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Chapter 16 Evolutionary Theory. Pre-class Question 5/21/09 Why were the beaks of the finches that Darwin observed on the Galapagos Islands different on.

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Presentation on theme: "Chapter 16 Evolutionary Theory. Pre-class Question 5/21/09 Why were the beaks of the finches that Darwin observed on the Galapagos Islands different on."— Presentation transcript:

1 Chapter 16 Evolutionary Theory

2 Pre-class Question 5/21/09 Why were the beaks of the finches that Darwin observed on the Galapagos Islands different on different islands? Homework (due Friday) Active Reading “Developing a Theory”

3 Developing a Theory Evolution is the process by which species change over time. Charles Darwin was responsible for developing the modern theory of evolution A broad explanation that has been scientifically tested and supported

4 3 Types of Selection Artificial Selection Humans can choose what traits are favorable in a species and breed plants and animals to have these traits Natural Selection The process by which individuals that are better adapted to their environment survive and reproduce more successfully than those that are less adapted to do so.

5 3 Types of Selection Continued Sexual Selection An evolutionary process by which a mate is chosen on the basis of a particular trait

6 It’s Who You Know and What They Know Darwin came up with the theory of evolution based on his observations and those of others: Lamarck Observed that each organism is usually well adapted to its environment. Malthus In 1798,Malthus observed that human food supply was increasing at a slower pace than the human population and hypothesized that many humans would die off due to disease, war and famine. Lyell Geologist that though that processes such as erosion and the formation of fossils was gradual and constant.

7 Evolution by Natural Selection Darwin’s theory predicts that over time, the number of individuals that carry advantageous traits will increase in a population Step1 Overproduction Every population is capable of producing more offspring than can possibly survive. Step 2 Variation Variation exists in every population in the form of inherited traits. Step 3 Selection Based on traits one individual is more likely to survive than another and reproduce. Step 4 Adaptation Over time, those traits that improve the survival and reproduction will become more common.

8 Pre-class Question 5/27 Why do you think that giraffes evolved to have long necks? What is the selective pressure that caused this change to occur? Homework Study for Chapter 16 Vocab Quiz (Friday, 5/29) Hint: Selective pressure is any phenomena which alters the behavior and fitness of living organisms within a given environment.

9 Darwin – The Origen of Species by Natural Selection Darwin presents evidence of evolution from multiple fields of science, where some species of animals have common characteristics  The Fossil Record The study of fossils or traces of living things from the past  Biogeography The study of the location of organisms around the world.  Developmental Biology The development of organisms from embryos  Anatomy The study of bodily structure of animals  Biochemistry The study of biomolecules such as amino acids and DNA

10 Evaluating Darwin’s Ideas – 3 major strengths 1.Evidence of evolution 2.A mechanism for evolution Natural Selection 3.The recognition that variation is important Prior to Darwin’s theory, species were classified by Common appearance, and ignored variation which Was a starting point for evolution

11 Evaluating Darwin’s Ideas – Weaknesses Inherited variation was important to Darwin’s theory, but he did not have a clear idea of how traits were inherited. He did not have an understanding of genetics. There was roughly 100 years between when Darwin published his theory and the structure of DNA was discovered.

12 Pre-Class 5/28 Take out yesterday’s activity Reading Selection: How Do Species Change Over Time? Homework Study for tomorrow’s chapter 16 vocab quiz

13 Studying Evolution at all Scales The formation of new species as a result of evolution The appearance of new species over time Change in the genes of a population

14 Microevolution vs. Macroevolution

15 Processes of Microevolution (5) Natural Selection Migration Mate Choice Can be random or through sexual selection Mutation The numbers and types of alleles can change from generation to generation although it is rare Genetic Drift Genetic drift affects genetic makeup of the population through an entirely random process..

16 Patterns of Macroevolution (6) Covergent Evolution When evolution is strongly directed by the environment, species living in a similar environment should evolve similar adaptations. Coevolution Species that share an environment can affect each others evolution. They develop adaptations to coexist

17 Patterns of Macroevolution Cont. Adaptive Radiation Species splint into two or more lines of descent Extinction Gradualism Many small changes occur gradually over time Punctuated Equilibrium New species suddenly appear after some environmental change.

18 Gradualism vs. Punctuated Equilibrium


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