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Unit 5 Evolution

Unit 5 Evolution. Ch. 15 Darwin’s Theory of Evolution. The Puzzle of Life’s Diversity. Evolution - modern organisms have descended from ancient organisms (change over time) Theory - a well-supported, testable explanation of phenomena that have occurred in the natural world.

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Unit 5 Evolution

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  1. Unit 5 Evolution Ch. 15 Darwin’s Theory of Evolution

  2. The Puzzle of Life’s Diversity • Evolution - modern organisms have descended from ancient organisms (change over time) • Theory - a well-supported, testable explanation of phenomena that have occurred in the natural world

  3. Voyage of the Beagle • Charles Darwin contributed most to our understanding of evolution • He made observations & collected evidence that led him to propose a hypothesis about the way life changes over time

  4. Voyage of the Beagle • That hypothesis, now supported by a large amount of evidence, has become the theory of evolution

  5. Darwin’s Observations • Darwin collected the preserved remains of ancient organisms - Fossils • Some of these fossils resembled organisms that were still alive • Others looked unlike any creature ever seen

  6. Darwin’s Observations • The Galapagos Islands influenced Darwin the most • He observed that the characteristics of animals & plants varied among the different Islands

  7. An Ancient, Changing Earth • Hutton & Lyell helped scientists recognize that Earth is millions of years old • They also noted that the processes that changed Earth in the past are the same processes that are changing Earth now

  8. Lamarck’s Evolution Hypothesis • The year that Darwin was born, Lamarck published his hypothesis • He proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime • Over time, this process led to change in a species

  9. Lamarck’s Explanation

  10. Population Growth • English economist, Malthus, published a book, noting that babies were being born faster than people were dying • He stated that if the human population continued to grow unchecked, sooner or later there would be insufficient living space & food for everyone

  11. Darwin Presents His Case • Darwin published the results of his work in a book, On the Origin of Species • In his book, he proposed a mechanism for evolution called natural selection • He stated that evolution has been taking place for millions of years, & continues in all living things

  12. Inherited Variation & Artificial Selection • Artificial selection - nature provided the variation, & humans selected those variations that they found useful • It has produced diverse plants & animals by selectively breeding for different traits

  13. Evolution by Natural Selection • Struggle for existence - the members of each species compete regularly to obtain food, living space, & other necessities of life • Predators that are faster & better at catching prey are more likely to survive

  14. Evolution by Natural Selection • Fitness - the ability of the organism to survive & reproduce in its specific environ. • Fitness is the result of adaptations

  15. Evolution by Natural Selection • Adaptation - any inherited characteristic that increases an organisms’ chance of survival • Successful adaptations allow organisms to become better suited to their environ. & thus better able to survive

  16. Evolution by Natural Selection • Individuals that are better suited to their environ., with adaptations that enable fitness, survive & reproduce most successfully - Survival of the Fittest

  17. Evolution by Natural Selection • Since it is similar to artificial selection, Darwin referred to survival of the fittest as - Natural Selection • In both AS & NS, only certain individuals of a population produce new individuals

  18. Evolution by Natural Selection • However, in NS, the traits being selected, & therefore, increasing over time, contribute to an organism’s fitness • NS takes place without human control or direction

  19. Evolution by Natural Selection • NS results in changes in the inherited characteristics of a population, that increase a species’ fitness in its environ. • Over time, NS produces organisms that have different structures, & occupy different habitats

  20. Evolution by Natural Selection • As a result, species today look different from their ancestors • Each living species has descended, with changes, from other species over time - Descent with Modification

  21. Evolution by Natural Selection • Descent with modification also implies that all living organisms are related to each other • Common descent - all species (living & extinct) were derived from common ancestors

  22. Evidence of Evolution • Darwin argued that living things have been evolving on Earth for millions of years • Evidence of this could be found: in the fossil record, the geographical distribution of living species, homologous structures of living organisms, & similarities in early development

  23. Evidence of Evolution • The Fossil Record: • Darwin noticed that the sizes, shapes, & varieties of related organisms preserved in the fossil record, changed over time

  24. Evidence of Evolution • Geographic Distribution of Living Species: • Darwin realized that similar animals in different locations were the product of different lines of evolutionary descent

  25. Evidence of Evolution • Homologous Body Structures: • Homologous structures - structures that have different mature forms but develop from the same embryonic tissues • Not all homologous structures serve important functions • Organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs

  26. Homologous Structures

  27. Evidence of Evolution • Homologous Body Structures: • Vestigial organs - may resemble miniature legs, tails, or other structures, a trace of a homologous structure

  28. Evidence of Evolution • Similarities in Early Development: • The early stages or embryos, of many animals with backbones are very similar

  29. Summary of Darwin’s Theory • Individual organisms differ, & some of this variation is heritable • Organisms produce more offspring than can survive, & many that do survive do not reproduce

  30. Summary of Darwin’s Theory • Because more organisms are produced than can survive, they compete for limited resources • Individuals best suited to their environ., survive & reproduce most successfully

  31. Summary of Darwin’s Theory • These organisms pass their heritable traits to their offspring • This process of NS causes species to change over time

  32. Summary of Darwin’s Theory • Species alive today are descended with modification from ancestral species that lived in the distant past • This process, where diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life

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