Sexual and asexual reproduction and meiosis

What is Sexual Reproduction?

Sexual reproduction involves the fusion of gametes (sperm and egg in animals, pollen and egg in plants).

What is Asexual Reproduction?

Asexual reproduction involves one parent, and offspring are genetically identical to the parent.

Advantages of Sexual Reproduction

• increases genetic variation

• due to variation species can adapt to new environments

• disease is less likely to wipe out whole population

Disadvantages of Sexual Reproduction

More energy needed → For gamete production and fertilization.

Fewer offspring → Compared to asexual reproduction.

Takes longer → Organisms must find a mate.

Advantages of Asexual Reproduction

• Fast reproduction → Can produce many offspring quickly.
  ✅ No need for a mate → Useful for isolated organisms.
  ✅ 100% of genes passed on → No loss of beneficial alleles so good if parent is well adapted to their environment

What are the disadvantages of asexual reproduction?

• No genetic variation → If environment changes, the entire population could die.
  ❌ More susceptible to disease → Since all individuals are identical.

• poor ability to adapt

What is meiosis?

Meiosis is the type of cell division that produces gametes (sperm and egg cells). It halves the chromosome number, creating haploid cells (23 chromosomes in humans).

Where does meiosis take place?

Meiosis occurs in the testes (males) and ovaries (females) in animals, and in flowers (anthers and ovaries) in plants.

How does meiosis increase genetic variation?

Crossing over → Chromosomes swap sections of DNA.

Fertilization → Combines DNA from two parents, increasing variation.

differences between mitosis and meiosis

Feature	Mitosis 🧬	Meiosis 🧬🧬
Function	Growth, repair, and asexual reproduction.	Produces gametes (sperm and egg cells) for sexual reproduction.
Number of Divisions	1 cell division.	2 cell divisions.
Number of Cells Produced	2 identical daughter cells.	4 genetically different gametes.
Chromosome Number	Diploid (46 in humans) – full set of chromosomes.	Haploid (23 in humans) – half the chromosome number.
Genetic Variation	No genetic variation – daughter cells are clones of the parent cell.	Genetic variation occurs due to crossing over and independent assortment.
Where It Occurs	In body cells (e.g., skin, liver, bone marrow).	In reproductive organs (testes and ovaries in animals, anthers and ovaries in plants).
When It Happens	Throughout an organism’s life for growth and repair.	Only during gamete formation for reproduction.
Importance	Helps organisms grow, replace damaged cells, and reproduce asexually.	Ensures genetic diversity, which helps populations adapt and evolve.

explain meiosis

When a cell divides to form gametes:

• copies of the genetic information are made

• the cell divides twice to form four gametes, each with a single set of chromosomes

• all gametes are genetically different from each other.

why do gametes rejoin at fertilisation

Gametes join at fertilisation to restore the normal number of chromosomes.