Limiting Factors and Population Growth 8/13
Integrated Science 3-4 Name ______Per. _____
There are a number of factors that must be considered when studying populations. First, there are limiting factors. Those factors that limit how large a given population can grow. Limiting factors are either density independent (natural disaster, weather, etc.) or density dependent (competition, adaptability, reproduction, etc.).
Next, there are the factors that determine the actual size of the population itself. These factors include: natality; mortality; immigration and emigration. Populations will increase in size if natality and immigration are greater than mortality and emigration. Conversely, populations will decrease in size when mortality and emigration are greater than natality and immigration. Population growth rates reflect the percent increase (or decrease) in population size for a given time period. Doubling time is the number of years required for a population to double its overall size. These quantitative measures allow scientists to evaluate a population's current status in comparison with known patterns of population growth and population decline.
All of the factors discussed above are analyzed as scientists work to estimate the carrying capacity of a given habitat for a particular population. In the absence of limiting factors, populations have the natural tendency to grow and grow. A population will continue to grow until it begins to place demands on the environment that the environment cannot meet. Remember there are only so many resources available to a population at any given time.
What happens to the population when it reaches that limit? There are two possible answers to that question, population growth may level off when it reaches its steady state, or it may die off due to its overuse of resources. Which scenario is the most likely scenario? Refer to your binder and Chapter 1 in your textbook to answer the questions about the following two scenarios.
Scenario 1:
Scenario 2:
On the above graph, draw how you predict a deer population (grey line) and a wolf population (blue line) would grow if they were together on the same island.
Reflection
Do you think population growth Scenario 1 or Scenario 2 is more likely in most ecosystems? Explain and support your response. Attach paper if needed.