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CHAPTER 22
DESCENT WITH MODIFICATION:
A DARWINIAN VIEW OF LIFE
State the two major points Darwin made in The Origin of Species
concerning the Earth's biota.
The two major points Darwin made in The origin of species was: the
occurrence of evolution and natural selection as its mechanism.
Describe Carolus Linnaeus' contribution to Darwin's theory of
evolution.
Carlus Linnaeus’ contribution to Darwin’s theory of evolution was that
Linnaeus provided Darwin with a connection to evolution by
recognizing that the great diversity of organisms could be ordered into
“groups subordinate to groups” or major taxonomy categories.
Describe Jean Baptiste Lamarck's model for how adaptations evolve.
Jean Baptiste Lamarck’s model for how adaptations evolve
incorporates two ideas that were popular during Lamarck’s era. The
first was use and disuse, the idea that those parts of the body used
extensively to cope with the environment become larger and stronger,
while those that are not used deteriorate. The second idea Lamarck
adopted was called the inheritance of acquired characteristics. In this
concept of heredity, the modification of an organism acquires during its
lifetime can be passed along to its offspring.
Explain what evidence convinced Darwin that species change over time.
The evidence that convinced Darwin that species change over time was
the finches he saw while in the Galapagos. Darwin collected 13 species
of closely related finches, some found in only one island. Thus, the
most striking difference among species is in their beaks, which adapted
for specific diets.
Explain why variation was so important to Darwin's theory.
Variation was so important to Darwin’s theory because a new species
would arise from an ancestral form by gradual accumulation of
adaptations to a different environment. Populations would diverge
more and more in appearance as ach adapted to local conditions. Thus,
Darwin anticipated that explaining how such adaptations arise was
essential to understanding evolution.
Define and state the basic principles in natural selection.
Natural selection is the mechanism for evolution or differential success
in the reproduction of different phenotypes resulting from the
interaction of organisms with their environment. Evolution occurs
when natural selection causes changes in relative frequencies of alleles
in the gene pool. According to Darwin’s concept of natural selection, a
population of organisms can change over time as a result of individuals
with certain heritable traits leaving more offspring than other
individuals. The basic principles are
1. Populations produce more individuals that can possibly survive.
2. Population sizes remain stable.
3. Resources are limited
4. “Heritable” variation exists among organisms
5. “Survival of the fittest.”
Using some contemporary examples, explain how natural selection
results in evolutionary change.
Natural selection results in evolutionary change by natural selection is
this differential success in reproduction, and its adaptation of organisms
to their environment. An example is Camouflage on plants.
Describe how molecular biology can be used to study the evolutionary
relationships among organisms.
An organism’s hereditary background is reflected in its genes and their
protein products. Thus, two species considered to be closely related by
other criteria should have a greater proportion of their DNA and
proteins in common than more distantly related species.
Explain the problem with the statement that Darwinism is "just a
theory".
Darwinism is no longer a theory because it has been proven countless
times by fossil records and fields of biology such as biogeography,
comparative anatomy and molecular biology.
CHAPTER 23
THE EVOLUTION OF
POPULATIONS
Explain what is meant by the "modern synthesis".
Modern synthesis is the focus on populations as units of evolution
Explain how microevolutionary change can affect a gene pool.
Modern synthesis is the focus on populations as units of evolution
In their own words, state the Hardy-Weinberg theorem.
The Hardy Weinberg theorem basically states that if a population is
large, shows no random mating, is totally isolated, shows no net
mutations, and has reproductive success for all individuals then no
evolution will occur.
Describe the usefulness of the Hardy-Weinberg model to population
geneticists.
This model would help these geneticists realize the gradual change of a
certain population over time because of little or no change in allele and
genotype frequencies.
Explain how genetic drift, gene flow, mutation, nonrandom mating and
natural selection can cause microevolution.
Each of these examples causes microevolution because they all affect the
allele frequencies of a population. They introduce a change in alleles or
genotypes.
Distinguish between the bottleneck effect and the founder effect.
The bottleneck effect describes a population that undergoes a dramatic
decrease in size. The founder effect describes allele frequencies in a
migrating group differ, by chance, from their population of origin.
Explain why mutation has little quantitative effect on a large
population.
Mutation is not harmful and has no effect in most cases, it is also
adaptive. Mutation is always on a small scale so it could never have a
lasting effect on a large population.
Give the cause of nearly all genetic variation in a population.
Genetic variation is caused by genetic drift, non random mating,
natural selection, mutation and gene flow.
Explain how genetic variation may be preserved in a natural
population.
Genetic variation is preserved through diploidy (presence of two copies
of each chromosome) and polymorphism (heterozygous advantage and
frequency dependent selection).
Describe what selection acts on and what factors contribute to the
overall fitness of a genotype.
Genetic variation is preserved through diploidy (presence of two copies
of each chromosome) and polymorphism (heterozygous advantage and
frequency dependent selection).
Give examples of how an organism's phenotype may be influenced by
the environment.
Distinguish among stabilizing selection, directional selection and
diversifying selection.
Stabilizing selection acts against extreme phenotypes and favors the
more common intermediate variants. Directional selection shifts the
frequency curve for variations in some phenotypic character in one
direction or the other by favoring what are initially relatively rare
individual the deviate from the average for that character. Diversifying
selection occurs when environmental conditions are varied in a way that
favors individual in both extremes of a phenotypic range over
intermediate phenotypes
Give at least four reasons why natural selection cannot breed perfect
organisms.
*Organisms are locked into historical constraints.
*Adaptations are often compromises.
*Not all evolution is adaptive.
*Selection can only edit variations that exist
CHAPTER 2 4
THE ORIGIN OF SPECIES
Define biological species (E. Mayr).
*Organisms are locked into historical constraints.
*Adaptations are often compromises.
*Not all evolution is adaptive.
*Selection can only edit variations that exist
Describe some limitations of the biological species concept.
Some limitations of the biological species concept are that the criterion
of interbreeding is useless for organisms that are completely asexual in
their reproduction; it is also inadequate as a criterion for grouping
extinct forms of life, and if two populations are geographically
segregated from each other, they do not interbreed, although they may
be so much alike that they are placed in the same species on
morphological grounds.
Distinguish between prezygotic and postzygotic isolating mechanisms.
Prezygotic barrier is a reproductive barrier that impedes mating
between species or hinders fertilization of ova if interspecific mating is a
hempted. Postzygotic barrier is any of several species-isolating
mechanisms that prevents hybrids produced by two different species
from developing into viable, fertile adults.
Describe five prezygotic isolating mechanisms and give an example of
each.
There are five different types of prezygotic isolating mechanisms.
Habitat Isolation is when two species that live in different habitats
within the same area encounter each other rarely, for example, two
species of parasites living on different hosts will not have a chance to
mate.
Behavioral Isolation is that special signal that attracts mates, as well as
elaborate behavior unique to a species like male fireflies of different
species signal to females of their kind by blinking their lights in
particular patterns.
Temporal Isolation is when two species that breed during different
times of the day, different seasons, or different years cannot mix their
gametes.
Mechanical Isolation, is when closely related species may attempt to
mate, but fail to consummate the act because they are anatomically
incompatible.
Gametic Isolation is when even if the gametes of different species meet,
they rarely fuse to form a zygote. Gamete recognition may be based on
the presence of specific molecules on the coats around the egg, which
adhere only to complementary molecules on sperm of the same species.
Distinguish between allopatric and sympatric speciation.
Allopatric speciation is a mode of speciation induced when a
geographical barrier segregates the ancesteral population.
Sympatric speciation is a mode of speciation occurring because of a
radical change in the genome that produces a reproductively isolated
subpopulation in the midst of its parent population.
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.
1. One island in this cluster of three is seeded by a small colony founded
by individuals of species A, blown over from a mainland population.
2. Its gene pool isolated from the parent species, the island population
evolves into species B as it adapts to its new environment.
3. Storms or other agents of dispersion spread species B to a second
island,
4. where the isolated colony evolves into species C.
5. Later, individuals from species C recolonize the first island and
cohabit with species B, but reproductive barriers keep the species
distinct.
6. A colony of species C may also populate a third island,
7. where it adapts and forms species D.
8. Species D is dispersed to the two islands of its ancestors,
9. forming a new species, E, on one of those islands.
The story could go on, with a series of allopatric speciation episodes
made possible by the combination of isolation and occasional dispersal.
Define sympatric speciation and explain how polyploidy can cause
reproductive isolation.
1. One island in this cluster of three is seeded by a small colony founded
by individuals of species A, blown over from a mainland population.
2. Its gene pool isolated from the parent species, the island population
evolves into species B as it adapts to its new environment.
3. Storms or other agents of dispersion spread species B to a second
island,
4. where the isolated colony evolves into species C.
5. Later, individuals from species C recolonize the first island and
cohabit with species B, but reproductive barriers keep the species
distinct.
6. A colony of species C may also populate a third island,
7. where it adapts and forms species D.
8. Species D is dispersed to the two islands of its ancestors,
9. forming a new species, E, on one of those islands.
The story could go on, with a series of allopatric speciation episodes
made possible by the combination of isolation and occasional dispersal.
List some points of agreement and disagreement between the two
schools of thought about the tempo of speciation (gradualism vs.
punctuated equilibrium).
One view of speciation is that it usually occurs gradually by an
accumulation of micro evolutionary changes in gene pools. In contrast,
the punctuated equilibrium model views species as changing most when
they bud from an ancestral species and then undergoing relatively little
change for the rest of their existence.
CHAPTER 26
EARLY EARTH AND
THE ORIGIN OF LIFE
Provide evidence to support the hypothesis that chemical evolution
resulting in life's origin occurred in 4 stages:
One view of speciation is that it usually occurs gradually by an
accumulation of micro evolutionary changes in gene pools. In contrast, the
punctuated equilibrium model views species as changing most when they
bud from an ancestral species and then undergoing relatively little change
for the rest of their existence.
a. Abiotic synthesis of organic monomers
b. Abiotic synthesis of polymers
c. Formation of protobionts
d. Origin of genetic information
Describe Whittaker's five-kingdom system.
Munera, Plantae, Animalia, Protists,
Describe three alternatives to the five-kingdom system and explain the
rationale for each.