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Biology 101 Ch. 25 - Evolutionary Processes
Professor Abu's Class
23
Biology
Undergraduate 1
11/14/2012

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Cards

Term

What are the five things that stop evolution?

Also needed for Hardy-Weinburg Equilibrium

Definition

No Natural Selection

No Genetic drift

No Gene flow

No Mutation

random mating

Term
What makes Natural Selection special in evolution?
Definition
can cause adaptations by itself
Term

Describe Directional Selection

what does it reduce?

Definition

phenotype is pushed in one direction

reduced genetic variation

Term
Describe Purifying selection
Definition
When bad alleles are lost
Term

Describe Stabalizing Selection

what is reduced?

Definition

reduces extremes in a population

no change in average traits

genetic variation is reduced

Term

Describe Disruptive Selection

why is it important?

Definition

extreme traits are favored

important for speciation

Term

Describe Balancing Selection

what causes it?

Definition

no alleles are at an advantage

heterozygote advantage

                    -better fitness than homozygotes

 

Term
When does the heterzygote advantage take place?
Definition

1. when environment changes over time

2. When Frequency-dependent selection occurs

 

Term
Describe Frequency-dependent Selection
Definition
When rare alleles are sought after
Term
What does Natural Selection do simply
Definition
it increases fitness and leads to adaptation
Term
Describe Genetic Drift
Definition
Changes in allele frequency due to chance
Term
What are two types of Genetic Drift?
Definition

1. Bottleneck effect

2. Founder effect

Term
Describe the Bottleneck effect
Definition
when a large population's alleles are suddenly reduced
Term
Describe the Founder effect
Definition
when organisms move from a population, changes allele frequency
Term

Describe Gene Flow

effect on fitness and variation?

what does it cause?

Definition

movement of alleles from one population to another

can increase or decrease them

allele frequency to equalize

Term
What can mutations do to genetic variation?
Definition
it can increase genetic variation
Term
Describe deleterious alleles
Definition
alleles that lower fitness
Term
What is the ultimate source of genetic variation?
Definition
mutations
Term
describe effects of inbreeding
Definition
affects genotype frequency but not allele frequency
Term

Describe Inbreeding Depression.

Why does it have that affect?

Definition
fitness is decreased because of an increase in homozygous recessive individuals
Term
Describe Sexual Dimorphism
Definition
any trait that varies between two forms
Term
What can Genetic Drift lead to?
Definition
fixation or loss of alleles
Term
If you decrease genetic variation in a population, what is true about surrounding populations?
Definition
they are more different
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