Evolution

Scientists believe that all living organisms on earth share a common ancestor. Newer species arise from older species by evolution. Evolution is the process by which populations accumulate inherited changes over many, many generations.

How does evolution happen? ________________, born in 1810, is credited with the first theory explaining evolution. Charles Darwin

Darwin observed that different species of birds were uniquely adapted to their environment. _____________ - a group of organisms that can mate with one another to produce fertile offspring. species

_______________ – a characteristic that helps an organism survive and reproduce in its environment examples: ________________________________________ ________________________________________ adaptation Sharper teeth to eat meat, lungs to live on land, longer neck to reach food

He learned from plant and animal breeders. They could select for desirable traits by picking what animals will breed together. He reasoned that this could happen in nature but it would take MUCH longer.

He learned about populations. Species can produce too many offspring but starvation, disease, war, and predators limit the population size. So there must be something special about the survivors— they must inherit traits that help them survive in their environment.

Darwin proposed that evolution occurred by _____________________ acting on the adaptations natural selection

Darwin’s theory of Evolution by Natural Selection the process by which organisms with favorable traits survive and reproduce more than organisms without the favorable trait.

__________________- more offspring are produced than can survive overproduction

__________________- there is variation within the traits in a population; some individuals in a population are better able to survive than others because of their traits Genetic Variation

__________________- the environment does not have enough food, water, and other resources to support every individual; there is going to be competition for survival within a population and not all individuals will survive to adulthood Struggle to survive _______________________- The individuals with the favorable adaptations will be more successful at producing offspring and eventually will take over the population Successful reproduction

How has evolutionary theory changed since Darwin? Darwin didn’t know anything about genes. Now we know that it is changes in the DNA or mutations that cause the variation in a population. ________________ - changes in the DNA mutation

mutations lead to the variations or differences in the genes which then cause differences in traits sometimes those differences can cause an individual in the population to survive better.

Evidence supporting the theory of evolution

1. _______________ __________ – solidified remains or imprints of once-living organisms Using fossils, scientists have constructed a fossil record or historical sequence of life. Gaps exist but they are being filled in all time. Fossil record fossils

2. ___________________ Vestigial structures are remnants of structures that had a useful role at one time but no longer do. The presence of these structures suggests that the organism evolved from another life form where that structure played a more important role. examples: _________________________________________________ Vestigial structures remnants of hind-limb bones in whales and some snakes tailbone in humans

3. comparing organisms that are alive today a. ___________________ – bone structures of mammals are very similar suggesting a common origin (see figure 9 on.156 in your textbook) Skeletal structures

b. ________ – all living organisms have the same genetic material organisms that are more closely related have DNA that is more similar example: human and chimp genes are ~ _________% identical human and mouse genes are ~ _________% identical DNA

c. _________ – cells are the basic unit of all life; all living organisms start from a single cell cells