natural selection evolution

original of species hypothesis I

aristotle believed all plants+animals had been placed on the Earth at its beginning and none have ever changed. this latest 2000 years and it was wrong

origin of species hypothesis Ii: life has changed over time

1) A.Lamarck’s theory

2) B.Darwin’s theory

lamark’s theory of evolution

consists of “Law of use and disuse” and “inheritance of acquired characteristics”

law of use and disuse

the more often a body part is used, the more developed it will be.

inheritance of acquired characteristics

the more developed or underdeveloped traits are passed onto their children

disproving lamark’s theory

august weismann cut tails off 20 generations of mice. Hypothesis: if lamarck is correct, then after 20 generations, the mice will have small, underdeveloped tails because of the Lawnof use and disuse, and inheritance of acquired characteristics. the result was no change in tail length/size

darwin’s theory of evolution

his theory of evolution was: evolution happens because of natural selection

darwin theory natural selection

a phenomenon occuring in the natural world where organisms possessing traits that are highly suited to their environment have a greater likelihood of survival and a higher rate of reproductive success

4 key conditions necessary for natural selection to occur

struggle for survival, inheritable variation, variation of fitness, lots of time