1. 15-3: Darwin Presents His Case Part 1
Biology 2

2. Darwin returned to England is 1836, with lots of information
Introduction
Darwin returned to England is 1836, with lots of information
Brought back many specimens of what he studied (plants and animals)
Found that every Galapagos island, and continent, had its own species

3. On The Origin of Species
1859: Published book – On The Origin of Species
Proposed natural selection causes evolution
Showed evidence that evolution has been happening for millions of years-and continues now

4. Inherited Variation and Artificial Selection
Darwin saw that species naturally vary
Example: Some cows give more milk than others
Sometimes parents pass these traits to offspring
Wild plants and animals vary
Domestic plants and animals vary

5. Inherited Variation and Artificial Selection
Darwin said the variation is VERY important
Others thought it was an accident, or something wrong
Farmers and breeders use variations to improve crops and livestock
Example: Only breed fastest horse, cows that produce more milk, plants that give bigger food
ARTIFICIAL SELECTION: selection by humans for breeding of useful traits from the natural variation among different organisms

6. Evolution by Natural Selection
STRUGGLE FOR EXISTENCE: competition among members of a species for food, living space, and the other necessities of life
Members of same species have to compete for food, shelter
Predators that move faster or hunt better catch more prey
Prey that hides better, protects themselves or can avoid being caught lives longer

8. Evolution by Natural Selection
Important to struggle for existence is how well living organisms “fit” their environment
FITNESS: ability of an organism to survive and reproduce in its environment
ADAPTATION: inherited characteristic that increases an organism's chance of survival
BETTER ADAPTATION = BETTER FITNESS!

9. Evolution by Natural Selection
SURVIVAL OF FITTEST: process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection
Living organisms that have better adaptations have better fitness
Better fitness = more offspring!

10. Evolution by Natural Selection
NATURAL SELECTION: process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest
Only certain individuals can survive and reproduce offspring!

11. Evolution by Natural Selection
In natural selection better adaptations = better fitness
Better fitness = more offspring
More offspring = increase in population with better adaptations!
Causes change in population
More individuals with better adaptations increase over time
More individuals without adaptations will die and decrease