1. Natural Variation & Artificial Selection

2. Natural Variation & Artifical Selection
Darwin, through many observations, explained evolution by natural variation
In 1859, Darwin published “On the Origin of Species” where he proposed his theory of evolution
Natural variation – differences among individuals of a species and is found in all types of organisms (inherited traits)
Breeders routinely used variations to improve crops and livestock = selective breeding aka artificial selection
Artificial selection – nature provided the variation among different organisms, and humans selected those variations they found useful
Ex. Only cows that produce the most milk are bred

3. Evolution by Natural Selection
Struggle for existence – members of each species compete regularly to obtain food, living space, and other necessities

4. Evolution by Natural Selection (continued)
Survival of the fittest – how well suited an organism is to its environment
Fitness – ability of an individual to survive and reproduce in its specific environment
Adaptation – leads to fitness – any inherited characteristic that increases an organism’s chance of survival – can be physical or behavioral adaptations

5. Survival of the Fittest (continued)
Generation after generation, individuals compete to survive and produce offspring
Individuals with characteristics that are NOT well suited to their environment die or leave few offspring
Individuals with characteristics that ARE well suited to their environment survive and reproduce most successfully

6. Natural Selection Takes place without human control or direction
Over time, natural selection results in changes in the inherited characteristics of a population

7. Descent with Modification
Over long periods of time, natural selection produces organisms that have different structures or occupy different habitats. As a result, species today look different from their ancestors.
All living organisms are related to one another through common ancestors = common descent