BIO 182 EXAM 2, ANIMAL PHYSIOLOGY &
DIVERSITY PART 1 – EVOLUTION
COMPREHENSIVE STUDY GUIDE &
REVISION NOTES 2026
Part 1 – Evolution
⭐ The Big Picture
Everything in Module 3 comes back to one simple idea:
Evolution is the change in allele frequencies within a population over time.
Notice two important words:
Population
Over time
Individuals do not evolve.
Populations evolve because the frequencies of alleles change generation after
generation.
1. Darwin & Wallace
Charles Darwin
Darwin spent nearly five years aboard the HMS Beagle observing organisms
around the world.
His observations included:
Fossils
Geographic distribution
Exam 2 Study Guide 1
, Variation within species
The Galápagos Islands
He noticed that:
Individuals in the same species were not identical.
Some individuals survived better than others.
Those successful individuals left more offspring.
Alfred Russel Wallace
Wallace independently reached almost the same conclusions as Darwin.
Instead of competing:
The two scientists published together.
Because of Wallace' s work, Darwin finally published On the Origin of Species.
⭐ Professor Tip
Know why Darwin' s observations mattered.
Your professor is much more interested in:
How did Darwin develop the idea?
than
What year did he publish it?
2. Natural Selection
Natural selection happens whenever:
1. Individuals vary.
2. Some variation is inherited.
3. More offspring are produced than survive.
4. Individuals with advantageous traits reproduce more successfully.
Exam 2 Study Guide 2
, Those traits become more common over generations.
Easy Formula
Variation
↓
Selection
↓
Inheritance
↓
Evolution
Common Trap
Many students say:
"Animals evolve because they need to."
❌ Wrong.
Correct:
Random mutations occur first.
Natural selection favors mutations that improve survival or reproduction.
Example
Some bacteria randomly possess an antibiotic resistance gene.
Antibiotics kill susceptible bacteria.
Resistant bacteria survive.
They reproduce.
Soon most bacteria are resistant.
The bacteria did not become resistant because they "tried."
Exam 2 Study Guide 3
, 3. Types of Natural Selection
These are almost guaranteed to appear on the exam.
Directional Selection
One extreme phenotype is favored.
Example:
Small birds
Medium birds
Large birds
If large birds survive best:
Population gradually shifts toward large birds.
Graph:
Think:
➡ The whole curve moves.
Stabilizing Selection
The middle phenotype is favored.
Very small and very large individuals are selected against.
Graph:
Exam 2 Study Guide 4
DIVERSITY PART 1 – EVOLUTION
COMPREHENSIVE STUDY GUIDE &
REVISION NOTES 2026
Part 1 – Evolution
⭐ The Big Picture
Everything in Module 3 comes back to one simple idea:
Evolution is the change in allele frequencies within a population over time.
Notice two important words:
Population
Over time
Individuals do not evolve.
Populations evolve because the frequencies of alleles change generation after
generation.
1. Darwin & Wallace
Charles Darwin
Darwin spent nearly five years aboard the HMS Beagle observing organisms
around the world.
His observations included:
Fossils
Geographic distribution
Exam 2 Study Guide 1
, Variation within species
The Galápagos Islands
He noticed that:
Individuals in the same species were not identical.
Some individuals survived better than others.
Those successful individuals left more offspring.
Alfred Russel Wallace
Wallace independently reached almost the same conclusions as Darwin.
Instead of competing:
The two scientists published together.
Because of Wallace' s work, Darwin finally published On the Origin of Species.
⭐ Professor Tip
Know why Darwin' s observations mattered.
Your professor is much more interested in:
How did Darwin develop the idea?
than
What year did he publish it?
2. Natural Selection
Natural selection happens whenever:
1. Individuals vary.
2. Some variation is inherited.
3. More offspring are produced than survive.
4. Individuals with advantageous traits reproduce more successfully.
Exam 2 Study Guide 2
, Those traits become more common over generations.
Easy Formula
Variation
↓
Selection
↓
Inheritance
↓
Evolution
Common Trap
Many students say:
"Animals evolve because they need to."
❌ Wrong.
Correct:
Random mutations occur first.
Natural selection favors mutations that improve survival or reproduction.
Example
Some bacteria randomly possess an antibiotic resistance gene.
Antibiotics kill susceptible bacteria.
Resistant bacteria survive.
They reproduce.
Soon most bacteria are resistant.
The bacteria did not become resistant because they "tried."
Exam 2 Study Guide 3
, 3. Types of Natural Selection
These are almost guaranteed to appear on the exam.
Directional Selection
One extreme phenotype is favored.
Example:
Small birds
Medium birds
Large birds
If large birds survive best:
Population gradually shifts toward large birds.
Graph:
Think:
➡ The whole curve moves.
Stabilizing Selection
The middle phenotype is favored.
Very small and very large individuals are selected against.
Graph:
Exam 2 Study Guide 4
