Calculating the Number of Surviving Bacteria

Oct 13, 2025 by wbrum.org 90 views

Introduction

In the field of biology, understanding the effects of antibiotics on bacterial populations is crucial for developing effective treatment strategies. When a population of bacteria is exposed to an antibiotic, the number of surviving bacteria decreases over time. In this scenario, we have a sample of 5,000 live bacteria that are treated with an antibiotic. After each day of treatment, 40% of the sample remains alive. In this article, we will explore the graph that represents the population of bacteria over time.

Understanding the Problem

To begin, let's consider the initial population of bacteria, which is 5,000. After the first day of treatment, 40% of the bacteria remain alive. This means that 60% of the bacteria are killed by the antibiotic. To calculate the number of surviving bacteria, we can multiply the initial population by 0.4 (40% as a decimal).

Initial population = 5,000
Surviving bacteria after 1 day = 5,000 \times 0.4 = 2,000

Calculating the Number of Surviving Bacteria

As the treatment continues, the number of surviving bacteria decreases by 40% each day. To calculate the number of surviving bacteria after each day, we can multiply the previous day's population by 0.4.

Day 1: 5,000 \times 0.4 = 2,000
Day 2: 2,000 \times 0.4 = 800
Day 3: 800 \times 0.4 = 320
Day 4: 320 \times 0.4 = 128
Day 5: 128 \times 0.4 = 51.2

Graphing the Population of Bacteria

The graph of the population of bacteria over time is a classic example of exponential decay. The population decreases rapidly at first, but the rate of decrease slows down as the population gets smaller.

Exponential Decay

Exponential decay is a mathematical process where a quantity decreases at a rate proportional to its current value. In this case, the population of bacteria decreases at a rate proportional to its current size. The equation for exponential decay is:

P(t) = P0 \times (1 - r)^t

where:

P(t) is the population at time t
P0 is the initial population
r is the rate of decay (40% in this case)
t is the time (in days)

Graphing the Equation

To graph the equation, we can plug in different values of t and calculate the corresponding population values.

t	P(t)
0	5,000
1	2,000
2	800
3	320
4	128
5	51.2

Interpreting the Graph

Conclusion

In conclusion, the graph of the population of bacteria under antibiotic treatment is a classic example of exponential decay. The population decreases rapidly at first, but the rate of decrease slows down as the population gets smaller. This is because the rate of decay is proportional to the current population size.

References

[1] "Exponential Decay" by Khan Academy
[2] "Biology" by Campbell and Reece

Introduction

In our previous article, we explored the graph of a population of bacteria under antibiotic treatment. We calculated the number of surviving bacteria after each day of treatment and graphed the equation for exponential decay. In this article, we will answer some frequently asked questions about the topic.

Q: What is exponential decay?

A: Exponential decay is a mathematical process where a quantity decreases at a rate proportional to its current value. In the case of the bacteria population, the number of surviving bacteria decreases at a rate proportional to the current population size.

Q: Why does the population decrease at a rate proportional to its current size?

A: The rate of decay is proportional to the current population size because the antibiotic is more effective at killing bacteria when there are more bacteria present. As the population gets smaller, the rate of decay slows down.

Q: How can we calculate the number of surviving bacteria after each day of treatment?

A: We can calculate the number of surviving bacteria after each day of treatment by multiplying the previous day's population by 0.4 (40% as a decimal).

Q: What is the equation for exponential decay?

A: The equation for exponential decay is:

P(t) = P0 \times (1 - r)^t

where:

P(t) is the population at time t
P0 is the initial population
r is the rate of decay (40% in this case)
t is the time (in days)

Q: How can we graph the equation for exponential decay?

A: We can graph the equation by plugging in different values of t and calculating the corresponding population values.

Q: What is the significance of the graph of the population of bacteria under antibiotic treatment?

A: The graph of the population of bacteria under antibiotic treatment is a classic example of exponential decay. It shows how the population decreases rapidly at first, but the rate of decrease slows down as the population gets smaller.

Q: What are some real-world applications of exponential decay?

A: Exponential decay has many real-world applications, including:

Modeling the spread of diseases
Predicting the decay of radioactive materials
Understanding the growth and decline of populations

Q: How can we use the concept of exponential decay to develop effective treatment strategies for bacterial infections?

A: We can use the concept of exponential decay to develop effective treatment strategies for bacterial infections by:

Understanding the rate of decay of the bacteria population
Developing antibiotics that target the bacteria at a rate proportional to the current population size
Monitoring the population size over time to adjust the treatment strategy as needed

Conclusion

In conclusion, the graph of the population of bacteria under antibiotic treatment is a classic example of exponential decay. We have answered some frequently asked questions about the topic and explored the significance of the graph. We hope that this article has provided a better understanding of the concept of exponential decay and its applications in real-world scenarios.

References

[1] "Exponential Decay" by Khan Academy
[2] "Biology" by Campbell and Reece