Problem 6 - Campbell Biology Concepts & Connections

Question

With regard to its rate of growth, a population that is growing logistically a. grows fastest when density is lowest. b. has a high intrinsic rate of increase. c. grows fastest at an intermediate population density. d. grows fastest as it approaches carrying capacity.

Step-by-Step Solution

Answer

Option c: grows fastest at an intermediate population density.

Step 1: Understand Logistic Growth

Logistic growth describes a population that grows rapidly at first and then slows as the population size approaches the carrying capacity of the environment, forming an S-shaped curve.

Step 2: Identify Characteristics of Logistic Growth

Key characteristics include initial exponential growth, slowing growth as resources become limited, and eventually reaching a stable population size (carrying capacity).

Step 3: Analyze Growth Rate and Density Relationship

In logistic growth, the rate of population increase is highest at an intermediate population density, where resources are not too abundant (leading to very low density) or too scarce (leading to high density near carrying capacity).

Step 4: Select the Correct Option

From the analysis, it's clear that the population grows fastest at an intermediate population density. Thus, the correct answer is option c.

Key Concepts

Understanding Population Density

Population density refers to the number of individuals of a species present in a specific area or volume. It is a crucial factor in ecological studies because it influences how species interact with each other and with their environment. The density of a population can tell us not just about the population's current health but also forecasts its future dynamics.
Populations can be dense, meaning many individuals are packed into a small area, or sparse, with few individuals spread over a large area. The density of a population affects resource availability, competition, and survival rates. In logistic growth, population density directly impacts the growth rate until it adjusts according to the environment’s carrying capacity.

Defining Carrying Capacity

Carrying capacity is the maximum number of individuals of a species that an environment can sustainably support. This concept is pivotal in understanding logistic growth because it signifies the upper limit of population size that the environment's resources can sustain.
Several factors influence carrying capacity, including:

• Availability of food and water.
• Space for habitation.
• Environmental conditions like climate.
• Interactions with other species, such as predators or competitors.

As a population grows and nears its carrying capacity, resource competition intensifies, slowing the growth rate until the population levels off. In logistic growth, this results in an S-shaped curve, where the population stabilizes when it reaches carrying capacity.

Exploring Growth Rate in Logistic Growth

The growth rate of a population describes how quickly the number of individuals in the population increases over time. In logistic growth, the growth rate changes based on the population's density.
Initially, when the population is small and resources are abundant, the growth rate is high, resembling exponential growth. However, as the population increases, resources become limited, slowing down the growth rate until it eventually stabilizes at the carrying capacity. It’s key to note that logistic growth shows the fastest growth when the population density is intermediate—not too high or too low, ensuring resources are sufficiently available but not overly competed for.