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Chapter 15

Chapter 15. Darwin’s Theory of Evolution. “…the single most important scientific idea that anyone has ever had…”. 15-1 The Puzzle of Life’s Diversity. Evolution : change over time p rocess by which modern organisms descended from ancient organisms Do you remember what a theory is?.

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Chapter 15

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  1. Chapter 15 Darwin’s Theory of Evolution “…the single most important scientific idea that anyone has ever had…”

  2. 15-1 The Puzzle of Life’s Diversity • Evolution: change over time • process by which modern organisms descended from ancient organisms • Do you remember what a theory is?

  3. Voyage of the Beagle 1831- England Charles Darwin Recorded observations Collected data/specimens Proposed evolutionary theory about how life changes over time

  4. Darwin’s Data • Diversity • Galapagos Islands- different plants/animals on each island • Patterns • Reproductive, habitats, etc. • Fossils: preserved remains/evidence of ancient organisms • Connected old and new

  5. 15-2 Ideas that shaped Darwin’s thinking • Old belief: Earth was “young” and hadn’t changed since life began • Discoveries in geology: • James Hutton • Geological change • Effects of natural forces (rain, wind) • Happens slowly/constantly • Charles Lyell • Wrote Principle’s of Geology • Earth has changed over time…could life?

  6. Jean-Baptiste Lamarck Organisms adapt If you use it, it will stay (get passed on) If you don’t, it will go away Tendency toward perfection Inheritance of acquired traits*

  7. Population Growth Thomas Malthus- economist More people are born than are dying Uncontrolled population growth = high competition for resources What makes some survive and others die?

  8. 15-3 Darwin Presents his case • 1859- publishes On the Origin of Species: • Evolution has been happening for millions of years and is still happening today • Mechanism of evolution = natural selection

  9. Variation and Artificial Selection • Genetic variation found everywhere • Breeders use it to make “the best”: • Fastest horses • Plants with biggest fruit • Artificial selection: selection by humans for breeding of desired traits from the natural genetic variation of organisms

  10. Evolution by Natural Selection Darwin questioned: How does “selection” happen in nature? Struggle for existence: competition among members of a species for food, living space, reproduction, etc.

  11. Survival of the Fittest Process by which individuals better suited to their environment survive and reproduce most successfully Fitness: ability of an organism to survive and reproduce Adaptation: inherited characteristic that increases an organisms chance of survival (structural, physiological, behavioral, etc.)

  12. Survival of the Fittest = Natural Selection Successful adaptations will increase fitness If you survive/reproduce, you pass on genes = more of those genes in nature

  13. Descent with Modification Each living species has descended- with changes- from other species over time Common descent: all living things come from a common ancestor

  14. Darwin’s Evidence #1 fossil record- organisms have come and gone but can be related/connected to current organisms

  15. Darwin’s Evidence #2 • geographical distribution of living species- descent with modification • As organisms changed, they adapted to different habitats and spread out

  16. Darwin’s Evidence #3 • homologous body structures: structures that have different mature forms in different organisms but developed from the same embryonic tissue • Ex: limbs (arms, wings, flippers) • Increased similarities = more closely related • Ex: bats and humans, birds and reptiles

  17. Vestigal Structures Structures that serve no useful function Homologous structures that the organisms no longer needs Ex: whale “legs”

  18. Darwin’s Evidence #4 similarities in embryology- many embryos look the same common cells growing in similar ways

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