Key Idea: Given adequate resources and an absence of disease or predators, populations of organisms in ecosystems can increase at rapid rates. Finite resources and other factors limit their growth.
Students are expected to know that:
- Individual organisms are added to a population by birth and removed by death so that populations increase when the number of births is greater than the number of deaths and populations decrease when the number of births is smaller than the number of deaths.
- Disease, predators, and availability of resources can affect how many individuals in a population die and how many offspring are produced and how the size of a population can change over time.
- In the absence of factors that lead to the death of organisms in a population or a reduction in the number of offspring they produce, the size of a population will grow faster and faster (more and more between consecutive equal time points).
- Populations do not grow infinitely large in nature because there is always at least one factor, including disease, predators, and availability of resources, that limit the growth of a population.
Boundaries:
- The idea that immigration or emigration (organisms moving into or out of a population or environment) can affect the size of the population of organisms in a particular environment is not part of the scope of this idea.
| Item ID Number |
Knowledge Being Assessed | Grades 6–8 |
Grades 9–12 |
Select This Item for My Item Bank |
|---|---|---|---|---|
Populations increase when the number of births is greater than the number of deaths. | 73% |
81% |
|
|
70% |
80% |
|
||
Populations decrease when the number of births is less than the number of deaths. | 71% |
79% |
|
|
Both disease and the number of predators can limit population growth. | 65% |
79% |
|
|
Disease and the availability of resources can limit population growth. | 62% |
81% |
|
|
67% |
73% |
|
||
63% |
74% |
|
||
54% |
72% |
|
||
55% |
69% |
|
||
57% |
64% |
|
Misconception |
Student Misconception |
Grades |
Grades |
|---|---|---|---|
16% |
11% | ||
Populations exist in states of either constant growth or decline (Munson 1991). | 9% |
7% |
Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.