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Natural Selection, Adaptation, and Extinction

Explore the principles of natural selection, the observations of Charles Darwin, and the various types of adaptations that organisms develop. Learn about the process of evolution and how it leads to the extinction of certain species.

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Natural Selection, Adaptation, and Extinction

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  1. Chapter Menu Lesson 1:Natural Selection Lesson 2:Adaptation and Extinction Click on a hyperlink to view the corresponding lesson.

  2. 5.1 Natural Selection evolution naturalist natural selection adaptation

  3. 5.1 Natural Selection Charles Darwin • Evolution is change over time. • The naturalist Charles Darwin was the first person to write a thorough collection of evidence supporting evolution. • Darwin’s theory serves as the basis of all biological research today.

  4. 5.1 Natural Selection Charles Darwin (cont.) • Darwin explored South America and its remote islands, such as the Galapagos, on the HMS Beagle.

  5. 5.1 Natural Selection Darwin’s Observations • Darwin made observations about the diversity and uniqueness of organisms. • Many of the animals on the Galapagos were similar, but not the same as organisms in mainland South America. • Darwin reasoned that perhaps the organisms in the Galapagos originally came from South America and over time, they had evolved.

  6. 5.1 Natural Selection Tortoises • Darwin found giant tortoises on all the Galapagos Islands, but nowhere else. • He reasoned that each new population changed slightly, or evolved, to fit its unique environment on the island.

  7. 5.1 Natural Selection Finches • Darwin was impressed by the diversity of finches on the Galapagos. • Darwin explained that if individuals from a species were separated, future generations might look and behave differently. • The finches became different because they became suited to the different habitats on the islands.

  8. 5.1 Natural Selection Selective Breeding • Selective breeding is breeding plants and animals to get offspring with desired characteristics. • This does not lead to a new species—the organism can still breed with other members of its species.

  9. 5.1 Natural Selection Darwin’s Theory of Natural Selection • Organisms with traits that allowed them to survive under particular environmental conditions produced more offspring. • Eventually those traits would be common in the species. How can natural selection be modeled?

  10. 5.1 Natural Selection Genetic Variation • Sometimes changes occur in genes and a new trait is created. • If the trait is beneficial, the organism may survive and pass the trait on to the next generation. • Genetic variation is necessary for evolution to occur.

  11. 5.1 Natural Selection Population Growth and Struggle to Survive • Although resources are limited, animals often produce more offspring than could survive. • Darwin decided this was a natural process that selected which organism survived, and called it natural selection. • Adaptation refers to traits that increase the likelihood of surviving and reproducing in a particular environment.

  12. 5.1 Natural Selection Natural Selection • Four steps or requirements of Darwin’s theory of evolution by natural selection: • Step 1: Overproduction • Step 2: Relative similarity • Step 3: Inherited variation • Step 4: Natural selection

  13. 5.1 Natural Selection Natural Selection (cont.) Overproduction Inherited Variation Variation Natural Selection

  14. 5.1 Natural Selection Lesson 1 Review • A • B • C • D What did Darwin observe about the tortoises and finches in the Galapagos? A their large size B their similarity to those on the mainland C their adaptations to their environments D their friendliness

  15. 5.1 Natural Selection Lesson 1 Review • A • B • C • D What is necessary for evolution to occur? A selective breeding B genetic variation C populations isolated on islands D none of the above

  16. 5.1 Natural Selection Lesson 1 Review • A • B • C • D What is not a main source of genetic variation? A differences in diet B sexual reproduction C mutations D gamete formation

  17. End of Lesson 1

  18. 5.2 Adaptation and Extinction structural adaptation camouflage mimicry behavioral adaptation extinct

  19. 5.2 Adaptation and Extinction Adaptations • Humans can change their environment to meet their needs. • Organisms have evolved adaptations to their environment by the process of natural selection.

  20. 5.2 Adaptation and Extinction Understanding Adaptations • Adaptations are inherited traits that increase an organism’s chance of surviving and reproducing in a particular environment. • Adaptations are the final products of the long process of natural selection. • Adaptations are naturally selected for, not intentional. • Not all traits are adaptations.

  21. 5.2 Adaptation and Extinction Types of Adaptations • Structural adaptations are aspects of the physical body that help organisms survive and reproduce. • Camouflage—coloring that blends with the environment—makes organisms difficult to see.

  22. 5.2 Adaptation and Extinction Types of Adaptations (cont.) • Mimicry is when one species (the mimic) looks like another species (the model) in order to deceive a third species. • Behavioral adaptations are actions or behaviors that help organisms survive and reproduce.

  23. 5.2 Adaptation and Extinction Extinction • A species becomes extinct when all the individuals of a particular species die off. • There have been several major extinction events in history.

  24. 5.2 Adaptation and Extinction Causes of Extinction • Loss of habitat • Loss of genetic diversity • Competition with exotic species • Inability to adapt

  25. 5.2 Adaptation and Extinction Causes of Extinction (cont.)

  26. 5.2 Adaptation and Extinction Lesson 2 Review • A • B • C • D What is not an example of an adaptation? A inbreeding B camouflage C mimicry D behavior

  27. 5.2 Adaptation and Extinction Lesson 2 Review • A • B • C • D Why do some non-desirable traits remain in a population? A selective breeding B mutation C they are genetically linked to more beneficial traits D they may be useful in the future

  28. 5.2 Adaptation and Extinction Lesson 2 Review • A • B • C • D What cause for extinction would most likely be involved in rapid environmental changes such as climate change? A loss of habitat B inability to adapt C loss of genetic diversity D competition with exotic species

  29. End of Lesson 2

  30. Chapter Resources Menu Chapter Assessment California Standards Practice Image Bank Science Online Interactive Table Virtual Lab Click on a hyperlink to view the corresponding feature.

  31. Chapter Assessment 1 • A • B • C • D What is evolution? A adaptations to particular environments B genetic change in a population over time C natural selection D differences in traits

  32. Chapter Assessment 2 • A • B • C • D What is necessary for natural selection to occur? A genetic variation B constant environmental conditions C isolate populations D shortage of offspring

  33. Chapter Assessment 3 • A • B • C • D Which of the following is NOT one of the main sources of genetic variation in a population? A mutations B learned abilities C formation of gametes D sexual reproduction

  34. Chapter Assessment 4 • A • B • C • D Which of the causes of extinction is not influenced by human actions? A inability to adapt B loss of genetic diversity C loss of habitat D competition with exotic species

  35. Chapter Assessment 5 • A • B • C • D Why do desert rabbits have mottled fur? A behavioral adaptations B mimicry C camouflage D incomplete dominance

  36. SCI 3.a CA Standards Practice 1 • A • B • C • D What causes evolution? A genetic variation B environmental factors C both D neither

  37. CA Standards Practice 2 SCI 3.e • A • B • C • D What is one reason exotic species can sometimes outcompete native species? A they have no natural predators B there are more of them C the new environment is more favorable D the natives are not adapted

  38. CA Standards Practice 3 SCI 3.e • A • B • C • D When do we designate a species as threatened or endangered? A when there is one population left B when the number of individuals falls below a certain level C when population numbers are declining D when genetic variation is low

  39. CA Standards Practice 4 SCI 3.a • A • B • C • D Which is required for natural selection to occur? A inherited variation B overproduction of offspring C genetic variation D all of the above

  40. CA Standards Practice 5 SCI 3.b • A • B • C • D Which of the following did not contribute to Darwin’s development of the theory of natural selection? A overproduction of offspring B competition with exotic species in the Galapagos C an essay on human population growth D similarities and differences of species in the Galapagos

  41. Image Bank

  42. Interactive Table

  43. End of Resources

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