Mechanisms of Evolution Lab Date: 10/17 – 10/18 Topic: Mechanisms of Evolution Learning Target: Analyze different scenarios to determine mechanisms of evolution

Bell Ringer: Unit Test 1 Re-Cap 14. The ecological process of succession is represented below Which of the following statements best describes the events of this process? . Community B modifies the environment, making it suitable for community C. . Community D modifies the environment, making it suitable for community D. . Community E will develop into community A, if the environment remains stable. . Community A organisms will automatically develop into community D organisms Directions: Complete all of the following for the question above. GIST: (In one sentence, explain what the question is about) (2 points) ___________________________________________________________________ CORRECT ANSWER: (1 point) EXPLANATION: (Why is this the correct answer?) (4 points) REFLECTION: (After grading this question answer the following) (3 points) I was CORRECT INCORRECT (Check one!) BECAUSE _____________________________________________________________

Primary Succession No Soil - Growth starts on bare rock. Ex: Volcanic eruptions or Glacier retreat. *Pioneer Plants - Lichens and Moss “I do” 3

Secondary Succession Secondary succession is far more common. It occurs in an area where life once existed but has then been destroyed. “I do” 4

Agenda Bell Ringer (10 minutes) Review (10 minutes) Scenario Practice (10 minutes) Group Activity (25 minutes) Exit Quiz (25 minutes) Closure (10 minutes)

Essential Question How does overproduction, inherited variation and the struggle to survive allow for natural selection?

Natural Selection Overproduction + inherited variation + struggle to survive = differential reproductive success Differential reproductive success=individuals with certain traits are more likely to survive and reproduce; those traits will be more frequent in the population

Natural Selection Example Which rabbit has a better chance of surviving in the North Pole? Why?

Natural Selection Example Oh, snap, I just found dinner. Gosh darn it, no rabbits here.

All the brown rabbits die Only one white rabbit dies

White rabbits have babies

Now we have ALL white rabbits!

Now assume only fat rabbits can survive the cold

Now we have all fat white rabbits

- We can say that the rabbits evolved into fat white rabbits - We can say that the rabbits evolved into fat white rabbits. - The process is called evolution.

What is natural selection? Natural selection selects for traits advantageous for survival. 16

What are mutations? Mutations produce the genetic variation needed for evolution. 17

What is gene flow? Gene flow moves alleles from one population to another. 18

What is nonrandom mating? Nonrandom mating is reproduction in which only preferred individuals mate 19

What is genetic drift? Genetic drift changes allele frequencies due to chance alone. 20

Group Activity We will analyze several mechanism of evolution It is crucial that you follow ALL INSTRUCTIONS and LISTEN CAREFULLY If you are not following instructions, you will not participate First, let’s practice together!

What can cause changes in allele frequencies? Mutation Gene Flow Non-random mating Genetic Drift Natural Selection 22

Which mechanism is it? For the allelic frequency to remain constant in a population at equilibrium, no new alleles can come into the population, and no alleles can be lost. Both immigration and emigration can alter allelic frequency. 23

Which mechanism is it? Gene Flow Gene Flow For the allelic frequency to remain constant in a population at equilibrium, no new alleles can come into the population, and no alleles can be lost. Both immigration and emigration can alter allelic frequency. 24

Which mechanism is it? A large breeding population helps to ensure that chance alone does not disrupt genetic equilibrium. In a small population, only a few copies of a certain allele may exist. If for some chance reason the organisms with that allele do not reproduce successfully, the allelic frequency will change. This random, nonselective change is what happens in genetic drift or a bottleneck event. 25

Which mechanism is it? Genetic Drift Genetic Drift A large breeding population helps to ensure that chance alone does not disrupt genetic equilibrium. In a small population, only a few copies of a certain allele may exist. If for some chance reason the organisms with that allele do not reproduce successfully, the allelic frequency will change. This random, nonselective change is what happens in genetic drift or a bottleneck event. 26

Which mechanism is it? In a population at equilibrium, no alleles are selected over other alleles. If selection occurs, those alleles that are selected for will become more common. For example, if resistance to a particular herbicide allows weeds to live in an environment that has been sprayed with that herbicide, the allele for resistance may become more frequent in the population. 27

Which mechanism is it? Natural Selection Natural Selection In a population at equilibrium, no alleles are selected over other alleles. If selection occurs, those alleles that are selected for will become more common. For example, if resistance to a particular herbicide allows weeds to live in an environment that has been sprayed with that herbicide, the allele for resistance may become more frequent in the population. 28

Which mechanism is it? In a population at equlibrium, mating must be random. In assortative mating, individuals tend to choose mates similar to themselves; for example, large blister beetles tend to choose mates of large size and small blister beetles tend to choose small mates. Though this does not alter allelic frequencies, it results in fewer heterozygous individuals than you would expect in a population where mating is random. 29

Which mechanism is it? Nonrandom mating In a population at equlibrium, mating must be random. In assortative mating, individuals tend to choose mates similar to themselves; for example, large blister beetles tend to choose mates of large size and small blister beetles tend to choose small mates. Though this does not alter allelic frequencies, it results in fewer heterozygous individuals than you would expect in a population where mating is random. 30

Group Activity Directions Spread all Scenarios Cards out across the top of your lab table. As a group, examine the information on each of the card, one at a time, to determine what type of evolutionary change is being described. Sort the cards into groups (columns) based on the five mechanisms of evolutionary change. Record the “Scenario #” under the column you and your group decided best described the mechanism of evolutionary change. Under the rows labeled “Reasoning”, choose a scenario for each mechanism and explain your “reasons” for its placement under that column. 31

Collaborative Activity Data Table: Mechanisms of Evolutionary Change Natural selection Mutation Gene flow Genetic drift Nonrandom mating 32

Exit Quiz Unit 2 Exam: Review Packet

Homework Vocabulary Homework. Study for your Unit 2 Exam!!! Look back at the PPTs posted in our classroom website to help you study for your exam.