Evolution
A species is a group of interrelated organisms that can interbreed to produce fertile offspring. Each species is given a scientific name, written as Genus species, for example a cheetah is Acinonyx jubatus.
Variation exists within populations of organisms, and these are due to genetic and environmental factors.
Discontinuous variation is where a trait is found in a number of discrete forms, for example blood type.
Continuous variation is where a trait can have a range of values. There is often a normal distribution (bell curve) in a quantitative trait.
Selective breeding by humans has produced many breeds of domestic animals and plants with very different characteristics to the original species. Examples include domestic dogs (Canis lupus familiaris) and cruciferous vegetables (Brassicacae).
Related organisms share anatomical features, for example the homologous tetrapod skeletons of a whale and a hummingbird.
All living organisms are related to each other, and the closeness of the relationship can be measured by comparing anatomy, physiology and genetics.
All living organisms have evolved over the last 3 or 4 billion years.
Each organism produces more offspring than would be needed for replacement. It passes on inherited traits to its offspring.
The organisms which are best adapted to survive in their environment survive longer and reproduce more. Their genes are selected for and become more common in the species.
Small changes to genes accumulate over time, and changes to anatomy and physiology of organisms can be observed.
Over time, species evolve, and dramatic changes are seen as new solutions to problems of survival emerge.
Significant milestones in evolution include the evolution of photosynthesis, aerobic respiration, multicellular life and the notochord.
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