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Evolution
California Biology/Life Science Standard 7 3.a
Quick Review
Evolution is any change in time in the relative
frequencies of alleles in a population.
Evolution studies the varieties and interactions of living
things across time.
A great diversity of species increases the chance that at
least some living things will survive in the face of large
changes in the environment.
Questions
1. What is a population?
2. Suggest a reason why the population of brown
lizards decreased.
1. A group of individuals that belong to the same species and live in the same area.
2. Answers will vary. Students may suggest that environmental factors caused more brown lizards to be eaten.
Evolution
California Biology/Life Science Standard 7 3.b
Quick Review
During his travels, Darwin made numerous observations and
collected evidence that led him to propose his theory of
evolution.
Geologists James Hutton and Charles Lyell helped scientists
recognize that the Earth was very old and that the processes
that changed Earth in the past were the same processes that
operate today.
Questions
1. What are some ways Earth has changed over time?
2. How did Hutton and Lyell influence Darwin’s thinking?
1. Students may suggest that mountains have been built up, or earthquakes
have buried other rock
2. Darwin thought that if Earth could change,
life could change as well.
Evolution
California Biology/Life Science Standard 7 3.c
Quick Review
Homologous structures provide evidence that all four-limbed
vertebrates share a common ancestor.
Limbs of different vertebrates have different functions but
are structurally similar and develop from the same embryonic
tissues.
Fossils of ancient whale-like animals with legs suggest
that whales and other mammals likely share a
common ancestor.
Questions
1. How are the bones similar across the four groups?
2. Would lighter bones be more advantageous for an
animal that lived in the air or on land?
1. Similar arrangement and number
3. In air. (Lighter bones are easier to lift, such as in flight; heavier bones offer more structural
support, as needed to bear weight on the ground.)
Cell Biology
California Biology/Life Science Standard BI 1.a
Quick Review
The phenotype of an organism is its physical
characteristics.
The genotype of an organism is its genetic makeup.
Natural selection works on the phenotype of an organism.
Questions
1. Why might the red lizard population have
disappeared?
2. Which lizard population—brown or black—is more
successful in this example?
1. They may have been more visible to predators
2. black
Evolution
California Biology/Life Science Standard BI 7.b
Quick Review
Organisms that have two identical alleles for a particular
trait are homozygous.
Organisms that have two different alleles for the same trait
are heterozygous.
A genetic disorder caused by a recessive allele, such as TaySachs disease, only appears if the individual inherits two
recessive alleles for the trait.
A heterozygous individual still contributes the allele to
the gene pool even if the person doesn’t have the
disorder.
Question
Both parents are heterozygous for Tay-Sachs disease. What is
the chance that their offspring will have Tay-Sachs? (Hint:
Use a Punnett square for help.)
1 in 4 chance.
Evolution
California Biology/Life Science Standard BI 7.c
Quick Review
The two main sources of genetic variation are mutations and
the genetic shuffling that results from sexual reproduction.
Plant breeders use several methods to increase genetic
variation in plants and to produce new types of plants.
A mutation is any change in the sequences of DNA. Some
mutations affect an organism’s phenotype, while others do
not.
Questions
1. Describe one way in which natural selection could
act on a plant characteristic.
2. Name one characteristic that plant breeders might
select for.
1. Sample answer: If average temperatures in an area increase over time, plants with greater heat tolerance will be more likely to
survive and reproduce.
2. Sample answer: Resistance to pests
© Pearson Education, Inc., Publishing as Pearson Prentice Hall. All rights reserved.
Evolution
California Biology/Life Science Standard Bl 7.6
Quick Review
Sample Population
The number of phenotypes a given trait has is determined
by how many genes control the trait.
Genetic variation is studied in populations. A gene pool
consists of all genes, including all of the different alleles
that are present in a population.
Genetic variation is present within and between species of
animals.
Questions
Frequency of Alleles
1. Describe the characteristics of two breeds of
dogs. What variation is present within the
species?
2. Compare the characteristics of frogs and
earthworms. What variation is present between
the species?
1. Answers will vary. Students may compare any two types of dogs, noting the variation present between the types.
2. Sample answers: Students may note the presence of limbs on a frog or differences in body systems between the species.
Evolution
California Biology/Life Science Standard *BI 7.e
Quick Review
According to the Hardy-Weinberg principle, in order for
genetic equilibrium to be maintained, five conditions must be
met:
1. There must be random mating;
2. The population must be large;
3. There can be no movement into or out of the
population;
4. There can be no mutations; and
5. There can be no natural selection.
If all of these conditions are met, evolution will not occur.
Questions
1. Why can there be no movement into or out of the
population?
2. Is it likely that all five conditions can be meet for
long periods of time?
1. New organisms moving into the population will bring new alleles
2. No
Evolution
California Biology/Life Science Standard *BI 7.f
Quick Review
The Hardy-Weinberg equation states:
p+q=1
where p = the frequency of one allele and q = the frequency of
another allele.
The three genotypes possible are:
pp (p2), pq, and qq (q2).
The equation that shows this is:
p2 + 2pq + q2 = 1.
Questions
1. If p = 0.1, what does q equal?
2. What are the frequencies of the alleles p2, 2pq, and
q 2?
1. q = 0.9
2. p2 = 0.01, 2pq = 0.18, q2 = 0.81
Evolution
California Biology/Life Science Standard BI 8.a
Quick Review
An adaptation is a genetic change in an organism that helps it
survive in its environment.
The Galápagos finches likely descended from one population
that became geographically isolated.
Questions
1. What helped the finches adapt to local food sources?
2. During a dry season, which finches may have a
better chance of survival?
1. Changes to their beaks
2. Seed-eating
Evolution
California Biology/Life Science Standard BI 8.b
Quick Review
A species’ traits may change over many generations due to
environmental influences, such as changes in climate or
landforms; interspecies interaction; and genetic mutations.
Natural selection favors helpful traits in a way that increases
the species’ fitness over time.
Questions
1. Is a parrotlike beak better adapted to feeding on
fruit or insects?
2. What would likely happen to the population size of
the vegetarian tree finch if trees on the island did
not produce fruit one year?
1. Fruit
2. The population size would probably decline.
Evolution
California Biology/Life Science Standard BI 8.c
Quick Review
Natural selection is not the only source of evolutionary
change. Mutations, migration, genetic drift, and nonrandom
mating can also result in evolution.
In small populations, individuals that carry a particular allele
may leave more descendants than other individuals, just by
chance.
Over time, a series of chance occurrences can cause an allele
to become common in a population.
Questions
1. How do the descendant populations in the diagram differ
from the original population?
2. What is genetic drift?
3. What is the founder effect?
1. They are different colors and
have different markings.
2. A random change in allele
frequency
3. A situation in which allele frequencies change as a result
of a migration of a small subgroup of a population
Evolution
California Biology/Life Science Standard BI 8.d
Quick Review
Reproductive isolation occurs when members of two
populations cannot interbreed.
There are three types of reproductive isolation: behavioral
isolation, geographic isolation, and temporal isolation.
Questions
1. What type of reproductive isolation has occurred
when a barrier, such as a river, separates two
populations?
2. When two populations are capable of breeding, but
don’t because of different courtship rituals, what
type of reproductive isolation has occurred?
1. geographic isolation
2. behavioral isolation
Evolution
California Biology/Life Science Standard BI 8.e
Quick Review
During the Paleozoic Era, the continents were one large
landmass.
As the continents drifted farther and farther apart, ancestors
of mammal groups were isolated from one another.
Mammals that feed on ants and termites evolved in five
different regions.
Question
What characteristics do these mammals share?
Front claws, long snout, and long tongue
© Pearson Education, Inc., Publishing as Pearson Prentice Hall. All rights reserved.
Genetics
California Biology/Life Science Standard *BI 8.f
Quick Review
The exact sequence of nitrogen bases in DNA is unique to
each species.
Organisms with similar DNA sequences are more closely
related than those with different sequences.
Comparing genes of different species helps to determine
possible relationships among species.
Questions
1. Is the DNA of giant pandas more similar to the
DNA of bears or lesser pandas?
2. When did all four groups share an ancestor?
3. Which have more similar DNA sequences,
raccoons and lesser pandas or giant pandas and
bears?
1. Bears
2. More than 40 million years ago
3. Giant pandas and bears
Evolution
California Biology/Life Science Standard *BI 8.g
Quick Review
Many genes are shared by a wide range of
organisms.
Cytochrome c is a protein found in most eukaryotic cells.
The more closely two organisms are related, the more closely
their genes resemble one another.
Questions
1. Is a turkey more closely related to a chicken or to a
rattlesnake? How can you tell?
2. With which animal does a donkey share the most
recent ancestor?
1. a chicken because they have more amino acid sequences in common
2. horse