The difference between individuals of the same or different species Variation The difference between individuals of the same or different species
Objectives Be able to Define the term variation Discuss the fact that variation occurs within as well as between species Describe the differences between continuous and discontinuous variation using examples Explain both genetic and environmental causes of variation Outline the behavioural, physiological and anatomical adaptations of organisms to their environments.
Interspecific variation Differences between individuals of different species are used as criteria for classification
Intraspecific Within the same species there are differences
Causes of variation Genetic The particular combination of alleles passed on by two parents by sexual reproduction. Mutation during either sexual or asexual reproduction. Environmental Plant features are easily influenced by light, mineral nutrition, availability of water- especially the amount and direction of growth. Animal features may be influenced by diet, temperature, and developmental environment.
Example of environmental variation
Two types of variation 1 Discontinuous variation A few discrete categories no intermediate forms Usually controlled by one gene Less likely to be influenced by environment
Two types of variation 2 Continuous There is a range of many intermediates between two extremes Represented using a frequency histogram where the range has to be split up into classes Controlled by the influence of several genes ( polygenic)