Much of the genetic variation that makes evolution possible comes through sexual reproduction. The average is about one mutation in every 100,000 genes per generation Mutations rates are often lower in prokaryotes and higher in viruses 11. How does gene duplication occur? How might it play a role in evolution? Chromosomal mutations that delete, disrupt, or rearrange many loci are typically harmful Duplication of large chromosome segments is usually harmful Duplication of small pieces of DNA is sometimes less harmful and increases the genome size Duplicated genes can take on new functions by further mutation Mutation rates are low in animals and plants The transport of organic nutrients in the phloem of vascular plants. How could it be beneficial? During protein synthesis the third stage in the elongation cycle when the RNA carrying the growing polypeptide moves from the A-site to the P-site on the ribosome. What is translocation? An aberration in chromosome structure resulting from attachment of a chromosomal fragment to a non-homologous chromosome.
#CHAPTER 33 AP BIO STUDY GUIDE ANSWERS CODE#
What occurs in a point mutation? A point mutation is a change in one base in a gene The effects of point mutations can vary: Mutations in noncoding regions of DNA are often harmless Mutations in a gene might not affect protein production because of redundancy in the genetic code The effects of point mutations can vary: Mutations that result in a change in protein production are often harmful Mutations that result in a change in protein production can sometimes increase the fit between organism and environment 9. These mutations provide the raw material from which new traits may arise and be selected. Mutations are any change in the nucleotide sequence of an organisms DNA. What is the ultimate source of new alleles? Mutations are changes in the nucleotide sequence of DNA Mutations cause new genes and alleles to arise Only mutations in cells that produce gametes can be passed to offspring 8. What external factors might produce a cline? Why does the existence of a cline suggest natural selection? Most species exhibit geographic variation, differences between gene pools of separate populations or population subgroups Some examples of geographic variation occur as a cline, which is a graded change in a trait along a geographic axisħ. Geographic variation may be shown in a graded manner along a geographic axis known as a cline. Using the techniques of molecular biology, what are the two ways of measuring genetic variation in a population? Population geneticists measure polymorphisms in a population by determining the amount of heterozygosity at the gene and molecular levels Average heterozygosity measures the average percent of loci that are heterozygous in a population Nucleotide variability is measured by comparing the DNA sequences of pairs of individuals 6. Variation Within a Population Both discrete and quantitative characters contribute to variation within a population Discrete characters can be classified on an either-or basis Quantitative characters vary along a continuum within a population 5. In looking at genetic variation, what are discrete characters, and what are quantitative characters?
Because Darwin did not know about the work of Gregor Mendel, he could not explain how organisms pass heritable traits to their offspring. Which is the only mechanism that is adaptive, or improves the match between organisms and their environment? Natural selectionĬoncept 23.1 Mutation and sexual reproduction produce the genetic variation that makes evolution possible4. What are the three main mechanisms that can cause changes in allele frequency? Natural selection, genetic drift (chance events that alter allele frequency) and gene flow (transfer of alleles between populations). What is microevolution? Microevolution is a change in allele frequencies in a population over generations 2. The Smallest Unit of Evolution One misconception is that organisms evolve, in the Darwinian sense, during their lifetimes Natural selection acts on individuals, but only populations evolve Genetic variations in populations contribute to evolution 1. Dont lose sight of the conceptual understanding by getting lost in the details! As in the last chapter, first read each concept to get the big picture and then go back to work on the details presented by our questions. The Overview looks at the work of Peter and Rosemary Grant with Galpagos finches to illustrate this point, and the rest of the chapter examines the change in populations over time. Chapter 23: The Evolution of Populations This chapter begins with the idea that we focused on as we closed the last chapter: Individuals do not evolve! Populations evolve.