Evolution over time
Evolution is a change in the inherited characteristics of a population over a number of generations, through the process of natural selection, which may result in the formation of new species.
A A type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully. is a group of organisms that are capable of interbreeding together to form fertile offspring. If, through evolution, organisms become so different that they can no longer interbreed, then The formation of new and distinct species in the course of evolution. has occurred. Speciation is more likely to occur if organisms become isolated from one another.
For example, a population of birds become isolated on an island with different food sources to the mainland. Through natural selection, the birds on the island will evolve to have different beaks in order to eat the food. Eventually, they will look very different to the population on the mainland and so will be a new species.
The idea behind the theory of The process of change in the inherited traits of a population of organisms from one generation to the next. through the process of natural selection is that all species of living things have evolved from simple life forms over a period of time. The Earth is about 4.5 billion years old and there is scientific evidence to suggest that life on Earth began more than 3 billion years ago.
This slideshow shows key events in evolution, from the first Single-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium. to humans.
Image caption, An evolution timeline
Archean eon
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