Answer Key_
Name: _
Pretest: _____/50
Posttest: ______/50
Pretest Ch 17 & 19.2: Patterns of Evolution
Part 1: Matching Vocab. Match the term on the right with the definition on the left by
placing the letter on the blank where it best matches.
1. __
2. __
3. __
J__ all of the genes and alleles in an entire
population
A. adaptive radiation
B. behavioral isolation
one extreme, e.g. feet keep getting
smaller and smaller
C. bottleneck effect
D. coevolution
E. convergent evolution
to a middle point, e.g. medium sized
feet naturally selected
F. directional selection
G. disruptive selection
H. divergent evolution
F__ evolution keeps making things more to
S__ evolution tends to make organisms more
I
4. __ __ when organisms move to a new habitat
and start their own population and
gene pool
I. founder effect
J. gene pool
K. genetic drift
5. __
L. genetic equilibrium
M. geographic isolation
R__ the processes where an organism becomes
its own species
6. __
7. __
8. __
9. __
B__ members of a population start to act
differently and stop breeding together
N. Hardy-Weinberg Principle
O. molecular clock
when organisms became different species
P. punctuated equilibrium
Q. reproductive isolation
and the gene frequency changes
R. speciation
S. stabilizing selection
O__ looking at DNA and rate of mutation to tell
C__ a disaster wipes out part of a population
D__ when organisms live together and evolve
T. temporal isolation
together (e.g. coral and algae)
10. __
T__ when populations that live in the same
area mate at different times and become separate species
11. __
P__ when evolution happens quickly in very short time frames, not little by little over
very long time frames
12. __
Q__ when members of a population stop breeding and become their own species
13. __
G__ evolution tends towards both extremes, not the middle, e.g. big and small
feet are good, medium is bad
14. __
A__ when organisms evolve and fit all parts of an ecosystem, e.g. live in the
ground, on the ground, in the trees, in the air….
15. __
M__ populations that get separated physically (e.g. by a river) become different
species
16. __
H__ when organisms evolve into many different organisms, but still have
similarities (homologous structures)
17. __
L__ when populations do not evolve
18. __
K__ over time, in small population, one allele becomes more common than
another but not by natural selection
19. __
E__ when organisms in similar environments evolve to have similar traits
(analogous structures)
20. __
N__ says that all allele frequencies in a population should remain the same, and
the organisms will not evolve
Here is a graph of the range of phenotypes in
a population. Explain what each of the
following is and draw what the graph
would look like after each:
Proportion
of
individuals
21. - 22. Directional selection
Evolution tends towards one
extreme, e.g. small hands, or
tallness only
23. – 24. Stabilizing selection
Evolution selects against the
extremes, e.g. big/small hands
are bad, close to medium is good
25. – 26. Disruptive selection
Evolution selects extremes,
e.g. tall and short are good,
medium is bad
Trait value
Genetic equilibrium is the idea that allele frequencies in a population do not change
over time. In other words, a population in genetic equilibrium does not evolve.
There are five things that can disrupt genetic equilibrium and cause evolution
to happen. Name and explain them.
27.
28.
29.
30.
31.
Non-random mating (artificial selection) …
choosing what traits get passed down (e.g.
fast horses)
Small population size, genetic drift can
happen more easily (random accidents do
selection instead of nature) e.g. a landslide
wipes out an endangered plant
Immigration (or Emigration): organisms can
join (or leave) the population and bring (or
take) alleles. This called gene flow. e.g.
black squirrels in Kent
Mutations: introduce new alleles into the
gene pool e.g. four leaf clovers
Natural selection: learned about that in the
last unit….environment changes to favor a
trait.
When a population is in genetic equilibrium, it is said to be in Hardy-Weinberg
Equilibrium. If p = the frequency of the dominant allele, and q = the frequency
of the recessive allele, use these two equations to solve the following.
p2 + 2pq + q2 = 1
p+q = 1
In humans, Rh-positive individuals have the Rh protein on their red blood cells, while
Rh-negative individuals do not. The Rh-positive phenotype is produced by a
dominant gene (A), and the Rh-negative phenotype is due to its recessive allele (a). If
16% of a population is Rh-negative…
32. What is the allele frequency for Rh-positive (A)?
2
q =.16
q = .4
p+q=1
p = .6
(16% are Rh neg. that’s a phenotype,
so that’s q2)
(40% of this population have the q
allele)
so
(60% of this population have the p
allele)
33. What is the phenotype frequency for homozygous dominant (AA)?
2
Homozygous dominant = p
p= .6 so
p2 = .36 (36% of this population are AA)
34. What is the phenotype frequency for heterozygous dominant (Aa)?
Heterozygous dominant = 2pq
p= .6 and q = .4
so
2pq = .48 (48% of this population are Aa)
As a population of organisms evolves, it eventually reaches a point where some of the
members can not breed with the others. They have evolved to become a new
species and the process is called speciation. There are 4 ways this can
happen. Name and explain them.
35.
36.
Reproductive isolation: organisms don’t
breed anymore
Behavioral isolation: mating rituals change,
so no inbreeding
37.
38.
Temporal isolation: mate at different times
of the year
Geographic isolation: separated by mountains
or islands or a river and can’t inbreed
39. – 40. What is the difference between a background extinction and a mass
extinction? Which happens more frequently?
A background extinction is the kind you hear
about in the news…one single species goes
extinct
A mass extinction is when some calamity
happens on the planet and large quantities
of species go extinct around the same time.
This has happened 5 times in the past, the
last time 66 my ago when the dinosaurs
died out
Explain each of these four patterns of evolution (how they happen, what they lead to):
Two species look alike through
different ancestors (just by adapting the
same way to a similar environment). Leads
to analogous structures
41. convergent evolution:
Two species descend from a
common ancestor. Leads to homologous
structures and/or vestigial structures
42. divergent evolution:
Two species evolve at the same time
in the same place in the same way. e.g.
coral and algae that gives it color
43. coevolution:
When an organisms evolves to fill
many niches (roles) in an ecosystem. e.g.
dinosaurs in the air, in the water, in the
ocean, on the land, in the swamps….
44. adaptive radiation:
45. – 46. What is the difference between
gradualism and punctuated
equilibrium?” Explain which
picture to the right is which.
Gradualism is when
changes in a
population happen
slowly over time,
bit by bit. The
picture on the left
shows this.
Punctuated equilibrium is when there are long
periods of no change followed by small
bursts of sudden change. The picture on the
right shows this.
Above are pictures 2 identical diagrams called cladograms. They show how closely
related organisms are and some of the characteristics that separate one from
another.
According to the diagram, what is most closely related to:
47. birds
lizards
48. lobsters
spiders
49. mammals
50. lungfish
lizards and birds
flounder (& perch) or lizards and birds