1. 6.2 Charles Darwin & His Theory of Natural Selection
Image from: Biology by Miller and Levine; Prentice Hall Publishing©2006

2. Slide by Kim Foglia@ http://www.explorebiology.com/

3. Who Was Charles Darwin?
In 1831, 22-year old Charles Darwin left England as naturalist aboard the HMS Beagle for 5 year voyage around the world.
Mission: Chart the South American coastline
Darwin noticed plants
and animals were different
from those he knew in Europe
Wrote thousands of pages
of observations and
collected vast number of
specimens

4. Who Was Charles Darwin?
Darwin spent a month observing life on the Galapagos Islands
Each island has different rainfall
and vegetation and its own unique
assortment of plant and animal
species.
Biology by Miller and Levine; Prentice Hall Publishing©2006

5. Who Was Charles Darwin? Although animals on Galapagos
resemble species on the
South American mainland,
many species were found no
where else in the world = ENDEMIC

6. DARWIN’S
FINCHES
Darwin collected 14 species of finches and hypothesized that the Galapagos had be colonized by organisms from the mainland that had then diversified on the various

7. Who Was Charles Darwin?
After Darwin returned to England in 1836, he spent years examining specimens he brought back from voyage and filling notebooks with his ideas.
He did not rush to publish his ideas because they
disagreed with the fundamental scientific views of his
day.
In 1844 he wrote an essay describing his ideas and
asked his wife to publish it if he died.

8. In 1858 Alfred Russel Wallace, another
Naturalist working in the West Indies,
wrote an essay describing his work that
summarized the same ideas Darwin had
been thinking about for 25 years!

9. Suddenly Darwin had incentive to publish the results of his work!
On the Origin of Species by Means of Natural Selection
presented evidence
and proposed a
mechanism for evolution
that he called
NATURAL SELECTION

10. Darwin’s Theory of Evolution Darwin Presents his Case
Image from: Biology by Miller and Levine; Prentice Hall Publishing©2006

11. Isn’t evolution “just a theory”?
In every day usage “theory” often refers to a hunch or a speculation. When people say, “I have a theory about what happened,” they are often drawing a conclusion based on fragmentary or inconclusive evidence.
The formal scientific definition of “theory” is quite different from the every day meaning.
It refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence.

12. Isn’t evolution just a theory?
In Science a theory is a well supported, testable explanation of phenomena that have occurred in the natural world.
Example:
Cell theory
Atomic theory
Gravitational theory

13. VOCAB
ADAPTATION- Any inherited characteristic that increases an organism’s chance of survival

14. WHAT IS DARWIN’S THEORY?
OVERPRODUCTION of OFFSPRING
Capacity to over-reproduce seems characteristic of all species.

15. WHAT IS DARWIN’S THEORY?
STRUGGLE FOR EXISTANCE means
that members of each species must
compete for food, space, and
other resources.

16. WHAT IS DARWIN’S THEORY?
GENETIC VARIATION is found naturally in all populations
Image from

17. WHAT IS DARWIN’S THEORY?
Some organisms in a population are less likely to survive.

18. VOCAB
Ability of an individual to survive and reproduce in its specific environment = FITNESS

19. WHAT IS DARWIN’S THEORY?
SURVIVAL OF THE FITTEST =
Organisms which are better adapted
to their environment tend to produce
more offspring than organisms without
those traits.
Competition for limited resources results in differential survival.

20. results in changes in the inherited characteristics of a population.
WHAT IS DARWIN’S THEORY?
Over time,
NATURAL SELECTION
results in changes in the
inherited characteristics of a population.
These changes increase a
species’ fitness in its environment.
How Does Evolution Really Work?

21. IMPORTANT TO REMEMBER ! POPULATIONS evolve NOT INDIVIDUALS.
NATURAL SELECTION only works on heritable traits.
A trait that is favorable in one environment may be useless or detrimental in another.

22. DESCENT WITH MODIFICATION
WHAT IS DARWIN’S THEORY?
DESCENT WITH MODIFICATION
suggests that each species has
descended with changes
from other species over time.
This idea suggests that all living
species are related to each other
and that all species, living and extinct,
share a common ancestor.