Download Genetic Drift and Gene Flow

Warm-up Questions:
• A population has a better chance of
survival if the population is more
genetically _____________.
Diverse
• What the difference between a genetic trait
and an acquired trait?
An genetic trait is inherited from the parents,
an acquired trait is learned to deal with an
immediate need.
Genetic Drift:

Random changes in the frequency of a gene
in a small isolated population, presumably
owing to chance rather than natural selection.
Bottleneck Effect:

 A period in the history of a population during which
the number of individuals is reduced to a low
number, perhaps by disease or extreme
environmental conditions.
 Can be the cause of genetic drift.
Founder Effect

 A founder effect occurs when a new colony is started
by a few members of the original population. This
small population size means that the colony may
have:
 reduced genetic variation from the original
population.
 a non-random sample of the genes in the original
population.
Gene Flow

 Transfer of alleles or genes from one population to
another
Allopatric Speciation:

 Occurs when biological populations of the same
species become isolated from each other which
prevents or interferes with genetic mixing.
Genetic Isolation:

 Organisms that have little genetic mixing with other
organisms within the same species.
 This may result in new species, but not always.
Prezygotic Reproductive
Isolation:

 Type of reproductive isolation that keeps species
from mating with others.
 Prezygotic isolation prevents the fertilization of eggs.
Geographic Isolation:

 A population of animals, plants, or other organisms
that are separated from exchanging genetic material
with other organisms of the same species.
 This can lead to multiple new species from the
original parent species.
Habitat Isolation:

 Two or more species live in the same area but
different habitats. ( Encounter each other rarely, not
geographically isolated)
 Example: water snakes VS land snakes.
Behavioral Isolation:

 Species-specific signals and elaborate behavioral
patterns that are used by closely related species to
insure contact with the proper mate.
Temporal Isolation

 Evolutionary mechanism that keeps individuals of
different species from interbreeding, even if they live
in the same environment.
 Example: breeding during certain times of year only.
Mechanical Isolation

 Anatomical incompatibility that prevents breeding.
Postzygotic Isolation:

 Prevents the formation of fertile offspring