Answer :
Answer: B. An exponential growth curve
Explanation: There are two main curves used to showcase population growth.
An exponential curve is used when a population grows exponentially with no sign of slowing down or reaching a carrying capacity. This type of growth occurs when the amount of resources available greatly dwarfs the amount of resources necessary for the current population. This curve would accurately determine population growth since over the course of the 20th century, the rate of human population growth only continued increasing exponentially with no sign of slowing down.
On the other hand, a logistic growth curve starts out with population growth being exponential, and then tapering off into logarithmic growth until the population reaches carrying capacity. This type of growth models a population in an environment where limiting factors put a limit on population growth. Initially, population growth is exponential due to the abundant amount of resources available per individual. However, as the population increases, individuals within that population compete more and more over the same resources. Limiting factors such as water and space eventually limit population growth until the population hits a limit as to what the ecosystem can support.
A logistical growth curve would not model 20th century population growth since human population growth never slowed down or approached a limit during this time period. Thus, choice C is incorrect.
Choice A is incorrect because a survivorship curve measures the population of a species as that same population ages. It more so measures the mortality rate of organisms at different stages of their life rather than population growth.
Choice D is incorrect because a life span curve is synonymous with a survivorship curve. As stated previously, this type of graph measures survival rate rather than population growth.
