natural selection Flashcards
what is natural selection
Natural selection is the process by which an environmental factor acts on a population and results in some organisms having a greater chance of survival and producing more offspring than others.
it ensures that a species becomes gradually better adapted to its environment.
what is the environmental factor known as
The environmental factor that acts on a population is knowns as the selective agent.
what is the selective agent
The selective agent may be a biotic factor (another living thing) such as a bacterial infection, a competitor or a predator.
The selective agent may be an abiotic factor (a physical factor) such as a temperature, water, soil nutrients or fire.
what is the effect of a selective agent
The effect of the selective agent on the population is know as the selection pressure.
how do selective agents act
most selective agents act by killing individuals as they are often less suited to surviving and are referred to as ‘poorly adapted’ or ‘less fit’.Not all selective agents act by killing. For example, female birds often select brighter coloured males for breeding, these males will produce more offspring in the next generation. Darwin called this sexual selection.
what is variation
Darwin concluded that natural selection can only take place if there is variation within a population.
The exact mechanism for creating population variation was unknown to Darwin.
