MTTC MTTC Biology 4 — Questions and Answers
Question 1: In a food web, an organism that can occupy both the second and third trophic levels is called a(n):
- Producer
- Omnivore (Correct answer)
- Apex predator
- Detritivore
Correct answer: Omnivore
Omnivores consume both plants (acting as primary consumers) and animals (acting as secondary consumers), so they occupy multiple trophic levels.
Question 2: Which of the following best describes the function of the lac operon in E. coli?
- It codes for enzymes that synthesize lactose
- It regulates expression of lactose-metabolizing enzymes (Correct answer)
- It enables DNA replication in the presence of lactose
- It encodes repressor proteins that activate glucose uptake
Correct answer: It regulates expression of lactose-metabolizing enzymes
The lac operon controls transcription of genes needed to metabolize lactose; it is induced when lactose is present and glucose is absent.
Question 3: A cell placed in a hypotonic solution will:
- Lose water by osmosis and shrink
- Gain water by osmosis and may lyse (Correct answer)
- Remain unchanged because osmosis does not apply
- Actively pump water out to maintain homeostasis
Correct answer: Gain water by osmosis and may lyse
In a hypotonic solution, water moves into the cell by osmosis (from higher water potential outside to lower inside), causing the cell to swell and potentially burst.
Question 4: Which of the following correctly describes C4 photosynthesis compared to C3 photosynthesis?
- C4 plants use less ATP but fix CO2 less efficiently
- C4 plants pre-fix CO2 in mesophyll cells to reduce photorespiration (Correct answer)
- C4 plants only perform photosynthesis at night
- C4 plants lack the Calvin cycle entirely
Correct answer: C4 plants pre-fix CO2 in mesophyll cells to reduce photorespiration
C4 plants fix CO2 into a 4-carbon compound in mesophyll cells and deliver it to bundle sheath cells, concentrating CO2 and minimizing photorespiration.
Question 5: A student is performing a chi-square test on genetic cross data. If the calculated chi-square value is less than the critical value, the student should conclude:
- The results support the null hypothesis of expected ratios (Correct answer)
- There is a significant deviation from expected ratios
- The experiment must be repeated
- The cross did not follow Mendelian genetics
Correct answer: The results support the null hypothesis of expected ratios
A chi-square value below the critical value indicates that observed deviations from expected ratios are due to chance, supporting the null hypothesis.
Question 6: Which layer of the skin contains melanocytes responsible for producing skin pigment?
- Stratum corneum
- Stratum granulosum
- Stratum basale (Correct answer)
- Dermis
Correct answer: Stratum basale
Melanocytes are found in the stratum basale (deepest epidermal layer) and produce melanin, which is transferred to keratinocytes to protect against UV radiation.
Question 7: Which process describes bacteria gaining new genetic material through direct cell-to-cell contact via a pilus?
- Transformation
- Transduction
- Conjugation (Correct answer)
- Replication
Correct answer: Conjugation
Conjugation is the transfer of genetic material (often plasmids) between bacterial cells through a physical connection called the sex pilus.
MTTC MTTC Biology 4
In a food web, an organism that can occupy both the second and third trophic levels is called a(n):