Transcript 11.3 Other Mechanisms of Evolution

11.3 Other Mechanisms of Evolution
KEY CONCEPT
Natural selection is not the only mechanism through
which populations evolve.
Five factors that can lead to evolution.
11.3 Other Mechanisms of Evolution
1. Gene flow is the movement of alleles (genes) in and out of
populations.
occurs when individuals
join new populations and
reproduce-migrate
Increase genetic variation
in the receiving
population
Animal move
Plants and fungi-wind,
“hitchhikers”
bald eagle migration
11.3 Other Mechanisms of Evolution
• Gene flow moves alleles from one population to another.
11.3 Other Mechanisms of Evolution
2. Genetic drift is a random change in allele frequencies due to
chance.
Causes a LOSS of genetic diversity in a population.
More common in small populations
Example1: Bottleneck Effect- natural or man-made disaster leads to a
drastic reduction in population size.
11.3 Other Mechanisms of Evolution
Example 2: Founder Effect
Few individuals colonize a new population
Occurs after start of new population.
11.3 Other Mechanisms of Evolution
Negative Effects on a Population.
Less likely to have some individuals that can adapt
Harmful alleles can become more common due to chance
Reduces variation and adaptability
11.3 Other Mechanisms of Evolution
3. Mutations produce the genetic variation needed for
evolution.
11.3 Other Mechanisms of Evolution
4. Sexual selection selects for traits that improve mating
success.
11.3 Other Mechanisms of Evolution
3. Non-random mating-Sexual selection occurs when
certain traits increase mating success.
– males produce many
sperm continuously
– females are more
limited in potential
offspring each cycle
11.3 Other Mechanisms of Evolution
• Two Types
– intrasexual selection: competition among males
– intersexual selection: males display certain traits to
females
11.3 Other Mechanisms of Evolution
5. Natural selection selects for traits advantageous for
survival.