All living things share one basic feature in life: reproduction. It is this motivation to reproduce that ensures the continuation of the species. This reproduction can occur in one of two ways:
- asexual reproduction;
- sexual reproduction.
Asexual reproduction involves just one parent and does not involve any sexual contact. Part of the parent splits away then grows and develops into a new and individual living thing. The process of asexual reproduction can be quick and simple, however it does also mean that both the parent and offspring share the same genetic material and therefore any genetic defects are passed on. Most asexual reproduction takes place in plants although some animals such as the hydra (a tiny animal living in ponds) also reproduce asexually. The sea anemone is one animal that can reproduce asexually as well as sexually, so too is the aphid.
Plants reproduce asexually:
- by sending out runners which develop young plants at the end and send down roots into the soil. The stems then die back and the new plant becomes independent of its parent;
- by producing bulbs which will grow and develop into independent plants. This explains why, if left in the ground, a few daffodil bulbs will develop over the years into a large number of plants;
- through their roots when small sections of root remain in the ground and then develop into new plants.
Sexual reproduction requires there to be two parents. Each parent is responsible for the production of sex cells or gametes. These cells, the male sperm and the female egg, are combined during fertilization and a new cell is formed from which the new plant or animal develops. Sexual reproduction takes longer than asexual reproduction and the offspring inherit half of their genes from one of their parents and half from the other. Genetic weaknesses are not always be carried on from one generation to another, but may happen when the gene carrying a particular characteristic is dominant.
Sexual reproduction can take place in one of two ways:
- external reproduction where animals are able reproduce in a way that requires no sexual union. Eggs laid by the female are fertilized outside the body by the male’s sperm. Animals that reproduce in this way tend to lay large numbers of eggs to increase the chances of fertilization and survival of the offspring;
- internal reproduction: in some animal species, internal reproduction involves the sexual joining togther of the male and female. The male injects his sperm into the female so that fertilization can take place inside the female’s body. In mammals, the female then carries the young as it grows. This is the gestation period and varies from one species to another. Animals that reproduce in this way tend to produce fewer sex cells as there is more likelihood of successful fertilization taking place.
See also Relationships and Sex Education.