Transcript Pesticide Resistance and Natural Selection

Natural Selection
Evolution: Teachable Tidbit
• Context:
• Introductory biology for science majors
• 2 full class periods and a follow-up exam question
• Learning Goal: We want students to understand that natural
selection is a phenomenon that applies to their lives
• Learning Outcomes:
• Students will be able to describe and list the steps of natural
selection
• Students will be able to attribute anthropogenic influences
on the environment to natural selection events
• Students will be able to explain MRSA infections in terms of
natural selection
• Diversity: multiple learning styles and assessments
Unit Timeline
• 1st lecture—background information (Darwin & Natural Selection)
Steps for natural selection to occur:
1. There are variations in traits of individuals, and these variations
are heritable
2. There is selection pressure due to a change in the environment
3. Some individuals survive longer and reproduce more
4. There is change in the frequency of traits within the population
over time
• 2nd lecture—formative assessment
• Future lecture—population genetics, genetic drift, gene flow, etc.
• Unit exam – Summative question
Rats and Humans
Rodent Population Control
The name warfarin stems from the acronym WARF, for Wisconsin Alumni Research Foundation +
the ending -arin indicating its link with coumarin, the base chemical.
Resistant Individuals Through Time
Time
What are the steps of natural
selection?
• By yourself:
– Think of the steps in natural selection
– Write the steps involved in natural selection
• 1 step per 3x5 index card
Steps in natural selection, cont.
• With a partner:
– Discuss the steps of natural selection
– What element of the rat scenario corresponds to
each step?
Clicker Question
• Is Warfarin resistance in rats an example of
natural selection?
A. Yes
B. No
Clicker Question
• In this example, humans apply the selection
agent.
• Is Warfarin resistance in rats an example of
natural selection?
A. Yes
B. No
Clicker Question
• Does warfarin cause the resistance in rats?
A. Yes
B. No
Summative Assessment
Of the following two situations, one or both is an example of natural selection in action.
a. List the steps of natural selection.
b. For each scenario, identify the elements matching the steps of natural selection.
c. For each scenario, decide whether or not it is an example of natural selection and justify
your answer.
Scenario 1
R. Koch’s best friend, Chuck, just returned from Student Health Services; he’s just been told
he has a MRSA infection. The doctor at Student Health Services gave Chuck a prescription for
antibiotics and strict instructions to complete the entire course of antibiotics.
Staphylococcus aureus is the SA in MRSA and is a bacteria routinely found on human skin
and mucous membranes. Overtime, SA has become resistant to the common antibiotic
methicillin, hence the MR (methicillin resistant) in MRSA.
Scenario 2
Jane’s mom and dad can both roll their tongues into a U shape, but Jane can’t. Her two
brothers, Dan and Kevin, can also roll their tongues and always teased Jane mercilessly.
Most of Jane’s nieces and nephews can roll their tongues too. Jane’s husband can roll his
tongue and so can their three children. Kevin’s wife just had a new baby and the family is
eagerly awaiting the opportunity to challenge the new family member to roll her tongue!