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The Theory of Natural Selection

The Theory of Natural Selection. Over time, those not adapted most likely die. Artificial Selection. Humans have shown that breeding can cause changes over time Dogs, Crops, Livestock Humans (not nature) have selected desirable traits

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The Theory of Natural Selection

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  1. The Theory of Natural Selection Over time, those not adapted most likely die

  2. Artificial Selection • Humans have shown that breeding can cause changes over time • Dogs, Crops, Livestock • Humans (not nature) have selected desirable traits • What’s the point? Proves that breeding can lead to change over a period of time Pigeons have been bred to enhance tail feathers….breast feathers…etc… Wild mustard has been bred by farmers into numerous other foods Dog traits have been selected by breeders for centuries to enhance certain traits.

  3. Natural Selection With adaptation Without adaptation Not all these wildebeest will survive These kittens have variations • Four factors: 1) Overpopulation: more offspring are born than can survive 2) Variation: individuals of a population have differences 3) Adaptation: Some variations allow a better chance of survival 4) Over time, those with advantages make up most of the population

  4. The Myth

  5. Which rabbit is best adapted? Do the dark rabbits turn white? No! They get eaten.

  6. Struggle for Survival Predation Competition • Populations do not grow unchecked • “Limiting Factors” prevent overpopulation • Fitness: measure of the ability to survive & produce more offspring Disease Clean water Shelter Acts of Nature

  7. New environments are continually created. What happens to life that has favorable traits to survive the change?

  8. Changing Environments

  9. Natural Selection in Action: The Peppered Moth Analysis Before the industrial revolution, the trees in the forest around Manchester, England were a light grey/green due to the color of lichens (fungus) on their trunks. Peppered moths, or Bistonbetularia, which lived in the area, were mostly lightly colored with dark spots. However, there was some color variation between the moths. The most common moth color was light with dark spots and the least common were dark with light spots. Because there were not enough resources to support the entire population, the members of this species had to compete for survival. Their coloring, when against a similar background, served as camouflage against predators such as birds and lizards, thus increasing chances of survival.

  10. Natural Selection in Action: The Peppered Moth Analysis As the Industrial Revolution progressed, the trees became covered with sulfur dioxide, turning the trunks dark.

  11. Kobe Kuiz • What is artificial selection? • What is natural selection? • How does natural selection lead to population changes? • Explain why scientists believe the Earth’s environments have been changing for millions of years. • Why don’t populations (such as deer) continue to grow unchecked?

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