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Introduction to Evolution

Explore Lamarck and Darwin's ideas on evolution, including natural selection, adaptations, evidence of evolution, mechanisms of evolution, and speciation. Learn about the role of microevolution and macroevolution in shaping biodiversity. Discover the impact of genetic drift, mutations, and more in the process of species formation.

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Introduction to Evolution

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  1. Introduction to Evolution Chapter 16

  2. Jean-Baptiste de Lamarck (1809) Early Ideas • Use and disuse of organs: Failure to use an organ could result in the inability to use it later. • Inheritance of acquired traits: Acquired traits are passed to offspring • I.e. If you were to lose a limb before you reproduced, your offspring would be missing the same limb Lamarck’s theory was disproven by Weismann’s experiments on mice.

  3. Who was Charles Darwin? • Naturalist who traveled around South America and the South Pacific in the early 1800’s examining the diversity of the wildlife. • Observations in the Galapagos Islands were evidence for much of his theory.

  4. Darwin’s Theory Theory of Natural Selection has these parts • Overproduction • Variation • Competition (not covered in our text) • Selection • Adaptation

  5. 1. Overproduction • More offspring produced than can be supported by the environment

  6. 2. Variation • traits vary within each population

  7. 3. Competition • between individuals within the same population and between different populations

  8. 3. Selection • The environment selects favorable traits which allow individuals within a population to survive and reproduce.

  9. 4. Adaptation • Traits that improve the chances of survival will be more common.

  10. often referred to as “Survival of the fittest” The environmentselects organisms with beneficial traits. Organisms with traits well suited to the environment survive and reproduce at a greater rate. Offspring, therefore, receive favorable traits from the parents. NATURAL SELECTION

  11. Adaptations There are three types of adaptations that may occur • Structural: changes in the anatomy I.e.: Mole rats developed teeth and claws. • Physiological: changes in metabolic processes I.e.: Some bacteria are now resistant to penicillin. • Behavioral: changes in behavior I.e.: Some animals hibernate as a means of surviving the winter.

  12. Evidence of Evolution • Fossils: • provide a record of earlier life • show changes that have occurred; supporting evidence • Anatomical: • Homologous structures: body parts with the same basic structure; supporting evidence • Analogous structures: body parts similar in function but not in structure; not evidence of a common ancestor • Vestigial structures: structures with reduced function; supporting evidence

  13. Homologous Structures

  14. Analogous Structures • Although they have the same function, insect and bird wings are not similar in structure • Bird wings are composed of a set of bones • Insect wings are composed of the protein chitin

  15. Picture of a Vestigial Structure Taken from www.giddings.txed.net/biology/ch18.htm (site no longer exists)

  16. Evidence of Evolution • Embryological: • Common structures and development in the embryos of different species; similar order of development • Embryofetusoffspring; supportive evidence • Biochemical: • Common molecular building blocks that make up different organisms; supportive evidence • Ex. DNA, hemoglobin

  17. Embryological Evidence of Evolution Note that the earlier the stage, the more strikingly similar the different groups are http://chsweb.lr.k12.nj.us/psidelsky/comparative_embryology.htm

  18. Evolution Under Study • Evolution can be studied at different scales. • The range of scales is from: • Microevolution is a change in the genes of populations. • Macroevolution is an appearance of new species over time. • Speciation micro and macro together. It is the creation of a new species. Microevolution speciation Macroevolution

  19. Mechanisms of Evolution Populations evolve; individual organisms do not. Only those organisms with traits favorable for survival in the environment will reproduce and pass the traits onto the next generation. Random mutations can cause these changes in traits.

  20. Microevolution:Change in the genes of populations • There are five processes that can affect the kinds of genes in a population: • Natural Selection • Migration • Mate Choice • Mutation • Genetic Drift

  21. Processes of Microevolution • Natural Selection can cause an increase or decrease of alleles. • Changes in the population because of migration can also affect allelic frequency. • Mate Choice can influence whether the traits are limited or random due the choices available to the parents. • Mutations can also be caused by external factors like radiation or chemicals. • Genetic drift is when this change in allelic frequency happens by chance.

  22. Speciation: The development of a new speciesIt is the link between macroevolution and microevolution. • How it happens: 1. groups within a population become geographically isolated; 2. changes in the separate environments result in different natural selection; 3. after time the gene pools are so different that new species are formed B. Whole random changes in chromosome sets resulting in many normal sets of chromosomes within a species

  23. Macroevolution:The appearance of new species over time • Macroevolution consists of the direction, diversity and speed of change to understand the development of a new species. • Patterns and time models are studied through: • Convergent evolution • Coevolution • Gradualism • Punctuated equilibrium • Adaptive radiation • Extinction

  24. Patterns of Evolution http://www.biologie.uni-hamburg.de/b-online/library/cat-removed/u4aos2p4.html http://www15.homepage.villanova.edu/matthew.reudink/yucatan_photos.htm A. Divergent: when species that used to be simi- lar become more and more different due to different niches C. Coevolution: changes in two or more species that affect their interactions • Convergent: • when very distantly related organisms • develop similar structures; could be due • to similar environments when evolving

  25. Time Models for Evolution • Gradualism: The change rate is slow but constant. B. Punctuated Equilibrium: Quick change, then a long period of stabi- lity with similar organisms. A species could form in as little as 10,000 years.

  26. Diversity of Evolution • Adaptive Radiation: Species may split into two or more lines of descendants (lineages) causing anew species. • Extinction: All members of a lineage fail to reproduce and die off.

  27. Types of Selection • Directional Selection: favors one extreme phenotype This demonstrates that the original population was lighter in color, but that darker-colored mice had a more favorable trait and were eventually selected

  28. Types of Selection • Stabilizing selection: eliminates the extreme phenotypes; favors the average This demonstrates that the original population had more lighter and darker mice, but eventually, the medium color was selected for

  29. Types of Selection • Disruptive (diversifying) selection: favors all extreme phenotypes This example demonstrates that the darker- and lighter-colored mice are selected for, while the medium-colored mice become eliminated

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