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strand 7 - Coggle Diagram
strand 7
abiotic factors
topography (altitude, slope, drainage)
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climate (includes rainfall, wind exposure and temperature)
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pollution (air, land or water, respiratory issues and eutrophication)
light (affected by cloud cover, altitude, seasons, light pollution)
humidity (amount of water in the air, affects transpiration)
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natural selection
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only the fittest individuals will survive to breed, the phenotypes which are selected against, won’t.
this variation is acted upon by selection pressures (the environmental factors which limit the population size e.g. predation, competition, disease).
natural selection relies upon mutations within a species creating genetic variation creating a variety of phenotypes.
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selection and evolution
evolution ~ changes in allele frequency in a gene pool over time as a result of gene mutation and natural selection.
types of selection
stabilising
when environmental conditions remain stable, this favours individuals with characterisics closest to the mean
disruptive
opposite of stabilising. favours extreme phenotypes at the expense of intermediates. least common form, but most important in terms of evolutionary change. opposite extremes favoured, mean is eliminated, occurs when an environmental factor takes two extremes.
directional
when a single phenotype is favoured, causing allele frequency to shift in one direction
eutrophication
excess of nutrients from fertilisers are flushed from the land into lakes and rivers via rainwater.
these pollutants cause aquatic plant growth of algae
algae blooms, oxygen is depleted as algal blooms prevent sunlight reaching other aquatic plants. plants die and oxygen is depleted.
decomposition further depletes oxygen, dead plants are broken down by bacterial decomposition using up even more oxygen in the water.
death of the ecosystem as oxygen levels reach such low levels that no life is possible so fish and other aquatic organisms die.