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Evolution

Evolution. The process of change over time Charles Darwin developed the theory of how living things evolve. Darwin's Theory of Evolution.

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Evolution

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  1. Evolution • The process of change over time • Charles Darwin developed the theory of how living things evolve

  2. Darwin's Theory of Evolution • Based on his findings on the Galapagos Islands and elsewhere, Darwin said that all living things are descended (with modifications) from a common ancestor. • “Descent With Modification”

  3. Descent with Modification • The Earth is about 4.5 billion years old • The first living cells (similar to bacteria) are believed to have appeared on Earth about 3.5 billion years ago • Darwin theorized that all living things on Earth are ancestors of an ancient organism from the past. • This ancient organism is the “common ancestor” for all living things on Earth.

  4. Descent with Modification (cont.) • Small changes every generation for billions of years have led to different organisms branching off into new species, and forming the “Tree of Life”. • We now know that these small changes occur in the DNA as mutations.

  5. How does Decent with Modification occur? • Darwin proposed that evolution occurs by Natural Selection • Natural Selection- the process by which organisms with variations most suited to their environment survive and leave more offspring.

  6. How Natural Selection Works A. “The Struggle For Existence” - If more individuals are born than can survive, there must be competition for food, living space, etc. - Darwin wanted to know which individuals would come out on top

  7. How Natural Selection Works B. “Variation and Adaptation” - Some variations in individuals are better suited for a certain environment - Adaptation- any heritable characteristic that increases an organism’s ability to survive in a certain environment - Well adapted individuals survive and reproduce Yeti Crab

  8. How Natural Selection Works C. “Survival of the Fittest” - Fitness- how well an organism can survive and reproduce in its environment - If an organism is well adapted to its environment and successfully reproduces it has “high fitness” - Over time, the traits of the well adapted individuals become the more common traits of the population Snowy egret nest

  9. 1. Grasshopper lays eggs 2. Yellow and green grasshoppers hatch 3.Predator eats the grasshoppers that are easy to see 4.Green grasshoppers are left to reproduce Example of Natural Selection After many generations, almost all grasshoppers will be __________. green Thus, nature has “selected for” green grasshoppers!

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