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Natural Selection

Natural Selection

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Natural Selection

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  1. Natural Selection Evolution & Adaptation Bio 3.4.2 Explain how natural selection influences the changes in species over time.

  2. Essential Questions: How does the process of natural selection bring about changes in species over time? ? ? ? ? ? ? ?

  3. Where are We headed? We just learned about the inheritance of traits in INDIVIDUALS and their families. We are now going to learn about the inheritance of traits in WHOLE POPULATIONS! A population is: A group of individuals of a species living in a specific area at given time.

  4. What is Evolution? Evolution is a change in species over time! Species today are different from organisms millions of years ago. The HUGE diversity of life we see today resulted from evolution! First organism

  5. Who was Charles Darwin? • Considered the “father of evolution” • Published “On the Origin of Species by Natural Selection” • Worked as a naturalist on the HMS Beagle. • Collected and catalogued plants and animals for over 5 years.

  6. Who Was Charles Darwin? Click this link and open in a new tab! DARWIN VIDEO

  7. Darwin’s Travels

  8. Theory of Evolution • NaturalSelection: Process by which individuals that are better suited to their environment survive and reproduce most successfully. • Also called “survival of the fittest”

  9. Struggle for Existence • Organisms with certain (+) variations can survive, reproduce and pass their variations on to the next generation. • Organisms without these variations are less likely to survive and reproduce.

  10. Natural Selection is influenced by an organism’s environment. Fitness: the ability of an organism to survive and reproduce in its environment. Organisms with greater the fitness, are able to survive and therefore are able to have more offspring.

  11. Fitness is a result of adaptation. • Adaptation: any inherited characteristic that increases an organisms chance of survival. • Some adaptations provide an adaptive advantage which is a favorable trait an organism has over another.

  12. Darwin’s Theory of Natural Selection Darwin’s theory of Natural Selection has 5 key principles: There is GENETIC VARIATIONin a population. There is LOTS of variation in the human population. People have different: • Ages • Heights • Weights • hair colors • skin colors • eye colors, etc.

  13. Where does Genetic Variation come from? Genetic variation comes from two sources: Mutations Sexual Reproduction (Sorting and Recombining chromosomes)

  14. Darwin’s Theory of Natural Selection Organisms produce MORE OFFSPRING THAN CAN SURVIVE. Frogs produce hundreds to thousands of eggs. Very few will survive! Most will be eaten by other organisms before reaching adulthood!

  15. Darwin’s Theory of Natural Selection COMPETITION:Because more organisms are produced than can survive, members of a species must compete for limited resources. Limited resources organisms compete for: Food/Water Space/shelter Mates Etc.

  16. Darwin’s Theory of Natural Selection Some members of population have ADVANTAGEOUS TRAITS (ADAPTATIONS) in the struggle for existence. These organisms survive, reproduce, and pass on those advantageous traits. Camouflage is an adaptation many organisms have that helps them survive by avoiding predators.

  17. Darwin’s Theory of Natural Selection SPECIATION: Over long periods of time, and given a steady input of new variation into a population, these processes lead to the development of new species.

  18. example of Natural Selection: There are 2 VARIATIONSof beetles in this population: Green& Blue

  19. example of Natural Selection: The beetles are eaten by crows that favor the Green variety Green beetles taste delicious!

  20. example of Natural Selection: For the beetles, being blue is an ADAPTATION The blue beetles survive… and reproduce... We’re full of yummy green beetles

  21. example of Natural Selection: There are now more blue beetles in the population. If this continues for MANY generations the blue beetles could become a NEW SPECIES(SPECIATION)!

  22. Another Example of Natural Selection: Watch another example of Natural Selection here → Then answer the questions on your note sheet.,

  23. Darwin’s observation of finches (a bird) on the Galapagos Islands led him to believe that different species may have descended from a common ancestor. • Descent with modification: newer forms appearing in the fossil record are actually modified descendants of older species.

  24. Antibiotic Resistance Antibiotics kills those bacteria that are not resistant. Those that are resistant survive and continue to reproduce, making more bacteria that are resistant. The antibiotic is now not effective.

  25. SUMMARY Questions: Answer the questions below on your note sheet: Who is Charles Darwin? What is his theory? What are Darwin’s 5 principles? Give an example of genetic variation. Give an example of competition Give an example of an adaptation.