THEORIES OF EVOLUTION Theories Confirmed through tests and observations Explain a wide variety of data and observations Can be used to make predictions Video Video Section 1: Darwins Influences Who was Darwin? Charles Darwin ( ) Darwins Influences: Geology Traditional Beliefs of Darwins Time: Earth less than 10,000 years old and unchanging James Hutton and Charles Lyell (geologists): Earth is many millions of years old Changes through processes like volcanism and erosion Darwins Influences: Jean-Babtiste de Lamarck Related fossil forms to living animals Species change as they adapt to their environments Lamarcks Explanation 1. Acquired traits passed on to offspring Acquired trait - arises during an organisms lifetime 2. Use and disuse Use it gets bigger Dont use it gets smaller Examples of Lamarcks Explanations Lamarcks Rejection Lamarcks hypotheses were discarded Acquired traits cannot be inherited No genetic basis Darwins Influences: Population Growth Thomas Malthus Malthus human populations outgrow resources leads to suffering Darwin applies to all living organisms Darwins Influences: Artificial Selection Humans select plants and animals to breed End up with a variety of domesticated animal breeds and plant crops Nature provides variations, and humans select those they find useful Darwins Journey Darwins Finches Observed 13 species of finches on the Galapagos Islands Descended from single South American species Offspring of original finches adapted to different environments and food sources Darwins Observations What else did Darwin observe? Video Video Darwins Observations What characteristics made Darwin especially well suited for science? What did Darwin see and do on his five-year voyage aboard the Beagle? Why was the publication of On the Origin of Species a courageous act? Section Two Darwins Theory The Origin of Species (1859) Darwins Theories 1. Descent with Modification Newer forms appearing in the fossil record are modified descendants of older species All species descended from one or a few original types of life Darwins Theories 2. Modification by Natural Selection How evolution occurs a) Variation exists among individuals in a species b) Many of those differences can be passed on to offspring Darwins Theories 2. Modification by Natural Selection c) Competition leads to the death of some individuals while others survive d) Individuals that had advantageous variations are more likely to survive and reproduce Important Concepts A population adapts to its environment as the proportion of genes for favorable traits increases Trees Darken Important Concepts Do individuals adapt? Do individuals evolve? A single organisms genetic contribution to the next generation is its fitness Important Concepts High fitness = well adapted, reproduces more successfully Does survival of the fittest always mean survival of the strongest? Video Video If YES How would Darwin explain the evolution of a particular trait? If NO Why isnt this an example of natural selection? Natural Selection: Yes or No? Polar bears developed light fur from darker-colored ancestors. Do you think natural selection was involved? Many species of finches are found on the Galapagos, each with differently-shaped beaks. They are all related to a finch in South America. Was natural selection involved? Blue Tits in GB (related out our Chickadees) have learned to open the tops of milk jars to drink the fat. Birds teach their offspring to do the same. Is this an example of natural selection? Some might argue that kangaroos have small forearms because they dont use them much. Is this an example of natural selection? These stick bugs are very hard to see. Do you think natural selection was involved? Cactus spines are just modified leaves. Do you think natural selection was involved? Why is Evolution Controversial Or is it? Video Video