unit 4.2 natural selection

Pregunta	Respuesta
Define natural selection	natural selection is the process by which an environmental factor acts on a population & results in some organisms having a greater chance of survival & producing more offspring than others.
Define selective agent	an environmental factor that acts on a population during natural selection
What is the difference between biotic factors & abiotic factors?	Biotic factors are living things such as plants, animals, bacteria, fungi etc. Abiotic factors refer to non living things such as air and water.
Define selection pressure.	the effect of the selective agent on a population.
Most selective agents act by killing individuals & are often less suited to surviving & refer to 'poorly adapted' or 'less fit'. Give an example.	for example predators may find them easier to catch because they are slow runners, have poorer eyesight and are more easily seen.
define sexual selection	a special case of natural selection, in which the environment factor is the selection of a mate.
Define variation	differences in characteristics due to different genes
what is a more modern definition for natural selection?	natural selection is the change of a particular genetic make up of a species over many generations due to environmental selection of a particular characteristic.
Give evidence for natural selection	it only becomes obvious after many generations, this makes the effects of natural selection impossible to observe in organisms that have long generation times such as humans and elephants.
What was the peppered moth?	it was studied my Kettlewell and existed in 2 forms. the normal color was white with black specks.
Explain Kettlewells experiment on peppered moths	He placed 2 different colors of moths on tree trunks, observed birds feeding on the moths, counted the numbers of light & dark moths eaten.
What are insecticides?	a chemical that is sprayed onto crops to kill insects. it was only active for a few years but later had no effect.
Define resistance	the inherited ability of a species to withstand chemicals
How did Alexander Fleming find a way to kill bacteria?	he discovered that some fungi make special chemicals to defend themselves against bacteria.
Define antibiotics	Chemcials by organisms such as fungi to defend themselves against bacteria
Name a dangerous type of bacteria	Golden Staph. it is resistant to many antibiotics and difficult to kill.
Define biodiversity	the number and range of different species that exist.
Define Speciation	the process by which one or more species splits into 2 or more species.
What are the 3 steps of the process of speciation?	variation, isolation and selection.

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