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Chapter 22
1. State the two major points Darwin made in The Origin of Species concerning the Earth's
biota.
Darwin's two major points were the the evolution of new species by descent with
modification from ancestral species, and natural selection as the mechanism for this evolution.
3. Describe Carolus Linnaeus' contribution to Darwin's theory of evolution.
Linnaeus provided Darwin with a system of classification. He was the founder of
taxonomy, the binomial naming system still used today where organism are classified according
to genus and species. Also, he developed a filing system for grouping species into hierarchy of
increasingly general categories (i.e. Kingdom, phylum, etc).
7. Describe Jean Baptiste Lamarck's model for how adaptations evolve.
Lamarck believed that evolution responded ro organisms or "felt needs". His suggested
mechanism was the inheritance of acquired characteristics. Lamarck saw the ground level of
the ladder of life as the microscopic organisms, which Lamarck believed were continually
generated spontaneously from inanimate material. At the top of the evolutionary escalators
were the most complex plants and animals. Evolution was driven by an innate tendency toward
the greater and greater complexity, which Lamarck seemed to equate with perfection.
11. Explain what evidence convinced Darwin that species change over time.
Darwin was convinced that species change over time by evidence found in artificial
selection, the breeding of domesticated plants and animals. Humans have modified other
species over many generations by selecting individuals with the desired traits as breeding
stock. The plants and animals we grow for food bear little resemblance to their wild ancestors.
13. Explain why variation was so important to Darwin's theory.
Though some variations hold more advantageous over others, the favorable variations will
accumulate in the population after many generations of being disproportionately perpetuated
by natural selection. Natural selection involves interactions between individual organisms and
their environment, but individuals do not evolve. Evolution can be measured only as changes in
relative proportions of variations in a population over a succession of generations. Natural
selection can only amplify or diminish those variations that are heritable.
Heritable variation is at the heart of Darwin's theory of evolution, for variation provides the
substrate on which natural selection works.
15. Define and state the basic principles in natural selection.
Natural selection deals with the differential success in reproduction, made possible
because of variation among the individuals of any population and the tendency for a population
to produce more offspring than the environment can support. On average, the individuals best
adapted to the local environment leave the most offspring and thereby pass on their adaptive
characteristics. Natural selection involves interactions between individual organisms and their
environment, but individuals do not evolve. Evolution can be measured only as changes in
relative proportions of variations in a population over a succession of generations. Natural
selection can only amplify or diminish those variations that are heritable.
17. Using some contemporary examples, explain how natural selection results in evolutionary
change.
Natural selection results in exolutionary change in a variety of ways. A particular example,
illustrated by Darwin, tries the beak evolution of finches. The medium ground finch uses its
strong beak to crush seeds. Given a choice of small needs or large seeds, the birds eat mostly
small seeds. During wet years, small seeds are produced in such abundance that ground finches
consume relatively few large seeds. This changes during dry years when the birds resort to
eating a larger proportion of large seeds. Field studies comparing offspring to parents confirm
that this trait is inherited rather than acquired. The most likely explanation is that those birds
that happen to have stronger beaks have a feeding advantage during droughts and pass the
genes for this trait to their offspring.
20. Describe how molecular biology can be used to study the evolutionary relationships among
organisms.
Molecular biology can be used to study the evolutionary relationships among organisms in that
species that are closely related show uncanny similarities in their DNA and proteins.
21. Explain the problem with the statement that Darwinism is "just a theory".
Darwin's theory as "just a theory" is flawed for it fails to separate Darwin's two claims: that
modern species evolved from ancestral forms, and that natural selection is the main
mechanism for this evolution. The conclusion that life has evolved is based on historical
evidence. Thus, the "just a theory" argument concerns Darwin's second claim, his theory of
natural selection. As applied to evolution, the term theory refers to models for how to
evolution occurs.
Chapter 23
1. Explain what is meant by the "modern synthesis".
Modern synthesis is a comprehensive theory of evolution emphasizing natural selection,
gradualism, and populations as the fundamental units of evolutionary change
2. Explain how microevolutionary change can affect a gene pool.
Microevolution is a change in allele or genotype frequencies in a population. This takes
place when the conditions required for Hardy-Weinberg equilibrium are not met
3. In their own words, state the Hardy-Weinberg theorem.
The Hardy-Weinberg Theorem states that the frequencies of alleles and genotypes in a
population's gene pool remain constant over the generations unless acted upon by agents other
than sexual recombination.
7. Describe the usefulness of the Hardy-Weinberg model to population geneticists.
The Hardy-Weinberg model is useful to population geneticists for the Hardy-Weinberg
equation enables the calculations of frequencies of alleles in a gene pool if the frequencies of
genotypes are known.
9. Explain how genetic drift, gene flow, mutation, nonrandom mating and natural
selection can cause microevolution.
Genetic drift can cause evolution by way of fluctuation in a small populations gene pool.
Gene flow can cause evolution by transferring alleles between populations. Mutations can
cause evolution by substituting one allele for another in a gene pool. Mutation can theoretically
affect allele frequencies in a gene pool, but it is usually insignificant over the short term for
large populations. Mutation is mainly important in evolution because it generates new
variations.
Nonrandom mating can cause evolution by shifting the frequencies of genotypes in a gene pool.
Nonrandom mating, such as inbreeding or assortative mating, does not ordinarily affect allele
frequencies, but does affect the ration of genotypes in populations. Natural selection can cause
evolution via differential reproductive success among varying members of a population. Natural
selection is the only agent of microevolution that tends to be adaptive.
11. Distinguish between the bottleneck effect and the founder effect.
The bottleneck effect is the genetic drift resulting from the reduction of a population, typically
by a natural disaster, such that the surviving population is no longer genetically representative
of the original population.
The founder effect is a cause of genetic drift attributable to colonization by a limited number
of individuals from a parent population.
12. Explain why mutation has little quantitative effect on a large population
Mutation does not have much quantitative effect on a large population in a single
generation.
18. Give the cause of nearly all genetic variation in a population.
Nearly all-genetic variations in a population are due to Polymorphism where polymorphic
characters existent.
19. Explain how genetic variation may be preserved in a natural population.
Genetic variation may be preserved in a natural population where natural selection is able
to maintain diversity in a population,this is called balanced polymorphism. One of the
mechanisms for this preservation of variation is heterozygote advantage.
24. Describe what selection acts on and what factors contribute to the overall fitness of a
genotype.
Selection favors certain genotypes in a population by acting on the phenotype of individual
organisms. The whole organism is the object of selection.
25. Give examples of how an organism's phenotype may be influenced by the environment.
I know the contents of this question.
26. Distinguish among stabilizing selection, directional selection and diversifying selection.
In Natural selection frequency of a phenotype is affected in three different ways:
stabilizing selection, which discriminates against extreme phenotypes; directional selection,
which favors relatively rare individuals on one end of the phenotypic range; and diversifying
selection, which favors individuals at both extremes of a range over intermediate phenotypes.
28. Give at least four reasons why natural selection cannot breed perfect organisms.
Natural selection cannot breed perfect organisms for structures result from modified
ancestral anatomy, adaptations are often compromises, the gene pool can be affected by
genetic drift, and natural selection can act only on available variation.
Chapter 24
3. Define biological species.
The biological species concept defines a species as a population or group of populations
whose members have the potential to interbreed with one another in nature to produce viable,
fertile offspring, but who cannot successfully interbreed with members of other species.
4. Describe some limitations of the biological species concept.
The biological species concept has various limitations. The criterion of interbreeding is
useless for organisms that are completely asexual in their reproduction, as are all prokaryotes,
some protists, some fungi, and even some plants and some animals. The biological species
concept is also inadequate as a criterion for grouping extinct forms of life, the fossils of which
must be classified according to morphology.
6. Distinguish between prezygotic and postzygotic isolating mechanisms.
Prezygotic barriers impeded mating between species or hinder the fertilization of ova if
members of different species attempt to mate. Postzygotic barriers usually prevent the
interspecific hybrids from developing into adults, breeding with either parent species, or
producing viable fertile offspring.
7. Describe five prezygotic isolating mechanisms and give an example of each.
Species that occupy the same geographic are often live in separate habitats (habitat
isolation); breed at different times (temporal isolation); possess unique, exclusive mating
signals and courtship behaviors (behavioral isolation); and/or have anatomical incompatible
reproductive organs (mechanical isolation) or incompatible sex cells (gametic isolation).
10. Distinguish between allopatric and sympatric speciation.
Allopatric speciation is a mode of speciation induced when the ancestral population
becomes segregated by a geographical barrier.
Sympatric speciation is a mode of speciation occurring as a result of a radical change in the
genome that produces a reproductively isolated subpopulation in the midst of its parent
population.
13. Describe the adaptive radiation model and use it to describe how it might be possible to
have many sympatric closely related species even if geographic isolation is necessary for them
to evolve.
I am familiar with the adaptive radiation model.
14. Define sympatric speciation and explain how polyploidy can cause reproductive isolation.
Sympatric speciation occurs without geographic separation when a segment of the
population experiences a genetic change that results in reproductive isolation. Sympatric
speciation is most common in plants, in which the mutation is usually the doubling of the
chromosome number.
16. List some points of agreement and disagreement between the two schools of thought about
the tempo of speciation (gradualism vs. punctuated equilibrium).
As far as the theory of punctuated equilibrium, a species changes most when it buds from
an ancestral species and then remains fairly static in morphology for the rest of its duration.
Some believe that speciation gradually by an accumulation of micro-evolutionary changes in
gene pools.
Chapter 26
3. Provide evidence to support the hypothesis that chemical evolution resulting in life's origin
occurred in 4 stages:
1. Abiotic synthesis of organic monomers - Abiotic synthesis is a testable hypothesis.
Laboratory experiments performed under conditions simulating those of the primitive Earth
have produces diverse organic molecules from inorganic precursors. Stanley Miller and Harold
Urey used an apparatus to stimulate chemical dynamics on the primitive Earth. A warmed flask
of water simulated the primeval sea. The "atmosphere" consisted of H2O, H2, CH4, and NH3.
Sparks were discharged in the synthetic atmosphere to mimic lightning. A condenser cooled the
atmosphere, raining water and any dissolved compounds back to the miniature sea. As material
circulated through the apparatus, the solution in the flask changed from clear to murky brown.
After one week, Miller and Urey anayzed the contents of the solution and found a variety of
organic compounds, including some of the amino acids that make up the proteins of organisms.
2. Abiotic synthesis of polymers - Laboratory simulations of the early Earth conditions have
produced organic polymers. Small organic molecules polymerize when they are concentrated
on hot sand, rock, or clay. This process vaporizes water and concentrates the monomers on the
substratum. Using this method, Sidney Fox of the University of Miami had made what he calls
Proteinoids, which are polypeptides produced by abiotic means. Perhaps waves or rain splashed
dilute solutions of organic monomers onto fresh lava or other hot rocks on the early Earth and
then rinsed proteinoids and other polymers back into the water.
3. Formation of protobionts - Protobionts can form by self-assembly. Organic molecules
synthesized in the laboratory have spontaneously assembled into a variety of droplets microspheres, liposomes, and coarcervates - with some of the properties associated with life.
4. Origin of genetic information - The first genes may have been abiotically produced RNA,
whose base sequence served as a template for both alignment of amino acids in polypeptide
synthesis and alignment of complementary nucleotide bases in a primitive form of selfreplication. Once genetic information became incorporated inside membrane-enclosed
compartments, protobionts would have acquired heritability and the ability to evolve as units.
4. Describe Whittaker's five-kingdom system.
Whittaker's five-kingdom system consists of Monera (prokaryotes), Protista (relatively simple
eukaryotes), Plantae, Fungi, and Animalia
5. Describe three alternatives to the five-kingdom system and explain the rationale for each.
The six kingdom alternative divides the prokaryotes into two kingdoms. This modification
is based onmolecular evidence for an early evolutionary divergence between eubacteria (most
bacteria) and archaebacteria, an ancient lineage of prokaryotes with many unique
characteristics. Another possible alternative emphasizes on the ancient evolutionary split
between eubacteria and archeabacteria by using a superkingdom taxon called the domain.
Furthermore, the eight-kingdom system is one example of a "kingdom-splitting" solution to the
taxonomic problems posed by certain distinct lineages of microorganism. In addition to two
separate prokaryotic kingdoms, this system also splits the protists into three kindgoms.
Virginia Gil