproduce. The variation harmed the species' current numbers but saved it from extinction — yet for the majority of individual bacteria, it provided no benefit.

Source: Chapter 7, Section 7.1.1 — The Importance of Variation

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• Examiners want two clear sides: benefit to species (survival of population over time) vs. no guaranteed benefit to individual.
• The bacteria + global warming example from the textbook is the expected one — use it directly.
• Key phrase to include: "survival of species over time."
• Don't write about DNA copying or modes of reproduction — stay focused on the variation distinction.

(i) Yeast – Budding: A small outgrowth (bud) develops on the parent cell, grows, and eventually separates to become a new individual.

(ii) Amoeba – Binary Fission: The cell splits into two equal halves in any plane, each developing into a new Amoeba.

(iii) Plasmodium – Multiple Fission: The nucleus divides repeatedly, then the cell splits simultaneously into many daughter cells.

(iv) Leishmania – Binary Fission: It splits into two, but division occurs in a definite orientation relative to its whip-like structure (flagellum).

Source: Chapter 7, Section 7.2.1 Fission

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• The question has four parts, so address each organism separately with its mode name and a brief mechanism — that earns full marks.
• Note the key contrast: Amoeba divides in any plane; Leishmania divides in a definite orientation — examiners often look for this distinction.
• Plasmodium's multiple fission (many daughter cells at once) is what sets it apart from the binary fission of Amoeba/Leishmania.
• "Budding" in Yeast is a favourite MCQ/short-answer topic — don't confuse it with fission.

Leishmania has a whip-like structure (flagellum) at one end, so binary fission occurs in a definite orientation relative to it. Amoeba lacks such a fixed structure, so fission can occur in any plane.

The examiner expects you to link the presence of the flagellum in Leishmania to its fixed orientation of division. The key contrast is organised body structure (Leishmania) vs. no such structure (Amoeba). One crisp sentence covering both organisms earns full marks. Source: Chapter 7, Section 7.2.1.

Fragmentation is the breaking up of a mature organism into smaller pieces (fragments), each of which grows into a new individual. Example: Spirogyra.

Source: Chapter 7, Section 7.2.2 – Fragmentation

The answer needs two parts: define fragmentation + give one example. Spirogyra is the textbook example given in this section. Examiners expect the keyword "breaks/fragments into pieces" and that each piece grows into a new individual. Do not confuse fragmentation with regeneration (Hydra/Planaria) — regeneration involves cut pieces regrowing, while fragmentation in Spirogyra occurs naturally upon maturation.

Spirogyra has a simple body organisation with no specialised tissues or organs. When it breaks into fragments, each piece contains all the necessary cell types to grow into a new individual.

In humans, cells are highly specialised and organised into specific tissues and organs placed at definite positions in the body. Such complex organisation makes cell-by-cell division through fragmentation impractical.

Source: Chapter 7, Section 7.2.2 Fragmentation

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The key contrast examiners look for is:

• Spirogyra = simple body, no tissue/organ specialisation → fragments can grow independently.
• Humans = specialised cells → tissues → organs at fixed positions → fragmentation cannot recreate this complex organisation.

Avoid writing a long essay. Two focused points, one for each organism, is exactly what a 2-mark answer needs.

This ability is called regeneration. It is made possible by specialised cells that proliferate and differentiate to form various cell types and tissues.

Source: Chapter 7, Section 7.2.3 Regeneration

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For a 1-mark question, examiners expect two things in one line: the correct term (regeneration) and the type of cells (specialised cells). Don't confuse regeneration with reproduction — the passage explicitly states they are not the same. Both parts are needed for full credit.

In Hydra, a bud originates as an outgrowth due to repeated cell division at one specific site. Once fully mature, the bud detaches from the parent body and becomes a new independent individual.

Source: Chapter 7, Section 7.2.4 Budding

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This is a direct textbook-based question. Examiners look for two key points: (1) the origin of the bud (outgrowth from repeated cell division at a specific site) and (2) what happens when it matures (detaches and becomes an independent individual). Both points together earn the 1 mark. Avoid vague language like "it grows" — use precise terms like "detach" and "independent individual."

(C) It introduces greater genetic variation than sexual reproduction.

Vegetative propagation produces offspring genetically similar to the parent (clones). Greater genetic variation is a feature of sexual reproduction, NOT vegetative propagation.

The passage explicitly states: "all plants produced are genetically similar enough to the parent plant to have all its characteristics." Options A, B, and D are all genuine features of vegetative propagation mentioned in the textbook. Only option C is incorrect — genetic diversity/variation is a feature of sexual reproduction, not vegetative propagation, making it the right answer to a "NOT a feature" question.

This illustrates that leaves are capable of vegetative propagation, as buds produced at the leaf margins of Bryophyllum fall on soil and develop into new plants.

Source: Chapter 7, Section 7.2.5 Vegetative Propagation

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The question directly targets the Bryophyllum example from Activity 7.5/7.2.5. The key term examiners look for is "leaves" (or "leaf margins"). Mentioning that the buds fall on soil and grow into new plants adds completeness for a 1-mark answer and shows understanding, not just recall.

The thick walls of spores protect them from harsh conditions until they come into contact with a moist surface and can begin to grow.

Source: Chapter 7, Section 7.2.6 – Spore Formation

The answer is directly from the passage: "The spores are covered by thick walls that protect them until they come into contact with another moist surface and can begin to grow." For 1 mark, state the protective function clearly in one line — no extra detail needed.

When two germ-cells (sperm and egg) fuse during fertilisation, the resulting zygote must have the normal chromosome number. If each germ-cell had the full number of chromosomes, the zygote would have double the normal number, which would be non-viable. Therefore, germ-cells contain only half the chromosomes so that their fusion restores the correct chromosome number in the offspring.

Source: Chapter 7, Reproduction

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The examiner wants you to show you understand the logic of halving: fertilisation = fusion of two cells, so each must contribute exactly half. Key terms to use: germ-cells, fertilisation, zygote, and chromosome number. Two marks = two linked points — (1) fusion doubles the count, (2) so halving beforehand keeps it normal. Avoid vague statements like "so reproduction works."

In asexual reproduction, a single individual produces offspring by copying its own DNA. Although DNA copying is not perfectly accurate and introduces small variations, this process is slow.

In sexual reproduction, DNA from two different individuals is combined. Each parent already carries different patterns of accumulated variations. Combining these creates new combinations of variants, producing greater diversity in each generation.

Since all variations come from living, surviving individuals, they are unlikely to be harmful. These new combinations help a species adapt better to changing environments, improving chances of survival.

Source: Chapter 7, Section 7.3.1 — Why the Sexual Mode of Reproduction?

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• Examiners look for two key ideas: (1) DNA copying introduces slow variations; (2) sexual reproduction combines DNA from two individuals, generating far greater variation faster.
• Mention that accumulated variations from both parents are already "tested" (non-lethal) — this is a scoring point many students miss.
• Avoid writing long paragraphs about meiosis or gametes; focus on the variation argument as asked.
• The phrase "new combinations of variants" directly mirrors the textbook language — use it.

The process is meiosis (a special type of cell division).

Problem: In sexual reproduction, two individuals combine their DNA to form a new individual. If each parent contributes a full set of chromosomes, the offspring would have twice the DNA of the parents, disrupting the cellular apparatus.

Solution: Special reproductive cells (germ-cells) are formed in specialised organs through meiosis, which halves the number of chromosomes and the amount of DNA. When two such germ-cells (gametes) combine during fertilisation, the normal chromosome number and DNA content are restored in the new generation.

Source: Chapter 7, Section 7.3.1 — Why the Sexual Mode of Reproduction?

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• The examiner expects you to name meiosis, state the problem (doubling of DNA each generation), and explain the solution (halving via meiosis in germ-cells, restoration at fertilisation). These are three distinct points matching the 3 marks.
• Don't confuse meiosis with mitosis — meiosis specifically halves the chromosome number; mitosis keeps it the same.
• Key terms to use: meiosis, germ-cells, gametes, chromosomes, fertilisation — these signal to the examiner you know the concept precisely.

(C) It creates new combinations of genetic variants, increasing the chances that some individuals survive environmental changes.

The passage in section 7.1.1 directly states that variation is useful for the survival of species over time — if a niche changes drastically, individuals with variations have a chance to survive. Modes of sexual reproduction allow greater variation to be generated (from "What you have learnt"). Options A and D describe advantages of asexual reproduction; Option B describes asexual reproduction (identical offspring). Always link sexual reproduction → variation → survival in changing environments.

The sperm (male gamete) is tiny, contains mainly genetic material, and has a long tail for movement. The egg (female gamete) is large, immobile, and contains no tail.

Source: Chapter 7, Section 7.3.3(a) & (b)

The key contrast examiners expect is: size (sperm = tiny; egg = large), mobility (sperm has a tail and can move; egg is immobile), and composition (sperm = mostly genetic material; egg = larger cytoplasm). Even for 1 mark, mentioning at least one clear structural difference with both gametes named is essential.

The stigma (the terminal, sticky part of the pistil) receives the pollen grain during pollination.

Source: Sexual Reproduction in Flowering Plants, chapter 7, section 7.3.2

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The pistil has three parts: ovary, style, and stigma. The stigma is the topmost, sticky part designed to trap pollen grains — this is the key term examiners expect. Don't write "ovary" (where fertilisation occurs later) or "style" (the passage tube). One word — stigma — earns the mark.

Self-pollination: When pollen grains are transferred from the anther to the stigma of the same flower, it is called self-pollination.

Cross-pollination: When pollen grains are transferred from the anther of one flower to the stigma of another flower, it is called cross-pollination. This transfer is achieved by agents like wind, water, or animals.

Source: Chapter 7, Section 7.3.2 – Sexual Reproduction in Flowering Plants

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• The textbook gives a direct, one-sentence definition for each term — reproduce those definitions precisely.
• The key distinguishing word is same flower (self) vs. another flower (cross). Examiners look for this contrast.
• Mentioning agents (wind, water, animals) for cross-pollination adds the extra detail expected in a 2-mark answer.
• No diagram is needed for this question type.

After pollination, the pollen grain lands on the stigma and a pollen tube grows through the style to reach the ovary. Here, the male germ-cell fuses with the egg cell in the ovule — this is fertilisation, forming a zygote.

The zygote divides repeatedly to form an embryo inside the ovule. The ovule develops a tough coat and becomes the seed. Simultaneously, the ovary grows and ripens to form the fruit. The petals, sepals, stamens, style, and stigma shrivel and fall off.

Source: Chapter 7, Section 7.3.2 — Sexual Reproduction in Flowering Plants

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Examiners look for the correct sequence: pollination → pollen tube growth → fertilisation → zygote → embryo (inside ovule) → seed (ovule with tough coat) → fruit (ripened ovary). Three marks typically map to three key stages, so naming and briefly describing each step (pollen tube, fertilisation, seed/fruit formation) earns full marks. Avoid vague language — use terms like zygote, embryo, ovule, and ovary precisely.

Testes are located in the scrotum outside the abdominal cavity because sperm formation requires a lower temperature than the normal body temperature.

This is a direct one-line fact from the textbook. Examiners expect the key phrase "lower temperature than normal body temperature" — without it, you will lose the mark. No extra detail is needed for 1 mark.

Source: Chapter 7, Section 7.3.3(a) — Male Reproductive System

(B) Testes → Vas deferens → Urethra → Penis

The passage states sperms are delivered through the vas deferens, which unites with the tube from the urinary bladder to form the urethra (common passage for sperms and urine), exiting through the penis. Prostate and seminal vesicles add secretions along the vas deferens path but are not stops in the sperm's route.

Fertilisation normally takes place in the oviduct (fallopian tube).

After the egg is fertilised there, it becomes a zygote, which immediately starts dividing to form a ball of cells called an embryo. This embryo then travels to the uterus and gets implanted in its lining.

Source: Chapter 7, Section 7.3.3(b) — Female Reproductive System

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• Examiners expect two clear points for 2 marks: (1) site = oviduct/fallopian tube and (2) immediate outcome = zygote formation → cell division → embryo.
• A common mistake is saying fertilisation occurs in the uterus — it does not; implantation does.
• The word "immediate" outcome means zygote/cell division, not implantation (that comes later). Mention both zygote and division to be safe.

The placenta is a special disc-like tissue embedded in the uterine wall that connects the embryo to the mother. It has villi on the embryo's side, surrounded by blood spaces on the mother's side, providing a large surface area for exchange.

Its roles are:

1. Nutrition: Glucose and oxygen pass from the mother's blood to the embryo through the placenta.
2. Waste removal: Waste substances produced by the embryo are transferred into the mother's blood through the placenta for elimination.

Source: Chapter 7, Section 7.3.3(b) – Female Reproductive System

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Examiners expect three clear functional points for 3 marks:

• Structure of placenta (disc embedded in uterine wall, villi, blood spaces) — sets context.
• Nutrient/gas transfer (glucose + oxygen from mother to embryo).
• Waste removal (embryo's waste transferred to mother's blood).

Avoid vague statements like "it helps the baby grow." Use correct terms: villi, blood spaces, uterine wall. These specific terms earn marks. The answer should be concise — around 70–80 words is ideal for 3 marks.

Menstruation occurs every month because the ovary releases one egg every month, and the uterus prepares itself by thickening its lining with blood and mucous to nourish a possible embryo. If the egg is not fertilised, this lining is no longer needed, so it breaks down and comes out through the vagina as blood and mucous — a process called menstruation.

Source: Chapter 7, Section 7.3.3(c)

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The examiner expects two linked points: (1) the monthly release of an egg causes the uterine lining to thicken, and (2) when fertilisation does not occur, that lining sheds as menstruation. Always mention both the cause (unfertilised egg) and the effect (shedding of uterine lining) to secure both marks.

(C) Oral hormonal pills

Oral hormonal pills work by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur.

The passage explicitly states that one category of contraceptives "acts by changing the hormonal balance of the body so that eggs are not released." This directly matches oral hormonal pills. Copper-T prevents implantation, condoms act as a mechanical barrier, and surgical blocking of fallopian tubes prevents the egg from reaching the uterus — none of these prevent egg release.

Physical changes in boys during puberty:

1. New thick hair growth appears on the face (moustache and beard).
2. The penis occasionally becomes enlarged and erect; voice begins to crack.

Physical changes in girls during puberty:

1. Breast size begins to increase, with darkening of the skin of the nipples.
2. Girls begin to menstruate (onset of menstrual cycle).

Importance of puberty for reproduction:

Puberty is important because reproductive tissues mature during this stage, enabling the body to produce germ-cells (sperms in males, eggs in females). As general body growth slows, the body directs resources toward sexual maturation. Changes like erection of the penis (needed for transfer of sperms) and development of breasts and uterus (needed for carrying and feeding the baby) prepare the body for the complete reproductive process.

Source: Chapter 7, Section 7.3.3

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• The question asks for two specific to boys and two specific to girls — examiners will deduct marks if you list common changes (hair in armpits, pimples) here.
• The "why important" part needs to connect puberty → maturation of reproductive tissues → ability to produce germ-cells and carry out reproduction. Don't just say "the body matures."
• With 5 marks, budget roughly: 1 mark each for the four changes + 1 mark for the explanation of importance.
• Avoid listing voice cracking AND facial hair as two separate boy-specific points if pressed for space; combine them or pick the two strongest examples.

Testes are located in the scrotum because sperm formation requires a lower temperature than the normal body temperature.

Source: Chapter 7, Section 7.3.3(a) — Male Reproductive System

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This is a direct one-line fact from the textbook. Examiners expect the key phrase "lower temperature than normal body temperature." Do not add extra details about testosterone or vas deferens — this is only 1 mark.

After release from the ovary, the egg passes through the following structures in order:

1. Fallopian tube (oviduct) — carries the egg from the ovary towards the uterus; this is also the site of fertilisation.

The egg travels: Ovary → Fallopian tube (oviduct) — where fertilisation by sperm occurs.

Source: Chapter 7, Section 7.3.3(b) Female Reproductive System

The question asks only up to the site of fertilisation, which is the fallopian tube/oviduct — so the uterus, cervix, and vagina are not required here. Examiners expect you to name the structures in order and identify the fallopian tube as the site of fertilisation. Mentioning both names (fallopian tube / oviduct) is good practice and shows complete knowledge. The 2 marks are typically split: 1 mark for naming the structure(s) in correct order, 1 mark for identifying the site of fertilisation.

The placenta is a special disc-shaped tissue embedded in the uterine wall. It plays the following roles:

1. Nutrition: It transfers glucose and oxygen from the mother's blood to the embryo through villi, which provide a large surface area for exchange.
2. Waste removal: Waste substances produced by the developing embryo are transferred into the mother's blood through the placenta for elimination.
3. Connection: It connects the embryo to the uterine wall, allowing the embryo to receive all necessary nourishment from the mother throughout the approximately nine months of development.

Source: Chapter 7, Section 7.3.3(b)

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Examiners expect three distinct functions for 3 marks — typically: (1) nutrient/gas transfer, (2) waste removal, and (3) the structural role connecting embryo to uterus. Mention villi and blood spaces to show textbook accuracy. Avoid writing a vague one-liner like "it provides nutrition" — split the functions clearly. The approximate 3-point structure maps directly to the 3 marks awarded.

The thick, spongy lining of the uterus is shed as blood and mucus during menstruation because the egg is not fertilised and the lining is no longer needed.

Source: Chapter 7, Section 7.3.3(c)

The answer must include two parts: what is shed (uterine lining/blood and mucus) and why (egg not fertilised, so the prepared lining breaks down). Examiners expect both for the 1 mark.

A condom acts as a mechanical barrier covering the penis, thereby preventing direct contact between body fluids during sex and thus blocking the transmission of many sexually transmitted infections like gonorrhoea, syphilis, and HIV-AIDS.

Source: Reproductive Health, Section 7.3.3(d), Chapter 7

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The key point examiners look for is the mechanism (physical/mechanical barrier) and the outcome (prevents transmission of STIs). Naming one or two example infections (gonorrhoea, HIV-AIDS) strengthens the answer but is not strictly required for 1 mark. Do not confuse this with the contraceptive function — the question is specifically about STI prevention.

(C) Oral contraceptive pills

Oral contraceptive pills work by changing the hormonal balance of the body so that eggs are not released, thus preventing fertilisation.

The passage clearly states that one category of contraceptives "acts by changing the hormonal balance of the body so that eggs are not released." These drugs are "commonly taken orally as pills." Copper-T works by irritating the uterus; condom is a mechanical barrier; surgical blocking of fallopian tube prevents the egg from reaching the uterus — none of these involve hormonal changes to stop egg release.

If the vas deferens is blocked, sperms cannot be transferred to the female reproductive tract, so they cannot reach the egg and fertilisation will not occur.

Source: Chapter 7, Section 7.3.3(d)

The examiner wants you to directly link the function of the vas deferens (sperm transport) to the consequence of its blockage (no fertilisation). One clear causal sentence is enough for 1 mark. The textbook explicitly states: "If the vas deferens in the male is blocked, sperm transfer will be prevented… fertilisation will not take place."