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Natural Selection. Todays Objectives: SOL BIO.8b-d TSW investigate and understand how populations change through time, including: –How variation of traits,

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Presentation on theme: "Natural Selection. Todays Objectives: SOL BIO.8b-d TSW investigate and understand how populations change through time, including: –How variation of traits,"— Presentation transcript:

1 Natural Selection

2 Todays Objectives: SOL BIO.8b-d TSW investigate and understand how populations change through time, including: –How variation of traits, reproductive strategies, and environmental pressures impact on the survival of populations –Recognizing how adaptations lead to natural selection –How new species emerge

3 Charles Darwin On the Origin of Species Sailed with the HMS Beagle Observations made in the Galapogos Islands These observations helped him form the theory of how species change over time called natural selection

4 What is Natural Selection? Natural selection is governed by the principles of genetics.

5 Types of Adaptations Protective Coloring –Camouflage –Mimicry Physiological Adaptations –Reproductive Changes –Other changes Behavioral Adaptations

6 Evidence for Evolution Fossil record Anatomy –Homologous structures –Analagous structures Vestigial structures Embryology Molecular biology (DNA differences)

7 What is a Population? Populations evolve over many generations, individuals dont Populations are groups of interbreeding individuals that live in the same place at the same time Individuals in a population compete for resources with each other

8 How Does Evolution Work? Populations produce more offspring than the environment can support The unequal ability of individuals to survive and reproduc leads to the gradual change in a population over many generations

9 Mechanism for change in a population of organisms Animals who have greater fitness survive in environment and live to reproduce Random changes (mutations) can lead to greater or less fitness Adaptations allow an organism to survive better in their environment

10 Mutations & Variety Produced by Sexual Reproduction Allow for Diversity within a Population Genetic drift (caused by chance) –Bottleneck –Founder effect Genetic equilibrium –Hardy-Weinberg law –In H-W equilibrium, does not occur

11 Adaptations Can arise in response to environmental pressures –Temperature –Antibiotic resistance in bacteria –Pesticide resistance –Morphological changes in peppered moths

12 Types of Selection Directional –Extreme form favored by natural selection Stabilizing –Middle form most successful Disruptive –Two extreme forms successful in separate environments

13 How are new species created? Geographic isolation Reproductive barriers Change in chromosome numbers Adaptive radiation

14 Types of Evolution Convergent evolution –Dolphins & fishes –Wings of bees & bats Divergent evolution –Darwins finches –Adaptive radiation

15 How fast does evolution occur? Gradualism –Darwin –Species change slowly over time Punctuated Equilibrium –Gould & Lewontin –Species can make rapid leaps in evolution Modern Synthesis –Parts of both are correct


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