Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Think about it and respond…… What adaptations might you expect in a desert plant or animal? Would these be equally helpful in the rainforest? Explain.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How Does Evolution Happen? Chapter 7

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Evidence for Evolution… 1. The Fossil Record shows how organisms have changed over time. 2. Comparing Skeletal Structures- similarities suggest a common ancestor 3. Comparing DNA Scientists find that species that have many traits in common do have similarities in their DNA. that cats,

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Adaptations due to natural selection make an organism Better fit for its environment… ?v=7NQUqR_YpsA XpdoDBYuHIA

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu daptation%20webpage/animal_mimicry.htm Mimics… Monarchs and Viceroys Robber flies and Bumble Bees

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Natural Selection in Action Objectives Give three examples of natural selection in action. Outline the process of speciation. Chapter 7

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Natural Selection in Action Changes in Populations Adaptation to Hunting People hunt elephants for their tusks. As a result, fewer of the elephants that have tusks survive to reproduce, and more of the tuskless elephants survive. Insecticide Resistance Insecticides have been used so much that now more than 500 kinds of insects have developed resistance to certain insecticides. Chapter 7

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu IMAGE CREDIT: MISTERMISTER

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Natural Selection in Action Changes in Populations, continued Chapter 7

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Natural Selection in Action Changes in Populations, continued Competition for Mates Many species have so much competition for mates that interesting adaptations result. For example, the females of many bird species prefer to mate with males that have colorful feathers. Chapter 7

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Natural Selection in Action Forming a New Species Sometimes, drastic changes that can form a new species take place. The formation of a new species as a result of evolution is called speciation. Chapter 7

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Natural Selection in Action Chapter 7

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Natural Selection in Action Forming a New Species, continued Separation Speciation often begins when a part of a population becomes separated from the rest. Adaptation Populations constantly undergo natural selection. After two groups have separated, natural selection may act on each group in different ways. Chapter 7

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu secrets.com/australian_animals.html

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Kaibab squirrel (Sciurus aberti kaibabensis, left) became geographically isolated from the common ancestor with its closest relative, the Abert squirrel (Sciurus aberti aberti, right) in the North Rim of the Grand Canyon about 10,000 years ago. speciation.html

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Speciation due to climate differences adaptations – feet, ears, color Snowshoe Hare Desert Jack Rabbit

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Natural Selection in Action Forming a New Species, continued Division Over many generations, two separated groups of a population may become very different until the point when they can no longer mate with one another. At this point, the two groups are no longer the same species. Chapter 7