1. Chapter 15: Darwin’s Theory of Evolution
Section: 15 – 3: Darwin Presents His Case

2. Key Concepts: How is natural selection related to a species’ fitness?
What evidence of evolution did Darwin present?

3. A. Publication of “On the Origin of Species”
In 1859, Darwin published the results of his work. It was called On the Origin of Species
In this book Darwin proposed NATURAL SELECTION - a mechanism for evolution.
The theory of natural selection takes into account several ideas about a species survival.

4. B. Evolution by Natural Selection
Darwin said that organisms must compete for resources (food, water, shelter, mates, etc.). He called this STRUGGLE FOR EXISTENCE.
Darwin then said that in this struggle for existence that the stronger animal survived; the one more suited for its environment. He called this the FITNESS ADAPTATION

5. These ideas are combined into what is known as “The Survival of the Fittest”
Individuals that are better suited to their environment (better adaptations) survive and reproduce most successfully.
Natural Selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment.

6. C. Evidence of evolution
Fossil Record – Darwin said that comparing fossils showed how organisms have changed over time.
Geographic Distribution of living Things – Similar organisms lived in similar habitats in different parts of the world

7. Geographic Distribution of Living Species
Section 15-3
Beaver
Beaver
Muskrat
Beaver and Muskrat
Coypu
Capybara
Coypu and Capybara
NORTH AMERICA
Muskrat
Capybara
SOUTH AMERICA
Coypu

8. Homologous Structures – limbs that have the same basic bones, but vary in form and function

9. Homologous Body Structures
Section 15-3
Turtle
Alligator
Bird
Mammal
Ancient lobe-finned fish

10. Embryology – The early stages of vertebrate animals are very similar in structure.

11. Concept Map Section 15-3 Evidence of Evolution includes
The fossil record
Geographic distribution of living species
Homologous body structures
Similarities in early development
which is composed of
which indicates
which implies
which implies
Physical remains of organisms
Common ancestral species
Similar genes