Reminders

• End of the semester is in a week a half!

• Check your student view• Make an appointment

with Miss Baker for make-up work!

• Re-take for Natural Selection Exam Due Friday

Variation Lab

Purpose

• Why did we do this lab?• What relevance does it have to

your life?

http://www.youtube.com/watch?v=von7j2zIoaU

How we look at our data:•Did you all get measurements in cm?• If you didn’t take all your measurements in cm, can you

easily compare heights using different units of measurement? Why or why not?•Did you all measure the apple circumferences the same

way as neighboring groups from which you received data? How can you be sure?•Why were our graphs so problematic?•Do your graphs tell you anything with a degree of certainty

about a population of spinach plants? Why or why not?•Can we learn about selective pressures from our small

amount of data? Why or why not?•Why do we need a larger sample size?

Let’s combine our data to make a class data set

• Report your data on the white boards around the classroom.

• Write down the total variation for spinach leaf width in the population in a data table in your lab and create a new graph.

• Answer the questions in the end of your lab packet with the new data set.

• You will have 15 minutes to do this!• Use this new information to answer your

homework, this power point is on the wiki page.

Types of Selection:

• Stabilizing• Directional• Disruptive

Directional Selection:

Stabilizing Selection:

Disruptive Selection:

Re-evaluating the data:

• What are some possible reasons (selection pressures) for the shape of the class spinach leaf graph?• How could we test these

hypotheses?

Make some predictions:• If we saw the

population of an apple-eating-insect grow in size, and we saw an apple fruit circumference size grow over time, what could we call this evolution pattern?

Definitions

Adaptation-a trait that provides some type of advantage to organisms in the struggle for survival

examples

Selection Pressure• Anything that can

prevent an organism from passing on its genetic material

• Some good examples are: predators, and competition for food, shelter, or mates

Variation

• Variety (or differences) of traits WITHIN A SPECIES.

How do we get variation?1. Genetic Shuffling in Anaphase I of

meiosis2. Mutation to DNA passed down to

offspring (very rare!)

Evolution is:

• Genetic change in population over time.• These changes are seen in

populations not in individuals