Textbook Question
Natural selection changes allele frequencies because some _________ survive and reproduce better than others.
a. Alleles
b. Loci
c. Species
d. Individuals
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Ch. 23 - The Evolution of Populations
Urry12th EditionCampbell BiologyISBN: 9785794169850
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Table of contents
- Ch. 1 - Evolution, the Themes of Biology, and Scientific Inquiry8
- Ch. 2 - The Chemical Context of Life8
- Ch. 3 - Water and Life6
- Ch. 4 - Carbon and the Molecular Diversity of Life9
- Ch. 5 - The Structure and Function of Large Biological Molecules9
- Ch. 6 - A Tour of the Cell6
- Ch. 7 - Membrane Structure and Function6
- Ch. 8 - An Introduction to Metabolism6
- Ch. 9 - Cellular Respiration and Fermentation10
- Ch. 10 - Photosynthesis7
- Ch. 11 - Cell Communication7
- Ch. 12 - The Cell Cycle11
- Ch. 13 - Meiosis and Sexual Life Cycles10
- Ch. 14 - Mendel and the Gene Idea14
- Ch, 15 - The Chromosomal Basis of Inheritance6
- Ch. 16 - The Molecular Basis of Inheritance9
- Ch. 17 - Gene Expression: From Gene to Protein9
- Ch. 18 - Regulation of Gene Expression10
- Ch. 19 - Viruses6
- Ch. 20 - DNA Tools and Biotechnology7
- Ch. 21 - Genomes and Their Evolution8
- Ch. 22 - Descent with Modification: A Darwininan View of Life6
- Ch. 23 - The Evolution of Populations5
- Ch. 24 - The Origin of Species6
- Ch. 25 - The History of Life on Earth8
- Ch. 26 - Phylogeny and the Tree of Life8
- Ch. 27 - Bacteria and Archaea6
- Ch. 28 - Protists7
- Ch. 29 - Plant Diversity I: How Plants Colonized Land7
- Ch. 30 - Plant Diversity II: The Evolution of Seed Plants6
- Ch. 31 - Fungi5
- Ch. 32 - An Overview of Animal Diversity4
- Ch. 33 - An introduction to Invertebrates6
- Ch. 34 - The Origin and Evolution of Vertebrates7
- Ch. 35 - Vascular Plant Structure, Growth, and Development10
- Ch. 36 - Resource Acquisition and Transport in Vascular Plants8
- Ch. 37 - Soil and Plant Nutrition11
- Ch. 38 - Angiosperm Reproduction and Biotechnology8
- Ch. 39 - Plant Responses to Internal and External Signals8
- Ch. 40 - Basic Principles of Animal Form and Function8
- Ch. 41 - Animal Nutrition7
- Ch. 42 - Circulation and Gas Exchange7
- Ch. 43 - The Immune System5
- Ch. 44 - Osmoregulation and Excretion6
- Ch. 45 - Hormones and the Endocrine System8
- Ch. 46 - Animal Reproduction9
- Ch. 47 - Animal Development8
- Ch. 48 - Neurons, Synapses, and Signaling6
- Ch. 49 - Nervous Systems8
- Ch. 50 - Sensory and Motor Mechanisms5
- Ch. 51 Animal Behavior6
- Ch. 52 - An Introduction to Ecology and the Biosphere7
- Ch. 53 - Population Ecology9
- Ch. 54 - Community Ecology9
- Ch. 55 - Ecosystems and Restoration Ecology8
- Ch. 56 - Conservation Biology and Global Change6
Chapter 23, Problem 2
No two people are genetically identical, except for identical twins. The main source of genetic variation among humans is
a. New mutations that occurred in the preceding generation.
b. Genetic drift.
c. The reshuffling of alleles in sexual reproduction.
d. Environmental effects.
Verified step by step guidance1
Understand the concept of genetic variation: Genetic variation refers to the differences in DNA sequences among individuals within a population. This variation is crucial for evolution and adaptation.
Consider the role of mutations: Mutations are changes in the DNA sequence that can introduce new genetic variations. They occur randomly and can be passed to the next generation if they occur in germ cells.
Explore genetic drift: Genetic drift is a mechanism of evolution that refers to random changes in allele frequencies in a population. It can lead to genetic variation but is more significant in small populations.
Examine the reshuffling of alleles in sexual reproduction: During sexual reproduction, alleles are reshuffled through processes like meiosis and fertilization, leading to new combinations of genes in offspring. This is a major source of genetic variation.
Consider environmental effects: Environmental factors can influence gene expression and phenotype but do not directly change the genetic code. They can lead to phenotypic variation but are not a primary source of genetic variation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Genetic Variation
Genetic variation refers to the differences in DNA sequences among individuals within a population. It is crucial for evolution and adaptation, as it provides the raw material for natural selection. Variation arises from mutations, gene flow, and sexual reproduction, leading to diverse traits that can affect an organism's survival and reproduction.
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Sources of Genetic Variation
Mutations
Mutations are changes in the DNA sequence that can occur spontaneously or due to environmental factors. They are a primary source of genetic variation, introducing new alleles into a population. While many mutations are neutral or harmful, some can be beneficial and increase an organism's fitness, contributing to evolutionary change.
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02:29Mutations
Allele Shuffling in Sexual Reproduction
During sexual reproduction, alleles are reshuffled through processes like independent assortment and crossing over during meiosis. This reshuffling creates new combinations of alleles in offspring, contributing significantly to genetic diversity. It ensures that each individual has a unique genetic makeup, except in the case of identical twins.
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Related Practice
Textbook Question
If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?
a. gene variability = 0%; number of alleles = 0
b. gene variability = 0%; number of alleles = 1
c. gene variability = 0%; number of alleles = 2
d. gene variability > 0%; number of alleles = 2
Textbook Question
There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from
a. Genetic drift.
b. Gene flow.
c. Nonrandom mating.
d. Directional selection.
Textbook Question
A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?
a. 0.7
b. 0.49
c. 0.42
d. 0.21