Download Evolution - Pearland ISD

Evolution
Objectives:
7A - Analyze & evaluate how evidence of common ancestry
among groups is provided by the fossil record, biogeography, and
homologies, including anatomical, molecular, and developmental
7E - Analyze & evaluate the relationship of natural selection to
adaptation & to the development of diversity in & among species
I. Population Genetics - study of
the traits in a population
A. Population – a group of interbreeding
organisms (a species) living in a given
area
B. Gene Pool – combined genetic
material of all the members of a
population
C. Allele – forms that a gene can take
D. Allele Frequency – the number of each
allele for a trait as a fraction of all the
alleles for a particular trait
a. Example:
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8 alleles total, 4 are green.
Allele frequency of green = 4/8 or 1/2
II. How do you get NO EVOLUTION
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- NO evolution = genetic equilibrium
- Five conditions must be met to have
genetic equilibrium.
1. Random mating
2. Large Populations
3. No Immigration or Emigration
4. No Mutation
5. No Natural Selection
- Genetic Equilibrium does not occur
- It is only theoretical
III. Generalization
1. If gene pools do not remain the same
over time, they must change.
 2. This “changing of the gene pool” (allele
frequency) has a name —› Evolution.
 3. Evolution – the changes in the gene pool
of a population over time
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IV. Speciation – formation of a new species
 1.
Behavioral Isolation
- occurs when 2 populations are capable
of interbreeding but have differences in
courting rituals or other reproductive
strategies
 2.
Geographic Isolation
- 2 populations are separated by geographic
barriers
●examples: rivers, mountains, bodies of water
 3.
Temporal Isolation
- 2 or more species reproduce at different
times
What a Beak! Lab
Natural Selection
Objectives:
7C - Analyze & evaluate how natural selection
produces changes in a population, not individuals
7D - Analyze and evaluate how the elements of
natural selection, including inherited variation, the
potential of a population to produce more offspring
than can survive, and a finite supply of
environmental resources, result in reproductive
success
V. Natural Selection:
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a. Artificial Selection – humans select for variations
in plants and animals that they find useful.
b. Natural Selection
– also means “Survival of the Fittest”.
- Fitness in this sense does not mean strongest.
- Fitness in Darwin terms means reproduction.
The one who survives long enough to
reproduce the most is the one with the
highest fitness.
VI. Types of Selection
-Evolution acts on the phenotype of the
individual, not the genotype.
 - There are 3 types of selection that can
occur on a population.
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i. Directional Selection
 – when individuals at one end of the curve have a
higher fitness than individuals in the middle or at
the other end of the curve.
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 ii.
Stabilizing Selection
 – when individuals near the center of the
curve have higher fitness than individuals at
either end of the curve, narrowing of the
graph.
 iii.
Disruptive Selection
 – when individuals at either end have a higher
fitness and individual near the middle of the
curve are selected against.
- Over time with enough selection a
population can go through genetic drift.
a. genetic drift – random change in
allele frequency.
VII. Adaptation- an inherited trait that
increases a population’s chance of survival
and reproduction in a particular environment
A. Through adaptations, populations often
become suited to a specific job called a
niche.
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1. niche – a habitat and the role a
population plays in that habitat
- job, profession, role
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2. Competition arises when 2 populations
occupy the same niche.
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B. Mimicry
- Definition: The advantageous resemblance
of one species to another
Purpose:
 Deceives
predators
 Provides a form of camouflage for protection
 Example: The viceroy butterfly is a mimic of
the monarch butterfly because the monarch is
toxic and the viceroy is non-toxic.
M & M Allele
Activity