Microorganisms: Friend and Foe – Very Short Answer Type Questions
Class 8
Science
Chapter 2
Microorganisms: Friend and Foe — 50 Very Short Answer Questions (Topic-wise)
CBSE Class 8 Science – Chapter Wise Study Materials Based on NCERT
CBSE Board Examinations — Chapter Presentation (Systematic):
- Focus: types, habitats, useful and harmful roles of microbes, control methods and simple experiments.
- Question Style: Very Short Answers (one-line or short phrase) for quick revision.
Topic 1: Basics & Types of Microorganisms (Q1–Q8)
- Q1: What is a microorganism?A tiny living organism not visible to the naked eye.
- Q2: Give two examples of bacteria.A: Escherichia coli and Rhizobium.
- Q3: Name one unicellular fungus used in food.A: Yeast (Saccharomyces).
- Q4: What are viruses made of?A protein coat and genetic material (DNA or RNA).
- Q5: What is a protozoan? Give one example.A single-celled eukaryote; example: Amoeba.
- Q6: Are algae always multicellular?A: No — some algae are microscopic and unicellular.
- Q7: How do bacteria generally reproduce?A: By binary fission (splitting into two).
- Q8: Define pathogen.A microbe that causes disease.
Topic 2: Habitats & Growth Requirements (Q9–Q14)
- Q9: Name one environment where extremophiles live.A: Hot springs (high temperature).
- Q10: Which two factors are most important for microbial growth?A: Moisture and temperature.
- Q11: Do microbes require nutrients to grow?A: Yes — carbon, nitrogen, minerals and energy sources.
- Q12: Give one habitat for fungi.A: Decaying organic matter (e.g., rotting fruit).
- Q13: Where are microbes found in the human body?A: Skin, mouth, gut and other surfaces (normal flora).
- Q14: What condition favours mould growth on bread?A: Moist, warm conditions.
Topic 3: Beneficial Microorganisms (Q15–Q26)
- Q15: Name one microbe used to make curd.A: Lactobacillus (beneficial bacteria).
- Q16: Which microbe is used in bread making?A: Yeast (Saccharomyces cerevisiae).
- Q17: Give one use of Penicillium mould.A: Source of the antibiotic penicillin.
- Q18: Which bacteria fix nitrogen in legume roots?A: Rhizobium.
- Q19: Name one role of microbes in the environment.A: Decomposition of organic matter.
- Q20: Which microbe is used to make alcohol?A: Yeast (fermentation produces ethanol).
- Q21: How do microbes help in wastewater treatment?A: They break down organic pollutants biologically.
- Q22: Name one industrial product made using microbes.A: Insulin (via recombinant bacteria) or enzymes.
- Q23: Which microbe is important for making cheese?A: Specific bacteria and molds like Lactococcus and Penicillium.
- Q24: What is bioremediation?A: Use of microbes to clean pollutants (e.g., oil spills).
- Q25: How do microbes contribute to soil fertility?A: By decomposing matter and fixing nitrogen.
- Q26: Name one microbe used in yogurt production.A: Lactobacillus bulgaricus (and Streptococcus thermophilus).
Topic 4: Harmful Microorganisms & Diseases (Q27–Q36)
- Q27: Name a bacterial disease of humans.A: Tuberculosis.
- Q28: Give one viral disease.A: Influenza (flu) or common cold.
- Q29: What causes cholera?A: The bacterium Vibrio cholerae.
- Q30: Name one plant disease caused by microbes.A: Blight or wilt (caused by fungi/bacteria).
- Q31: How do microbes spread through food?A: Contamination, improper storage and poor hygiene.
- Q32: What is food spoilage?A: Deterioration of food by microbes, making it unsafe or unpalatable.
- Q33: Which microbe causes common cold?A: Various viruses (e.g., rhinoviruses).
- Q34: Why are viral infections harder to treat with antibiotics?A: Antibiotics target bacteria, not viruses.
- Q35: What is a vector? Give an example.A: An organism that transmits disease (e.g., mosquito).
- Q36: Name one symptom of microbial infection.A: Fever, vomiting, diarrhoea or inflammation (any one).
Topic 5: Controlling Microorganisms (Q37–Q44)
- Q37: What is sterilisation?A: Killing all microorganisms and spores on an object.
- Q38: Define pasteurisation.A: Mild heating to kill most pathogens (e.g., milk treatment).
- Q39: Name one antiseptic.A: Alcohol or iodine solution.
- Q40: What does an antibiotic do?A: Kills or inhibits bacteria.
- Q41: Why are vaccines important?A: They stimulate immunity to prevent infections.
- Q42: Give one method to preserve food from microbial spoilage.A: Refrigeration or drying.
- Q43: How does boiling water help control microbes?A: Kills many microbes by heat.
- Q44: What is the difference between disinfectant and antiseptic (short)?A: Disinfectants used on surfaces; antiseptics safe for skin.
Topic 6: Practical Activities & Quick Revision (Q45–Q50)
- Q45: Name one experiment to show yeast activity.A: Mix yeast + sugar + warm water and observe bubbles (CO₂).
- Q46: How to prepare curd in a simple way?A: Add a spoon of curd to cooled boiled milk and keep warm until set.
- Q47: What simple test shows food spoilage?A: Visible mould or foul smell indicates spoilage.
- Q48: Give one safety rule while doing microbe experiments.A: Work with teacher supervision and avoid tasting samples.
- Q49: What is meant by normal flora?A: Microbes that normally live on/in the human body without causing harm.
- Q50: Why is handwashing important?A: Removes microbes and prevents disease transmission.
Note: These Very Short Questions with Answers are organised topic-wise and strictly follow the NCERT syllabus, making them ideal for CBSE Class 8 board exams standard.