Transcript Evidence for Mechanisms of Evolution (PowerPoint) Southeast 2012

Evolution I
Scott Bowling
Topher Gee
Stan Schneider
Beth Schussler
Randy Small
Min Zhong
Facilitator: Paula Lemons
Evolution I
• Topic: Evidence for and mechanisms of
evolution
• Introductory Biology (majors), Large
enrollment (200+/section)
• We are assuming students “know”:
– Definition of evolution
– Hardy-Weinberg Equilibrium and problem solving
– Evolutionary processes
Tidbit Learning Goal
• Students will demonstrate an understanding
of evolutionary processes
Tidbit Learning Objectives
• recall Hardy-Weinberg and evolutionary
processes
Given a scenario, students will:
• identify whether evolution has occurred and
articulate the evidence
• predict the mechanism(s) driving evolutionary
change and identify the necessary evidence
• Pea plants have two flower
colors: purple and white
• Trait controlled by one gene:
purple dominant to white
Frequency of
white flower allele (q)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 1 2 3 4 5 6 7 8 9 10 11
Generation
On your own,
summarize what this
figure is telling you.
Frequency of
white flower allele (q)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 1 2 3 4 5 6 7 8 9 10 11
Generation
In small groups,
share your ideas.
Frequency of
white flower allele (q)
1
0.8
0.6
A
B
C
Graph here
0.4
0.2
0
0 1 2 3 4 5 6 7 8 9 10 11
Generation
Look at the shaded Regions (A, B, and C). Over which, if any of these regions has
evolution occurred for the flower color gene?
1.
2.
3.
4.
5.
6.
7.
8.
A only
B only
C only
Both A and B
Both A and C
Both B and C
All three regions
None of these regions
100%
0%
0%
1
2
0%
0%
3
4
5
0%
0%
6
7
0%
8
Frequency of
white flower allele (q)
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
A
B
C
0 1 2 3 4 5 6 7 8 9 10 11
Generation
Discuss the importance of the following factors in deciding
whether evolution has occurred:
•Allele frequencies
•Number of generations
•Magnitude of change
Frequency of
white flower allele (q)
1
0.8
0.6
A
B
C
Graph here
0.4
0.2
0
0 1 2 3 4 5 6 7 8 9 10 11
Generation
Look at the shaded Regions (A, B, and C). Over which, if any of these regions has
evolution occurred for the flower color gene?
1.
2.
3.
4.
5.
6.
7.
8.
A only
B only
C only
Both A and B
Both A and C
Both B and C
All three regions
None of these regions
100%
0%
1
2
0%
0%
3
4
0%
5
0%
0%
6
7
0%
8
Each group will be assigned one evolutionary
process to discuss and explain to the rest of the
class:
1.
2.
3.
4.
5.
Genetic drift
Mutation
Non-random mating
Migration (gene flow)
Natural selection
• Dr. Sally Slither conducted a
study on two populations of
lizards: one on an isolated
island and the other on the
mainland.
– Generation time = 2 years
– Island population
(N = 1,000)
Googly-eyed
– Mainland population
(N = 100,000)
• In each population, some
have googly-eyes (dominant)
and some have small eyes
(recessive).
Small-eyed
Dr. Slither’s 20-yr study of eye size in lizard populations
Dr. Slither’s 20-yr study of eye size in lizard populations
Graph here
Based on the figure above, what is the most likely explanation for why the island
population’s allele frequency is more erratic than the mainland’s?
100%
1.
2.
3.
4.
5.
Genetic drift
Mutation
Non-random mating
Migration (gene flow)
Natural selection
0%
1
0%
2
0%
3
4
0%
5
• Googly-eyed lizards are more sensitive to
light and prefer dimmer conditions.
• The mainland habitat is being deforested by
human activity.
Dr. Slither’s 20-yr study of eye size in lizard populations
Given what you know, what could explain the mainland
population’s gradual shift in allele frequency over time?
Genetic drift
Mutation
Non-random mating
Migration (gene flow)
Natural selection
Homework
• For either lizard population (mainland or
island), what evidence would you need to
support the hypothesis that EACH of the
following is occurring:
– Natural selection
– Non-random mating
– Migration
Summative Assessment
A population of spiders includes individuals with plain legs
(recessive) as well as individuals with yellow bands on their
legs (dominant). You have a data set that spans multiple
generations for this population. In the first generation your
data indicate that of 100 spiders, 64 had yellow bands on their
legs. Five generations later, the population had grown to
10,000 spiders and included 1,600 with plain legs.
1. Has evolution occurred over these generations? Explain
your reasoning and show supporting work.
2. Has natural selection occurred on the yellow band
phenotype? Why or why not?
3. What data set(s) would you need to collect to identify the
mechanism of evolution?
Learning
Objective
Assessment
Active learning
Low Order/
High Order
Recall HardyWeinberg
principles and
evolutionary
processes
Formative: Explain HW principles
Group discussion
Low Order
Identify whether
evolution has
occurred & the
evidence
Formative: Evaluating population
data to identify when evolution has
occurred; pinpointing the evidence
Clicker questions – discussion – repoll
High order
Predict the
mechanism(s)
driving evolutionary
change and identify
the necessary
evidence
Formative: Evaluating population
data in scenario to identify potential
evolutionary mechanisms.
Clicker questions – discussion – repoll (multiple sections of a scenario)
High order
Formative: Homework assignment.
Summative: Exam question to test
student ability to identify whether or
not evolution has occurred, and
what mechanisms might have
resulted in that evolution.
Diversity
Female scientist named in scenario.
Group members presenters are diverse.
Read clicker questions & group discussion questions to students to accommodate learning style diversity & students with
Diversity:
disabilities.
Active learning includes both group and individual activities.
OPTIONAL?
What evidence is necessary to know whether
evolution has occurred within a population?
• Individually, write a one-minute essay
• Brief group discussion
Island population (1000 total)
Generation
1
10
Googly-eye
360
640
Small-eye
640
360
Generation
1
10
Googly-eye
75,000
70,000
Small-eye
25,000
30,000
Mainland population (100,000 total)
• The island habitat is undisturbed and
heavily forested.