The World of Microbes
Each subtopic includes About section, revision page link, 10 preview questions, and practice CTAs.
Classification of Microorganisms
SubtopicClassification of Microorganisms under The World of Microbes for Grade 8 CBSE.
Preview questions (no answers)
- 1.
Which of the following is an example of a protozoan?
A.B.C.D. - 2.
To which group does the organism belong?
A.Bacteria
B.Fungi
C.Protozoa
D.Algae
- 3.
Which microbe is known as the 'social' microbe because it often grows in large clusters or colonies?
A.B.C.D.None of these
- 4.
Which of these statements is true about viruses?
A.They are bigger than bacteria
B.They are considered non-living outside a host cell
C.They can be seen with the naked eye
D.They belong to the Algae group
- 5.
Organisms that can only be seen with the help of a microscope are collectively known as:
A.Macro-organisms
B.Microorganisms
C.Multicellular organisms
D.Parasites
- 6.
Which of the following is a filamentous alga that has a spiral-shaped chloroplast?
A.Chlamydomonas
B.Chlorella
C.Spirogyra
D.Amoeba
- 7.
The process by which bacteria divide into two equal daughter cells is called:
A.Budding
B.Fragmentation
C.Binary fission
D.Spore formation
- 8.
If you observe a slide of under a microscope, the brush-like structures producing chains of spores are called:
A.Basidia
B.Conidiophores
C.Sporangiophores
D.Rhizoids
- 9.
Which of the following is a characteristic feature of the microorganism ?
A.It moves by means of cilia and is autotrophic
B.It is a parasitic protozoan that moves by means of a flagellum
C.It is a fungus that causes skin diseases
D.It is a bacterium that fixes nitrogen
- 10.
How do the cells of differ from the cells of a typical bacterium?
A.cells have no cell wall, while bacteria do
B.cells have a nucleus and chloroplasts, while bacteria lack them
C.is prokaryotic and bacteria are eukaryotic
D.has circular DNA and bacteria have linear DNA
Download the worksheet for The World of Microbes - Classification of Microorganisms to practice offline. It includes additional chapter-level practice questions.
Friendly Microorganisms in Food and Industry
SubtopicFriendly Microorganisms in Food and Industry under The World of Microbes for Grade 8 CBSE.
Preview questions (no answers)
- 1.
Which of the following is used in the commercial production of citric acid for soft drinks?
A.B.C.D. - 2.
During the preparation of bread, why does the dough become porous?
A.Due to the evaporation of water
B.Due to the escape of Carbon dioxide bubbles
C.Due to the addition of salt
D.Due to the presence of flour
- 3.
In the nitrogen cycle, which organisms convert nitrogenous waste into nitrogen compounds in the soil?
A.Insects
B.Bacteria and fungi
C.Birds
D.Fish
- 4.
Which of these is used as a source of food because it is rich in proteins and produced using microorganisms?
A.Single Cell Protein (like Spirulina)
B.Sand
C.Coal
D.Petroleum
- 5.
Yeast reproduces rapidly. Which method of reproduction does it typically use?
A.Spore formation
B.Fragmentation
C.Budding
D.Binary fission
- 6.
When microorganisms decompose animal waste in a biogas plant, the gas produced is primarily a mixture of:
A.Oxygen and Nitrogen
B.Methane and Carbon dioxide
C.Hydrogen and Chlorine
D.Helium and Argon
- 7.
What is the main objective of the 'Pulse Polio' program in India?
A.To distribute antibiotics for free to everyone
B.To eradicate polio by vaccinating all children under 5 years
C.To teach children how to see microbes under a microscope
D.To provide high-protein pulses to all households
- 8.
Which of the following describes the 'Probiotic' function of certain friendly bacteria in the human gut?
A.They produce toxins to kill the host cells.
B.They compete with and inhibit the growth of harmful pathogenic bacteria.
C.They help in the digestion of heavy metals.
D.They produce antibodies against viral infections.
- 9.
Identify the organism used in the 'Curing' of tea and tobacco leaves to impart characteristic flavor and aroma.
A.Certain species of bacteria and fungi
B.Only green algae
C.Ferns and mosses
D.Protozoans like Amoeba
- 10.
Why is the use of antibiotics like Penicillin effective against but completely ineffective against a 'Cold' or 'Flu'?
A.The flu virus is much larger than bacteria.
B.Penicillin works by blocking cell wall synthesis; viruses do not have cell walls.
C.Penicillin is digested by the stomach before it can reach the flu virus.
D.Flu viruses produce their own antibiotics.
Download the worksheet for The World of Microbes - Friendly Microorganisms in Food and Industry to practice offline. It includes additional chapter-level practice questions.
Medicinal Use of Microorganisms and Vaccines
SubtopicMedicinal Use of Microorganisms and Vaccines under The World of Microbes for Grade 8 CBSE.
Preview questions (no answers)
- 1.
Which of these is NOT a common antibiotic?
A.Streptomycin
B.Tetracycline
C.Erythromycin
D.Calcium Carbonate
- 2.
Antibiotics are primarily used to treat which type of infection?
A.Bacterial
B.Viral
C.Nutritional
D.Mental
- 3.
Which of these is used for the large-scale production of medicines?
A.Microbes
B.Sand
C.Plastic
D.Paper
- 4.
The protection against diseases through vaccines is called:
A.Immunization
B.Fermentation
C.Nitrogen fixation
D.Pasteurization
- 5.
In the context of vaccines, what does 'attenuated' mean?
A.Highly poisonous
B.Weakened or made less virulent
C.Genetically modified to be bigger
D.Dead and dried
- 6.
Which organization provides global guidelines and support for vaccination campaigns like Polio eradication?
A.WHO (World Health Organization)
B.WTO (World Trade Organization)
C.UNESCO
D.NASA
- 7.
Vaccines help in the production of memory cells. What is the role of these cells?
A.They help the brain remember facts
B.They remember the specific pathogen to launch a quick attack in the future
C.They store energy for the body
D.They help in the repair of broken bones
- 8.
What is the primary role of yeast in the pharmaceutical industry apart from medicine production?
A.To produce carbon dioxide for surgery
B.To serve as a source of Vitamin B complex
C.To act as a microscopic surgical tool
D.To color the medicines green
- 9.
Which of the following is a vital precaution to be taken before starting a course of antibiotics?
A.Antibiotics should be taken only on the advice of a qualified doctor
B.Antibiotics should be taken after every meal, whether needed or not
C.Antibiotics should be taken along with fruit juice only
D.Antibiotics should be taken only when one has a viral fever
- 10.
Antibiotics are ineffective against which of the following?
A.Typhoid
B.Cholera
C.AIDS
D.Anthrax
Download the worksheet for The World of Microbes - Medicinal Use of Microorganisms and Vaccines to practice offline. It includes additional chapter-level practice questions.
Harmful Microorganisms and Disease Causation
SubtopicHarmful Microorganisms and Disease Causation under The World of Microbes for Grade 8 CBSE.
Preview questions (no answers)
- 1.
Food poisoning is caused by eating food contaminated by:
A.Vitamins
B.Minerals
C.Microorganisms
D.Pure water
- 2.
Which of the following is a way to stop the spread of Tuberculosis?
A.Keeping the patient in isolation
B.Drinking pond water
C.Sharing towels with the patient
D.Avoiding vaccination
- 3.
Microbes that cause diseases in humans are also known as:
A.Germs
B.Pollutants
C.Parasites
D.Decomposers
- 4.
What is the main purpose of boiling milk before storing or using it?
A.To increase its volume
B.To kill microorganisms
C.To make it thick
D.To change its flavor
- 5.
Which of the following is NOT a method used for food preservation?
A.Heating
B.Salting
C.Adding water
D.Canning
- 6.
The microorganism responsible for 'Rust of wheat' belongs to which group?
A.Bacteria
B.Fungi
C.Protozoa
D.Algae
- 7.
Which of these diseases has 'Water' as its primary mode of transmission?
A.Tuberculosis
B.Measles
C.Typhoid
D.Chicken Pox
- 8.
Study the transmission pathways shown in the diagram. Path X represents the transmission of a disease like Tuberculosis, while Path Y represents the transmission of a disease like Malaria. Based on the NCERT curriculum, which of the following statements correctly explains the difference in the prevention and management strategies required for these two diseases?
A.Path X diseases can be effectively prevented by using mosquito nets and repellents, while Path Y diseases require the mandatory use of face masks and social distancing.
B.For Path X, isolation of the patient and their belongings is critical because the pathogen is spread through moisture droplets in the air, whereas for Path Y, the focus is on preventing the breeding of the vector in stagnant water.
C.Path X represents diseases that are exclusively non-communicable, while Path Y represents diseases that are caused only by fungi and can be treated with high-dose salt solutions.
D.Consuming boiled drinking water is the primary way to prevent diseases in Path X, whereas Path Y diseases can only be prevented by maintaining high personal hygiene and eating properly cooked food.
- 9.
If we stop the breeding of mosquitoes, which of the following diseases can we primarily prevent?
A.Typhoid and Cholera
B.Malaria and Dengue
C.Tuberculosis and Polio
D.Measles and Chicken Pox
- 10.
Which of the following is a method of preserving amla, raw mangoes, and tamarind?
A.Salting
B.Pasteurization
C.Refrigeration
D.Fermentation
Download the worksheet for The World of Microbes - Harmful Microorganisms and Disease Causation to practice offline. It includes additional chapter-level practice questions.
Food Preservation Techniques
SubtopicFood Preservation Techniques under The World of Microbes for Grade 8 CBSE.
Preview questions (no answers)
- 1.
Why is salt used in the preservation of raw amla?
A.To make it sweet
B.To check microbial growth
C.To increase its moisture
D.To change its color to red
- 2.
Food spoilage can be identified by which of the following?
A.Fresh aroma
B.Bright colors
C.Foul smell
D.Crunchy texture
- 3.
Which of these food items is preserved by adding a layer of oil on top?
A.Juice
B.Pickle
C.Bread
D.Dry fruits
- 4.
Vegetables, fruits, and cooked food are often kept in a refrigerator to ________.
A.Make them taste better
B.Check the growth of microbes
C.Increase the water content
D.Kill all the microbes completely
- 5.
In the preservation of fish, dry salt is used primarily to prevent the growth of:
A.Viruses
B.Bacteria
C.Algae
D.Protozoa
- 6.
How does sudden chilling in the pasteurization process affect the microbes?
A.It provides a better environment for them
B.It helps them to reproduce
C.It prevents the growth of microbes that survived the heat
D.It converts them into useful microbes
- 7.
Which of these processes is essentially 'dehydration' used as a preservation technique?
A.Boiling
B.Sun-drying
C.Freezing
D.Pasteurization
- 8.
In food science, what does 'Commercial Sterility' mean for canned products?
A.The food is free of every single microbe and atom of dirt
B.The food is free of microorganisms capable of growing under normal non-refrigerated storage conditions
C.The food was produced by a commercial company, not at home
D.The food contains small amounts of antibiotics to keep it sterile
- 9.
What is the specific role of 'Sodium metabisulphite' when used in the preservation of fruit juices?
A.It acts as a sweetener
B.It releases sulfur dioxide gas which inhibits yeasts, molds, and bacteria
C.It helps the juice to freeze faster
D.It removes the fiber from the juice
- 10.
Why is it dangerous to thaw frozen meat at room temperature on a kitchen counter for many hours?
A.The interior stays frozen forever
B.The surface temperature reaches the 'Danger Zone', allowing rapid bacterial growth while the center is still frozen
C.The meat loses all its protein through evaporation
D.The meat will turn into a liquid state too quickly
Download the worksheet for The World of Microbes - Food Preservation Techniques to practice offline. It includes additional chapter-level practice questions.
Nitrogen Fixation and the Nitrogen Cycle
SubtopicNitrogen Fixation and the Nitrogen Cycle under The World of Microbes for Grade 8 CBSE.
Preview questions (no answers)
- 1.
Which of these is a part of the nitrogen cycle?
A.Fixation of nitrogen by microbes
B.Melting of ice caps
C.Erosion of soil by wind
D.Burning of fossil fuels
- 2.
Biological nitrogen fixation is carried out by:
A.Humans
B.Chemicals in factories
C.Living organisms like bacteria
D.Solar energy
- 3.
What is the form of nitrogen found in the air?
A.Liquid nitrogen
B.Solid nitrogen
C.Gaseous nitrogen
D.Nitrate crystals
- 4.
Pulses are a great source of protein because they are:
A.Water-loving plants
B.Leguminous plants that fix nitrogen
C.Cereal plants
D.Flowering plants only
- 5.
How do legumes benefit from the bacteria in their root nodules?
A.The bacteria provide the plant with water
B.The bacteria protect the plant from pests
C.The bacteria provide usable nitrogen for plant growth
D.The bacteria produce glucose for the plant
- 6.
Look at the simplified diagram. Which label represents the action of denitrifying bacteria?
A.Label P
B.Label Q
C.Label R
D.Label S
- 7.
Which of these processes describes the conversion of ammonia into nitrites and then into nitrates by soil bacteria?
A.Nitrogen fixation
B.Nitrification
C.Denitrification
D.Ammonification
- 8.
If all the nitrogen-fixing bacteria on Earth were to suddenly go extinct, what would be the most likely long-term consequence for the biosphere?
A.The atmosphere would become 100% nitrogen.
B.Life would eventually cease as the available pool of usable nitrogen would be depleted and not replenished.
C.Plants would evolve to use carbon dioxide as a source of protein.
D.Lightning would increase in frequency to compensate for the lost biological fixation.
- 9.
What is the main reason for the formation of 'nodules' on the roots of leguminous plants?
A.To store excess water for the plant during droughts.
B.To provide a specialized protective housing for Rhizobium bacteria to fix nitrogen.
C.To store the starch produced during photosynthesis.
D.To protect the plant from being eaten by soil-dwelling insects.
- 10.
Which chemical form of nitrogen is most likely to be 'washed away' or 'leached' from the soil into groundwater during heavy rains?
A.Ammonia ()
B.Organic Nitrogen (Proteins)
C.Nitrates ()
D.Atmospheric Nitrogen ()
Download the worksheet for The World of Microbes - Nitrogen Fixation and the Nitrogen Cycle to practice offline. It includes additional chapter-level practice questions.