This assignment is worth 20% toward your final grade in the course. There are two parts to the assignment. Part A (worth 15 marks) provides you with the opportunity to become familiar with basic concepts and theories associated with population growth and population interactions with the environment. In Part B (worth 20 marks) you examine a current issue in population dynamics through a case study of the Lesser Snow Goose of North America and apply the principles of population dynamics to understand the impacts on the structural and functional aspects of the Arctic ecosystem.
In particular, by completing the assignment you will:
- demonstrate knowledge of population dynamics by reviewing concepts and examining growth curve simulations;
- understand the changes that arise in population size in response to changes in birth rate and carrying capacity;
- apply basic concepts regarding population dynamics to a case study of snow goose populations in North America; and
- describe the abiotic and biotic changes in an ecosystem as a response to population growth.
In completing the assignment, be sure to provide reference sources for your information to avoid plagiarism by using a standard citation system as described in the following:
Part A. Population Growth Dynamics (15 marks)
Before beginning assignment 1, read the relevant sections from your textbook (pages 68 to 73. You should also view the Snow Geese in Peril
Based on your readings and research, answer the following:
- Draw graphs to illustrate the relationship between time and population size for each of (i) exponential and (ii) logistic growth patterns. Identify the following phases on the appropriate graph(s) (4 marks):
- lag phase
- exponential phase
- stationary phase/carrying capacity
How are these growth patterns similar and how do they differ? (1 mark)
- Outline the environmental conditions that are required for populations to achieve exponential and logistic growth patterns. Based on this, which of the two growth patterns do you believe is most realistic in the natural environment? Why? (3 marks)
- What happens when populations are not regulated in their environment? Answer this by drawing your growth curves in question 1. once again and include the outcome(s) of unregulated growth and their consequences within your graph. (2 marks)
- Examine the simulations available at Otherwise.com (also available in appendix at the end of the assignment) to see how birth rate overall influences population growth patterns. Based on your review, briefly describe how birth/growth rate (e.g., slow growing vs. rapidly growing) influences overall patterns of exponential and logistic growth. Which of these birth rates is most sustainable and why? (5 marks)
Part B. Lesser Snow Goose Population (20 marks)
Snow Geese in Peril ©1998. Ducks Unlimited, Inc. All rights reserved. No alteration, duplication or downloading is permitted without authorization. Reproduced with permission from Ducks Unlimited, Inc.
Based on your independent research and the Snow Geese in Peril video, answer the following:
- Outline the features of the two major ecosystems used by snow geese during their annual migration. Describe how each of these ecosystems affects the carrying capacity and growth rate for the North American population overall. Is this a human driven problem or a natural phenomenon? Justify your answer.(5 marks)
- Surveys by the Canadian Wildlife Service and the U.S. Fish and Wildlife Service have been conducted since the early 1940s. Information for the snow goose midwinter population in the Southern U.S. is available in Table 1 below.
Table 1: Number of lesser snow geese surveyed in mid-continental U.S during midwinter surveys. Taken from North American Migratory Bird Survey Data.
|Year||Number of Birds (thousands)||Year||Number of Birds (thousands)|
Use graph paper or Excel and graph the relationship of lesser snow goose population estimates over time using the data provided in Table 1. Connect the individual values and label your graph with the key features of the growth curve as described in Part A above (e.g., lag phase, exponential phase, stationary phase/carrying capacity). What overall trends do you observe in the snow geese population over time? Do you find evidence of possible population overshoot and population dieback/crash as has been projected in the video? Justify your answer. (10 marks)
- Lastly, given the problem of an exploding population of Lesser snow geese, how can Society mitigate or fix this issue and protect the Arctic ecosystem in the future? (5 marks)
Resource and References
Simulation models: Lesser Snow Geese – https://alaska.usgs.gov/science/biology/avian_influenza/species/species.php?code=LSGO
Light Goose Dilemma – http://www.ducks.org/conservation/national/light-goose-dilemma
Arctic Ecosystems in Peril – https://searchworks.stanford.edu/view/8421098
Appendix (Output from exponential and logistic growth simulations available at Otherwise.com) Exponential Growth
Experiment 1: Exponential growth simulation by varying birth rate (# of offspring) as follows: birth rate of 1.0 (red), birth rate of 1.4 (blue), and birth rate of 2.0 (green). Taken from Otherwise.com (http://www.otherwise.com/population/exponent.html)
Experiment 2: Exponential growth simulation using an initial birth rate of 1.5 which is changed to 0.8 following 15 generations.
Experiment 1: Logistic growth simulations using a constant birth rate of 1.5 individuals and varying carrying capacity as follows: 200 (red); 400 (royal blue); 800 (light green); and 1000 (light blue). Taken from Otherwise.com (http://www.otherwise.com/population/logistic.html)
Experiment 2, 3 and 4: Logistic growth simulations using a constant carrying capacity of 1000 individuals and varying birth rates of 1.2 (red), 1.8 (royal blue), 3.0 (green), and 5.0 (light blue) Taken from Otherwise.com (http://www.otherwise.com/population/logistic.html)