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Chapter 18: Problem 10

Which best describes what happens when an antibiotic is applied to a population of bacteria? a. The bacteria develops resistance to the antibiotic in direct response to its application. b. The bacteria鈥檚 genetic material mutates in response to the antibiotic, resulting in resistance. c. A gene for resistance, already present in the population, decreases in frequency. d. A gene for resistance, already present in the population, increases in frequency

Short Answer

Expert verified
d. A gene for resistance, already present in the population, increases in frequency.

Step by step solution

01

Understand the Question

The question asks what happens to a population of bacteria when an antibiotic is applied. Focus on how resistance to antibiotics develops in bacteria.
02

Analyze Each Option

Evaluate each option to understand how they describe the development of antibiotic resistance:a. Implies bacteria develop resistance as a direct result of antibiotic application.b. Implies bacteria mutate in response to the antibiotic to develop resistance.c. Implies a pre-existing resistance gene reduces in frequency.d. Implies a pre-existing resistance gene increases in frequency.
03

Apply Biological Concepts

Antibiotic resistance typically arises because some bacteria in the population already have a gene for resistance. When the antibiotic is applied, bacteria without the resistance gene are killed off, while bacteria with the gene survive and reproduce.
04

Narrow Down Options

Options a and b suggest that resistance develops as a response to the antibiotic, which is not accurate. Option c suggests that the frequency of the resistance gene decreases, but it actually increases because resistant bacteria survive.
05

Choose the Correct Answer

The correct answer is d. The gene for resistance, already present in the population, increases in frequency because the antibiotic kills off non-resistant bacteria.

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Key Concepts

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

evolutionary biology
Evolutionary biology helps us understand how organisms change over time through processes like natural selection. When we apply an antibiotic to a population of bacteria, we are essentially creating an environment where only certain bacteria can survive. This is a clear example of natural selection in action. The bacteria that survive have certain genetic traits 鈥� in this case, resistance to the antibiotic. These surviving bacteria then reproduce, passing on their resistant genes to their offspring. Over time, the population evolves to become more resistant to the antibiotic. Understanding evolutionary biology in this context can help us grasp how quickly antibiotic resistance can spread. It's essential to manage antibiotic use carefully to slow down this process.
bacterial genetics
Bacterial genetics play a crucial role in how antibiotic resistance develops. Bacteria can carry genes that confer resistance to antibiotics, and these genes can be located on their chromosomes or on plasmids, which are small DNA molecules that can transfer between bacteria. This transfer can happen through several mechanisms:
  • Conjugation: Direct transfer of DNA from one bacterium to another through a physical connection.
  • Transformation: Uptake of free DNA fragments from the environment by a bacterium.
  • Transduction: Transfer of DNA from one bacterium to another via a bacteriophage (a virus that infects bacteria).
Each of these processes can help spread resistance genes within a bacterial population more quickly. Understanding these mechanisms highlights the importance of preventing horizontal gene transfer to curb the spread of antibiotic resistance.
natural selection
Natural selection is a key driver behind the development of antibiotic resistance. When an antibiotic is introduced, it creates a selective pressure on the bacterial population. Here's how it works:
  • Bacteria without resistance genes are killed by the antibiotic.
  • Bacteria with resistance genes survive and reproduce.
  • The frequency of resistance genes in the population increases.
This process ensures that the trait for antibiotic resistance becomes more common in future generations. Natural selection acts on variation within the population, favoring those individuals who are best adapted to survive the antibiotic's presence. By understanding natural selection, we see why it's crucial to use antibiotics carefully and only when necessary to avoid accelerating the rise of resistant bacteria.

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Most popular questions from this chapter

Given your understanding of evolutionary theory and the relationship between evolution and the genetic makeup of populations, which statement is false? a. Homologous characteristics that have evolved more recently are shared only within smaller groups of organisms. b. The genetic code is a homologous characteristic shared by all species because they share a common ancestor in the deep past. c. DNA sequence data would likely support any evolutionary tree drawn from anatomical data sets. d. The degree of relatedness between groups of organisms is only sometimes reflected in the similarity of their DNA sequences.

The human immunodeficiency virus (HIV) reproduces very quickly. A single virus can replicate itself a billion times in one 24-hour period. In a hypothetical treatment situation, a patient鈥檚 HIV population consists entirely of drug- resistant viruses after just a few weeks of treatment. How can this treatment result best be explained? How does this explanation illustrate that evolution is an ongoing process? a. The resistant viruses passed their genes to the non-resistant viruses so that 100% of the viruses became resistant. This illustrates evolution as an ongoing process because the genes of the population changed in real time. b. The non-resistant viruses died, and the resistant ones survived and rapidly reproduced. This illustrates evolution as an ongoing process because the change in the HIV population is the result of natural selection. c. The viruses developed resistance to the drug after repeated exposure to it. This illustrates evolution as an ongoing process because the viruses were able to adapt to changing conditions. d. The drug-resistant viruses were more fit than their non-resistant counterparts to begin with, and over time they dominated the population. This illustrates evolution as an ongoing process because natural selection favored one phenotype over another.

Prior to 1800 in England, the typical moth of the species Biston betularia (peppered moth) had a light pattern. Dark colored moths were rare. By the late 19th century, the light- colored moths were rare, and the moths with dark patterns were abundant. The cause of this change was hypothesized to be selective predation by birds (J.W. Tutt, 1896). During the industrial revolution, soot and other wastes from industrial processes killed tree lichens and darkened tree trunks. Thus, prior to the pollution of the industrial revolution, dark moths stood out on light- colored trees and were vulnerable to predators. With the rise of pollution, however, the coloring of moths vulnerable to predators changed to light. Which of the following aspects of Darwin鈥檚 theory of evolution does the story of the peppered moth most clearly illustrate? a. There is competition for resources in an overbred population. b. There is great variability among members of a population. c. There is differential reproduction of individuals with favorable traits. d. The majority of characteristics of organisms are inherited.

Which of the processes described is divergent evolution? a. Groups of organisms evolve in different directions from a common point. b. A new species develops rapidly when an event cuts off a portion of a population. c. Groups of organisms independently evolve to similar forms. d. A species evolves when a few members move to a new geographical area

In a hybrid zone, in addition to interacting, what else do two closely related species do? a. compete b. reproduce c. transition d. fuse
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