Download Evolution

Evolution
How Gene Pool
Change Occurs
What exactly is a
SPECIES?
• Species: Group of similar
organisms that can breed and
produce fertile offspring
• Example: Labrador and Pitt
Bull
• Non-example: Horse and
Donkey
The formation of a new species
from a preexisting population is
called: SPECIATION.
Causes of Change
Changes in the gene pool
can cause the population
to evolve
Changes in the gene pool
may be a result of many
different causes
Standard 8d
•
Students know
reproductive or
geographic isolation
affects speciation.
Causes of Change
1.Mutations
in the genes (DNA) of
individuals causing new adaptations.
Are mutations always bad?
2.Reproductive Isolation:
individuals unable to breed
together: behavior or physical
characteristics
Types of Reproductive
Isolation
1. Geographic Isolation-
2.
population is split by some physical
barrier: river, mountain, ocean
i.e. Albert & Kaibab squirrels of the
Grand Canyon
Behavioral Isolation- two
populations are capable of
interbreeding but have different
mating rituals or routines. i.e.
eastern & western meadowlarks
3. Temporal
Isolation- two
or more
species
reproduce at
different
times.
i.e. three
types of rain
forest orchids
Standard 8c
• Students know the effects
of genetic drift on the
diversity of organisms in a
population.
Sometimes the gene pool
just changes……
Genetic Drift is cause of
evolution by random chance
No Natural Selection
Happens in small populations
2 types of Genetic Drift
1. Bottleneck Effect- a high
percentage of a population is
killed by a random act reducing
variation in the gene pool.
2. Founder Effect- change in
allele frequencies as a result of
the migration of a small
subgroup of a population