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Block Day- May 23, 2012

Block Day- May 23, 2012. Homework : pGLO Corrections/Retakes by Friday Finish DOTS activity questions- due Friday. Warm up: the horse on the left is an ancestor of the horse on the right. How could the average horse wind up looking like the one on the right? Use leg length as your example.

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Block Day- May 23, 2012

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  1. Block Day- May 23, 2012 Homework: pGLO Corrections/Retakes by Friday Finish DOTS activity questions- due Friday

  2. Warm up: the horse on the left is an ancestor of the horse on the right. How could the average horse wind up looking like the one on the right? Use leg length as your example

  3. EVOLUTION (We will make an entry for the notes handout later ) GIVE YOUR OWN DEFINITION AND AN EXAMPLE

  4. Definition of Evolution: Change in the heritable (genetic) traits of a population over time Note: when we discuss evolution, we are talking about populations changing, not individuals

  5. Natural selection: The main mechanism by which evolution occurs

  6. 4 Conditions for Natural Selection: • Variation: Individuals in a population are not identical to each other. • Inheritance:Traits are passed to offspring; traits have a genetic basis • Environmental population limits:Environmental limiting factors prevent all individuals from surviving to reproduce; some die young.

  7. Environmental selection: • Individuals in the population with more favorable (advantageous) traits are the ones that survive to reproduce. • Individuals without advantageous traits die before reproducing. These factors result in a change in the average trait of the population… Biologists call this EVOLUTION!

  8. 1. VARIATION • Members of a population have traits similar to the average trait of the entire population, but they are not identical. YOUR TURN: Using height as an example, sketch a graph to represent the statement above. Mean (average) height Your height? Frequency Height (cm)

  9. 2. INHERITANCE • DNA determines the traits of individuals • Individuals inherit DNA from their parents • This causes the traits of the offspring to resemble the traits of the parents trait DNA mRNA protein

  10. 3. ENVIRONMENTAL POPULATION LIMITS • For all species, if every individual born into a population were to reproduce, the population would grow exponentially Population Time

  11. 3. ENVIRONMENTAL POPULATION LIMITS • Environmental factors (limiting factors) prevent the majority of individuals from surviving to reproduce Population Time

  12. 4. SELECTION • Individuals without advantageous traits die before reproducing. • Individuals with advantageous traits survive to reproduce. Frequency These individuals die without reproducing These individuals survive to reproduce Characteristic

  13. Populations change, not individuals • The “average” characteristic or other measure of the population changes over generations average, 3rd gen. average, 2nd gen. average, 50th gen. average, 1st gen. Frequency These individuals die without reproducing These individuals die without reproducing These individuals survive to reproduce Characteristic

  14. Entry 54: Dots Activity • Get 1 data table and 1 handout per person from front counter and begin reading directions for today’s activity

  15. Color Identification Key

  16. Make a table heading (not an entry) “class data” Get a set of class data

  17. 45% 35% 29% 13% 50%

  18. Gen 1 Gen 2 Gen 3 Gen 4 Gen 5

  19. Get a set of questions- (1 per person) from the front counter • Answer the questions using the class data

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