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Evolution (Part 2)

Evolution (Part 2). Growth of Populations Darwin was influenced by Thomas Malthus He wrote: Populations grow as much as the environment allows. Evolution by Natural Selection. The process of: “ Survival of the Fittest ”

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Evolution (Part 2)

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  1. Evolution(Part 2)

  2. Growth of Populations • Darwin was influenced by Thomas Malthus • He wrote: Populations grow as much as the environment allows.

  3. Evolution by Natural Selection • The process of: “Survival of the Fittest” • Organisms that adapt to their environment survive while those that do not adapt disappear • N.S. leads to adaptations in a population.

  4. Genetic Variation • a. • b. • Overproduction of Offspring a. • b. • Struggle for Existence a. • b. • Differential Survival & Reproduction a. • b. Natural Selection Video http://www.pbs.org/wgbh/evolution/library/11/2/e_s_4.html 6 min 39 sec

  5. Darwin’s Ideas Updated 1) Change Within Populations • N.S. causes the frequency of certain alleles in a population to change over time. 2) Species Formation • Under certain conditions, change within a species due to reproductive isolation can lead to new species. 3) The Tempo of Evolution • Gradualism is a process of evolution in which speciation occurs gradually • Punctuated Equilibrium is a process in which speciation occurs rapidly between periods of little or no change.

  6. Evidence of Evolution--Formation of Fossils • Evidence of orderly change can be seen when fossils are arranged according to their age.

  7. Anatomy and Development Vestigial Structures • Reduced or nonfunctional vestigial structures • hind limbs in whales • provide evidence of an organism’s evolutionary history.

  8. Whale Evolution Video Label Paper 1-5 http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html 5 min, 9 sec

  9. Homologous Structures • Structures in different organism that indicate a shared ancestry • include vertebrate forelimb.

  10. Evidence of Evolution-- Biological Molecules Proteins • MORE differences in amino acid sequences of distantly related species • LESS differences between species that are more closely related. Nucleic Acids (what is a nucleic acid???) • MORE differences in DNA sequences b/t distant relatives • LESS differences between species that are more closely related.

  11. So look at the amino acid sequence given According to the chart, who would be most closely related to fish?

  12. Examples of Evolution-- Natural Selection at Work 1) Factors in Natural Selection • Organisms w/traits helping them survive—reproduce & pass genes. 2) Evolution of Antibiotic Resistance • Experiments show that evolution through N.S. has occurred within populations of antibiotic-resistant bacteria • Tuberculosis bacteria 3) Evolution in Darwin’s Finches • Experiments show that evolution through N.S. has occurred in beak size in Darwin’s Finches.

  13. Formation of New Species 1)Speciation • Speciation begins as a population adapts to its environment. 2) Forming Subspecies • Populations of the same species that differ genetically b/c of adaptations to different living conditions are called: subspecies. • Newly formed subspecies are on the road towards speciation. 3) Maintaining New Species • Reproductive isolation through barriers keeps species from breeding with one another.

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