Transcript Chapter 7
Chapter 7 Section 2 How Does Evolution Happen? Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Adaptations due to natural selection make an organism Better fit for its environment… http://www.youtube.com/watch?v= XpdoDBYuHIA http://www.youtube.com/watch ?v=7NQUqR_YpsA Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Mimics… Monarchs and Viceroys Robber flies and Bumble Bees http://www.alleghany.k12.va.us/animal%20a daptation%20webpage/animal_mimicry.htm Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 7 Section 3 Natural Selection in Action Objectives • Give three examples of natural selection in action. • Outline the process of speciation. Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 7 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 menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. IMAGE CREDIT: MISTER http://news.bbc.co.uk/2/hi/africa/180301.stm Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 7 Section 3 Natural Selection in Action Changes in Populations, continued Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 7 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 menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 7 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 menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 7 Section 3 Natural Selection in Action Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 7 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 menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. http://www.outback-australia-travelsecrets.com/australian_animals.html Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. 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. http://www.sbs.utexas.edu/levin/bio213/evolution/ speciation.html Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Speciation due to climate differences • adaptations – feet, ears, color • Snowshoe Hare Desert Jack Rabbit Chapter menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 7 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 menu Resources Copyright © by Holt, Rinehart and Winston. All rights reserved.