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A breeding group of foxes is introduced into a protected area, and the population growth follows a logistic pattern. After \(t\) years the population of foxes is given by $$ N=\frac{37.5}{0.25+0.76^{t}} \text { foxes } $$ a. How many foxes were introduced into the protected area? b. Make a graph of \(N\) versus \(t\) and explain in words how the population of foxes increases with time. c. When will the fox population reach 100 individuals?

Short Answer

Expert verified
a. 30 foxes were introduced. b. The fox population grows logistically, starting at 30 and approaching 150. c. The population reaches 100 foxes in about 18 years.

Step by step solution

01

Determine the Initial Population

To find out how many foxes were introduced, we plug in \(t = 0\) into the equation: \[ N = \frac{37.5}{0.25 + 0.76^0} \]Since \(0.76^0 = 1\), the equation simplifies to:\[ N = \frac{37.5}{0.25 + 1} = \frac{37.5}{1.25} = 30 \text{ foxes} \]Thus, 30 foxes were introduced into the protected area.
02

Describe the Population Growth Over Time

To analyze how the population grows, observe the logistic function:- Initially, the population starts at 30.- As \(t\) increases, \(0.76^t\) decreases towards zero, causing the term \(0.25 + 0.76^t\) to approach 0.25.- The graph of \(N\) versus \(t\) will show an S-shaped curve typical of logistic growth, starting at 30 and approaching a maximum (carrying capacity). - The carrying capacity can be calculated as \(\frac{37.5}{0.25} = 150\), meaning the population will asymptotically approach 150 foxes.
03

Find When the Population Reaches 100 Foxes

To determine when the population reaches 100 foxes, set \(N = 100\) and solve for \(t\):\[ 100 = \frac{37.5}{0.25 + 0.76^t} \]Rearranging gives:\[ 0.25 + 0.76^t = \frac{37.5}{100} = 0.375 \]Subtract 0.25 from both sides:\[ 0.76^t = 0.125 \]Taking the logarithm of both sides, \(\ln(0.76^t) = \ln(0.125)\), simplifies to:\[ t \ln(0.76) = \ln(0.125) \] Calculating \(t\): \[ t = \frac{\ln(0.125)}{\ln(0.76)} \approx 17.96 \]Therefore, the population will reach 100 foxes in about 18 years.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Population Growth
Population growth, particularly in ecological contexts, refers to the change in the size and makeup of populations over time. In the context of the exercise, the fox population follows a logistic growth model. This model often describes populations that start growing exponentially but then slow down as resources become limited. As the number of individuals increases, competition for resources such as food, space, and shelter intensifies.

This results in a tapering off and, eventually, a plateau in population size, known as the carrying capacity. Logistic growth is characterized by an S-shaped curve, where growth starts slowly, speeds up, and then slows again as it approaches the carrying capacity. Understanding these dynamics is critical for managing wildlife and conservation efforts.
Initial Population
The initial population is the number of individuals present at the beginning of the observation or experiment period. Knowing the initial population helps in setting the baseline for measuring growth. In the exercise, we calculated this by finding the population at time zero (when the foxes were first introduced).

By substituting zero for the time variable in the logistic equation, we determined that 30 foxes were initially released into the protected area. This step is crucial for understanding how much change occurs over time and can inform necessary conservation measures.
Carrying Capacity
Carrying capacity is the maximum population size that an environment can sustain indefinitely. It is determined by available resources like food, water, and habitat. In the logistic growth model given, the carrying capacity is reached as the population grows and resource limitations kick in, slowing growth.

In our exercise, we derived the carrying capacity by inspecting the logistic function's maximum possible value. We plugged in the condition when the denominator becomes minimal, \(0.25\), to find that the fox population will stabilize at 150. Recognizing this limit helps in assessing environmental health and gauging the sustainability of wildlife populations.
Logarithmic Functions
Logarithmic functions are utilized in analyzing exponential growth and decay in real-world contexts, like population dynamics described by logistic models. In this exercise, logarithms were essential for solving when the fox population would reach a specified number.

After setting the population equation equal to 100, we manipulated the equation \(100 = \frac{37.5}{0.25 + 0.76^t}\) to isolate \(t\). Solving for \(t\) involved taking the natural logarithm. Logarithms reverse the exponentiation process, making calculations involving growth and time pragmatic. Understanding how to apply them is a valuable mathematical skill in ecology and other scientific fields.

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Most popular questions from this chapter

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