Download Evolutionary Theory

Evolutionary
Theory
Some Definitions to Remember…
• Evolution is the process by which species
change over time
• A theory is a broad explanation that has
been scientifically tested and supported
• The Theory of Evolution explains the
evidence suggesting that life on Earth has
changed
• The Theory of Evolution was proposed by
Charles Darwin
The Evolutionary Theory was Influenced
by Darwin’s Life Experiences:
1. The Voyage of the Beagle
– 5 year trip around the world
– He collected & observed
natural objects from each
place that he visited
The Evolutionary Theory was Influenced
by Darwin’s Life Experiences:
1. The Voyage of the Beagle
– 5 year trip around the world
– He collected & observed
natural objects from each
place that he visited
•
Fossils of extinct armadillos
were similar but not identical
to living armadillos in the area
The Evolutionary Theory was Influenced
by Darwin’s Life Experiences:
1. The Voyage of the Beagle
– 5 year trip around the world
– He collected & observed
natural objects from each
place that he visited
•
•
Fossils of extinct armadillos
were similar but not identical
to living armadillos in the area
Finches from the Galapagos Islands were similar,
except for their beaks
The Evolutionary Theory was Influenced
by Darwin’s Life Experiences:
1. The Voyage of the Beagle
– 5 year trip around the world
– He collected & observed
natural objects from each
place that he visited
•
•
•
Fossils of extinct armadillos
were similar but not identical
to living armadillos in the area
Finches from the Galapagos Islands were similar,
except for their beaks
He noticed that all organisms were well suited to their
environments and diets
The Evolutionary Theory was Influenced
by Darwin’s Life Experiences:
2. Years of Reflection
• After returning from his
voyage on the Beagle,
Darwin (27 at the time)
studied his data for many
years.
• He did not report his data
until much later
The Evolutionary Theory was Influenced
by Darwin’s Life Experiences:
3. Breeding and Selection
• Darwin noticed that humans take advantage
of the variations among organisms of the
same species as they breed them
• In other words, humans choose to breed the
organisms with the “best” traits
• Darwin called this artificial selection
• What examples of artificial selection can
you think of?
The Evolutionary Theory was Influenced
by Darwin’s Life Experiences:
• Examples of Artificial
Selection
Flowers are often bred for
brighter and more varied
colors.
Horses are bred for
strength, speed, beauty,
and size
Corn is bred to have many
full kernels in straight rows
and to taste great.
Strawberries are bred for
color, size, and durability.
Wild berries taste better.
The Evolutionary Theory was Influenced
by Darwin’s Peers:
1. Lamarck
• First prominent scientist
to defend the idea that
species could change
• Thought that species
passed on acquired
traits due to use and/or
disuse
The Evolutionary Theory was Influenced
by Darwin’s Peers:
2. Malthus
– Economist
– Stated that the human population is limited
by resources
– Darwin applied this idea to all populations
The Evolutionary Theory was Influenced
by Darwin’s Peers:
3. Cuvier
– Argued that fossils in rock layers showed
differences in species over time
– Said that species from the past differed
from those in the present
The Evolutionary Theory was Influenced
by Darwin’s Peers:
4. Lyell
• His research pointed out that the Earth
was old enough for species to have
evolved gradually
Evolution by Natural Selection
• Darwin’s theory predicts that over time,
the number of individuals that carry
advantageous traits will increase in a
population due to nature SELECTING
FOR those traits.
Aspects of Darwin’s Theory:
1. Overproduction: Every population
produces more offspring than survive
2. Variation: There is variation in every
population (some inherited, some random)
3. Selection: In a given environment, some
traits give an organism a better chance at
survival, so that organism lives and
reproduces
4. Adaptation: Traits that improve survival
become more common in the population
Publication of his Theory
• After many years, Darwin wrote an
outline of his theory of evolution by
natural selection
• He didn’t publish it because he was
afraid that his ideas would be
controversial
• UNTIL…
Publication of his Theory
•
Darwin received a letter from
Alfred Wallace
• In the letter, Wallace wanted
Darwin’s opinion on his new
theory… one JUST like his!
• This prompted Darwin to publish
a book of his ideas
• In his book, Darwin:
– Explained his Theory
– Offered evidence that
suggested that evolution had
occurred