OBJECTIVE: You will be able to explain how natural

selection works

Natural Selection Notes

Natural Selection Notes

“How the changes in the environment can bring

about changes in species”

1. Artificial selection – breeding animals and plants for certain characteristics

2. Darwin explains evolution

a. 1858 Darwin writes “The Origin of Species”, explains evolution through the theory of NATURAL SELECTION.

b. Natural selection – the process where individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species. (“Survival of the Fittest”)

NATURAL SELECTIONStep 1: OVERPRODUCTION – each species

makes more offspring than will survive

NATURAL SELECTIONStep 2 – GENETIC VARIATION –

Any difference between individuals of the same species

- some traits help, some hurt them.

- Some variations are helpful = adaptation

Step 2 – GENETIC VARIATION

Not everyone is identicala. Different genes = different traits

b. Fast swimmers, better camouflage

NATURAL SELECTION

Step 3: STRUGGLE TO SURVIVE - COMPETITION

– A natural environment doesn’t have enough resources for everyone, so only some individuals survive to adulthood.

Step 3 - Competition: Usually indirect – no actual physical fights

Not enough food, not be able to escape from predators

Only strong organisms will survive long enough to reproduce

NATURAL SELECTIONStep 4: SUCCESSFUL REPRODUCTION

– the individuals that are well adapted to the environment are more likely to survive and reproduce. Their genes will be passed on.

**Over a long period of time, natural selection can lead to evolution.**

The Heike or Oni-gani (“demon spirit” crab, Dorippe japonica), whose name derives from a Japanese legend. The pattern on its shell is thought to resemble the face of a Samurai warrior.

Natural or artificial selection? Intentional or accidental?

Sexual Selection (“Darwin’s headache”)

Archaeopteryx, discovered 1861

Exit Slip1. Give me an adaptation that rabbits have to

help them survive?

2. A factor that controls natural selection isa. Inheritance of acquired traits

b. Unused traits become smaller

c. Organisms produce more offspring than can survive

d. The size of the organism