1. KEY CONCEPT Darwin proposed natural selection as a mechanism for evolution.

2. Several key insights led to Darwin’s idea for natural selection.
Darwin noticed variation in domesticated plants and animals.
Artificial selection is the process by which humans select traits through breeding.
cabbage, brussel sprouts, kale, cauliflower were all developed from a wild cabbage plant
all dogs have a common ancestor
neck feathers
crop
tail feathers

3. Natural selection is a process by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.
Heritability is the ability of a trait to be passed down.
There is a struggle for survival due to overpopulation and limited resources.
The environment is the selective agent – determines which traits are advantageous
being dark green may be good in a forest but not so in a desert
Darwin proposed that adaptations arise over many generations – descent with modification

4. Natural selection explains how evolution can occur.
There are four main principles to the theory of natural selection.
variation – in all populations there are slight differences caused by differences in DNA
overproduction – most organisms produce more
offspring than can survive; leads to competition
adaptation- a certain variation may allow individuals to survive at a greater rate in that particular environment; that trait is passed on to the offspring;
descent with modification- over time there will be more individuals with that trait, and the species will be changing
Fitness is the measure of survival ability and ability to produce more offspring (reproductive fitness)

5. Natural selection acts on existing variation.
Genes change by random mutations.
It the change is an advantage, then it will be selected for.
(may be harmful or neutral)
If the environment changes, the adaptation may not be beneficial anymore
wrist bone
five digits