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Introduction to Evolution
What is Evolution??
It is a theory explaining the
process by which modern
organisms have descended
from ancient organisms.
Charles Robert Darwin
(1809 – 1882)
• An Englishman
• Sailed on the HMS Beagle for 5 years
• Visited many places including
The Galapagos Islands
• Observed birds – Finches
• Attempted to explain evolution
• Author of “On The Origin of Species”
• 201 years old this year
The Galapagos Islands
Watch Video: Galapagos
ENJOY!!
Before Darwin
• Jean Baptiste de Lamarck
– 3 assumptions on adaptation
• A desire to change
• Use and disuse
• Passing on acquired traits
A Desire to Change
• Naturally want to be better
– Example: Bird’s ancestor wanted to fly,
therefore they developed wings.
Use and Disuse
• Organs could change in size depending on
the amount of usage.
• Vestigial structures
Passing on Acquired Traits
• Acquired: to gain ownership
• Trait: characteristic
• Acquired trait: a characteristic you
gained after you were born
– A woman dyes her hair purple,
her baby will be born with
purple hair.
– A swimming champion will produce
swimming champion babies.
Charles Darwin
•
His theory of evolution was influenced by
3 key people/group:
1. Lyell (Geological influences)
2. Farmers (Selective breeding)
3. Malthus (Overpopulation)
Lyell’s Idea
• Earth was very old
• It changed over time
• Evolution took MANY years to happen.
• It took MANY years for millions of species
to evolve from a common ancestor
Farmers
• Artificial Selection
• Farmers only chose the
traits that benefited them
• Darwin: Perhaps nature (environment)
also chose the trait that best suited for
survival/reproduction
Malthus
•
•
•
•
Population Controls
He noticed that Birth rate > Death rate
Not possible due to lack of space, food
Growth Prevention: Famine, disease, war
Who gets to stay alive?
The FIT ones
(Survival of the Fittest)
Genetic Variations in Species
• Individuals of the same species are
different from each other.
• Variations:
– Height, weight, hair colour, skin colour, eye
lids
• Variations that are:
– Well-suitable for the environment  survives
– Not well-suitable for the environment  dies
Darwin’s Survival of the Fittest
• Individuals whose characteristics are wellsuited to their environment survive and
reproduce.
FIT
• Individuals whose characteristics are not
well-suited to their environment either die
or leave fewer offspring
LESS-FIT
Going back to Malthus’ idea:
The fact that less-fit individuals of a
species don’t survive helps
prevent the species from
covering the Earth.
Peppered
Moths Case
• Where: England
• When: Early 1800s
Around Industrial Revolution Period
Before Revolution
After Revolution
Oak trees had light
brown bark
Oak trees bark got
stained dark brown
Most moths were
light brown
Most moths were
dark brown
What happened?
Before the revolution
Clean tree bark
After the revolution
Stained tree bark
Kettlewell’s Confirmation
Area A: Normal coloured trees Area B: Dark coloured trees
His Hypothesis??
His observations??
Kettlewell’s Confirmation
Light coloured
area
light colour moths
survived better
Dark coloured
area
dark colour moths
survived better
Conclusion: In each environment
the moths that were better
camouflaged had the
higher survival rate
A way to hide oneself
In conclusion
What changed the moths?
The nature did, that’s why it’s called
NATURAL SELECTION.
"Evolution is the result of genetic changes
that occur in constantly changing
environments."