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Date:_____________ Period:_____
Evolution Unit 5 – Overview
Schedule – February 11, 2009 through March 27, 2009; Unit Exam Tuesday 3/23/09
Unit 5. Evolution Key Standards (2nd Semester)
5a. The frequency of an allele in a gene pool of a population depends on many factors and may be
stable or unstable over time. Students will apply how natural selection affects the characteristics of
an organism and how mutations are maintained within a gene pool. (7a, 7b, 7c)
Key Elements:
1. Define the following concepts: natural selection, mutation, gene pool
2. Describe the process of natural selection.
3. Give an example of natural selection in nature.
4. Explain how natural selection affects the characteristics of an organism.
5. Explain how a mutation is formed.
6. Discuss how a mutation is maintained within a gene pool.
5b. The frequency of an allele in a gene pool of a population depends on many factors and may be
stable or unstable over time. Evolution is the result of genetic changes that occur in constantly
changing environments. Students will describe how greater variation within a species may lead to
greater survival of that species. (7d, 8b)
Key Elements:
1. Define variation, species.
2. Explain how variation affects a species survival.
3. Give a realistic example of how variation in a species has lead to its greater survival.
5c. Evolution is the result of genetic changes that occur in constantly changing environments.
Students will evaluate the effects of genetic drift and geographic isolation on a species. (8c, 8d)
Key Elements:
1. Define the following: genetic drift, gene pool, geographic isolation, and species
2. Evaluate how genetic drift will affect a species, its gene pool, and its survival.
3. Evaluate how geographic isolation will affect a species, its gene pool, and its survival.
5d. Evolution is the result of genetic changes that occur in constantly changing environments.
Students will identify that analysis of fossil, DNA, and anatomical evidence supports evolution. (8e, 8f)
Key Elements:
1. Define the following: fossil, DNA, anatomical evidence, evolution, homologous structures, and
analogous structures.
Evolution Unit Overview
2. Describe how fossil evidence supports evolution.
3. Describe how DNA evidence supports evolution.
4. Describe how anatomical evidence supports evolution.
5. Give a realistic example of how all of the following support evolution: fossil evidence, DNA,
and anatomical evidence.
Note: The abbreviation CCS stands for California Content Standards referenced below.
California Standards Evolution
7. The frequency of an allele in a gene pool of a population depends on many factors and may be
stable or unstable over time. As a basis for understanding this concept:
a) Students know why natural selection acts on the phenotype rather than the genotype of an
b) Students know why alleles that are lethal in a homozygous individual may be carried in a
heterozygote and thus maintained in a gene pool.
c) Students know new mutations are constantly being generated in a gene pool.
d) Students know variation within a species increases the likelihood that at least some members of
a species will survive under changed environmental conditions.
8. Evolution is the result of genetic changes that occur in constantly changing environments. As a
basis for understanding this concept:
a) Students know how natural selection determines the differential survival of groups of
b) Students know a great diversity of species increases the chance that at least some organisms
survive major changes in the environment.
c) Students know the effects of genetic drift on the diversity of organisms in a population.
d) Students know reproductive or geographic isolation affects speciation.
e) Students know how to analyze fossil evidence with regard to biological diversity, episodic
speciation, and mass extinction.
Textbook – Chapters 14 History of Life (pg 390 – 415) 15 Evolution (pg 416-449).
Class Website –;
Resources - FEMS Microbiology Letters Volume 162 Issue 2 Page 325-330, May 1998
Tentative Schedule
Week 1: 2/16 - 2/20 – President’s Day Holiday 2/16 Chapter 14 History of Life (due 2/23),
Week 2: 2/23 - 2/27 –Unit 5 Quiz 1, Chapter 15 Evolutionary Processes (due on 3/5)
Week 3: 3/2 - 3/6 – Unit 5 Quiz 2, Chapter 15 Evolution and Natural Selection
Week 4: 3/9 - 3/13 – Unit 5 Quiz 3, Chapter 17 Classification and Review for Exam
Week 5: 3/16 - 3/20 – Breeding Bunnies and Molecular Clocks and Review for Exam
Week 6: 3/23 – 3/27 – Unit 5 Exam 3/24/00; Portfolio preparation
Evolution Unit Overview
"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 ontogeny1 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. Being a Roman Catholic and 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.
1 Ontogeny: the development of an individual from the moment the egg is fertilized up till adulthood.
2 Protoorganisms: bacteria.
Evolution Unit Overview
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
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 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 type of changes are not gradual and called punctuated because
sudden and drastic changes can occur. So evolutionary changes are not always slow (gradualism) or
always rapid (punctuated equilibrium).
1. Adaptation________________________________________________________________
2. Analogous structures________________________________________________________
3. Anatomical evidence_________________________________________________________
4. Artificial Selection__________________________________________________________
5. DNA ____________________________________________________________________
6. Evolution _________________________________________________________________
7. Embryology_______________________________________________________________
Evolution Unit Overview
8. Era_____________________________________________________________________
9. Extinct___________________________________________________________________
10. Fitness _________________________________________________________________
11. Fossil ___________________________________________________________________
12. Founder effect_____________________________________________________________
13. Gene Pool ________________________________________________________________
14. Genetic Drift______________________________________________________________
15. Geographic Isolation_________________________________________________________
16. Geologic Time Scale_________________________________________________________
17. Gradualism________________________________________________________________
18. Interbreeding_____________________________________________________________
19. Homologous structures_______________________________________________________
20. Mass Extinction____________________________________________________________
21. Mimicry__________________________________________________________________
22. Mutation_________________________________________________________________
23. Natural selection ___________________________________________________________
24. Paleontology_______________________________________________________________
25. Period___________________________________________________________________
26. Phenotype ________________________________________________________________
27. Population_________________________________________________________________
Evolution Unit Overview
28. Punctuated equilibrium_______________________________________________________
29. Radioactive (radiometric) dating________________________________________________
30. Relative dating_____________________________________________________________
31. Reproductive isolation________________________________________________________
32. Survival of the fitness_______________________________________________________
33. Speciation________________________________________________________________
34. Species__________________________________________________________________
35. Theory___________________________________________________________________
36. Vestigial Structure (organ)____________________________________________________
37. Variation_________________________________________________________________
38. Darwin___________________________________________________________________
39. Diversity_________________________________________________________________
40. Index fossil_______________________________________________________________
41. Niche____________________________________________________________________
42. Pesticide_________________________________________________________________
43. Resistant_________________________________________________________________
44. Variation_________________________________________________________________
45. Galapagos Islands___________________________________________________________
Steps of Natural Selection
Evolution Unit Overview
Evolution Unit Study Guide
Evolution can be defined as any change in the relative frequency of alleles in the gene pool of a
Differences between the members of a population will most likely be passed onto future
generations if they are
Mutations that are lethal in homozygous individuals can survive in a population by being carried
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.
What process most likely led to an increase in the number of snails with yellow bands?
What is the most likely reason that there are more yellow-banded snails present in the
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.
Why was the pesticide less effective each year in its ability to control the target population of
Evolution Unit Overview
change over evolutionary time.
In a species of plant, the sudden appearance of one plant with a different leaf structure would
most likely be the result of
What would cause a mutation?
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
Describe natural selection.
The idea that evolution takes place at a continuous but very slow rate is knows as ______
The idea that evolution takes place at one point in time, followed by a long period without
change is
A genetic change will be maintained in a population if the change
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
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?
A change in a sequence of DNA is called a
Natural selection acts directly on
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?
genetic diversity provides a species with a higher probability of surviving
changes to its environment.
The difference in the fur color of the individual species in a population is described as
22. Two animals of different species would not be able to
23. 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
24. 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.
Evolution Unit Overview
25. 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
27. A random change in gene frequency in a small population is called
28. Genetic drift is most likely to effect
29. Geographic and reproductive isolation can result in
30. 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
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
32. All the genes of all members of a particular population make up the population’s ___________.
33. Describe a gene pool.
34. In genetic drift, allele frequencies change because of
35. Genetic drift tends to occur in populations that
Evolution Unit Overview
36. 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?
37. The separation of populations by barriers such as rivers, mountains, or bodies of water is called
38. The geographic isolation of two populations of a species tends to increase differences between
their gene pools because it
39. What kind of animal would be best adapted to survive extreme change in temperature?
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
40. According to the table, which pair of organisms is least closely related?
According to the table, which pair of organisms is most closely related?
42. 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
Evolution Unit Overview
43. In the early stages of development, the embryos of dogs, pigs, and humans resemble each
other. This observation suggests that these animals may have
44. An example of a structure that would be homologous to a bird wing would be a
45. Fossil trees are petrified when the wood is replaced with
46. The long, slow process of change in species over time is
47. 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
48. Modern sea star larvae resemble some primitive vertebrate larvae. This similarity may suggest
that primitive vertebrates
49. 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
50. 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
51. What are three types of mutation?
Sunny says Hi and Good Luck on your studies. Bunny out.
Evolution Unit Overview