Natural Selection

Charles Darwin’s “suggestion” about how species change over

time.

Evolution refers to changes in a SPECIES,

not an individual

4 Key Features to Charles Darwin’s theory of Natural Selection:

Variation Competition Fitness Adaptation

Part 1: Variation Individual members of a population have

HERITABLE DIFFERENCES: small differences in the base sequence of their DNA

The differences that individuals have in their DNA gets passed on to their offspring

Happens because of– Random mutations– Sexual reproduction: combinations of gametes

Peppered moths

Part 2: Competition The struggle for survival The amount of resources in a habitat

is fixed– Food, water, living space, mates,

sunlight, minerals, shelter MANY more individuals are produced

during reproduction than will survive There is a limit to how large a

population can grow for a given area= carrying capacity

During spring, oak trees have FLOWERS, which produce pollen and egg cells.

Pollen will fertilize the egg cells, producing the oak tree seed= the ACORN

In one single year, an oak tree may produce up to 2000 acorns. MOST will not grow to be mature oak trees

What eats acorns? Blue jays Pigeons Ducks Mice Squirrels Chipmunks Skunks Raccoons

Deer Bears possums Crows Wild pigs Moth larva Weevil larva NOT HORSES:

acorns are toxic to them!

Mice A single field mouse can have up to 17

litters of babies each year Each litter can have up to 13 babies That’s 221 baby mice per year from one

female MOST get eaten or die:

– Hawks, owls, foxes, weasels, snakes

Sunflower One sunflower plant can produce up to

1000 seeds MOST get eaten!!

Part 3: Fitness Genetically, some individuals have

traits, either physical or behavioral, that make them better at surviving and reproducing

What determines which traits it is good to have??? – THE ENVIRONMENT

Part 4: Adaptation Eventually, as more and more time

goes by, and more and more individuals inherit a particular trait, ADAPTATION of the population occurs

Neck stretching

Natural selection?