Population evolution | Practice Problems, Examples & Solutions

Genetic Variation

Evolutionary Analysis, Global Edition

a. A common objection to genetically modified food, and to genetic engineering in general, is that it is "not natural for genes to cross the species barrier." Comment on whether this argument is logically sound.
b. Whether or not it is "natural" for genes to cross species barriers, many people have additional worries about genetically modified food. One such concern is the possibility that the genetically modified organisms might escape into the natural environment, where they could, conceivably, compete with other organisms and cause problems. Is this also a concern for research projects aimed at evolving self-replicating RNA populations? Which are more likely to survive if they escape into the natural environment: genetically engineered modern organisms or self-replicating RNA populations? Why?
c. Do you think either of these research endeavors is unwise in any way? Why? If you were on a panel charged with developing guidelines for research, what safety measures would you support?

The Origins of Life and Precambrian Evolution

03:38

Biology: Concepts and Investigations

Write a paragraph that describes the connections among the following terms: gene, nucleotide, allele, phenorype, population, genetic variation, natural selection, and evolution.

The Forces of Evolutionary Change

06:41

Biology: Concepts and Investigations

How did James Hutton, Georges Cuvier, Georges-Louis Buffon, Jean Baptiste de Lamarck, Charles Lyell, and Thomas Malthus influence Charles Darwin's thinking?

The Forces of Evolutionary Change

The Hardy-Weinberg Equation

23 Practice Problems

00:59

Principles of Genetics

Mice with the genotype $H b$ are twice as fit as either of the homozygotes $H H$ and $b b$. With random mating, what is the expected frequency of the $b$ allele when the mouse population reaches a dynamic equilibrium because of balancing selection?

Population Genetics

00:36

Principles of Genetics

A trait determined by an X-linked dominant allele shows 100 percent penetrance and is expressed in 36 percent of the females in a population. Assuming that the population is in Hardy-Weinberg equilibrium, what proportion of the males in this population express the trait?

Population Genetics

04:20

Principles of Genetics

The frequency of an allele in a large randomly mating population is $0.2 .$ What is the frequency of heterozygous carriers?

Population Genetics

Natural Selection

53 Practice Problems

04:35

Essential Cell Biology

Natural selection is such a powerful force in evolution because organisms or cells with even a small reproductive advantage will eventually outnumber their competitors. To illustrate how quickly this process can occur, consider a cell culture that contains 1 million bacterial cells that double every 20 minutes. A single cell in this culture acquires a mutation that allows it to divide faster, with a generation time of only 15 minutes. Assuming that there is an unlimited food supply and no cell death, how long would it take before the progeny of the mutated cell became predominant in the culture? (Before you go through the calculation, make a guess: do you think it would take about a day, a week, a month, or a year?) How many cells of either type are present in the culture at this time? (The number of cells $N$ in the culture at time $t$ is described by the equation $N=N_{0} \times 2^{t / G},$ where $N_{0}$ is the number of cells at zero time and $G$ is the generation time.

Cells: The Fundamental Units of Life

02:00

Introduction to Genetic Analysis

In a sample of adult women from the United States, the average height was $164.4 \mathrm{cm}$ and the standard deviation was $6.2 \mathrm{cm} .$ Women who are more than 2 standard deviations above the mean are considered very tall, and women who are more than 2 standard deviations below the mean are considered very short. Height in women is normally distributed.
a. What are the heights of very tall and very short women?
b. In a population of 10,000 women, how many are expected to be very tall and how many very short?

The Inheritance of Complex Traits

03:23

Evolutionary Analysis, Global Edition

Review the kinds of evidence for evolution analyzed in Sections $2.1-2.5 .$ List the sources of evidence that were available to Darwin and those that appeared later. For example, of the evidence for microevolution discussed in Section $2.1,$ Darwin knew, and wrote, about divergent strains of domestic plants and animals and about vestigial structures. However, in Darwin's day no one had ever directly observed change across generations in natural populations. For each section, indicate which evidence you consider strongest and which you consider weakest. Explain why.

The Pattern of Evolution

Genetic Drift

29 Practice Problems

03:03

Biology: Concepts and Investigations

Describe examples of directional, disruptive, and stabilizing selection other than those mentioned in the chapter.

The Forces of Evolutionary Change

08:08

Biology: The Essentials

List and describe five mechanisms of evolution.

Forces of Evolutionary Change

01:24

Biology Concepts and Applications

______ among populations can keep them similar to one another.
a. Genetic drift
b. Gene flow
c. Mutation
d. Natural selection

Processes of Evolution

Gene Flow

22 Practice Problems

05:43

Biology Concepts and Applications

Match the terms with the most suitable description.
________fitness
________fossils
________natural selection
________homeotic genes
________half-life
________analogous structures
________homologous structures
________sedimentary rock
________neutral mutation
a. does not affect fitness
b. best fossil content
c. survival of the fittest
d. characteristic of a radioisotope
e. similar across diverse taxa
f. evidence of life in distant past
g. insect wing and bird wing
h. human arm and bird wing
i. measured by reproductive success

Evidence of Evolution

01:00

Biology Concepts and Applications

_______ is the original source of new alleles.
a. Mutation
b. Narural selection
c. Gene flow
d. Genetic drift

Processes of Evolution

03:25

Biology Concepts and Applications

Natural selection may occur when there are ____.
a. differences in forms of traits
b. differences in survival and reproduction among individuals that differ in one or more traits
c. both a and b

Processes of Evolution

Sexual Selection

10 Practice Problems

03:10

Evolutionary Analysis, Global Edition

Briefly describe (one sentence each) the three main models of the origin of Homo sapiens from Homo erectus. Which have been rejected, and why? What is the most likely scenario, given the evidence? What questions about the origins of present-day geographic variation remain?

Human Evolution

02:25

Evolutionary Analysis, Global Edition

What is the difference between adaptation from new mutation and adaptation from existing genetic variation? Why is this distinction important?

Genome Evolution and the Molecular Basis of Adaptation

04:50

Evolutionary Analysis, Global Edition

There is a great variation in the social structure of insects. Some are solitary, some are semisocial, some are facultatively eusocial, and some are primitively eusocial. According to you, what are the best reasons for the evolution of eusociality?

The Evolution of Social Behavior

Balancing Selection

70 Practice Problems

04:29

Chemistry: Introducing Inorganic, Organic and Physical Chemistry

Identify the products and write balanced equations for the following reactions (Section 26.7 ):
(a) adding beryllium to sodium hydroxide solution;
(b) heating strontium carbonate;
(c) heating barium oxide in air.

s-Block chemistry

03:54

Chemistry: Introducing Inorganic, Organic and Physical Chemistry

Identify the products and write balanced equations for the following reactions (Section 26.2):
(a) adding caesium to water;
(b) burning rubidium in an excess of air;
(c) heating lithium nitrate.

s-Block chemistry

04:22

Chemistry: Introducing Inorganic, Organic and Physical Chemistry

Predict the products and write balanced equations for the following reactions (Section 25.2):
(a) $\quad \mathrm{CsH}+$ water
(b) $\quad B_{2} H_{6}+$ pyridine
(c) $\quad \mathrm{S}_{2} \mathrm{H}_{6}+$ oxygen
(d) $\quad \mathrm{N}_{2} \mathrm{H}_{4}+\mathrm{HNO}_{3}(\mathrm{aq})$

Hydrogen