A) Define reproduction. b) How is the egg cell produced in flowering plants? c) Describe pollination to fertilization in flowering plants.

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6.

a) Define the term reproduction.
Reproduction is the biological process by which new individual organisms, or "offspring," are produced from their parents. It is a fundamental feature of all known life, ensuring the continuation of a species from one generation to the next.

b) How is the egg cell produced in flowering plant?
In flowering plants, the egg cell is produced within the ovule, which is located inside the ovary.

• A diploid cell within the ovule, called the megaspore mother cell (or megasporocyte), undergoes meiosis to produce four haploid megaspores.
• Typically, three of these megaspores degenerate, and only one functional megaspore remains.
• This functional megaspore then undergoes three rounds of mitosis without cytokinesis, resulting in an embryo sac (female gametophyte) containing eight haploid nuclei.
• These nuclei differentiate and organize into seven cells: one large central cell with two polar nuclei, two synergids, three antipodal cells, and one egg cell. The egg cell is located near the micropyle, flanked by the two synergids.

c) Describe the mechanisms that occur from the time the pollen grains adhere on the stigma of a compatible flower until fertilization occurs.
The process from pollen adhesion to fertilization involves several key mechanisms:

1. Pollen adhesion and hydration: When a compatible pollen grain lands on the stigma, it adheres due to sticky secretions and begins to hydrate, absorbing water and nutrients from the stigma.
2. Pollen germination: The hydrated pollen grain germinates, forming a pollen tube that emerges from one of its pores. The growth of the pollen tube is guided by chemical signals released by the ovule.
3. Pollen tube growth through style: The pollen tube grows downwards through the style, secreting enzymes to digest the surrounding tissue and creating a path. The generative cell within the pollen grain divides mitotically to form two sperm nuclei (male gametes).
4. Entry into ovule: The pollen tube eventually reaches the ovule, typically entering through a small opening called the micropyle. It then penetrates one of the synergid cells within the embryo sac.
5. Double fertilization: The tip of the pollen tube ruptures, releasing the two sperm nuclei into the embryo sac.
   • One sperm nucleus fuses with the egg cell to form a diploid zygote, which will develop into the embryo.
   • The other sperm nucleus fuses with the two polar nuclei in the central cell to form a triploid primary endosperm nucleus, which will develop into the endosperm (food storage tissue for the embryo).

d) What are the conditions that favours self-pollination?
Conditions that favor self-pollination include:

• Bisexual flowers: The flower contains both male (stamens) and female (pistil) reproductive organs.
• Homogamy: The anthers and stigma mature at the same time.
• Cleistogamy: The flowers remain closed, preventing cross-pollination and ensuring self-pollination (e.g., in some violets and peanuts).
• Position of reproductive organs: The anthers are positioned directly above or very close to the stigma, making it easy for pollen to fall onto the stigma.
• Lack of external pollinating agents: In environments where pollinators are scarce or absent, self-pollination ensures reproduction.

7.

a) Define the following terms as used in Biotechnology:

i) Culture:
In biotechnology, culture refers to the growth of microorganisms (like bacteria or fungi), cells (like plant or animal cells), or tissues in a controlled artificial environment, typically in a nutrient medium. This allows for their study, propagation, or the production of specific substances.

ii) Inoculation:
Inoculation is the introduction of microorganisms, cells, or tissues into a culture medium or a living organism to initiate growth, infection, or an immune response. For example, adding bacteria to a petri dish with agar, or injecting a vaccine.

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• Question 2(d)
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• Question 5(a)

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