Biology ap question help?

Question

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Compare and contrast exponential and logistic growth. What factors contribute to each pattern?

Answer 1

Logistic Growth

In a population showing exponential growth the individuals are not limited by food or disease. However, in most real populations both food and disease become important as conditions become crowded. There is an upper limit to the number of individuals the environment can support. Ecologists refer to this as the "carrying capacity" of the environment. Populations in this kind of environment show what is known as logistic growth

I'll explain, in exponential growth you have perfect conditions where each parent divides into two progeny and those 2 divide and their children divide etc.  During the exponential growth none of the original parents die.  All of the progeny live, etc. and no of them die or run out of food.  So while this goes on, your population doubles, then doubles again, then doubles again, etc.  Producing an exponential growth, meaning it will follow an exponential graph if you plot population verus time.  

For logistic growth, you have an portion of the population dieing  out or running out of food, or dieing from disease, etc.  so the graph is skewed and can't quite reach the characteristics of the exponential graph leaving a graph that follows a logistic curve.  The exponent on a logistic curve would go up or down based on the environmental pressures that infulence the population growth, such as life expectancy, the number of children/progeny each produces, the effect of disease, etc. etc.