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Summary of natural evolution
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Complete summary on natural evolution for matrics, applies to Ieb and nsc
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ARTIFICAL SELECTION: EXAMPLE: NATURAL SELECTION: Definition → breeding of plants & animals for desirable characteristics and ↠ Peppered moths of Manchester:
not necessarily for what will enable them to survive better in the wild. - Light-coloured moths were in abundance
Also known as selective breeding - Manchester became industrialised → smoke from factories
Different from natural selection because humans choose which collected as black soot on trees.
characteristics should be selected. - Light-coloured were easily spotted by birds ∴ eaten!
HOW DOES IS WORK? - Dark-coloured blended in ∴ survived in greater numbers &
o Plant or animal with desirable characteristic is chosen by breeder reproduced!
o Bred with another of its kind with a similar characteristic
o Offspring have higher potential to display that characteristic
o Eg. Better milk-producing cows, high egg-producing chickens,
bigger fruits SPECIATION:
Artificial selection ensures combo of desirable characteristics: - Definition → formation of a new species
- Those of original species cannot interbreed with those of new species OR if
they do, offspring shouldn’t be fertile!
- TYPES → allopatric speciation & sympatric speciation
- Allopatric → formation of a new species as a result of separation of the
original species into different groups by a geographic barrier (eg. mountain /
river)
- Sympatric → formation of a new species without the presence of a
geographical barrier; brought about by radical change in genome of a small
group of individuals (causes reproductive barriers) in the original population.
ALLOPATRIC SPECIATION (geographic isolation):
o Eg. when migrating, a population may split & go on either side of the
mountain.
o Each population then reproduces separately & undergoes natural selection
independently, according to its own environment.
New varieties can be produced as a result of artificial selection after a
o 2 pops become genotypically & phenotypically different (no gene flow
number of generations. between them) → even if they mixed again, can’t interbreed
Starting with wolves, selective breeding has produced 100s of types of o ∴ 2 pops are now different species!
dog. (initially bred for hunting, now for intelligence, looks & character)
Varieties of wild mustard = cabbage, cauliflowers & broccoli
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