Module 8 Lesson 5 - 4

Self-Check

1. Caribou live in the tundra of the arctic and subarctic, feeding on lichens in the winter and willows, grasses, and sedges in the summer. Their most significant predator is the wolf. Their winter migration takes them from the open tundra to the protection of the boreal forests; in spring, they return to the calving grounds of the tundra. During the fall 'rut' (breeding period), the most dominant male breeds with as many as 15 to 20 females, with one calf born to each mother in the spring. The data in the chart above describe caribou population changes on St. Paul Island, Alaska, from 1910 to 1950.
   
   
   1. Graph the data from the table above. Label axes and provide a title and units.
      
      
   2. Considering the information you were given regarding caribou reproductive habits and predation, would you predict that the population growth curve to be logistic or exponential?
      
      
   3. Analyze the graph. In a statement, describe the growth pattern that existed from 1910 to 1950.
      
      
   4. Does the data support your prediction from b?
      
      
   5. Consider the information you have been given about caribou populations. Hypothesize as to two reasons for the observed growth pattern. Indicate whether each reason is density dependent or density independent.



2. In suitable abiotic conditions and with adequate food, E. coli bacteria undergo binary fission every 20 minutes. With each generation, populations double and each generation is only 20 minutes long. Typically, bacteria introduced onto a medium go through the following phases:
   
   

   • Lag phase: slow growth

   • Exponential growth: doubling with each generation

   • Death phase: population crashes due to competition for food and accumulation of toxins.
   
   Use your graphing calculator (using 2n as a function) or a spreadsheet to do the following:
   
   

   • Construct and complete a table similar to the following.

   • Graph the results.
     

   • Assume the environment can support only 1 million bacterial cells.

   
   
   
   
   1. At what generation has the population outstripped its environment and will begin to crash? If generation 1 was time 0, at what time did the population crash?
      
      
   2. Draw a graph showing the growth curve. Label axes correctly and provide a title. Label the graph with lag phase, exponential phase, and death phase.
      
      
   3. With each successive generation, what happens to the difference between N of the previous population and N of the current population?
      
      


3. A population of water lilies is growing exponentially with a generation time of 3 days. The water lilies threaten the species living below the surface by blocking sunlight. At this time, the lilies cover half the pond. How long before the whole pond is covered?

Self-Check

1. Which of the following is not an example of environmental resistance?
   
   
   1. Drought
   2. Increase in predators
   3. Disease due to waste accumulation
   4. Lack of food
   5. Lack of fertile mates
      
      
2. Exponential growth occurs only in
   
   
   1. organisms with high biotic potential
   2. organisms with low biotic potential
   3. organisms reproducing at their biotic potential
   4. organisms that have many offspring at a time
      
      
3. Match birth rates (b) and death rates (d) to the phases of the logistic growth curve:
   
   
   1. stationary phase: high b, low d
   2. lag phase: low b, high d
   3. exponential phase: high b, low d
   4. lag phase: b and d are equal
      
   
   
4. Which of the following is paired correctly?
   
   
   1. Exponential growth - population crash
   2. Logistic growth - J curve
   3. Exponential growth - carrying capacity
   4. Exponential growth - S curve