ANTA01H3 Lecture Notes - Lecture 3: Industrial Revolution, Overproduction, Allele
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25 Sep 2015
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ANTA01 – Lecture 2 – Evolution & Genetics
Natural Selection
•Darwin came up with these 3 facts by observing
1. Variability within species: between species, there were a great variety and a
lot of them are well suitable to their environment
2. Inheritance of variability: parents and offspring look alike
3. Overproduction & competition: in the natural world, animals had more
offspring then they could and would survive
•Advantageous traits are more likely to survive in an environment and reproduce
•Disadvantageous traits are less likely to survive and reproduce and show up less and
less in the environment compared to advantageous ones
•Because of variation, all animals are not born equal when it comes to competitive ability;
therefore, each generation won’t look like the previous generation
oEach generation is made of offspring of individuals who were successful at
surviving and reproducing
•Natural selection works on the level of the individual
•Evolution (change in species over time) works on level of population
•The definition of natural selection: differential reproductive success in the parallel
population
oThis results in changes in the population from one generation to the next. In
every generation, there is a resetting if the population is well suited to the
environment
•Example: peppered moth
oIn England 1950, the colour of a species of peppered moths allowed them to
camouflage with the bark they landed on, In the 1980s, some ended up being
completely black and in some environments that colour stood out on the bark
however, some tended to stay alive. Industrial revolution resulted in the bark
turning to black. With industrial revolution, 95% peppered moths were black
which resulted in the black moths having an advantage and the peppered ones
having a disadvantage (birds were picking them) this resulted in a shift. With
clean air laws however, black moth’s declines
•4 key points
1. Evolution was at the level of the population
2. Natural selection operates on the individual
3. Variation has to be there in the first place for these changes and shifts to
become advantageous occur
4. There is no such thing as a better variant, the variant depends on the
environment!
•Example: Galapagos finches
oWork of peter and rosemary grant - what they did was caught measured each
bird on the environment
oThere was a really big drought in mid 70s which led to a fundamental change in
the environment to a dry environment
oThis led to a failure of seed crops that these birds survive on
oOverexploitation of smaller seeds and then there was no food (this is the actual
shift)