Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Diagram 1.
Source: https://www.slideshare.net/slideshow/chapter-3-5-lecture-ecology-population-growth/1224549
Isle Royale, a remote island in Lake Superior, provides one of the world’s best long-term case studies on how biotic and abiotic factors interact to determine an ecosystem’s carrying capacity. The island has only a few large mammals - primarily moose and wolves - and a relatively simple food web dominated by balsam fir forests. Because human influence is limited, ecological data from Isle Royale reveal clear mathematical patterns linking population size to food resources, predators, and weather conditions.
Moose depend heavily on balsam fir as their primary winter food source. When balsam fir biomass is high, moose have abundant resources, and their population grows rapidly. However, as the moose population rises, they consume more fir than the trees can regrow. Overbrowsing reduces fir biomass, lowering food availability. This reduction in the abiotic resource base decreases the island’s carrying capacity for moose, causing the population to decline in following years.
Wolves introduce a major biotic limiting factor. As predators, they reduce moose population size and help prevent extreme overbrowsing. When wolf numbers are healthy, they stabilize the moose population by removing weaker individuals and slowing population expansion. But when wolf numbers fall - due to disease, inbreeding, or severe winters - the moose population can grow beyond sustainable levels. This leads to vegetation collapse, which in turn causes sharp moose population declines.
Abiotic factors also play a significant role. Winter severity determines how much energy moose must expend to survive and affects their access to food. Harsh winters increase mortality and reduce calf survival. Climate conditions also influence tree growth and regeneration, altering the ecosystem’s ability to support herbivores. These weather-driven fluctuations cause the carrying capacity of the island to change from decade to decade.
Table 1.
Year | Moose Population | Wolf Population |
|---|---|---|
2000 | 900 | 20 |
2005 | 1100 | 25 |
2010 | 700 | 10 |
2015 | 1400 | 3 |
2020 | 1000 | 15 |
Diagram 2.
Graph of Information - Figure 1.
Table 2.
Year | Fir Biomass t/ha | Winter Severity Index |
|---|---|---|
2000 | 32 | 4.2 |
2005 | 28 | 3.8 |
2010 | 22 | 5.1 |
2015 | 18 | 6.3 |
2020 | 20 | 4.9 |
Diagram 3.
Graph of Information - Figure 2.
Using Table 1 and Figure 1, describe the relationship between wolf population size and moose population size from 2000 to 2020.
According to Table 2, in which year was fir biomass lowest?
Using Diagram 2 and the reading, explain how interactions among moose, wolves, and vegetation demonstrate a stable ecosystem with cycling matter and energy.
Based on Figure 2, which abiotic factor MOST strongly contributes to reduced fir biomass during the years shown?
Using Table 2 and Figure 2, describe how changes in winter severity influence fir biomass and moose carrying capacity.
Explain how biotic and abiotic factors interact to determine the carrying capacity of the Isle Royale ecosystem.
Respond using Claim, Evidence, and Reasoning.