Pondering Population Answer Key

Name: Answer Key **Pondering Population Growth** Section 1: Pre-knowledge 1. What is a population? A group of individuals 2. How big can a population grow? Can it keep expanding forever? As big as its carrying capacity will allow. If it doesn't reach carrying capacity, it will continue to grow. 3. What limits the size of a population? Limiting factors such as: predators, lack of food, water, parasites, diseases, natural disasters. Section 2: The Lily Pad Dilemma Lily pads can grow fast! Imagine that you discover a variety of lily pads that can double in number every day. It only takes 10 days for them to grow to cover a pond halfway! 1. If it takes 10 days to cover the pond halfway, predict how many more days will it take to completely cover the pond? a. about 10 more days b. about 5 more days c. about 1 more day d. about 3 more days 2. Explain the reason for your prediction. It will take one more day because if you double one half (1/2) you get one whole (1). Section 3: Test Your Prediction Lab Table 40" 24" No tape 2 pieces total 1. Imagine that your lab table is a pond. 2. Using a ruler, measure a rectangle 24" x 10" on your lab table and mark the edge with masking tape. 3. Pretend each index card is a lily pad. 4. Lay one card in the corner of the pond to represent the first lily pad. Record on the back of this sheet. 5. Pretend a day has passed. Double the number of lily pads in your pond. Record on the back of this sheet. 6. Keep on doubling the population until the pond is half full. Name: **Pondering Population Growth** Generation (Number of Days) | Number of NEW Lily Pads in | TOTAL Number of Lily Pads the Population in the Population ------------------------------------------------------------------------------------------------ 1 1 1 2 1 2 3 2 4 4 4 8 5 8 16 6 16 32 7 32 64 Section 4: Application Questions: 1. Using your math skills, determine exactly how much time passed before the pond was precisely half full. 6 days 2. Based on your demonstration, determine exactly how many days will pass before the pond is completely full. 7 days 3. Now, make a graph of your results. [Image of a graph with x-axis labeled "Generation" and y-axis labeled "Population Size"] Exponential Growth Curve 4. Describe the shape of your graph. Compare the growth in Generation 1 and 2 to the growth in Generation 5 and 6. Non-linear, positive curve. Name: **Pondering Population Growth** Section 5: Analysis Questions 1. Describe the shape of your graph. Why isn't it a straight line? Why does the slope change over the generations? How do your math skills and knowledge help you understand the science content? 2. Predict the shape of the graph after the pond is completely full. (HINT: if you continued for generations 7 and 8, what would happen? How would that be shown on the graph?) 3. If the lily pads can no longer reproduce once the pond is full, what do you predict will happen to the size of the population and the shape of the graph? 4. Suppose a species is introduced to your pond that eats lily pads, how would this change the graph? 5. What if there was a sudden drop in temperature? What would happen to your lily pad population?