a) What is natural selection? b) Discuss three examples of natural selection in action.
a) 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; (2 mks)
b) Discuss three examples of natural selection in action.
1.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 were camouflaged.
The black varieties were easily noticed and fed upon by predatory birds; the white forms therefore reproduced and increased in number.
During industrialization, the smoke from industries coated tree trunks black. The black variety became camouflaged, reproduced and their population increased.
The white varieties were easily noticed and fed upon by predators; their population reduced.
2. Resistance against drugs and antibiotics, where microorganisms are continually exposed to a certain drug and develop resistance against the drug.
The population has some few variants micro-organisms cells that synthesise specific proteins, which counter the drug.
This ability to synthesize the protein is genetically passed onto the offspring. Those unable to synthesise the specific proteins die since they cannot counter the drug. Eventually the micro-organism population will have all its members resistant to the particular drug.
3. Resistance to pesticides by insects. Insects such as mosquitoes when continually exposed to a particular pesticide develop resistance.
Some mosquito variants synthesize a specific protein which make them resistant to the pesticide. This trait is then inherited by their offspring.
Those mosquitoes unable to synthesise the specific protein die.
Eventually the mosquito population will have all its members resistant to the particular pesticide. (Max. 18 mks)
(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; (2 mks)
b) Discuss three examples of natural selection in action.
1.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 were camouflaged.
The black varieties were easily noticed and fed upon by predatory birds; the white forms therefore reproduced and increased in number.
During industrialization, the smoke from industries coated tree trunks black. The black variety became camouflaged, reproduced and their population increased.
The white varieties were easily noticed and fed upon by predators; their population reduced.
2. Resistance against drugs and antibiotics, where microorganisms are continually exposed to a certain drug and develop resistance against the drug.
The population has some few variants micro-organisms cells that synthesise specific proteins, which counter the drug.
This ability to synthesize the protein is genetically passed onto the offspring. Those unable to synthesise the specific proteins die since they cannot counter the drug. Eventually the micro-organism population will have all its members resistant to the particular drug.
3. Resistance to pesticides by insects. Insects such as mosquitoes when continually exposed to a particular pesticide develop resistance.
Some mosquito variants synthesize a specific protein which make them resistant to the pesticide. This trait is then inherited by their offspring.
Those mosquitoes unable to synthesise the specific protein die.
Eventually the mosquito population will have all its members resistant to the particular pesticide. (Max. 18 mks)
The 21st century teacher, I lyk this Mr Makembu.
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