AP* Environmental Science Daily Lesson Plans Population Dynamics Unit

Transcription

1 AP* Environmental Science Daily Lesson Plans Population Dynamics Unit I. Topic: Selection Strategies Day 3 II. Warm-up: 5 minutes Prior to class, draw two columns on the board and title the one on the left K-selected and the one on the right r-selected. Write the following on the board: Under one of the columns, list one of the characteristics of organisms in that category. (K-selected: long life span, late sexual maturity, few offspring, etc.; r-selected: short gestation period, precocious young, broad niche, etc.) III. Activity One: Evolutionary Survival Strategies 20 minutes Objectives: a) TLW identify the different evolutionary survival strategies of r- and K-selected species. b) TLW come up with examples of r- and K-selected species to complement the information given on each description ( Survival Strategies ) card. Materials: For each student: one Survival Strategies Card Game handout and one set of 8 Survival Strategies cards. For the class: computers with Internet access, or a variety of field identification books (for insects, plants, amphibians, reptiles, mammals, birds, etc.) to be used by the lab groups as reference materials. Procedure: 1. Prior to class, photocopy the Survival Strategies page that follows this lesson plan onto cardstock paper so that each student will have a set of 8 cards. Cut out the sets of cards or, if there is time, give the students scissors to cut the cards out themselves before they begin the activity. (To prolong the life of the cards, you may want to laminate them.) 2. Discuss the warm-up, guiding the students to think of any characteristics not listed. 3. Ask the students to imagine that the right side of their desks represents r- selected characteristics and the left side of their desks represents K- selected characteristics. Tell the students to read the cards and place the Kristen Daniels Dotti 2007 AP* Environmental Science Daily Lesson Plans pg. 19

2 described organisms in order along an imagined continuum from left to right based on whether they have more r- or K-selected characteristics. There is no order that will be absolutely correct since each organism possesses various r- and K-selected characteristics but must be considered as a whole. However, the students should be able to identify definitively that the red-tailed hawk is more K-selected than the roadrunner, the Western rattlesnake is more K-selected than the Whiptail lizard and that the coyote is more K-selected than the Kangaroo mouse. 4. Ask the students to discuss their continuum order with a neighbor/lab partner. As an opportunity to create discussion, ask the students if there are any disagreements they would like to offer up or defend. 5. When the students are satisfied with the arrangement of their cards, ask them to complete the reflection questions (in the handout provided) with their neighbor/lab partner. 6. When they finish the reflection questions, ask them to use the Internet or field guides to create two additional Survival Strategies cards one for an r-selected species and one for a K-selected species. 7. Allow time to discuss the reflection questions if you think these concepts will be difficult for your students, or use the questions to decide whether or not the students need more reinforcement on the links between selection strategies and evolution. 8. Remind the students of the fruit fly data they have been collecting for the past few weeks. Ask the following questions to help them make the connections between this experience and the activity they have just completed: a. Are the fruit flies growing in an r- or K-selected pattern? (rselected) b. What type of population growth graph would correspond to an r- selected species? (Exponential or logarithmic growth.) c. What type of population growth graph would correspond to a K- selected species? (Sigmoid or logistical growth.) d. What do you predict happens to populations of r-selected species that continue to reproduce with unlimited resources? (They will eventually be overpopulated and be overcome with waste or bodies.) Special note: Maintain the growing population of fruit flies, using additional fresh food tubes as needed to keep the population healthy and prosperous. These flies will be used in a few weeks for a toxicity study on Day 3 of the Toxicity, Agriculture and Pesticides Unit. IV. Activity Two: Survivorship Curves 20 minutes Objectives: a) TLW relate r- and K-selected characteristics to survivorship curves. b) TLW practice good scientific graphing techniques. Kristen Daniels Dotti 2007 AP* Environmental Science Daily Lesson Plans pg. 20

3 Materials: For each student: map pencils/colored pens; a ruler; one sheet of graph paper; one copy of the Live for Today Life Table handout. Procedure: 1. Ask the students to take out their copy of the handout Guidelines for Creating Scientific Graphs as well as their notes on graphing. 2. Distribute the graph paper and the Live for Today Life Table handout and ask the students to create a high quality scientific graph of the handout data, using different colors to represent the various species. 3. Once they ve completed their graphs, ask the students to compare theirs with those created by their lab group. Have the students correct their graphs, adding anything they left out or addressing anything that needs improvement. 4. Ask the students to discuss the reflection questions with their lab groups and record their own responses on their handouts. 5. After they have completed their reflection questions and discussions, ask the following to ensure their depth of understanding: a. What type of survivorship curve best describes an r-selected species? (An early-loss curve.) b. What type of survivorship curve best describes a K-selected species? (A late-loss curve.) c. Using a new color, draw a curve that represents Leatherback sea turtles, which emerge from nests of about 100 eggs. The babies hatch and then crawl quickly towards the ocean with the threat of being eaten by waiting flocks of birds. Once in the ocean, they attempt to avoid sharks and large-mouthed fish until they can get to the safety of the Sargasso grass beds, where it is thought that they spend the next years of their lives eating and growing until their carapace is 30cm in diameter. When a Leatherback sea turtle leaves the sea grass, it ventures out into the coastal ocean to feed and becomes sexually mature around years of age. It mates seasonally and grows into a full adult with a carapace of about cm in diameter. Label the graph you have just made Male Sea Turtle Data. If the data included female sea turtles that lay eggs on the beach about 8 times a season every other year, what would its survivorship curve look like? Graph the expected curve and label this line Female Sea Turtle Data. When you have finished, turn in your work to be graded. (This last graph would look very similar to the first line they drew, but with a slight decrease in the curve at sexual maturity since some turtles are captured by humans when they come on shore to mate. Also, the curve should be smooth and not include any bumps for the number of nesting attempts or the every other year nesting cycle, since these data are averages for all the females of the entire Kristen Daniels Dotti 2007 AP* Environmental Science Daily Lesson Plans pg. 21

4 species.) HW: Ask the students to complete their Fruit Fly Population Study and write a lab report with their conclusions. HW: Ask the students to read the excerpts from Dr. Tatiana s Sex Advice for All Creation by Olivia Judson, which describes the evolutionary significance of reproductive strategies from all different parts of the animal kingdom. The letters and responses from chapters 11 and 12, pp , provide for a good discussion of the evolutionary advantages of sexual recombination. Kristen Daniels Dotti 2007 AP* Environmental Science Daily Lesson Plans pg. 22

5 Survival Strategies Cards Lifespan: 7 years Offspring per litter: 6 Gestation: 19 days 2-3 months Sexual maturity: 2.5 yrs. Lifespan: 4 years Offspring per litter: 15 Gestation: 1 month none Sexual maturity: 1 month Asex./sexual reproduct. Lifespan: 15 years Offspring per litter: 6 Gestation: 62 days minimum 1 year Sexual maturity: 1.5 yrs. Lifespan: Offspring per litter: Gestation: Sexual maturity: Lifespan: 15 years Offspring per litter: 2 Gestation: 30 days 3-4 months Sexual maturity: 3 years Lifespan: 30 years Offspring per litter: 15 Gestation: 90 days none Sexual maturity: 2 years Only sexual reproduct. Lifespan: 2 years Offspring per litter: 3 Gestation: 32 days 1 month Sexual maturity: 3 mos. Lifespan: Offspring per litter: Gestation: Sexual maturity: Lifespan: 7 years Offspring per litter: 6 Gestation: 19 days 2-3 months Sexual maturity: 2.5 yrs. Lifespan: 4 years Offspring per litter: 15 Gestation: 1 month none Sexual maturity: 1 mo. Asex./sexual reproduct. Lifespan: 15 years Offspring per litter: 6 Gestation: 62 days minimum 1 year Sexual maturity: 1.5 yrs. Lifespan: Offspring per litter: Gestation: Sexual maturity: Asex./sexual reproduct. population Lifespan: 15 years Offspring per litter: 2 Gestation: 30 days 3-4 months Sexual maturity: 3 yrs. Lifespan: 30 years Offspring per litter: 15 Gestation: 90 days none Sexual maturity: 2 yrs. Lifespan: 2 years Offspring per litter 3 Gestation: 32 days 1 month Sexual maturity: 3 mos. Lifespan: Offspring per litter: Gestation: Sexual maturity: Asex./sexual reproduct. population Kristen Daniels Dotti 2007 AP* Environmental Science Daily Lesson Plans pg. 23

6 Survival Strategies Cards Copy the next two pages back to back so that they become two-sided cards. Make your own card: Coyote Whiptail lizard Roadrunner Make your own card: Kangaroo mouse Western rattlesnake Red-tailed hawk Make your own card: Coyote Whiptail lizard Roadrunner Make your own card: Kangaroo mouse Western rattlesnake Red-tailed hawk Kristen Daniels Dotti 2007 AP* Environmental Science Daily Lesson Plans pg. 24

7 Reflection Questions Survival Strategies Card Game 1. Asexual reproduction tends to be found more often in r-selected species. Give two scientific explanations for this correlation. a. b. 2. Long-term parenting is often a trait of K-selected species. What is the evolutionary purpose of this characteristic? 3. Describe one evolutionary advantage and one disadvantage of precocious young. Advantage: Disadvantage: 4. Most species with stable population curves are K-selected. Give one scientific reason an r-selected species might have a stable population. 5. What correlations do you see between population s and r- or K-selection? 6. Describe one evolutionary advantage and one disadvantage of being a specialist. Advantage: Disadvantage: 7. Are humans an r- or K-selected species? Provide three supporting details for your answer. Kristen Daniels Dotti 2007 AP* Environmental Science Daily Lesson Plans pg. 25

8 Live for Today Life Table The following figures reflect the projected life expectancy for various species and the percentage of the birth group that survives to each stage at each listed age. Graph the following data points on a single graph using a different color line for each species. Use Lifespan as the independent axis and for the range so that all species can be compared equally, regardless of their life expectancy. Some information is just for background purposes and does not need to be graphed. Be sure that your graph contains all of the features of an excellent, scientifically accurate graph. Species: Black Phoebe Mountain Gorilla Southern Toad Number in cohort 3-6 eggs 1 young 30,000 eggs group at birth: Life expectancy 10 years 50 years 15 years Time: % of survivors: % of survivors: % of survivors: 0.0 of lifespan of lifespan of lifespan of lifespan of lifespan of lifespan of lifespan of lifespan of lifespan of lifespan of lifespan Reflection Questions: 1. Which species has a late-loss curve? An early-loss curve? A constant-loss curve? 2. K-selected species tend to reach sexual maturity late in life, which might put them at risk for dying before they get a chance to reproduce. However, most offspring survive to reproduction age. Explain why this is so. 3. Consider a species of organisms that molts three times in its lifespan. Draw a line to represent this species and label it molting species. 4. Name a species from your local area that you are familiar with:. Describe the survivorship curve for this species using the correct terminology. Kristen Daniels Dotti 2007 AP* Environmental Science Daily Lesson Plans pg. 27