Name: ___________________________
Period: ________ Date: _____________
BIOLOGY UNIT 5:
Evolution through Natural Selection and other Mechanisms
KEY IDEA/s
1. Natural selection is the process by which those
heritable traits that make it more likely for an
organism to
and successfully
_________________
to become more common in
a population over successive generations.
2. Genetic variation is essential for natural
selection.
-The natural genetic variation within a population
of organisms means that ___________
individuals will survive and reproduce more
successfully than others in their
________________environment.
3. -Natural selection acts on the
_________________, or the observable
characteristics of an organism, but it is the
genetic (heritable) basis of any phenotype which
gives a reproductive advantage that will become
more common in a population.
-Over time, this process can result in adaptations
that specialize organisms for particular
environment.
Answer/s
Natural selection is a key mechanism
of evolution
Why?
Why is variation important?
Can variation protect against
extinction? Why?
What are some examples of
phenotype:
What are some examples of
heritable basis of phenotype AKA
genotype:
Why does natural selection act on
phenotype NOT genotype?
4. The idea that evolution takes place at one point
in time, followed by a long period without change
is ______.
Your answer? ________
A
gradualism
Correct Answer? ________
B
punctuated equilibrium
Why?
C
artificial selection
D
succession
5. Charles Darwin proposed his theory of evolution
based on observations of nature. Which observation
that contributed to his theory is illustrated by this
population of beetles?
A. Species produce more offspring than can survive.
B. Populations remain stable over time.
C. Individuals within a population may vary widely.
D. Environmental resources are limited.
Your answer? ________
Correct Answer? ________
Why?
6. Genetic drift, along with natural selection,
mutation, and migration, is one of the basic
mechanisms of evolution.
-In each generation, some individuals may, just by
chance, leave behind a few more descendants (and
genes, of course!) than other individuals. The genes
of the next generation will be the genes of the “lucky”
individuals, not necessarily the healthier or “better”
individuals.
7. Genetic drift affects
the genetic makeup of the
population but, unlike
natural selection, through
an entirely random process. So although genetic
drift is a mechanism of evolution, it doesn’t work
to produce ____________________________.
Genetic Drift is random and occurs
whether or not the surviving individual
is better suit. How is this different from
natural selection?
8. Bottleneck and Founder Effects
Genetic drift can cause big losses of genetic
variation for small populations. Two types of
genetic drift are:
Bottleneck:
Why would genetic
drift affect small
populations more
than large
populations?
What does entirely random mean?
Founder Effect:
9. A small population of chimpanzees lives in a
habitat that undergoes no changes for a long
period. How will genetic drift probably affect this
population?
A It will accelerate the appearance of new traits
B It will promote the survival of chimpanzees
with beneficial traits.
C It will increase the number of alleles for
specific traits.
D It will decrease genetic variation.
Your answer? ________
Correct Answer? ________
Why?
Genetic drift is a ______________ process.
Your answer? ________
A.
B.
C.
D.
directed
selection-driven
random
co-evolutionary
Correct Answer? ________
Why?
A species is often defined as a group of
individuals that actually or potentially interbreed
in nature.
In this sense, a species is the biggest gene pool
possible under natural conditions.
-Speciation is a lineage-splitting event that
produces two or more separate species.
Causes of Speciation
1. Geographic Isolation
2. Reduction of Gene Flow
_______________________________ is just a fancy
name for speciation by geographic isolation
Why?
______________________________ refers
to the formation of two or more
descendant species from a single
ancestral species all occupying the
same geographic location.
This diagram illustrates what kind
of speciation?
A
Sympatric
B
Allopatric
C
Geographic
D
Catastrophic
A cladogram is a diagram used to show
ancestral relations between organisms, to
represent the evolutionary tree of life.
These are two identical cladograms
Analyzing a cladogram…
1. Which species are most closely
related?
2. Which is the common ancestor of flies
and bees?
3. Which insects share the most recent
ancestor?
What conclusions can you draw
from this ‘tree of life’?
According to the cladogram, which
two species are most closelyrelated?
A clubmosses and spikemosses
B spikemosses and ferns
C ferns and flowering plant
D flowering plants and clubmosss
Why?
Which species is the oldest and still
in existence?
Which species is extinct?
Fossils are the preserved remains or traces of
animals, plants, and other organisms from the
remote past. The totality of fossils, both
discovered and undiscovered, and their
placement in fossiliferous (fossil-containing) rock
formations and sedimentary layers (strata) is
known as the ____________________.
Fossil evidence indicates that over time
organisms of increasing ________________
appeared on Earth. Bacteria and blue-green
bacteria (cyanobacteria) are the first fossils that
were preserved from the Precambrian Time.
The fossil record contains many examples that
could be interpreted to mean that species
evolved from more ancient organisms.
In a section
of the Grand
Canyon,
scientists
have found
the fossil
remains of
several
different
groups of organisms. The diagram on the left
represents the number and age of the fossils
the scientists found. The width of each
shaded area in the diagram below indicates
the relative number of fossils found.
Which of the following statements is
supported by the fossil record?
A
Group C is the only group that
no longer exists for it’s now extinct.
B
Group B was the most
numerous organism 10 million years
ago.
C
Group D has been in
existence the longest.
D
Group A is the most recent
organism to come into existence.
Why?
Which of the following is usually most helpful
in determining the age of the fossils found in
rock strata?
A the size of the fossils
B
the color of the fossils
C
the water content of the rock
layer where the fossils were located
D
the depth of the rock layer
where the fossils were found
Why?
Which of the following best explains how the
fossil record provides evidence that
evolution has occurred?
Why?
Orchids were studied to determine if the
amount of humidity affected the flowering of
these plants. Which of these was the
independent variable in this study?
Why?
A
It indicates the exact cause of
structural and behavioral
adaptations of organisms.
B
It shows that the form and
structure of groups of organisms
have changed over time.
C
It shows how the embryos of
many different vertebrate species
are very similar.
D
It indicates that forms of life
existed on Earth at least 3.5 billion
years ago.
A
B
The percentage of humidity
The length of time required
for flowering
C The amount watered
D The number of flowers on
each plant
Your answer? ________
Correct Answer? ________
Why
Fossils help scientists classify extinct
species and determine their relationships to
current species. Fossils provide the most
information about extinct species’______
After a culture of cells is allowed to multiply
and is viewed through a microscope, the
cells are x-rayed with high-energy radiation
for less than 1/100th of a second. After the
radiation, many newly reproduced cells
appear different. What has probably
occurred?
a) Bacterial infection
b) Contaimination
c) Speciation
d) Mutation
___________________________________
-is the manipulated variable in the
experiment.
a.
b.
c.
d.
Why?
Structures
habitat
metabolism
reproduction
Your answer? ________
Correct Answer? ________
Why?
_________________________________
-is the variable that is measured at
the end of the experiment.