ompare and contrast logistic growth vs_ exponential growth. List the equations that describe each. Identify the variables of each equation Explain how populations grow under each and describe conditions that must be present’
The Correct Answer and Explanation is:
Correct Answer:
Exponential Growth:
- Equation:
N(t)=N0ertN(t) = N_0 e^{rt}N(t)=N0ert
Where:
N(t)N(t)N(t) = population at time ttt
N0N_0N0 = initial population
rrr = intrinsic rate of growth
eee = base of natural logarithm (approximately 2.718)
ttt = time
Logistic Growth:
- Equation:
N(t)=K1+(K−N0N0)e−rtN(t) = \frac{K}{1 + \left( \frac{K – N_0}{N_0} \right) e^{-rt}}N(t)=1+(N0K−N0)e−rtK
Where:
KKK = carrying capacity
All other variables are the same as in exponential growth
Explanation
Exponential growth and logistic growth describe how populations increase in size, but under very different environmental conditions.
Exponential growth occurs when resources are unlimited. The population grows rapidly over time because the growth rate is constant and not limited by food, space, or other environmental factors. In this model, the population size increases faster and faster as each generation produces more individuals. The graph of exponential growth has a J-shaped curve, indicating a steep rise in population. This kind of growth is typical during the early stages of colonization or in lab environments where conditions are controlled and resources are abundant.
In contrast, logistic growth accounts for environmental limits. As a population grows, it eventually encounters factors such as limited food, space, and competition. These slow the growth rate. The logistic model includes a carrying capacity (K), which is the maximum number of individuals that the environment can support sustainably. As the population nears this limit, growth slows and eventually levels off. The graph of logistic growth has an S-shaped or sigmoid curve. It begins like exponential growth but flattens as the population approaches the carrying capacity.
In exponential growth, the only requirement is the presence of unlimited resources and no constraints on reproduction. In logistic growth, the population initially grows like in the exponential model, but then environmental resistance reduces the growth rate as resources become limited. Logistic growth is more realistic for most natural populations because environmental limits are almost always present.
In summary, exponential growth assumes no limits and results in a constant rate of increase, while logistic growth reflects real-world limitations and shows how population growth slows as it nears the environment’s capacity.
