Transcript Natural Selection

More
embryo
examples
Darwin Goes Sailing
And finds
finches!
More
finches
Natural Selection
In 4 easy steps!
1.Overproduction
2. Genetic variation
3. Struggle to survive
4.Successful reproduction
1.
Overproduction
Why is over-production important?
For example, a rabbit can have a litter of 4
babies every month.
In one year, a rabbit can produce 48 babies!
If they all have babies the next year, how many
babies would that be?
2. Genetic Variation
We’re
all
unique!
3. Struggle to Survive
Organisms must
• Escape predators
• Find food
• Conserve energy
• Find mates
4. Successful Reproduction
Why is this important?
How does evolution happen?
One way is by “genetic drift”
Examples:
Horse
Peppered moth
How does evolution happen?
An important factor is ISOLATION.
The same species, in different
environments, can evolve differently.
This is how one common ancestor can
evolve into several different species.
Divergent evolution
Founder effect
If only a
small
population is
available to
breed, the
distribution
of traits
changes.
Mutations
Can be deadly, either prior to birth
(miscarriage), or shortly after.
Lethal white syndrome
Rye nose
Mutations
Can be neutral:
CGU
CGC
CGA
CGG
AGA
AGG
All code for Arginine.
What if you suffered a
mutation that
effected the
development of
your gill slits?
Mutations
Can be harmful but not deadly:
Down’s syndrome
Marfan’s syndrom
Dwarfism
Polydactyly
Mutations
Can be good!
Bohlinia  Samotherium  Giraffe!
Sickle cell anemia???
Giraffe Laws
In Atlanta, Georgia, it is illegal to tie a giraffe
to a telephone pole or street lamp.
In Idaho Residents may not fish from a
giraffe's back.
No, this has nothing to do with science.
Lack of Evolution
The Hardy-Weinberg Principle:
Will occur if the population is
• infinitely large
• isolated from other populations
• mating is random
• all genotypes are equally viable
Lack of Evolution
1. Extinction
2.
•
•
•
Lack of need to change:
Sharks
Horseshoe crabs
Cockroach
More about Natural Selection
http://evolution.berkeley.edu/evolibrary/articl
e/sneakermales_01