Title: Sources of Genetic Variation SOLs Bio 7.b.d. Lesson Objectives

Transcription

1 Title: Sources of Genetic Variation SOLs Bio 7.b.d. Lesson Objectives Resources Materials Safety Students will understand the importance of genetic variety and evolution as genetic change. Project Wild-Through the Bottleneck 1. Bag of beads 2. Long-neck bottle 3. Handouts (key to genetic characteristics, environmental situations, and activity sheet) 1. Beads may present a choking hazard if students put them in their mouths 2. Enforce lab rules about not throwing materials Engage (10 minutes) Recap of previous lesson Concept map using terms and ideas from last class Explore (55 minutes) 1. Bottleneck genes (45 minutes) a. Groups of 4 students (or partners depending on classroom) b. Give students a copy of key to genetic characteristics, environmental situations, and black-footed bottle neck scenario c. Shake the genes in the bottle d. Distribute a small handful of genes to each group and have students match the bead color to the gene key e. Students chose 3 Environmental Situation Cards randomly from deck f. Students complete Black-Footed Ferret Bottleneck Scenario activity sheet g. Based on the situation cards the students receive, have students make predictions to what they think will happen to the populations h. Discuss student predictions Explain (20 minutes) 1. Go over bottleneck genes activity (after activity) a. How does genetic diversity help protect a population? b. Why might a small population be more at risk for elimination than a bigger population?

2 2. Notes/Discussion a. Mutations b. Sexual reproduction c. Relative frequency d. Gradual changes e. Phylogenetic Trees 3. New Species a. Behavioral, temporal, and geographic isolation (brief demonstrations with class) b. Natural selection Elaborate (5 minutes) 1. Phylogenetic tree practice. Students completed part of this assignment in the classroom and at home. To be turned in next class Evaluate 1. Answers to activity sheets 2. Participation/answers to questions

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4 Environmental Situations 1. Farmer has been trying to protect his fields by exterminating prairie dogs. Very little prey is available. Given its genetic makeup, how would your population 3. A golden eagle hunts from high above and will prey on available animals such as the black-footed ferret. Does your population have the gene for precise vision to avoid being captured? Given its genetic makeup, how would your population 5. Black-footed ferret kits disperse from their home territory and are able to establish new populations in nearby prairie dog towns. Given its genetic 7. A plague has hit your prairie dog town, and most of the prairie dogs die from the disease. How does your black-footed ferret population adapt to a reduction in food supply? Given its genetic makeup, how would your population 9. Black-footed ferrets are nocturnal creatures that leave their burrows at night to feed. Does your ferret population have the camouflage gene to keep well hidden from the bobcat hunting for its dinner? Given its genetic make-up, how would your population 11. Fleas carrying bacteria which cause sylvatic plague have infested your prairie dog town. Biologists have not yet vaccinated the black-footed ferrets in your population? Given its genetic 13. A new generation of captive-born black-footed ferret kits has been preconditioned to live in the wild and are ready to be released at a nearby reintroduction site. Given its genetic 2. As a coyote silently prowls nearby, only its odor might warn of its presence. Does your population have the gene for an acute sense of smell to detect and avoid the coyote? 4. Black-footed ferrets eat prairie dogs and use prairie dog burrows for shelter. Does your ferret population have the agility gene to catch an aggressive prairie dog in its dark, narrow, winding tunnel system? Given its genetic makeup, how would your population 6. An interstate highway has been built near your prairie dog town. How does this road affect your black-footed ferret population? Given its genetic 8. A badger is moving quietly around the prairie dog town. Does your population have the gene for acute hearing to detect and avoid the predator? Given its genetic make-up, how would your population 10. A prairie dog colony has just been established in a state park only a few miles away. How does the colony affect your populations of ferrets? Given its genetic makeup, how would your population 12. It will be difficult for your population to take over and adapt to prairie dog burrows in hard soils without the gene for strong claws and forelegs. Given its genetic makeup, how would your population 14. Humans who are building homes have wiped out a prairie dog town 3 miles away. The surviving blackfooted ferrets from that area are moving into your territory. Given its genetic makeup, how would your population

5 Black-Footed Ferret Bottleneck Scenario Name of Team Members: On your Key to Genetic Characteristics, circle the COLORS and GENES that your population received through the bottleneck. 1. Calculate the percentage of genetic diversity of your population Nine genes (colors) represent 100% genetic diversity in the original population. genes received 9 original genes = (decimal) x100= % 2. List the genetic characteristics (colors) that your population received through the bottleneck 3. List the genetic characteristics that your population lost when it came through the bottleneck (Colors not received) 4. Using the environmental situation cards you received, write a prediction about what will happen to your population during the coming year. Is the population genetically equipped to survive in its environment? Why? How does a high (or low) percentage of genetic diversity affect the population s survival? How do random changes in the environment affect the population?

6 Chapter 16 Notes 1. Variation and Gene Pools a. Gene Pool: the genes present in a b. Relative frequency: of times an allele occurs in a gene pool with the number of times all other alleles for the same gene occurs. 2. Sources of Genetic Variation Mutations 1. Changes in DNA sequence 2. Can produce changes in 3. Can be, harmful, or to an organisms fitness or reproductive success Gene Shuffling 1. Results from sexual reproduction 2. Can produce many different phenotypes 3. Occurs during gamete production and crossing over in meiosis 4. Does not affect allele frequency 5. Example: Shuffling a deck of cards: you will always have a 4/52 chance of drawing a 4 3. Natural Selection on Single-Gene Traits a. Can lead to changes in allele frequencies and lead to evolution 4. Natural Selection on Polygenic Traits a. Can affect the distribution of phenotypes in 3 ways: directional, stabilizing, or disruptive selection Directional Selection Stabilizing Selection Disruptive Selection This occurs when. This occurs when. This occurs when Draw the picture of the graph Draw the picture of the graph Draw the picture of the graph

7 5. Genetic Drift a. In small populations, an allele can become more or less common simply by chance b. Individuals that carry a particular allele may leave more descendances than other individuals just by chance and over time this can cause an allele to become more common in a population. c. Founder effect is when a small part of a population but somehow got separated and inhabitated a new habitat i. Over time, the alleles in the founding population can become more common and have allele frequencies than those of the original species 6. Isolating Mechanisms Behavioral Geographic Temporal Example: Occurs when 2 populations are capable of interbreeding but have differences in courtship rituals or reproductive strategies that involve behavior 2 populations are separated by geographic barriers such as rivers, mountains, or bodies of water Example: 2 or more species reproduce at different times. Example: