1. health and fitness
2. disease

Chp 17-Evolution of
Populations
-Explain how natural selection can impact allele
frequencies of a population
-Describe the factors that can contribute to the
development of new species
Endosymbiosis
● First organisms believed to be prokaryotes
○ What are characteristics of prokaryotes?
● Eukaryotes came about by symbiosis (living
together) of single celled organisms
● What does natural selection directly act on,
phenotype or genotype?
○ Phenotype-can only act on characteristics, not
alleles
○ Indirectly affects genotype-affects what alleles are
passed on to next generation
● Gene pool-all the genes/alleles that are
present in a population
● Allele frequency-the number of times an
allele occurs in a gene pool
● Evolution-change in allele frequency over
time
What alleles are in the gene
pool?
After a lava flow, what will
happen to the allele
frequencies of:
Black fur?
Brown fur?
Genetic Recombination
● Genetic Recombination via sexual
reproduction is source of variation
○ ex-think about you, your parents/siblings/relatives
○ don’t all look the same, due to mixing up of parents
genes during meiosis (crossing over)
Polygenic Traits
● Traits controlled by more than one gene
○ result in spectrum of phenotypes, rather than a few
Directional Selection
● Individuals at one end
of curve more fit than
middle/opposite end
● What happens to the
mean?
Stabilizing Selection
● Individuals near
middle of the curve
more fit than those at
the ends
● What happens to the
mean?
Disruptive Selection
● Individuals at outer
ends have higher
fitness than those near
middle
● What happens to the
mean?
Examples:
How do you think giraffes got their long necks?
A. Directional Selection
B. Stabilizing Selection
C. Disruptive Selection
Draw a graph to back up your answer.
Genetic Drift
● RANDOM changes in allele frequency
● Is natural selection random?
Bottleneck Effect
● Dramatic reduction in
population size
○ disease, disaster etc
● Causes change in allele
frequency
Examples: cheetahs, elephant
seals
Founder Effect
● small group
migrates away from
rest of population,
causes change in
allele frequencies
○ ex: island populations
Adaptive Radiation
● process in which
organisms diversify rapidly
into a multitude of new
forms
○ change in the
environment makes
new resources
available
○ opens environmental
niches
Genetic Equilibrium
● If no evolution is taking place, what happens
to the allele frequencies?
● GE happens when pop not evolving, no
change in allele frequencies
Hardy-Weinberg Principle
● Used to predict allele frequencies in pops in
GE
○ if allele frequencies don’t match, pop evolving
● allele frequencies stay the same UNLESS:
○ non random mating (sexual selection)
○ small pop (genetic drift)
○ immigration or emigration (individuals
leaving/entering pop)
○ mutations
○ natural selection
Species
● population or group of populations who can:
○ interbreed
○ FERTILE offspring
● speciation-forms new species
Reproductive Isolation
● Species can’t breed anymore
● Splits gene pool
Types of repro iso:
● Behavioral Isolation
○ diff courtship rituals
■ ex: birds with different songs
Temporal Isolation
reproduce at different times
ex: flowers blooming at different times
Types of repro iso:
● Geographic/habitat Isolation
○ geographic barriers separating pops
■ ex: canyons separating squirrel populations
Types of repro iso:
● Gametic Isolation
○ produce gametes with different numbers of
chromosomes
ex: Horses have gametes with 32 chromosomes,
donkeys have gametes with 31 chromosomes.
Mules only have 63 chromosomes, and are
unable to reproduce
Gradualism: series of small
changes over time
(left)
Punctuated equilibrium:
sudden, dramatic changes
followed by period of no
change
(right)
Antibiotic Resistance
● Why is the Russian prison system considered to be
"ground zero" in the fight against TB?
● What is responsible for the evolution of TB strains that are
resistant to multiple drugs?
● How does the misuse of antibiotics affect the evolution of
disease-causing bacteria? Use the theory of natural
selection to explain the growing resistance to antibiotics.
● Why should we care about a resistant strain of TB in
Russia?
● https://www.youtube.com/watch?v=W-WumllRPLI
Read biology and society on pg 493
● Why do doctors tell you to finish your
antibiotics?
Crash Course:
5 things he mentions you remember from
yesterday
5 new things you learned
Concept map
Write Speciation in the middle of the paper.
Create a concept map using the information
your group wrote on their papers.