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Lamarck’s Theory of Evolution

Lamarck’s Theory of Evolution. Jean-Baptiste Lamarck , 1809 One Of First Scientists To Understand That Change Occurs Over Time Stated that Changes Are Adaptations To Environment acquired in an organism’s lifetime Said acquired changes were passed to offspring. Lamarck’s Theory of Evolution.

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Lamarck’s Theory of Evolution

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  1. Lamarck’s Theory of Evolution • Jean-Baptiste Lamarck, 1809 • One Of First Scientists To Understand That Change Occurs Over Time • Stated that Changes Are Adaptations To Environment acquired in an organism’s lifetime • Said acquired changes were passed to offspring

  2. Lamarck’s Theory of Evolution • Idea called Law of Use and Disuse • If a body part were used, it got stronger • If body part NOT used, it deteriorated

  3. Lamarck’s Theory of Evolution • Inheritance of Acquired Characteristics • Proposed That By Selective Use Or Disuse Of Organs, Organisms Acquired Or Lost Certain Traits During Their Lifetime • These Traits Could Then Be Passed On To Their Offspring • Over Time This Led To New Species

  4. Lamarck’s Mistakes • What problems do you see with Lamarck’s theory?

  5. Charles Darwin the Naturalist

  6. Voyage of the Beagle Charles Darwin • Born Feb. 12, 1809 • Joined Crew of HMS Beagle, 1831 • 5 Year Voyage around world • Astounded By Variety of Life

  7. The Galapagos Islands • Volcanic islands off the coast of South America • Island species varied from mainland species & from island-to-island species

  8. The Galapagos Islands • Finches on the islands resembled a mainland finch • More types of finches appeared on the islands where the available food was different (seeds, nuts, berries, insects…) • Finches had different types of beaks adapted to their type of food gathering

  9. Darwin’s Observations & Conclusions The Struggle for Existence

  10. Definition • Evolution is the slow , gradual change in a population of organisms over time

  11. Darwin’s Observations • Left unchecked, the number of organisms of each species will increase exponentially, generation to generation • In nature, populations tend to remain stable in size • Environmental resources are limited • CONCLUSION: Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals • Only a fraction of offspring survive each generation • Survival of the Fittest

  12. Darwin’s Conclusion • Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals • Called Natural Selection

  13. Darwin’s Theory of Evolution • The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection)

  14. Common Descent with Modification • Darwin proposed that organisms descended from common ancestors • Idea that organisms change with time, diverging from a common form • Caused evolution of new species

  15. Natural Selection • Driving force for evolution • During the struggle for resources, strongest survive & reproduce • Idea that at least some of the differences between individuals, which impact their survival and fertility, are inheritable .

  16. Natural Variation and Artificial Selection • Natural Variation • Differences Among Individuals Of A Species • Artificial Selection • Selective Breeding To Enhance Desired Traits Among Stock or Crops

  17. Natural Variation and Artificial Selection Key Concept: In Artificial Selection, Nature Provided The Variation Among Different Organisms, And Humans Selected Those Variations That They Found Useful

  18. Evolution By Natural Selection Concepts • The Struggle for Existence (compete for food, mates, space, water, etc.) • Survival of the Fittest (strongest able to survive and reproduce) • Descent with Modification (new species arise from common ancestor replacing less fit species)

  19. Survival of the Fittest • Fitness • Ability of an Individual To Survive & Reproduce • Adaptation • Inherited Characteristic That Increases an Organisms Chance for Survival

  20. Survival of the Fittest • Adaptations Can Be: • Physical • Speed, Camouflage, Claws, Quills, etc. • Behavioral • Solitary, Herds, Packs, Activity, etc.

  21. Survival of the Fittest • Fitness Is Central To The Process Of Evolution • Individuals With Low Fitness • Die • Produce Few Offspring

  22. Survival of the Fittest Key Concept Over Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment

  23. Descent With Modification • Species Today Look Different From Their Ancestors • Each Living Species Has • Descended • With Changes • From Other Species • Over Time

  24. Descent With Modification • Implies • All Living Organisms Are Related • Single Tree of Life • DNA, Body Structures, Energy Sources • Common Descent • All Species, Living & Extinct, Were Derived From Common Ancestors

  25. Theory of Evolution Today

  26. Homologous Structures

  27. Evidence for Evolution - Comparative Embryology Similarities In Embryonic Development

  28. Similarities in DNA Sequence

  29. Evidence of Evolution Key Concept Darwin Argued That Living Things Have Been Evolving On Earth For Millions of Years. Evidence For This Process Could Be Found In: • The Fossil Record • The Geographical Distribution of Living Species • Homologous Structures of Living Organisms • Similarities In Early Development

  30. Fossil Record • Earth is Billions of Years Old • Fossils In Different Layers of Rock (sedimentary Rock Strata) Showed Evidence Of Gradual Change Over Time

  31. Geographic Distribution of Living Species • Different Animals On Different Continents But Similar Adaptations To Shared Environments

  32. Review

  33. Darwin's Theory • Individual Organisms In Nature Differ From One Another. Some Of This Variation Is Inherited • Organisms In Nature Produce More Offspring Than Can Survive, And Many Of These Offspring Do No Reproduce

  34. Darwin's Theory • Because More Organisms Are Produced Than Can Survive, Members Of Each Species Must Compete For Limited Resources • Because Each Organism Is Unique, Each Has Different Advantages & Disadvantages In The Struggle For Existence

  35. Darwin's Theory • Individuals Best Suited To Their Environment Survive & Reproduce Successfully – Passing Their Traits To Their Offspring. • Species Change Over Time. Over Long Periods, Natural Selection Causes Changes That May Eventually Lead To New Species

  36. Darwin's Theory • Species Alive Today Have Descended With Modifications From Species That Lived In The Past • All Organisms On Earth Are United Into A Single Tree Of Life By Common Descent

  37. The Gene Pool • Members of a species can interbreed& producefertile offspring • Species have a shared gene pool • Gene pool – all of the alleles of all individuals in a population

  38. Populations • A group of the same species living in an area • No two individuals are exactly alike (variations) • More Fit individuals survive & pass on their traits

  39. Speciation • Formation of new species • One species may split into 2 or more species • A species may evolve into a new species • Requires very long periods of time

  40. Modern Evolutionary Thought

  41. Modern Synthesis Theory • Combines Darwinian selection and Mendelian inheritance (Father of Genetics) • Population genetics - study of genetic variation within a population • Emphasis on quantitative characters (height, size …)

  42. Modern Synthesis Theory • TODAY’S theory on evolution • Recognizes that GENES are responsible for the inheritance of characteristics • Recognizes that POPULATIONS, not individuals, evolve due to natural selection & genetic drift • Recognizes that SPECIATION usually is due to the gradual accumulation of small genetic changes

  43. Microevolution of Species

  44. Causes of Microevolution • Mutation • a change in an organism’s DNA • Mutations can be transmitted in gametes to offspring • Non-random mating • - Mates are chosen on the basis of the best traits

  45. Modes of Natural Selection

  46. Modes of Natural Selection • Directional Selection • Favors individuals at one end of the phenotypic range • Most common during times of environmental change or when moving to new habitats • Disruptive selection • Favors extreme over intermediate phenotypes • Occurs when environmental change favors an extreme phenotype

  47. Variations in Populations

  48. Geographic Variations • Variation in a species due to climate or another geographical condition • Populations live in different locations • Example: Finches of Galapagos Islands & South America

  49. Heterozygote Advantage • Favors heterozygotes (Aa) • Maintains both alleles (A,a) instead of removing less successful alleles from a population • Sickle cell anemia • > Homozygotes exhibit severe anemia, have abnormal blood cell shape, and usually die before reproductive age. • > Heterozygotes are less susceptible to malaria

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