Question

writing about population ecology

(reaction paper format)

150 words

Answer 1

Population ecology is the study of how populations — of plants, animals, and other organisms — change over time and space and interact with their environment. Populations are groups of organisms of the same species living in the same area at the same time. They are described by characteristics that include:

1. population size:the number of individuals in the population
2. population density:how many individuals are in a particular area
3. population growth:how the size of the population is changing over time.

Studying population growth gives scientists insight into how organisms interact with each other and with their environments.This is especially meaningful when considering the potential impacts of climate change and other changes in environmental factors.

For every organism — whether plant, animal, virus, or bacterium — there is an ideal set of circumstances that would allow a population of that organism to grow, uninhibited, at the highest possible rate.Changes in the factors that once allowed a population to grow can explain why growth slows or even stops.

Factors that enhance or limit population growth can be divided into two categories based on how each factor is affected by the number of individuals occupying a given area — or the population's density. As population size approaches the carrying capacity of the environment, the intensity of density-dependent factors increases. For example, competition for resources, predation, and rates of infection increase with population density and can eventually limit population size. Other factors, like pollution, seasonal weather extremes, and natural disasters — hurricanes, fires, droughts, floods, and volcanic eruptions — affect populations irrespective of their density, and can limit population growth simply by severely reducing the number of individuals in the population.

One of the most challenging applications of population growth research is to predict human population growth. The human population surpassed six billion people in 1999, and is expected reach nine billion before 2050. It is somewhat surprising to realize that it took all of human history for the human population to reach one billion people — which happened around 1800 — then a little over 100 years to double to two million, and just 40 years to double from three to six billion! The recent explosive (think exponential!) growth has been facilitated by advances in agriculture, science, and medicine, which have enabled more people to survive and have longer lifespans.