Sexual Reproduction

Definition and Role

Sexual reproduction is the process by which offspring are produced from the genetic material of two parents.
Involves the fusion of male and female gametes (sex cells) in a process known as fertilisation.
Offspring produced by sexual reproduction are genetically diverse, inheriting unique combinations of genes from both parents.

Stages of Sexual Reproduction

Gamete formation: Both males and females produce gametes. Males produce sperm cells, while females produce egg cells (ova). This process is controlled by sex hormones and occurs in the reproductive organs.
Fertilisation: A sperm cell from the male parent fuses with an egg cell from the female parent. The resulting cell (zygote) contains a mixture of genetic material from both parents.
Development: The zygote starts to divide and grow into an embryo, which eventually develops into a foetus.
Birth: Eventually, the foetus is born as a new individual.

Gametes

Male gametes or sperm are small and motile, produced by the testes in large quantities.
Female gametes or ova are larger, non-motile, and produced in smaller quantities by the ovaries.
Both types of gametes have only one set of chromosomes (haploid), so that, after fertilisation, the resulting zygote has two sets of chromosomes (diploid).

Fertilisation

Fertilisation is the fusion of a male and female gamete to form a zygote.
In mammals, fertilisation usually happens in the Fallopian tubes.
The fusion of gametes results in genetic variation because each gamete contains different genetic information due to meiosis and genetic recombination.

Pregnancy and Gestation

After fertilisation, the zygote travels down the Fallopian tube to the uterus and implants into the thickened uterine wall.
It develops into an embryo, and then into a foetus. This period of development is known as gestation.
In humans, gestation lasts approximately nine months, after which labour begins, leading to the birth of the baby.

Importance of Sexual Reproduction

Sexual reproduction introduces genetic variation among offspring, which can enhance survival of a species by promoting adaptation to changing environments.
It also enables natural selection by producing offspring with different traits, some of which may confer survival advantages.

Remember, sexual reproduction involves many complex processes, from gamete formation to fertilisation and gestation. These processes all contribute to the continuance of life and genetic diversity.