The Theory of Evolution

What is a Theory? A theory is the best explanation based on the evidence available. There is a great deal of evidence to support the theory of evolution.

Evolution Definition: Result: The process of change in a species over time Result: A species changes so much over time that the species is no longer the same as its original ancestor and would not be able to mate with the original ancestor.

Evolution in Bacteria Separate Species

Common Ancestor: 6 million years ago

Evolution is NOT: Evolution is NOT changes in population size Evolution is NOT individual organisms growing and going through metamorphosis such as a tadpole changing into a frog Evolution is NOT individual organisms evolving during their life time. THIS IS NOT POSSIBLE! An organism cannot acquire (get) a better trait during its life and then pass it on to its offspring.

How Does Evolution Happen? Mutations randomly occur to produce variations. Organisms with beneficial variations (adaptations) are better able to survive. Over time the beneficial mutations accumulate in the species. The accumulation of many changes over time can lead to the production of a new species!

Evolution of the Horse Different Species

Misconceptions on How Evolution Occurs: Organisms can’t get the mutations they need and evolve to suit their environment. Organisms of different species such as a dog and cat can’t mate together to produce a new species.

How Quickly Does Evolution Happen? The amount of time it takes for an organism to evolve depends on several things: Reproduction (type, rate, gestation period, number of offspring, etc.) A higher rate of mutation increases the chance of evolution occurring. Example: Bacteria evolve more rapidly than mammals.

9 years

Summarize… Organism Time Frame Numbers Bacteria 5 hours 3 million Cats 9 years 11 million Humans 1 So, which one do you think would have a faster rate of evolution? Yes, the bacteria!

Extinction Extinction is when all members of a species die. Extinction occurs when a species does not have the right adaptations to survive in the environment. All members of the species die.

Dinosaur Extinction One Theory: An asteroid hit the Earth and sent up a cloud of dust which blocked the sun. This caused climate change and affected plants. Dinosaurs were not well adapted to survive the changes.

The real reason dinosaurs went extinct!

Common Ancestors A common ancestor is a previous species that new species evolve from. Evolutionary theory suggests that monkeys and humans have a common ancestor. Misconception: Humans evolved from monkeys. THIS IS NOT TRUE!