In the 1800s, a disease ruined much of the potato crop in Ireland. Since many Irish people depended on potatoes as their main food source, mass hunger and migration resulted. The potato blight caused Ireland's population to drop.
For a population to be healthy, resources such as food, nutrients, water, and space, must be available. Limiting factors are any resources that can lower the population size by decreasing birth rates, increasing death rates, or leading to migration. Some examples of limiting factors include a low food supply and a lack of space.
Biotic limiting factors are living things in an environment, including available food and the number of predators. Limiting factors that are not living things are called abiotic factors. Some examples include available sunlight, water, nutrients, oxygen, and temperature of the habitat.
A struggle for resources like food and space causes a population to stop growing. When a population’s growth rate is decreasing, it is because the population has reached its carrying capacity. The carrying capacity is the largest population that can be supported in an area without destroying the habitat. Limiting factors decide the carrying capacity of a population. If there are 12 hamburgers at a lunch table and 24 people sit down at a lunch table, will everyone be able to eat? At first, you may just split hamburgers in half. However, if more and more people keep coming to sit at the lunch table, you will not be able to feed everyone. In nature, any organisms (living things) that cannot get food will either move to find a new place to live or they will die.
In nature, when the population size is small, there is usually plenty of food for everyone. Organisms can easily breed, so the birth rate is high. As the population increases, the amount of resources may drop.
When necessary resources like food and space disappear, some organisms will die. Then the birth rates drop, and population growth rate decreases. This natural cycle repeatedly happens until the population reaches equilibrium, where the number of organisms and the resources available is balanced.
1. How does a decrease in abiotic resources impact the population growth in an ecosystem?
A. The population size will increase
B. The population size will decrease
C. The population size will not change
2. What determines the carrying capacity in an ecosystem?
A. The number of different species in the ecosystem
B. Limiting factors
C. Only biotic factors
D. Only abiotic factors
3. Which of the following is an example of two organisms competing for an abiotic factor?
A. Two different species of insects competing for leaves from trees
B. Two different species of mammals competing for small rodents to eat
C. Two different species of birds competing for berries to eat
D. Two different species of mammals competing for the same water source
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