JAMB/WAEC Biology Objective Test: 30 Questions on Microorganisms
JAMB/WAEC Biology Objective Test: 30 Questions on Microorganisms
Microorganisms are widely distributed in the environment and can be found in air, water, food, and various parts of the human body. Laboratory experiments using culture media help to demonstrate their presence and understand their behavior.
For examination purposes, especially JAMB and WAEC, students are expected not only to recall procedures but also to interpret experimental setups, identify controls, and draw logical conclusions. The questions below are structured to test deeper understanding, application, and analytical reasoning.
Biology Objective Test: 30 Questions on Microorganisms
- In an experiment, growth appears in both the test and control plates. This most likely indicates that
A. the medium was nutrient-rich
B. sterilization was ineffective
C. incubation was insufficient
D. microorganisms are absent - The main reason for using a control plate is to
A. increase microbial growth
B. compare results and validate observations
C. provide nutrients
D. speed up incubation - If an inoculating wire is not cooled after heating, it may
A. increase contamination
B. kill the microorganisms being introduced
C. enhance growth
D. sterilize the agar - The gradual increase in colony size on agar indicates
A. mutation
B. reproduction of microorganisms
C. death of cells
D. lack of nutrients - Opening a Petri dish widely during inoculation will most likely
A. increase oxygen supply
B. introduce contaminants
C. sterilize the medium
D. improve visibility - Which factor would most likely lead to false experimental results?
A. Proper labeling
B. Use of sterile instruments
C. Talking or sneezing during inoculation
D. Immediate covering of plates - The absence of growth in the control plate confirms that
A. microorganisms cannot grow
B. contamination was avoided
C. nutrients are absent
D. incubation failed - In the mouth experiment, delaying sampling until after brushing will likely
A. increase microbial count
B. reduce microbial presence
C. have no effect
D. sterilize the agar - If no colonies appear in the test plate after incubation, the most likely reason is
A. insufficient nutrients
B. high contamination
C. failure in inoculation or sterilization error
D. excessive oxygen - The purpose of streaking the agar surface is to
A. sterilize the medium
B. distribute microorganisms for growth
C. increase temperature
D. prevent contamination - Which of the following best explains why agar is used instead of gelatin?
A. Agar is cheaper
B. Agar remains solid at higher temperatures
C. Agar contains more nutrients
D. Agar kills bacteria - In the expired air experiment, the presence of colonies confirms that
A. air is sterile
B. microorganisms are absent in air
C. exhaled air contains microorganisms
D. agar promotes contamination - Which of the following conditions would inhibit microbial growth?
A. Warm temperature
B. Presence of nutrients
C. Extremely high temperature
D. Moist environment - A student observes different colony colours in one plate. This suggests
A. only one species present
B. contamination occurred
C. presence of different microorganisms
D. agar is defective - Which precaution is most critical in preventing airborne contamination?
A. Using nutrient-rich media
B. Opening plates briefly
C. Sealing plates with tape
D. Incubating in light - Microorganisms entering through the skin are most likely when
A. the skin is dry
B. there are cuts or wounds
C. the body is warm
D. the skin is clean - Which of the following is both a vector and a carrier?
A. Air
B. Water
C. Mosquito
D. Food - The housefly transmits pathogens mainly through
A. injection
B. direct contact
C. contaminated body parts
D. respiration - If microorganisms are found on both hands and nails, the most logical conclusion is that
A. microorganisms exist only in soil
B. human body surfaces can harbor microbes
C. agar promotes growth
D. contamination is unavoidable - The function of labeling Petri dishes is to
A. prevent contamination
B. identify samples and results
C. increase growth
D. sterilize medium - Which of the following diseases is caused by a protozoan?
A. Cholera
B. Typhoid
C. Malaria
D. Plague - The role of incubation in culturing is to
A. sterilize equipment
B. provide suitable conditions for growth
C. kill microorganisms
D. introduce samples - If agar fails to solidify, the most likely cause is
A. excess nutrients
B. improper preparation
C. contamination
D. low temperature - Which observation best confirms successful aseptic technique?
A. Growth in all plates
B. Growth only in test plates
C. No growth in all plates
D. Rapid growth in control - Aedes mosquito is associated with
A. malaria
B. cholera
C. yellow fever
D. typhus - Which of the following best explains the role of vectors?
A. Destroy microorganisms
B. Carry microorganisms between hosts
C. Produce nutrients
D. Sterilize surfaces - In the food experiment, growth indicates that
A. food is sterile
B. microorganisms are present in food
C. agar caused contamination
D. incubation failed - Which factor is common to all successful culturing experiments?
A. High temperature
B. Aseptic technique
C. Exposure to air
D. Use of water - If plates are incubated in direct sunlight, the likely outcome is
A. increased growth
B. no effect
C. reduced or no growth
D. contamination - The overall conclusion from all experiments is that microorganisms
A. exist only in laboratories
B. are present in diverse environments and body parts
C. cannot be controlled
D. grow only in artificial media
Answers
1. B 2. B 3. B 4. B 5. B
6. C 7. B 8. B 9. C 10. B
11. B 12. C 13. C 14. C 15. B
16. B 17. C 18. C 19. B 20. B
21. C 22. B 23. B 24. B 25. C
26. B 27. B 28. B 29. C 30. B
