1. 14.1 Theories of Evolution

2. Early Theory- Lamarck  Lamarck believed that organisms adapted to their environments. His theory was based on 3 incorrect assumptions. 1. A Desire to Change: animals changed because they wanted to. Example: birds flew because they wanted to be airborne. 2. Use and Disuse: organisms could alter the shape and size of their organs and appendages based on their needs.

3. 3. Passing on Acquired Traits: if an animal acquired a body structure it could be passed on to its offspring. (I.e. weightlifting).  During Lamarck’s time there was no knowledge of genes Early Theory- Lamarck

4. Influences of Darwin’s Theory 1. Charles Lyell believed that the earth was very old. Darwin believed that it was even older than Lyell thought in order for millions of species to evolve from a common ancestor.

5. Influences of Darwin’s Theory 2. Artificial Selection by farmers: Darwin learned that there is much variation among domesticated animals. Farmers could ensure that animals with more desirable traits produce offspring. Farmers couldn’t cause variation to occur. Example: cows that produced a lot of milk.

6. 3. Malthus: Population Controls. At the time Malthus observed babies being born at a faster rate than they were dying. War, famine and disease would prevent overpopulation.  Darwin felt this also applies to plants and animals. Example: Maple trees, sunflowers, mussels. Influences of Darwin’s Theory

7. 14-2 Evolution by Natural Selection

8. Evolution by Natural Selection  We all know that the variety of living things is called diversity. Diversity is a result of our genetic material.  Individuals whose characteristics are well suited to their environments survive and reproduce. This is called survival of the fittest. Less fit individuals don’t survive.

9. Theories of Natural Selection  a. overproduction: the goal of all species is to reproduce and survive. When species do this they tend to produce more offspring than the environment can support. environment  b. competition: the animals must compete for limited food resources, some will not survive.  c. variation: no individual is alike; those with traits more suited to their environment were more likely to survive.

10.  d. survival of the fittest: organisms more suited to their environment are better able to adapt and survive when faced with hard times.  e. origin (speciation): new species arise due to inherited variations.  Video Video Theories of Natural Selection