Variation in chillies. Image credit

Variation in chillies. Image credit

ZIMSEC O Level Combined Science Notes: Variation

  • The living world has many thousands of different types of plants and animals
  • For example lions are different from hyenas which in turn are different from say goats
  • In plants the Msasa trees are different from say pine trees which are different from eucalyptus trees
  • Even similar animals have differences between themselves for example no two goats are alike
  • This is known as variation
  • Variation-refers to the differences between individual animals or plants
  • There is variation in animals for example humans can be tall, short, fair skinned or dark skinned
  • There can also be variation in plants for example the number of seeds in a pod can vary and so does the size of plant leaves
  • Not all of a plant’s seeds are the same size
  • Continuous and Discontinuous variation
  • Continuous variation-is variation that results from environmental effects rather than being a result of genetics
  • Examples of continuous variation include seed size, the weight and height of an individual, the number of seeds in a pod etc
  • Although these characteristics can be affected by genetics, the environment plays a dominant role in this case
  • For example the number of seeds in a pod is affected by such things as the whether or not all or some of the ovules are pollinated, the amount of water and nutrients received by the plant etc
  • An animal’s height and weight is greatly affected by the amount of nourishment it receives
  • With continuous variation the characteristics change from animal to animal, plant to plant or individual to individual
  • Thus continuous variation cannot be used to group individuals with similar characteristics
  • Discontinuous variation-are variations resulting from genetic factors only for example coat colour and sex
  • Discontinuous variation can be used to group animals into distinct groups
  • With discontinuous variation the characteristics are heritable i.e they can be inherited
  • Such characteristics are not affected by the environment
  • For example being male or female is an example of discontinuous variation

To access more topics go to the Combined Science Notes page.

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