MCA Test Preparation

Part 3

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”

ATGGCTTCCGACTAUGGCUUCCGACUUCAGCCUUCGGUATCAGCCTTCGGTA

+

25 pts. total

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 plateb. The solution on disk Ac. The size of the bacteriad. The species of bacteria used

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.

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.

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 soilb. Light and chlorophyllc. Carbon dioxide and waterd. 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. Diffusionb. Osmosisc. Active transportd. 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. Angle of lightb. Angle of stemc. Height of stemd. 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. Chemotropismb. Geotropismc. Phototropismd. Thigmotropism

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 plantsb. Change the type of plantc. Increase the number of trialsd. Increase the size of the light source.

White light

Blue light

Green light

Red light

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