Natural Selection

Natural Selection - What is Natural Selection WFC...

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1 What is Natural Selection? WFC 10 Nothing in biology makes sense except in the light of evolution Theodosius Dobzhansky 1973 Basic precepts of Natural Selection Variation Organisms vary! Why? 1 Environmental factors such as food, climate 2 Genetic factors , that is, inherited differences Of course, both factors may be involved. Student Heights 4.5 5.0 5.5 6.0 6.5 7.0 0 5 10 15 20 Mother Heights 4.5 5.0 5.5 6.0 6.5 7.0 Frequency 0 5 10 15 20 25 30 Father Heights Height (ft) 4.5 5.0 5.5 6.0 6.5 7.0 0 5 10 15 20 25 Your heights generally lie between those of your parents And they are positively related to the average of your parent’s heights The positive relationship reflects genetics The scatter, or “noise,” around this line reflects the environment Student Heights 4.5 5.0 5.5 6.0 6.5 7.0 0 5 10 15 20 Mother Heights 4.5 5.0 5.5 6.0 6.5 7.0 Frequency 0 5 10 15 20 25 30 Father Heights Height (ft) 4.5 5.0 5.5 6.0 6.5 7.0 0 5 10 15 20 25 WFC 10 -- Fall 2007 Mid-Parent Heights 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 Student Heights 4.6 4.8 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 r 2 = 0.26 And, this pattern is consistent, year after year after year . . . Fall 1998 -- r 2 = 0.22 5 6 4.5 5.0 5.5 6.0 6.5 5 6 4.5 5.0 5.5 6.0 6.5 Fall 2000 -- r 2 = 0.22 Fall 2005 -- r 2 = 0.28 Midparent Heights 5 6 4.5 5.0 5.5 6.0 6.5 5 6 Student Height 4.5 5.0 5.5 6.0 6.5 Fall 2001 -- r 2 = 0.27 5 6 Student Height 4.5 5.0 5.5 6.0 6.5 5 6 Student Height 4.5 5.0 5.5 6.0 6.5 Spring 2003 -- r 2 = 0.30 Fall 2002 -- r 2 = 0.26 5.0 5.5 6.0 6.5 4.5 5.0 5.5 6.0 6.5 Fall 2003 -- r 2 = 0.30 Mid-Parent Heights 5' 5'6" 6' Student Heights Fall 2004 -- r 2 = 0.25 Fall 2006 -- r 2 = 0.23 5 6 4.5 5.0 5.5 6.0 6.5 Fall 2007 -- r 2 = 0.26 5 6 4.5 5.0 5.5 6.0 6.5
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