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Evolution Unit 12 – Overview
Textbook – Chapters 15 Theory of Evolution (pg 296 – 315) 16 Population Genetics and Speciation (pg
316-335).
Class Website – http://shsbio1.wikispaces.com
Resources - http://www.phschool.com/science/biology_place/glossary/index.html
http://highered.mcgraw-hill.com/sites/0078695104/student_view0/
http://evolution.berkeley.edu/evosite/evo101/index.shtml
http://genetics.hannam.ac.kr/note/evolution.htm FEMS Microbiology Letters Volume 162 Issue 2 Page 325-330, May 1998
"In the broadest sense, evolution is merely change, and so is all-pervasive; galaxies, languages, and political
systems all evolve. Biological evolution ... is change in the properties of populations of organisms that transcend
the lifetime of a single individual. The ontogeny 1 of an individual is not considered evolution; individual
organisms do not evolve. The changes in populations that are considered evolutionary are those that are
inheritable via the genetic material from one generation to the next. Biological evolution may be slight or
substantial; it embraces everything from slight changes in the proportion of different alleles within a
population (such as those determining blood types) to the successive alterations that led from the earliest
protoorganism2 to snails, bees, giraffes, and dandelions." Douglas J. Futuyma in Evolutionary Biology
What changes in evolution? Actually what changes is the frequency of an allele. The frequency of an
allele in the gene pool of a population is how often an allele occurs in the genotypes of individuals of the
same species that are in the same area - the same population. How often the allele occurs depends on
lots of factors such as 1) what the allele codes for - is it a critical trait for survival and 2) is the allele a
dominant or a recessive allele. These factors determine whether the allele will be present for a long time
or a short time. Natural selection acts on population by changing the frequency of different alleles. If
an allele is harmful, it will be eliminated from the population or reduced in its frequency because those
individuals in the population exhibiting the trait will not survive. This leads to a fine difference between
genotype and phenotype. Remember genotype is the kinds of genes an individual has and phenotype is its
observable traits. It is the observable traits that are selected for or against resulting in increased
allele frequency or reduced allele frequency, respectively. Since we are also considering genotypes,
recall that the three ways that mutations happen most often are changes in the DNA (deoxyribonucleic
acid) sequence due to insertions, deletions, or substitutions.
It is very easy to get overly concerned about evolution if the focus is on human evolution. If instead the
focus is on the mechanisms of how organisms change over time, a lot of emotional distress can be
avoided. Believing that God created the Universe does not necessarily conflict with evolutionary theory.
Evolution can be thought of as an accumulation of changes that occur within a population resulting from
genetic and environmental changes. Within a population of organisms of the same species there are
differences between the individuals (variation). A species is a group of individuals that can interbreed
and produce fertile offspring (offspring that can reproduce). The greater the variation between
individuals, the greater the likelihood that the species will survive if the environment changes.
Since the Earth was created, many environmental changes have occurred and some species have
become extinct and others have apparently changed into different species. If an environment
1 Ontogeny: the development of an individual from the moment the egg is fertilized up till adulthood.
2 Protoorganisms: bacteria.
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changes too much and there is not enough variation within the population, few if any individuals will
survive the change, resulting in the species becoming extinct. But if there is sufficient variation so
that some “weirdoes” can survive, then those will be the ones that can reproduce and their
characteristic genes transmitted to the next generation. If there were a few before the change,
then after the change they will be the majority apparently evolving into another species. Looking at
fossils (mineralized remains of organisms) similarities can be observed. Paleontologists and
evolutionary biologists have developed relationships between existing and extinct species by tracing
anatomical and genetic similarities and differences.
Besides mutations and large scale environmental changes, more minor changes can result in
speciation. Speciation is the formation of a new species or group of organisms that can no longer
interbreed with an original species population. These organisms no longer interbreed because their
characteristics (either biological or behavioral) have become too different. This can happen
randomly and by geographic isolation of a species. A random change in the kinds of genes in a
population is called genetic drift. When populations of interbreeding individuals of the same species
are large, the the allele frequency of each successive population is expected to vary little from the
frequency of its parent population unless there are adaptive advantages associated with the alleles.
But with a small breeding population (a group separated by geography), a change in even one
individual can cause a disproportionately greater change in the population’s gene pool. Therefore
small populations are more subject to genetic drift effects than large populations. A situation
exists when large populations are quickly reduced. This population reduction is called a population
bottleneck. Like a bottleneck that is narrower than the bottle itself, genetic variation is reduced.
The reduced variation results in sudden changes in the allele frequency within the gene pool, and of
the population’s characteristics. These types of changes are not gradual and are called punctuated
because sudden and drastic changes can occur. So evolutionary changes are not always slow
(gradualism) or always rapid (punctuated equilibrium).
Vocabulary
1. Adaptation________________________________________________________________
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2. Analogous structures________________________________________________________
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3. Artificial Selection__________________________________________________________
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4. DNA____________________________________________________________________
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5. Evolution _________________________________________________________________
6. Fitness _________________________________________________________________
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7. Fossil ___________________________________________________________________
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8. Gene Pool ________________________________________________________________
9. Genetic Drift______________________________________________________________
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10. Geographic Isolation_________________________________________________________
11. PhylogeneticDiagram_________________________________________________________
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12. Homologous structures_______________________________________________________
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13. Behavior__________________________________________________________________
14. Mutation_________________________________________________________________
15. Natural selection ___________________________________________________________
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16. Phylogenetics______________________________________________________________
17. Population_________________________________________________________________
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18. Genetic Diversity_______________________________________________________
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19. Biological Species Concept________________________________________________
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20. Cladogram_____________________________________________________________
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21. Reproductive isolation________________________________________________________
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22. Speciation________________________________________________________________
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23. Species__________________________________________________________________
24. Theory___________________________________________________________________
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25. Vestigial Structure ____________________________________________________
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26. Darwin___________________________________________________________________
27. Biodiversity_______________________________________________________________
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28. Niche____________________________________________________________________
29. Genetic
Recombination_____________________________________________________________
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30. Galapagos Islands___________________________________________________________
Steps of Natural Selection
1.
2.
3.
4.
Evolution Unit Study Guide
1.
Evolution can be defined as any change in the relative frequency of alleles in the gene pool of a
_____________________
2.
Differences between the members of a population will most likely be passed onto future
generations if they are
3.
Mutations that are lethal in homozygous individuals can survive in a population by being carried
by
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A population of land snails colonized a field of yellow grass. At first, the
population contained two types of snails, one with brown bands on their shells
and another with yellow bands on their shells, as shown in the figure below.
After 10 years, most of the snails had shells with yellow bands.
4.
What process most likely led to an increase in the number of snails with yellow bands?
_________________________________________________________________
5.
What is the most likely reason that there are more yellow-banded snails present in the
grassland?
A field of crops was sprayed with pesticides to control a population of insects that was eating the
crop. Only 1% of the insects survived. The same amount and type of pesticide was sprayed on the
field each year for the next 4 years. The graph below shows the percentage of insects that survived
each year after the pesticide was used.
6.
Why was the pesticide less effective each year in its ability to control the target population of
insects?
__________________________
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7.
In a species of plant, the sudden appearance of one plant with a different leaf structure would
most likely be the result of
8.
What 3 processes cause a mutation?
9.
In carrier pigeons there is a rare inherited condition that causes the death of the chicks
before hatching. In order for this disease to be passed from generation to generation there
must be parent birds that
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10.
Describe natural selection.
_________________________________________________________________
11.
The idea that evolution takes place at a continuous but very slow rate is knows as ______
12.
The idea that evolution takes place at one point in time, followed by a long period without
change is
13.
A genetic change will be maintained in a population if the change
14.
According to Darwin’s theory of natural selection, individuals who survive are the ones best
adapted for their environment. Their survival is due to the
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15.
When mountain lions prey on a herd of deer, some deer are killed and some escape. Which part
of Darwin’s concept of natural selection might be used to describe this situation?
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16.
A change in a sequence of DNA is called a
17.
Natural selection acts directly on
18.
If a mutation introduces a new skin color in a lizard population, what factor might determine
whether the frequency of the new allele will increase?
_____________________________________________________________________
19.
genetic diversity provides a species with a higher probability of surviving
changes to its environment.
20. The difference in the fur color of the individual species in a population is described as
___________________________
21.
Two animals of different species would not be able to
22. Spraying DDT to kill mosquitoes became less effective each year the pesticide was used. This
decrease in the effectiveness was probably caused by the fact that
______
23. When penicillin was first introduced it was very effective in destroying most of the bacteria
that cause gonorrhea. Today, certain varieties of this bacterium are resistant to penicillin.
Explain the presence of these penicillin resistant bacteria.
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24. Although similar in many respects, two species of organisms exhibit differences that make
each well adapted to the environment in which it lives. The process of change that may account
for these differences is
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25.
______________________________
26. A random change in gene frequency in a small population is called
27. Genetic drift is most likely to effect
28. Geographic and reproductive isolation can result in
29. A species of finch (a type of bird) has been studied on one of the geographically isolated
Galapagos Islands for many years. Since the island is small, the lineage of every bird for
several generations is known. This allows a family tree of each bird to be developed. Some
family groups have survived and others have died out. The groups that survive probably have
30. A single species of squirrel evolved over time into two species, each on opposite sides of the
Grand Canyon. This change was most likely due to
31.
All the genes of all members of a particular population make up the population’s ___________.
32. Describe a gene pool.
______________________________________________________________
33. In genetic drift, allele frequencies change because of
34. Genetic drift tends to occur in populations that
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35. A small population of chimpanzees lives in a habitat that undergoes no change for a long period.
How will genetic drift probably affect this population?
______________________________________________________________________
36. The separation of populations by barriers such as rivers, mountains, or bodies of water is called
37. The geographic isolation of two populations of a species tends to increase differences between
their gene pools because it
Comparisons are made between two different organisms by finding the place where the two lines
intersect. The number where the columns and rows intersect shows how many amino acids are
different in the cytochrome c of both organisms. For example, the number of amino acids that are
different when comparing a rabbit's cytochrome c with a tuna's cytochrome c is 17. The larger the
number, the greater the difference in the structure of the cytochrome c molecules of the two
organisms.
38. According to the table, which pair of organisms is least closely related?
39. According to the table, which pair of organisms is most closely related?
40. In a certain area of undisturbed layers of rock, fossils of horseshoe crabs may be found in the
upper layer, and a lower layer contains fossils of trilobites. Trilobites are extinct aquatic
arthropods resembling modern horseshoe crabs. This information suggests that
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41.
In the early stages of development, the embryos of dogs, pigs, and humans resemble each
other. This observation suggests that these animals may have
42. An example of a structure that would be homologous to a bird wing would be a
43. The long, slow process of change in species over time is
44. In humans, the pelvis and femur, or thigh bone, are involved in walking. In whales, the pelvis
and femur shown in the figure above are
45. Modern sea star larvae resemble some primitive vertebrate larvae. This similarity may suggest
that primitive vertebrates
46. The number and location of bones of many fossil vertebrates are similar to those in living
vertebrates. Most biologists would probably explain this fact on the basis of
______
_______________________________________________________________________
47. Individuals within a population of rabbits have different colors of fur as shown in the diagram
below. The difference in the fur color of the individual rabbits is described as
_____________________.
48. What are three ways a mutation can affect an organism?
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1. The earliest
known butterflies
appeared about 130 million years ago. When did this occur in the geologic time scale?
2. This time accounts for most of the Earth’s history (approximately 88%) and while fossils are rare
evidence of fossilized cyanobacteria (formerly known as blue green algae) exists. What was this
time in the geologic time scale?
3. The first vascular plants appeared on land about 443 million years ago. Vascular plants with water
conducting tissues as compared with non-vascular plants such as mosses. When did this occur in
the geologic time scale?
4. During the end of this era 90% of all life on Earth died out. This era is the ________________
Era.(extra credit)
5. This period is known as the Age of the Fish when fish became abundant between 417 mya and 354
mya. When did this period occur in the geologic time scale?
6. Dinosaurs first appeared on Earth about 215 million years ago. When did this occur in the geologic
time scale?
7. Dinosaurs became extinct about 65 million years ago. When did this occur in the geologic time
scale?
8. The Cretaceous, Jurassic, and Triassic are all periods in the ________________ Era.
9. Humans and their ancestors have been around for about 4 million years. When did this occur in
the geologic time scale?
10. Humans with modern features appeared about 100,000 years ago. When did this occur on the
geologic time scale?
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