Unit 1 Cells

Question 1

What are the main reasons reproduction is important?

Answer 1

Reproduction ensures:
1. Sustainability: Environment and species can endure.
2. Continuity: Species can exist over generations.

Question 2

What is DNA, and why is it important in reproduction?

Answer 2

DNA (Deoxyribonucleic Acid) is the molecule of life that:
1. Stores genetic information.
2. Determines traits, functions, and behaviour of an organism.
3. Passes genetic material to offspring during reproduction.

Question 3

What is the structure of DNA?

Answer 3

DNA is a double-helix made of four nucleotides:

Adenine (A) pairs with Thymine (T).
Cytosine (C) pairs with Guanine (G).

Question 4

What are the differences between asexual and sexual reproduction?

Answer 4

1. Asexual: One parent, offspring are identical.
2. Sexual: Two parents, offspring are genetically diverse.

Question 5

How do organisms reproduce asexually?

Answer 5

1. Bacteria: Binary fission.
2. Yeast: Budding.
3. Mold: Spores.
4. Plants: Vegetative propagation (e.g., potatoes).

Question 6

How do bacteria reproduce?

Answer 6

Bacteria reproduce by binary fission, splitting into two identical daughter cells.

Question 7

How do yeast reproduce?

Answer 7

Yeast reproduce asexually by budding, where a small bud grows on the parent and detaches.

Question 8

How do moulds reproduce?

Answer 8

Moulds reproduce asexually by releasing spores from a structure called sporagium, which grow in favourable conditions such as warmth and moist and divde through mitosis and cytokinesis

Question 9

How do plants reproduce asexually?

Answer 9

Plants reproduce through vegetative propagation, where new plants grow from roots, stems, or leaves.

Question 10

What is the role of the cell cycle in eukaryotic cell reproduction?

Answer 10

The cell cycle allows cells to:
1. Replace old or damaged cells.
2. Produce new offspring in single-celled organisms.

Question 11

What are the stages of mitosis?

Answer 11

PMAT:

1. Prophase: Nuclear membrane disappears, chromosomes form.
2. Metaphase: Chromosomes line up in the middle.
3. Anaphase: Chromosomes separate to opposite ends.
4. Telophase: Two nuclei form.

Question 12

How does meiosis differ from mitosis?

Answer 12

Meiosis creates:

1. Four haploid gametes (sex cells).
2. Genetic variation through crossing over and independent assortment

Question 13

What are gametes, and how are they formed?

Answer 13

Gametes are sex cells (sperm and egg) formed through meiosis, each with half the chromosomes of the parent.

Question 14

What happens after fertilization in humans?

Answer 14

1. Zygote divides via mitosis.
2. Embryo implants in the uterus.
3. Development occurs over 38 weeks (8 weeks embryonic, 30 weeks fetal)

Question 15

What are the pros and cons of asexual reproduction?

Answer 15

Advantages:
Fast, requires one parent, many offspring.

Disadvantages:
Lack of genetic diversity; vulnerable to environmental changes.

Question 16

What are the pros and cons of sexual reproduction?

Answer 16

Advantages:
Genetic variation increases survival in changing environments.

Disadvantages:
Slower process, requires two parents, fewer offspring.

Question 17

How does sexual reproduction create genetic diversity?

Answer 17

1. Crossing Over: Exchange of genetic material during Prophase I of meiosis.
2. Independent Assortment: Random alignment of chromosomes during Metaphase I.

Question 18

What are some examples of sexual reproduction?

Answer 18

1. Mammals: Internal fertilization, offspring develop inside females.
2. Insects: Fertilization produces males or females (e.g., bees).
3. Fungi: (yeasts/moulds) - reproduce asexual and sexual
4. Fish, Frogs, and Birds: fertilized eggs develop outside the female
5. Plants: Pollination produces seeds.

Question 19

How does asexual and sexual
reproduction contribute to life on Earth?

Answer 19

1. Asexual Reproduction: Produces many identical offspring quickly.
2. Sexual Reproduction: Introduces genetic diversity, ensuring survival in changing environments.

Question 20

How does reproduction relate to sustainability?

Answer 20

Sustainability is the ability of an environment and the species it supports to endure over time. Reproduction ensures species can continue contributing to interconnected ecosystems.

Question 21

Why is reproduction important for continuity?

Answer 21

Continuity means the ongoing existence of a species over generations, which is only possible through reproduction.

Question 22

What is the difference between chromatin and chromosomes?

Answer 22

Chromatin: Coiled DNA within the nucleus.

Chromosomes: Condensed chromatin that forms before reproduction, carrying genetic material to offspring.

Question 23

Describe binary fission in detail.

Answer 23

1. The parent cell duplicates its DNA.
2. The cell elongates, pulling the DNA copies apart.
3. The cell splits into two identical daughter cells.

Question 24

How does budding work in yeast?

Answer 24

A small growth (bud) forms on the parent cell, grows, and detaches to form a new, smaller cell that eventually grows to full size.

Question 25

What happens during spore formation in mould?

Answer 25

Mould releases spores from a sporangium. When spores land in a warm, moist environment, they divide by mitosis and grow into new mould.

Question 26

What happens during interphase?

Answer 26

The cell grows, increases organelles, and duplicates its DNA to prepare for division

Question 27

What is cytokinesis?

Answer 27

Cytokinesis is the final stage of cell division, where the cytoplasm and organelles divide to form two separate cells.

Question 28

What is crossing over, and why is it important?

Answer 28

Crossing over occurs in Prophase I of meiosis when homologous chromosomes exchange genetic material, increasing genetic variation.

Question 29

How does independent assortment occur?

Answer 29

During Metaphase I, homologous chromosome pairs align randomly, creating unique combinations of chromosomes in gametes.

Question 30

What is the difference between haploid and diploid cells?

Answer 30

Diploid Cells: Contain two sets of chromosomes (e.g., body cells). Haploid Cells: Contain one set of chromosomes (e.g., gametes).

Question 31

What happens during fertilization?

Answer 31

A sperm cell and egg cell combine to form a zygote, restoring the diploid chromosome number and beginning the development of a new organism.

Question 32

Why is asexual reproduction beneficial?

Answer 32

1. Requires one parent. 2. Rapid reproduction and population growth. 3. Offspring mature quickly.

Question 33

What are the disadvantages of asexual reproduction?

Answer 33

1. Lack of genetic diversity. 2. Vulnerability to environmental changes (e.g., disease, drought).

Question 34

Why is sexual reproduction beneficial?

Answer 34

1. Creates genetic diversity. 2. Improves survival chances in changing environments.

Question 35

What are the disadvantages of sexual reproduction?

Answer 35

1. Slower process with fewer offspring. 2. Requires energy to find a mate and care for young.

Question 36

How is DNA stored in cells, and what happens during reproduction?

Answer 36

DNA is stored in the nucleus as chromatin, a coiled form that fits into the cell. Before reproduction, chromatin condenses further into chromosomes. Chromosomes are duplicated and transferred to offspring during reproduction.

Question 37

What role do chromosomes play in reproduction?

Answer 37

Chromosomes carry DNA, the genetic blueprint of an organism. During reproduction, chromosomes are copied and passed to offspring, ensuring the transfer of genetic information.

Question 38

How does reproduction differ between prokaryotic and eukaryotic cells?

Answer 38

Prokaryotic Cells: Reproduce through binary fission (e.g., bacteria). Eukaryotic Cells: Reproduce through the cell cycle, which includes mitosis and cytokinesis.

Question 39

How do mammals reproduce sexually?

Answer 39

Mammals use internal fertilization, where the sperm fertilizes the egg inside the female body. The zygote develops into an embryo and then into a fetus, receiving nourishment from the mother.

Question 40

Why is genetic variation important for survival?

Answer 40

Genetic variation allows some individuals to adapt better to environmental changes. Increases the likelihood of species survival during diseases, climate changes, or resource scarcity.