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  2. WHAT IS EVOLUTION? Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms.

  3. EVIDENCE OF CHANGE IN SPECIES -fossils -DNA sequences -anatomical similarities (body structures) -physiological similarities (body functions) -embryology

  4. FOSSILS • -fossils allow us to compare ancient organisms with modern ones. • -the sizes, shapes, and varieties of related organisms preserved in the fossil record changed over time. EXAMPLE: CEPHALOPODS

  5. 4 Types of Fossils: • 1) imprint- outline (feathers, leaves • 2) mold- deer depression (animal tracks) empty space left in rock showing exact shape or organisms • 3) cast- mold filled with minerals • 4) petrified- dissolved minerals replace hard parts (tree trunks, shells, bones, teeth) exact stone copy of original organism, the hard parts of which have penetrated and replaced by minerals

  6. FOSSILS • Rock layer in which fossil is found determines its relative age & relationship. (simple to more complex) • Top layers of rock are the youngest. • A single ancestor seems to have given rise to many different species.

  7. DNA & RNA • show relationships • closer sequence=more closely related • Similar DNA sequence results in similar proteins and amino acids Giant panda  bear Red panda  raccoon SHOW TRANSPARENCY

  8. ANATOMICAL SIMILARITIES(BODY STRUCTURES) Homologous structures-similar structures arm - human wing – bird leg - reptile flippers - seal, whale basically similar common ancestor

  9. PHYSIOLOGICAL SIMILARITIES(BODY FUNCTIONS) --Similarities in the way an organism’s body works can show a common ancestor. --Example: Dolphins resemble fish, but breathing by lungs instead of gills and giving live birth instead of laying eggs shows that they have a common ancestor with mammals, not fish.

  10. SIMILARITIES IN EMBRYOLOGY • The early stages, or embryos, of many animals with backbones are very similar. • Many embryos look especially similar during early stages of development.

  11. Charles Darwin (1809-1882) -Darwin developed the theory of evolution based on similarities he observed in living and fossilized organisms. -During his famous trip on the HMS Beagle (1831-1836) he charted flora (plants) & fauna (animals) around the world.

  12. -- In 1859 Darwin published On the Orgin of Species by Natural Selection that changed Biology --Darwin proposed that natural selection was the mechanism of evolution. --natural selection- organisms with the most favorable characteristics for an environment survive and pass these traits onto offspring. “Survival of the fittest”

  13. Theory of Evolution by Natural Selection: 1. organisms produce more offspring than can survive. 2. variations among individuals and individuals with certain characteristics are more likely to survive and reproduce. 3. surviving individuals pass these trait on to offspring. 4. enormous periods of time allow for gradual change. Ex: giraffe-short necked individuals could not reach upper level= died - long necked survived and reproduced.

  14. --Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species' fitness in its environment. --Natural selection cannot be seen directly; it can only be observed as changes in a population over many successive generations.

  15. NATURAL SELECTION & ADAPTATIONS • -organisms change to surrounding environment. -requires many generations ex. Peppered moth – 2 varieties light and dark 1850-mostly light Industry exploded-soot & smoke (turned trunks of trees black) 1900- mostly dark moths

  16. 3 Kinds of Adaptations: Structural, Physiological, Behavioral 1.) Structural—physical characteristics adapt Camouflage- allows organisms to blend into its surroundings 2.) Physiological—body processes adapt, such as tanning of skin in the sun 3.) Behavioral—animal behaviors adapt, such as hibernation in bears or migration in birds

  17. NATURAL SELECTION & SPECIATION As new species evolve, populations become reproductively isolated from each other and new species form over time. • Geographic Isolation – physical barrier separates a pop. into groups. Ex. Birds on islands, squirrels separated by Grand Canyon.


  19. NATURAL SELECTION & SPECIATION 2.) Behavioral Isolation- differences in behavior change so that the populations no longer breed (Example—Eastern and Western meadowlarks have a different song to attract mates.) 3.) Temporal Isolation- populations of species reproduce at different times. (Example-- plants release pollen on different days.)

  20. Geographic isolation Behavioral isolation Temporal isolation Physical separation Behavioral differences Different mating times Concept Map Section 16-3 Reproductive Isolation results from Isolating mechanisms which include produced by produced by produced by which result in Independentlyevolving populations which result in Formation ofnew species

  21. PHYLOGENY Phylogeny shows the evolutionary history of an organism as new species are created by natural selection over millions of years. Phylogenetic tree

  22. EXTINCTION • If a species cannot adapt to its changing environment, it is at risk of extinction. • More than 99% of all species that have ever lived are now extinct. • Reasons for Extinction: • Competition for resources • Changing environment • Mass extinctions • Can be caused by many large volcanoes erupting, continents moving, and sea levels changing which can cause global climate change.