Key: Fertilisation: Fusion of gamete nuclei.

Types of Reproduction

Asexual Reproduction

Process resulting in genetically identical offspring from one parent.

— One parent is only required; no fusion of gametes and no mixing of genetic information.

— As a result, offspring are genetically identical to the parent and to each other.

Does not involve sex cells or fertilisation.

Pros & Cons of Asexual Reproduction

• Wild Species:
  • Advantages:
    • Rapid population growth.
    • Can exploit suitable environments quickly
    • More time and energy-efficient
    • Reproduction is completed much faster than sexual reproduction
  • Disadvantages:
    • Limited genetic variation in population.
    • Vulnerability to habitat changes e.g. New Predator
    • Disease is likely to affect the whole population.
    • Slow evolution — No recombination of genes.
• Crop Plants:
  • Advantages:
    • Crops can be produced with desired characteristics e.g. disease-resistant.
    • Crops can be produced with uniform characteristics necessary for sale.
    • Faster in production of crops.
    • Cost of production will be less than investing in seeds.
  • Disadvantages:
    • Require human input and management.
    • If diseased parent plant is used in reproduction process, offspring also diseased.
    • Big financial loss for farmers — vulnerability to disease or pests.

Sexual Reproduction

Process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote (fertilised egg cell) and the production of offspring that are genetically different from each other.

Pros & Cons of Sexual Reproduction

• Wild Species:
  • Advantages:
    • Increase genetic variation.
    • Can adapt to new environments due to variation.
    • Disease is less likely to affect population due to variation.
  • Disadvantages:
    • Takes time and energy to find mates.
    • Difficult for isolated members of species to reproduce.
• Crop Plants:
  • Advantages:
    • Increased genetic variation.
    • Better produced, better coping mechanism with weather changes.
  • Disadvantages:
    • Variation may lead to offspring that are less successful than parent plant at growing well or producing a good harvest.

Gametes & Zygotes

— Gamete is a sex cell (in animals, sperm and ovum; in plants, pollen nucleus and ovum.)

— Differ from normal cells as they contain half the number of chromosomes found in other body cells, which we call them haploid nucleus.

— A normal body cell contains 46 chromosomes but each gamete contains 23 chromosomes; so when male and female gametes fuse, they become a zygote (fertilised egg cell.)

— Zygote, fertilised egg cell contains the full 46 chromosomes, half of which came form the father and half from the mother, which we say the zygote has a diploid nucleus.

Assisted Reproductive Method