Sexual Reproduction (CIE IGCSE Biology: Co-ordinated Sciences (Double Award))

• Sexual reproduction can be described as

A process involving the fusion of the nuclei of two gametes to form a zygote

• Sexual reproduction results in the production of offspring that are genetically different from each other

Sexual reproduction and species

• Sexual reproduction can contribute to the success of a species in the wild as it increases the genetic variation present in a population
• A species is a group of organisms that can reproduce to produce fertile offspring

Extended Tier Only

• The nuclei of gametes are haploid
  • They contain half the number of chromosomes of a normal body cell
  • In humans, this is 23 chromosomes
• The nucleus of a zygote is diploid
  • It contains the same number of chromosomes as a normal body cell
  • In humans, this is 23 pairs of chromosomes
  • The zygote continues to stay diploid as it grows into a fetus and embryo during pregnancy

Gametes nuclei are haploid, zygote nuclei are diploid

Extended Tier Only

• Advantages and disadvantages of sexual reproduction to a population in the wild include: