BIO 182 MODULE 3, HOW SPECIES EVOLVE
LATEST REVISED STUDY GUIDE 2026
Module 3.1 — Evolution: Darwin & The Voyage of the
Beagle
⭐ Big Picture
Evolution is the change in populations over time.
Charles Darwin and Alfred Russel Wallace explained how evolution occurs by proposing the theory of
natural selection.
Remember: Darwin did not invent the idea that organisms change over time. His major contribution
was explaining the mechanism behind that change.
Before Darwin
People had always wondered:
Where did life come from?
Why are organisms so different?
Why do some organisms resemble each other?
Early explanations were mostly based on:
Religion
Mythology
Philosophy
Examples mentioned in the lecture include:
Norse mythology
Greek mythology
Jeju creation narrative
Mande creation myth
Aristotle's "Great Chain of Being"
Aristotle proposed the Scala Naturae ("Ladder of Being").
Main Idea
Every living thing had a fixed place.
Species were believed to be permanent.
, Organisms did not evolve into new species.
This idea dominated scientific thinking for many centuries.
The Enlightenment
During the Age of Reason:
Scientists began relying on:
Observation
Experimentation
Evidence
instead of tradition or superstition.
This shift eventually allowed evolutionary ideas to be tested scientifically.
Before Darwin...
Many scientists believed species could change.
This idea was called:
Transmutation of species
However,
they had no convincing mechanism explaining how those changes occurred.
That was the missing piece Darwin and Wallace would provide.
Darwin and Wallace
Both scientists independently developed the same explanation:
Natural Selection
Natural selection requires four key ideas:
1. Variation
Individuals within a population are different.
Example:
Some birds naturally have:
larger beaks
smaller beaks
2. Overproduction
More offspring are produced than can survive.
,Resources are limited.
Competition occurs.
3. Selection
Individuals with helpful traits survive more often.
4. Reproduction
Those survivors reproduce more successfully.
Helpful traits become more common in future generations.
⭐ Exam Thinking
If your professor asks:
Which sequence correctly describes natural selection?
Think:
Variation
↓
Overproduction
↓
Selection
↓
Reproduction
Scientists Who Influenced Darwin
Darwin didn' t work in isolation.
Several scientists influenced his thinking.
Thomas Malthus
Main Idea
Populations grow faster than resources.
Result:
Competition
Limited food
Survival is not guaranteed
This inspired Darwin' s idea of the struggle for existence.
, Charles Lyell
Lyell showed that:
Earth changes slowly over long periods.
Geological processes continue today.
This suggested Earth was old enough for evolution to occur gradually.
Paleontology
Fossils showed:
Many organisms had gone extinct.
Ancient organisms often resembled living organisms.
These observations supported the idea that species change over time.
Darwin's "I Think" Sketch
One of Darwin' s notebook sketches resembles what we now call a:
Phylogeny
A phylogeny is a branching diagram showing evolutionary relationships among organisms.
The lecture introduces two important vocabulary terms:
Speciation – formation of new species.
Phylogeny – evolutionary history/relationships among organisms.
⭐ Exam Thinking
If you see:
A branching evolutionary tree...
Think:
➡ Phylogeny
If you see:
Formation of new species...
Think:
➡ Speciation
Common Trap
❌ Darwin invented evolution.
LATEST REVISED STUDY GUIDE 2026
Module 3.1 — Evolution: Darwin & The Voyage of the
Beagle
⭐ Big Picture
Evolution is the change in populations over time.
Charles Darwin and Alfred Russel Wallace explained how evolution occurs by proposing the theory of
natural selection.
Remember: Darwin did not invent the idea that organisms change over time. His major contribution
was explaining the mechanism behind that change.
Before Darwin
People had always wondered:
Where did life come from?
Why are organisms so different?
Why do some organisms resemble each other?
Early explanations were mostly based on:
Religion
Mythology
Philosophy
Examples mentioned in the lecture include:
Norse mythology
Greek mythology
Jeju creation narrative
Mande creation myth
Aristotle's "Great Chain of Being"
Aristotle proposed the Scala Naturae ("Ladder of Being").
Main Idea
Every living thing had a fixed place.
Species were believed to be permanent.
, Organisms did not evolve into new species.
This idea dominated scientific thinking for many centuries.
The Enlightenment
During the Age of Reason:
Scientists began relying on:
Observation
Experimentation
Evidence
instead of tradition or superstition.
This shift eventually allowed evolutionary ideas to be tested scientifically.
Before Darwin...
Many scientists believed species could change.
This idea was called:
Transmutation of species
However,
they had no convincing mechanism explaining how those changes occurred.
That was the missing piece Darwin and Wallace would provide.
Darwin and Wallace
Both scientists independently developed the same explanation:
Natural Selection
Natural selection requires four key ideas:
1. Variation
Individuals within a population are different.
Example:
Some birds naturally have:
larger beaks
smaller beaks
2. Overproduction
More offspring are produced than can survive.
,Resources are limited.
Competition occurs.
3. Selection
Individuals with helpful traits survive more often.
4. Reproduction
Those survivors reproduce more successfully.
Helpful traits become more common in future generations.
⭐ Exam Thinking
If your professor asks:
Which sequence correctly describes natural selection?
Think:
Variation
↓
Overproduction
↓
Selection
↓
Reproduction
Scientists Who Influenced Darwin
Darwin didn' t work in isolation.
Several scientists influenced his thinking.
Thomas Malthus
Main Idea
Populations grow faster than resources.
Result:
Competition
Limited food
Survival is not guaranteed
This inspired Darwin' s idea of the struggle for existence.
, Charles Lyell
Lyell showed that:
Earth changes slowly over long periods.
Geological processes continue today.
This suggested Earth was old enough for evolution to occur gradually.
Paleontology
Fossils showed:
Many organisms had gone extinct.
Ancient organisms often resembled living organisms.
These observations supported the idea that species change over time.
Darwin's "I Think" Sketch
One of Darwin' s notebook sketches resembles what we now call a:
Phylogeny
A phylogeny is a branching diagram showing evolutionary relationships among organisms.
The lecture introduces two important vocabulary terms:
Speciation – formation of new species.
Phylogeny – evolutionary history/relationships among organisms.
⭐ Exam Thinking
If you see:
A branching evolutionary tree...
Think:
➡ Phylogeny
If you see:
Formation of new species...
Think:
➡ Speciation
Common Trap
❌ Darwin invented evolution.
