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Natural Selection

Natural Selection. Charles Darwin. On the Origin of Species Sailed with the HMS Beagle Observations made in the Galapagos Islands These observations helped him form the theory of how species change over time called natural selection. What is Natural Selection?.

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Natural Selection

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  1. Natural Selection

  2. Charles Darwin • On the Origin of Species • Sailed with the HMS Beagle • Observations made in the Galapagos Islands • These observations helped him form the theory of how species change over time called natural selection

  3. What is Natural Selection? • the process whereby organisms better adapted to their environment tend to survive and reproduce more offspring. Natural selection is governed by the principles of genetics.

  4. Types of Adaptations • Structural Adaptations-physical features of an organism • Camouflage • Mimicry • Physiological Adaptations-happen inside the body of an organism. (Temperature regulation, ability to make venom, reproductive changes) • Behavioral Adaptations-things organisms do to survive. May be learned or instinct (a behavior an animal is born with) Migration, hibernation, etc.

  5. Adaptations Katydids have camouflage to look like leaves. Non-poisonous king snakes mimic poisonous coral snakes.

  6. Evidence for Evolution • Fossil record • Anatomy • Homologous structures • Analagous structures • Vestigial structures • Embryology • Molecular biology (DNA differences)

  7. What is a Population? • Populations evolve over many generations, individuals don’t • Populations are groups of interbreeding individuals that live in the same place at the same time • Individuals in a population compete for resources with each other

  8. How Does Evolution Work? • Populations produce more offspring than the environment can support • The unequal ability of individuals to survive and reproduce leads to the gradual change in a population over many generations

  9. Factors that affect Natural Selection: Overproduction most species produce far more offspring than will/can survive

  10. Mechanism for change in a population of organisms • Animals who have greater fitness survive in environment and live to reproduce • Random changes (mutations) can lead to greater or less fitness • Adaptations allow an organism to survive better in their environment

  11. Mechanism for change in a population of organisms • Genetic drift (caused by chance) • Bottleneck Effect-population’s size becomes very small very quickly. Caused by a catastrophic event, hunting a species to near extinction, or habitat destruction. Many alleles are lost and the genetic variation of the population decreases. • Founder Effect-a few individuals in a population colonize a new location that is separate from the old population. Reduces the population size as well as the genetic variability of the population.

  12. Genetic drift Bottleneck Effect

  13. Adaptations • Can arise in response to environmental pressures • Temperature • Antibiotic resistance in bacteria • Pesticide resistance • Morphological changes in peppered moths

  14. Types of Selection • Directional • Extreme form favored by natural selection • Stabilizing • Middle form most successful • Disruptive • Two extreme forms successful in separate environments

  15. Types of Selection

  16. How are new species created? • Geographic isolation • Reproductive barriers • Change in chromosome numbers (mutations) • Adaptive radiation- produces new species from a single, rapidly diversifying lineage. (Darwin’s finches)

  17. Reproductive barriers

  18. Types of Evolution • Convergent evolution • Dolphins & fishes • Wings of bees & bats • Divergent evolution • Darwin’s finches • Adaptive radiation

  19. Types of Evolution • Coevolution - When two different species influence each other's evolution

  20. How Fast does Evolution Occur

  21. How fast does evolution occur? • Gradualism • Darwin • Species change slowly over time • Punctuated Equilibrium • Gould & Lewontin • Species can make rapid “leaps” in evolution • Modern Synthesis • Parts of both are correct

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