Darwin’s Theory

1. Individual organisms differ and some of this variation is heritable.

2. Organisms produce more offspring than can survive.

3. They compete for limited resources. Food Water Shelter Mates

4. Individuals best suited for the environment will survive/reproduce These surviving and reproducing organisms will leave the most offspring. Their traits will be inherited and move on to the next generation

5. Descent With Modification Organisms alive today are descended from ancestors who lived in the distant past Modifications are changes that allow diverse species to have a common ancestor.

Darwin On HMS Beagle went to the Galapagos and wondered if the various species from each island had once been members of the same species. Organisms are considered to be the same species if they mate and have fertile offspring. Published “The Origin of Species”

James Hutton and Charles Lyell Both were Geologists and knew the Earth was Millions of years old, not thousands as most believed at that time. Both knew forces shaped the Earth over long periods of time Lyell said that the same forces that worked on shaping the Earth in the past were still happening in the present time.

Malthus Statistician – Used math to analyze populations Predicted that the human population would grow faster than the resources necessary to support it (Like food and places to live)

Jean-Baptiste Lamarck Traits are inherited Organisms became more complex and more perfect These “Acquired Traits” could be passed to offspring. This was ultimately proven wrong. If fruit fly wings were clipped, the offspring would not be born without wings.

Wallace Published “The Theory of Natural Selection” Pressured Darwin to publish his work on the “Origin of Species”

Natural Selection Struggle for existence Survival of the fittest Descent with modification

Artificial Selection Nature provides the variation Humans select the variations they find attractive or useful

What happens if there is no variation? Selective breeding can reduce the variation in a population. What are some of the risks?

Adaptation = Survival If you are not well adapted you may not survive to have offspring. Variation means that there are many different adaptations. When there is less variation one disease or predator could kill the whole population Variation = A better chance for the population to survive