Chapter 9 Lecture Outline

Chapter 9 Lecture Outline - CHAPTER 9 Natural Selection and...

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CHAPTER 9 Natural Selection and Evolution Natural Selection Charles Darwin First to describe natural selection Noticed finches from Galapagos Islands differed among islands Different beak size and shape Noted they lived in different environments Beak shape and size was associated with diet Natural selection Natural selection Survival of the fittest o organisms better fit for the environment are more likely to survive and reproduce. o “Fittest” genes get passed on Genes of individuals vary within a population As environment changes, the trait being selected for changes Part of ecology because it is based on individuals interactions with the environment Has to occur over many generations ~ a long period of time Causes of Natural Selection: Competition for food (e.g. Sand piper birds fighting for food) Predation (animals preyed upon; the weak, slow and diseased) Symbiosis ~ a long term relationship between organisms o Commensalism, parasitism, mutualism (e.g. bee gets pollen from flowers) Sexual selection – animals compete for and choose mates Types of Natural Selection: Stable – o Selecting the intermediate trait (Babies and birth weight was an example) Directional – o Selecting for a trait at one extreme (Flies were used as an example) Disruptive –
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o Selects against the intermediate trait and selects for the extremes (Birds and beaks example…for food consumption ease) Examples of natural selection:
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Chapter 9 Lecture Outline - CHAPTER 9 Natural Selection and...

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