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Populations & Variation. Populations. A population is a group of the same species living within a particular geographical area at a given time. Variation. Monomorphic Variation. Polymorphic Variation.

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Populations & Variation

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A population is a group of the same species living within a particular geographical area at a given time.


Monomorphic Variation

Polymorphic Variation

Members of a population may show two or more variations for a particular trait. Flower colour in lupins

  • Members of a population may show no variation for a particular trait.
  • Galahs are monomorphic in respect to plumage
  • As are sulphur crested cockatoos



  • Variation exists in members of a population.
  • Variation may be:
    • Structural
    • Biochemical
    • Physiological
    • Developmental
    • Behavioural
    • Geographic
structural variation
Structural Variation
  • Variation exhibited in members of a population in terms of one or more structural traits.
    • EG. Polydactyly in humans, tails (or lack of in cats, toe number in chickens.
biochemical variation
Biochemical Variation
  • Variation exhibited amongst members of a population of a biochemical trait.
    • EG. coloursof some animals are due to biochemical differences – budgerigars.
physiological variation
Physiological Variation
  • Variation in a population of physiological traits in a population
    • EG. Ability to taste and smell certain compounds in foods or odours, ability to distinguish between colours
developmental variation
Developmental Variation
  • Variations due to changes that normally occur during the life span of the species.
    • EG. Colour changes in pythons, magpies, silver gulls from juveniles to adults, ripening of fruit from green to red/dark (strawberries)
behavioural variation
Behavioural Variation
  • Difference in behaviour expressed in various traits.
    • EG. In dogs, retrieving, herding. In horses – natural trotters, or natural pacers.
geographic variation
Geographic Variation
  • Members of a population may differ from those in another part.
    • EG. Tawny frogmouth birds are smaller and paler in northern parts of their range and larger and darker in southern parts.
causes of variation
Causes of Variation
  • Genetic:
    • Polygenes and monogenes
    • Sexual reproduction:Recombination of alleles
    • Mutations – new alleles
  • Interactions with the environment
  • Environmental factors like soil pH, light, altitude,soilnutrients etc influence the phenotype
  • A mutation refers to any permanent change in the DNA nucleotide base sequence of an organism
can you inherit a mutation
Can you inherit a mutation?
  • Yes! if a mutation occurs in the germline cells the change will be passed on to the offspring.
  • If a mutation occurs somatic cells it will not be inherited, but it may affect the individual during their lifetime.