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Theories of Evolution

Theories of Evolution. Type I Cheetahs can reach top speeds of up to 60 mph; however, they were not always this fast. Explain how/why cheetahs may have evolved to be such fast animals. Lamarck. Jean Baptiste Lamarck (1744 – 1829) One of the first to propose a theory of evolution.

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Theories of Evolution

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  1. Theories of Evolution • Type I • Cheetahs can reach top speeds of up to 60 mph; however, they were not always this fast. Explain how/why cheetahs may have evolved to be such fast animals.

  2. Lamarck Jean Baptiste Lamarck (1744 – 1829) • One of the first to propose a theory of evolution. • First to state that organisms change over time, meaning newer generations of organisms are modified versions of older generations of organisms. • Theory is based on observed changes in the fossil record for the same species • Believed that organisms could pass down acquired traits which are traits not determined by genes; traits gained by experience or behavior Ex: Cheetahs exercised and increased leg strength, then passed it on to their offspring.

  3. Teleology • Comes from the root “telos” meaning end. • Teleology – idea that evolution is purposeful or has a pre-determined result. • Belief that everything happens for a reason. • Ex: Cheetahs were meant to become top predators, so they had to become faster to catch their prey.

  4. Creationism/Intelligent Design Belief in a “creator” or “higher power”. • Creationism • Belief in the literal meaning of the Bible and other religious documents. • Do not believe that species change significantly over time. • Intelligent Design • Belief that creator began the process of life. • Recognize that species change over time, but do not believe that new species are created. Ex: Cheetahs were created by “God” to be fast runners.

  5. Darwin • Charles Darwin – attended medical school and studied for the clergy • Hired as a naturalist for an expedition in 1831 – sailed on the H.M.S. Beagle – traveled through South America and South Pacific • Read books on geology. • Geologic changes take place over millions of years. Organisms must adapt to these changes. • Collected specimens and recorded data from various locations. • Noted differences between similar species living in different locations. Why were they different? • Developed a theory called evolution by natural selection. • Now most widely accepted evolutionary theory in scientific community.

  6. Darwin’s Theory • Based on Descent with Modification – newer species are modified descendents of older species. • Different from Lamarck’s idea of descent with modification • Believed that all species descended from a few original types of organisms. • Idea supported by Darwin’s observations from his specimens and travels • Similar species showed different characteristics in different locations. • Ex: Galapagos finches – compared birds on different islands • Beaks shaped differently when different food sources present • Large, wide beak for cracking seeds. • Small, thin beak for catching insects.

  7. Darwin’s Theory continued… • Darwin proposed the theory of Evolution by natural selection • Proposed hypothesis for how evolution happens. • He observed that environment can limit the size of populations. • Most populations do not grow unchecked. • 2 ways to limit population growth. • Increased death rate • Decreased reproduction rate

  8. Natural Selection Main points of Darwin’s theory • All populations contain some variation – Not all individuals are the same within a group. • Some organisms are more “fit” for their environment. Fitness – the ability of an organism to survive and reproduce in its environment • More fit organisms will have greater reproductive success. (Have more offspring!!) • As a result, genes for these traits will be passed on more often. • After time, the population as a whole may change. Adapt – a species changing genetically over time to become better suited for the environment EX: Cheetahs who were fast were more fit for the environment and more likely to survive and reproduce.

  9. Important to Remember • Evolution acts on populations, NOT individuals! • Individuals do not change spontaneously. • Changes may be seen in the population as a whole over millions of years. • Evolution is NOT purposeful! • Traits that are favorable in some environments may not be favorable in others. • Change in the environment may cause change in populations.

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