Natural Selection - KCSE Biology Essays
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- What is natural selection?
(Theory put forward by Charles Darwin that explains that) Nature selects for individuals that are well adapted to a particular environment; and against those that are less adapted
- Discuss three examples of natural selection in action
Melanic forms of peppered moths; in Europe, there are two forms of peppered moths; white and black; before industrialization, the tree trunks were white; therefore the white peppered moths were white; hence were camouflaged; the black varieties were easily noticed and fed upon by predatory birds; the white form therefore reproduced and increased in number; during industrialization, the smoke from industries coated tree trunks black; the black variety became camouflaged; reproduced and increased in population; the white variety were easily noticed and fed upon by predators; they reduced in population;
Resistance against drugs and antibiotics; where microorganisms are continually exposed to a certain drug; their cells synthesise specific proteins; which counter the drug; this ability to synthesize the protein is passed onto the offspring;
Resistance to pesticides by insects; insects such as mosquitoes when continually exposed to a particular pesticide; synthesize a specific protein which make them resistant to the pesticide; this is then inherited by their offspring;
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