Final answer:
The population growth from 1820 to 1850 is described as exponential, characterized by rapid increase where the human population grew quickly due to abundant resources and fewer limitations.
Step-by-step explanation:
The type of population growth seen from just 1820 - 1850 is best described as exponential. During this period, the human population grew significantly due to unlimited resources and fewer limiting factors such as diseases and wars, which would typically restrict population growth. An example of a density-independent factor is a forest fire, which affects a population regardless of its density, whereas a lack of food due to overpopulation would be a density-dependent factor. However, at some point, all populations will likely exhibit logistic growth when resources become limited.