Chapter-2 The Invisible Living World — Online MCQ Test
SCIENCE · Grade 8 · CBSE(NCERT)
Practice Chapter-2 The Invisible Living World with a free chapter-wise online MCQ test.
This chapter covers: microorganisms - bacteria - fungi - pasteurization - pathogens - antibiotics - vaccines.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-2 The Invisible Living World — Important Questions & Answers
Which of the following is an example of a microorganism?
- A. Bacteria
- B. Elephant
- C. Oak tree
- D. Butterfly
Answer: A. Bacteria
Bacteria are single-celled microorganisms that are too small to be seen with the naked eye, unlike the other visible organisms listed.
Bacteria are single-celled microorganisms that are too small to be seen with the naked eye, unlike the other visible organisms listed.
What is the main characteristic of fungi?
- A. They are green and produce food through photosynthesis
- B. They are heterotrophic and feed on organic matter
- C. They have a true nucleus but no cell membrane
- D. They are always unicellular organisms
Answer: B. They are heterotrophic and feed on organic matter
Fungi are heterotrophs that cannot produce their own food; instead, they feed on dead organic matter or live on other organisms.
Fungi are heterotrophs that cannot produce their own food; instead, they feed on dead organic matter or live on other organisms.
Which term describes organisms that cause disease?
- A. Antibodies
- B. Pathogens
- C. Vaccines
- D. Enzymes
Answer: B. Pathogens
Pathogens are disease-causing microorganisms such as bacteria, viruses, and fungi that harm their hosts.
Pathogens are disease-causing microorganisms such as bacteria, viruses, and fungi that harm their hosts.
What is pasteurization?
- A. A method to kill all microorganisms in food permanently
- B. A heat treatment process that reduces harmful microorganisms in food
- C. A technique to add more bacteria to milk
- D. A process of fermentation used in cheese making
Answer: B. A heat treatment process that reduces harmful microorganisms in food
Pasteurization uses controlled heating to reduce the number of harmful microorganisms in liquids like milk without completely sterilizing them.
Pasteurization uses controlled heating to reduce the number of harmful microorganisms in liquids like milk without completely sterilizing them.
Why is pasteurization of milk important?
- A. To add vitamins to milk
- B. To increase the fat content of milk
- C. To reduce harmful bacteria and extend shelf life
- D. To change the color of milk
Answer: C. To reduce harmful bacteria and extend shelf life
Pasteurization reduces pathogenic bacteria in milk, making it safer to drink and extending its shelf life by slowing spoilage.
Pasteurization reduces pathogenic bacteria in milk, making it safer to drink and extending its shelf life by slowing spoilage.
How do vaccines provide protection against diseases?
- A. By directly killing pathogens in the bloodstream
- B. By training the immune system to recognize and fight specific pathogens
- C. By eliminating all microorganisms from the body
- D. By providing instant immunity that lasts forever
Answer: B. By training the immune system to recognize and fight specific pathogens
Vaccines stimulate the immune system to produce antibodies and memory cells that recognize the pathogen, allowing for quick immune response upon actual infection.
Vaccines stimulate the immune system to produce antibodies and memory cells that recognize the pathogen, allowing for quick immune response upon actual infection.
Why is antibiotic resistance becoming a global health concern?
- A. Bacteria are learning to produce antibiotics
- B. Overuse of antibiotics has led to bacteria developing resistance to these medicines
- C. New viruses are replacing bacteria as disease agents
- D. Vaccines are no longer effective against any diseases
Answer: B. Overuse of antibiotics has led to bacteria developing resistance to these medicines
Excessive and improper antibiotic use allows bacteria to develop genetic mutations that make them resistant to the drugs, making infections harder to treat.
Excessive and improper antibiotic use allows bacteria to develop genetic mutations that make them resistant to the drugs, making infections harder to treat.
Compare the structures of bacteria and fungi. Which statement is accurate?
- A. Both bacteria and fungi are unicellular with a nucleus
- B. Bacteria lack a nucleus while fungi can be unicellular or multicellular with a nucleus
- C. Fungi are prokaryotic; bacteria are eukaryotic
- D. Both have identical cell structures and reproduce the same way
Answer: B. Bacteria lack a nucleus while fungi can be unicellular or multicellular with a nucleus
Bacteria are prokaryotic (no nucleus), while fungi are eukaryotic (with nucleus); fungi can be single-celled like yeast or multicellular like mushrooms.
Bacteria are prokaryotic (no nucleus), while fungi are eukaryotic (with nucleus); fungi can be single-celled like yeast or multicellular like mushrooms.
In a competitive exam scenario: Which combination correctly matches microorganism type, example, and characteristic?
- A. Bacteria - Yeast - Eukaryotic with nucleus
- B. Fungi - Streptococcus - Prokaryotic without nucleus
- C. Bacteria - E. coli - Prokaryotic without nucleus
- D. Fungi - Tuberculosis bacillus - Pathogenic unicellular organism
Answer: C. Bacteria - E. coli - Prokaryotic without nucleus
E. coli is a bacterium, which is prokaryotic without a nucleus. Yeast is a fungus (not bacteria), and Streptococcus is bacteria (not fungi), making only option C correct.
E. coli is a bacterium, which is prokaryotic without a nucleus. Yeast is a fungus (not bacteria), and Streptococcus is bacteria (not fungi), making only option C correct.
Which scenario best illustrates the principle of pasteurization and why it's preferred over sterilization in food industries?
- A. Pasteurization completely removes all bacteria, making food last indefinitely
- B. Pasteurization reduces harmful microorganisms while preserving taste, nutritional value, and beneficial bacteria; sterilization often damages food quality
- C. Sterilization is cheaper and faster than pasteurization for treating milk
- D. Pasteurization and sterilization are equally effective with no difference in application
Answer: B. Pasteurization reduces harmful microorganisms while preserving taste, nutritional value, and beneficial bacteria; sterilization often damages food quality
Pasteurization balances food safety with quality by reducing pathogens while maintaining nutritional content and flavor, whereas sterilization's extreme heat can degrade food quality.
Pasteurization balances food safety with quality by reducing pathogens while maintaining nutritional content and flavor, whereas sterilization's extreme heat can degrade food quality.