MCA Test Preparation
Part 3
25 pts. total
1. (1 pt.) Background: Bacteria divide fast, allowing large bacterial
colonies to be produced in a short period of time. Identify the
genetic material in this bacteria. (Place a “+” on the genetic
material.)
+
2. (1 pt.) When bacteria divide, DNA must be replicated using
complementary bases. Select the correct complementary sequence
for this piece of DNA – “TACCGAAGGCTGA”
ATGGCTTCCGACT
AUGGCUUCCGACU
UCAGCCUUCGGUA
TCAGCCTTCGGTA
Background: Scientists divide an agar plate into 4 areas. They add the same
species of bacteria to each area of the plate. Then, the scientists put a small
paper disk on each area. Each disk is first soaked in 1 of 4 different
solutions: A, B, C, or D. After 24 hours, the scientists examine the plates
and measure the width of the clear zone around each disk. This zone is the
area in which bacterial growth is reduced.
3. (1 pt.) This graph shows the growth of a bacteria population on an agar
plate over time. Which point on the graph shows where the bacteria
population exceeded the capacity of the agar plate to support it? Mark the
point on the graph where the bacteria population exceeded the capacity of
the agar plate.
x
4.
(1 pt.) Which solution is most effective against this
bacterial growth? (Place a “+” on the disk you want to
select.)
+
Background: The scientists look at the clear zone around disk A and find that
some bacteria are still growing in the clear zone. They take these bacteria that
are resistant to the effects of solution A and put them on a new plate. A new
disk A is then put on the new plate. The results after 24 hours are shown
below.
5. (1 pt.) What is the selective pressure in this experiment?
a. The agar in the plate
b. The solution on disk A
c. The size of the bacteria
d. The species of bacteria used
6. (1 pt.) Which of these characteristics best explains why bacteria are often
used in experiments that examine evolution?
a. They have a cell membrane.
b. They do not have organelles.
c. They have a short generation time.
d. They can only be seen using a microscope.
Background: Many soaps, lotions, and cleaning supplies contain
antibacterial compounds that prevent bacterial growth.
7. (2 pts.) Explain why the overuse of these products is a possible public
health risk.
When you use antibiotics, only the strong, resistant bacteria live to
reproduce, so you are causing the population of bacteria to become
more resistant to the soaps and cleaning products that you use. If
these bacteria mutate a little more, they could cause serious illness
in people.
8.
The experiments demonstrated genetic variability in a species of
bacteria.
a. (1 pt.) Explain how genetic variability occurs in organisms.
DNA mutates and causes genetic variability.
b.
(2 pts.) Explain why genetic variability is necessary for natural
selection to occur.
For natural selection to occur, there must be multiple traits that
the species has. Nature will favor some of the traits more
than others. Over time, the organisms with these traits will
out-survive and out-reproduce the organisms without these
traits.
9. It is important for the scientists performing this experiment to
publish their results in a scientific journal.
a. (1 pt.) Give 1 reason why it is important for scientists to
publish their results.
In order to show others what they have discovered, scientists
need to publish their results and let their interpretations of the
data be open to discussion.
b.
(1 pt.) Give 1 more reason why it is important for scientists to
publish their results.
Scientists can show that their experiment was valid only if
their experiment is reproduceable and the overall results of
the experiment can be replicated by other scientists.
Background: Two students perform a series of studies on corn plants. They begin
by examining the structures of plant tissues. They prepare cross-sections of a leaf,
a stem and a root for examination under a microscope.
10. (1 pt.) Which 2 plant structures transport food or water or both? Place a
“+” on the plant structures that transport food and water.
+ +
Background: The students re-examine the leaf cross-section under the microscope
and note the locations of the stoma, cuticle, xylem, phloem and mesophyll cells.
11. (1 pt.) What are the sources of most of a plant’s biomass?
a. Nutrients and soil
b. Light and chlorophyll
c. Carbon dioxide and water
d. Fertilizer and organic matter
Background: The students re-examine the leaf cross-section under the microscope and
focus on a single cell.
12. (1 pt.) What process moves materials through a cell membrane against the
concentration gradient?
a. Diffusion
b. Osmosis
c. Active transport
d. Facilitated diffusion
Background: The students also conduct experiments to study corn plants. In 1
experiment, the students place 3 corn seedlings at different angles. After 3
days, the students discover that the stems of all 3 plants grow upward, while
the roots of the plants grow downward.
13. (1 pt.) Which one of these questions is best answered by the results of
this experiment?
a. Can corn grow straight?
b. Do corn plants always grow upward?
c. Do corn plants need light to germinate?
d. Can corn plants live in a horizontal position?
14. (1 pt.) The students form the hypothesis that if the tips of the corn
plants are cut off, the stems will grow in a direction perpendicular to
the soil in the pot. The students plan to test this hypothesis with
another experiment. Which measurement will they use to determine
if the hypothesis is supported?
a.
b.
c.
d.
Angle of light
Angle of stem
Height of stem
Amount of light
Background: In another experiment, the students expose 4 corn plants to 4
different colors of light: 1 to white, 1 to blue, 1 to green and 1 to red. (As seen in
the picture from left to right) The lights shine on the plants from the side. After 1
week, the plants exposed to the white and blue lights are bent toward their light
sources. The plants exposed to red and green light are not bent toward their light
sources.
15. (1 pt.) Which tropism is shown in this experiment?
a. Chemotropism
b. Geotropism
White
Blue
light
light
c. Phototropism
d. Thigmotropism
Green
light
Red
light
16. (1 pt.) Which of these changes to the experiment would have helped the
students make sure that the bending of the plants was caused by the color of light?
a. Use shorter plants
b. Change the type of plant
c. Increase the number of trials
d. Increase the size of the light source.
17. (2 pts.) The sun is the primary energy source on Earth. Support this
statement with an explanation of photosynthesis and its products.
Plants use the energy from the sun to combine carbon dioxide and
water into molecules of glucose. The byproduct of
photosynthesis is oxygen gas.
18. (3 pts.) Describe an experiment that tests how the number of daylight
hours affects plant growth. Include the following items in your
answer: a question, a brief overview of the procedure, and the
variables that will be changed, controlled and measured.
How does a plant’s growth respond to different hours of
daylight?
Place 5 plants in varying amounts of light for a period of 1
month. Give each plant the same amount of light each day.
For instance, plant 1 always gets 12 hours of light. Plant 2
always gets 14 hours of light. Plant 3 always gets 16 hours
of light. Etc. After 1 month, measure the plants’ heights and
take each plants’ mass.
Variables to control: amount of water given to each plant, the
intensity of the light, the type of light, the temperature of the
room.
Variables to change: only the length of daylight the plant gets.
Variables to measure: the height and the mass of the plant.
25 pts. total