In this activity, a portion of the class was assigned to be deer and a portion was assigned to be the resources (food, water, and shelter). At the start of each round, each deer had to randomly pick a resource that they needed for that round, and each person on the resource side of the game had to choose a resource that they would become for that particular round. Then each deer had to rush over to the resource side to pick up the resource that they chose. Upon picking up the resource, the person representing the resource became a deer to signify how the deer reproduced as a result of its needs being satisfied. If a deer was unable to find the resource it desired, then it "died" and became a resource.
As the game progressed, increased competition for resources over successive rounds caused the deer population levels to reach a maximum and then fluctuate between the maximum level and a lower level. This was an example of density-dependent factors affecting population change.
Also, after a few rounds various scenarios were imposed on the resources, such as a forest fire (no shelter), and drought (no water) to simulate density independent factors affecting population change. Later during the game, individuals were chosen to act as the deer's predators. When a deer was caught by a predator, it became a predator to signify the predators reproducing after eating the deer.
This activity was meant to demonstrate the difference between density-dependent factors and density-independent factors affecting population change.
Density-dependent factors are factors influencing population changes that have a greater impact as population density increases or decreases. Some examples of density-dependent factors include:
- Intraspecific competition for resources. as population density increases, competition for resources also increases. This in turn causes the population density to decrease in subsequent generations.
- Predation. A higher population density of a prey species makes it easier for its predators to find and catch the prey. This keeps the prey population in check, since the higher the prey density, the more prey caught and eaten by predators, and the lower the prey density, the less prey caught and eaten.
- Disease. A higher population density means that pathogens are able to pass from host to host with greater ease than in a lower population density environment.
- Allee effect. When the density of a population becomes too low, then the individuals in the population may have difficulties finding mates to reproduce with. This can cause the population to die out.
Conversely, density-independent factors are factors that influence population changes regardless of population density. Some exampes of density-independent factors include:
- extreme temperatures and weather conditions
- pesticide use
- natural disasters
This information was found on pages 671-675 of the Nelson Biology 12 textbook.
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