Biology - Differences Between Organisms

There are not only differences between different species of plants and animals but also between individual organisms of the same species. These differences are due partly to the information they have inherited from their parents and partly to the different environments in which the individuals live and grow.

The information that results in plants and animals having similar characteristics to their parents is carried by genes, which are passed on in the sex cells (gametes) from which the offspring develop. Different genes control the development of different characteristics of an organism. Many genes are needed to carry all the genetic information for a whole organism.

Genes make up the chromosomes of an organism and are contained in the nucleus of each cell. In the gametes, the nucleus contains only half of the number of chromosomes required for the complete organism. When the male and female gametes come together, their nucleii fuse and the fertilized cell (zygote) contains a full set of chromosomes and can develop into and adult animal or mature plant.

Since half of the information for the new individual comes from the male gamete and half from the female, there are many similarities to, but some differences from, the parents. This difference between organisms of the same species is called variation.

Sometimes this variation creates a feature in a plant or animal that enables it to compete better. If that is the case, the organism will breed successfully and the new feature is likely to be passed on to the next generation. This is how evolution takes place.