Variation is the difference between individuals of the same species
Genotypic variation is variation resulting from genetics only.
Phenotypic variation is variation caused by both genetics and environmental factors
Continuous variation results in a range of phenotypes between two extremes.
E.G. -> Height in humans
Discontinuous variation results in a limited number of phenotypes with no intermediates. E.G. -> tongue rolling.
– DCV is mostly caused by genes alone.
– E.G. -> Blood group A A AB and O
Mutation is a genetic change.
– Mutation is the way in which new alleles are formed.
– Ionizing radiation and some chemicals increase the rate of mutation.
– Gene mutation is a change in the base sequence of DNA.
Adaptive feature is the inherited functional features of an organism that increases its fitness
Fitness is the the probability of an organism surviving and reproducing in the environment in which it is found.
Adaptations of xerophytes and hydrophytes.
Xerophytes
– sunken stomata to prevent water vapor loss.
– Thick wavy cuticle to prevent evaporation of water
– Small leaves for lesser surface area for evaporation
– Extensive roots for increased water uptake
Hydrophytes
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Small roots as water can be directly obtained by the leaf and the stem
Stomata always open to maximize gas exchange as there is a large supply of
– water
Large surface area to float on water and gain as much light for photosynthesis

Describe natural selection:
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There is variation in the population due to sexual reproduction.
When organisms reproduce, many offsprings are often produced
Organisms produced from sexual reproduction will show variation from their parents
However, not all the organisms are expected to survive as there is completion for resources.
For example, lions with larger muscle in it itʼs legs is able to run and get food faster than lions with smaller muscles
As resources are not unlimited, there is a struggle for survival
Organisms with favorable characteristics will be more likely to survive and in turn reproduce, organisms with disadvantageous characteristics will die before they get the chance to reproduce.
The organisms which survive reproduce and will pass on their alleles for the next generation in a changing environment