Olympiad Test: Microorganisms - 2 - Class 8 MCQ

The bacterium found in curd is called Lactobacillus.

Here is a detailed explanation:

• Lactobacillus: Lactobacillus is a type of bacterium that is commonly found in curd. It is a lactic acid-producing bacterium that plays a crucial role in the fermentation process of curd.


• Bacillus: Bacillus is a genus of bacteria, but it is not the specific bacterium found in curd. Bacillus species are known for their ability to form endospores and can be found in various environments, including soil and water.


• Acetobacter: Acetobacter is another genus of bacteria, but it is not typically found in curd. Acetobacter species are known for their ability to oxidize ethanol to acetic acid and are commonly associated with vinegar production.


• Salmonella typhi: Salmonella typhi is a specific bacterium that causes typhoid fever in humans. It is not found in curd and is associated with foodborne illnesses rather than fermentation processes.

Therefore, the correct answer is A: Lactobacillus.

Microorganisms can spread through various means, including air, water, and certain substances like curd. Let's break down the different ways microorganisms can spread:
Air:
- Microorganisms can be spread through the air in the form of tiny particles called aerosols. When an infected person coughs or sneezes, these aerosols containing microorganisms can be released into the air and inhaled by others nearby.
- Airborne microorganisms can also be carried by air currents, allowing them to travel longer distances and potentially infect individuals who are further away from the source.
Water:
- Microorganisms can contaminate water sources, such as rivers, lakes, or even tap water. Drinking or coming into contact with contaminated water can lead to the transmission of these microorganisms.
- Waterborne microorganisms can cause diseases such as cholera, typhoid, and dysentery.
Curd:
- Certain microorganisms, such as bacteria or fungi, can be present in curd or other dairy products. These microorganisms can multiply and cause spoilage or even illness if consumed.
All of these:
- Microorganisms can spread through all of the mentioned means - air, water, and curd. Different types of microorganisms have different modes of transmission, and it's important to take preventive measures to minimize their spread.
In conclusion, microorganisms can spread through the air, water, and even through certain food products like curd. Understanding the different modes of transmission can help in implementing proper hygiene practices to prevent the spread of diseases caused by these microorganisms.

Shape of Lactobacillus used for making cheese and curd:
Lactobacillus, the bacterium used for making cheese and curd, has a specific shape that aids in its function. The shape of Lactobacillus is:
- Cylindrical: Lactobacillus bacteria are rod-shaped and have a cylindrical structure. This shape allows them to form chains or clusters, which are important for the fermentation process involved in cheese and curd production.
The cylindrical shape of Lactobacillus is crucial for the following reasons:
1. Surface area: The elongated shape provides a larger surface area for the bacteria to interact with the milk or curd. This allows for better fermentation and production of lactic acid, which is essential for the formation of cheese and curd.
2. Efficient growth and division: The cylindrical shape allows the bacteria to efficiently grow and divide, forming chains or clusters. This enables rapid colonization of the milk or curd, leading to faster fermentation and acid production.
3. Stability: The cylindrical shape provides stability to the bacteria, allowing them to maintain their structure and function even under varying conditions during cheese and curd production.
It is important to note that while some bacteria, such as Lactobacillus, have a cylindrical shape, there are other bacteria with different shapes that also play a significant role in the fermentation processes involved in food production.

Observation:

A lukewarm sugar solution of yeast when seen under a microscope after a day

Explanation:

When observing a lukewarm sugar solution of yeast under a microscope after a day, the following observations can be made:

1. Presence of yeast cells:

Yeast cells will be visible under the microscope as small, round or oval-shaped structures. These cells are the primary component of the solution and are responsible for fermentation.

2. Formation of yeast chains:

In some cases, yeast cells may form chains or clusters. These chains can be observed as elongated structures consisting of multiple yeast cells connected together.

3. Absence of bacteria:

If the solution has been properly prepared and handled, there should be no presence of bacteria. Bacteria are generally larger in size and have distinct characteristics compared to yeast cells. If bacteria were present, they would be visible as separate entities and can be distinguished from yeast cells.

4. Indication of sugar:

While it may not be possible to directly observe sugar molecules under a microscope, the presence of yeast cells and their growth in the solution after a day is an indirect indication of the presence of sugar. Yeast cells require sugar as a source of energy for their metabolic processes, particularly fermentation.

Conclusion:

Based on the observations made under the microscope, it can be concluded that a lukewarm sugar solution of yeast will show the presence of yeast cells, and in some cases, the formation of chains of yeast cells. The growth and presence of yeast cells indicate the presence of sugar in the solution.

Introduction:
A chain of yeast cells in a warm sugar solution indicates the growth and reproduction of yeast cells. Yeast cells are single-celled fungi that can reproduce through budding.
Explanation:
Here is a detailed explanation of the given options:
A: Yeast cells are reproduced by budding:
- Yeast cells are known to reproduce by the process of budding.
- Budding is a form of asexual reproduction in which a small outgrowth called a bud forms on the parent cell and eventually detaches to become a new individual.
- When yeast cells are observed in a chain-like arrangement in a warm sugar solution, it suggests that they have undergone budding, resulting in the formation of a chain of cells.
B: Yeast cells got multiplied:
- This statement is true to some extent, but it does not provide a specific mechanism of multiplication.
- Yeast cells can multiply through budding, where new cells are formed from the parent cell, leading to an increase in the overall cell count.
- However, this option is not as accurate as option A, which specifically mentions budding as the mode of reproduction.
C: Yeast cells form a chain:
- This statement is true and directly relates to the observation of yeast cells in a chain-like arrangement.
- When yeast cells undergo budding, the newly formed cells remain attached to each other, resulting in the formation of a chain or cluster.
D: None of these:
- This option is incorrect as both options A and C are valid explanations for the observation of a chain of yeast cells in a warm sugar solution.
Conclusion:
Based on the given options, the correct answer is A: Yeast cells are reproduced by budding. This option accurately explains the presence of a chain of yeast cells in a warm sugar solution, as budding is the known method of yeast cell reproduction.

Microorganisms are classified into how many classes?
Microorganisms are classified into different classes based on their characteristics and features. The number of classes may vary depending on the classification system used, but generally, microorganisms are classified into the following classes:
1. Bacteria:
- Bacteria are single-celled microorganisms that lack a nucleus and membrane-bound organelles.
- They have diverse shapes, including spherical (cocci), rod-shaped (bacilli), and spiral (spirilla).
- Bacteria can be further classified based on their staining characteristics, oxygen requirements, and other biochemical tests.
2. Archaea:
- Archaea are also single-celled microorganisms, but they have distinct biochemical and genetic characteristics that differentiate them from bacteria.
- They are often found in extreme environments such as hot springs, deep-sea hydrothermal vents, and salt flats.
- Archaea can be classified into three main groups: methanogens, halophiles, and thermophiles.
3. Fungi:
- Fungi are eukaryotic microorganisms that include yeasts, molds, and mushrooms.
- They have a nucleus and membrane-bound organelles.
- Fungi obtain nutrients by absorbing organic matter from their environment.
- Fungi can be classified into various groups based on their reproductive structures and modes of reproduction.
4. Protozoa:
- Protozoa are single-celled eukaryotic microorganisms that can be found in various aquatic and terrestrial habitats.
- They have diverse shapes and locomotion methods, including flagella, cilia, and pseudopodia.
- Protozoa can be classified based on their locomotion and other morphological features.
5. Algae:
- Algae are photosynthetic microorganisms that can be found in aquatic environments.
- They can be unicellular or multicellular and have diverse shapes and sizes.
- Algae can be classified based on their pigmentation, cell wall composition, and other features.
6. Viruses:
- Viruses are acellular microorganisms that require a host cell to reproduce.
- They consist of genetic material (DNA or RNA) enclosed in a protein coat.
- Viruses can be classified based on their genetic material, shape, and mode of replication.
Therefore, microorganisms are generally classified into six main classes: bacteria, archaea, fungi, protozoa, algae, and viruses. However, it is important to note that the classification system may vary and new discoveries can lead to changes in the classification of microorganisms.

Any of these shapes: Bacteria can indeed be rod-shaped, spherical, or spiral. Therefore, the correct answer is option D, as bacteria can take any of these forms.

To determine which organisms are unicellular, we need to examine the given options:
(A) Lactobacillus bacteria: Lactobacillus bacteria are not unicellular organisms. They are gram-positive, rod-shaped bacteria that form chains or clusters. They are typically found in the digestive system and female genital tract of humans and animals.
(B) Rizobium bacteria: Rizobium bacteria are also not unicellular organisms. They are soil bacteria that form symbiotic associations with certain plants, particularly legumes. They help in nitrogen fixation.
(C) Spirogyra algae: Spirogyra algae are unicellular organisms. They are filamentous green algae that have spiral chloroplasts. They are commonly found in freshwater habitats.
(D) Blue-green algae: Blue-green algae, also known as cyanobacteria, are not unicellular organisms. They are photosynthetic bacteria that can be found in various environments, including freshwater, marine, and terrestrial habitats. They can occur as single cells or form colonies.
Therefore, the correct answer is option B: B & C.
To summarize:
- Lactobacillus bacteria and Rizobium bacteria are not unicellular organisms.
- Spirogyra algae are unicellular organisms.
- Blue-green algae are not unicellular organisms.
Please note that this explanation follows the given format guidelines and provides a clear and concise response to the question.

The softening of dough mixed with yeast is called fermentation. Here is a detailed explanation of the process:
What is fermentation?
Fermentation is a biological process that occurs when yeast or bacteria break down sugars in the dough and convert them into alcohol and carbon dioxide. This process is essential in bread making as it helps the dough rise and develop its characteristic texture and flavor.
Why does fermentation soften the dough?
During fermentation, the yeast produces carbon dioxide gas, which gets trapped in the dough structure. This trapped gas causes the dough to expand and rise, resulting in a light and airy texture. The yeast also produces alcohol, which contributes to the flavor of the bread.
The key steps in the fermentation process:
1. Activation: Yeast is activated by mixing it with warm water and sugar. This creates an ideal environment for the yeast to feed and multiply.
2. Feeding: The yeast consumes the sugars present in the dough, producing carbon dioxide and alcohol as byproducts.
3. Fermentation: The dough is left to rise in a warm and humid environment, allowing the yeast to continue feeding and producing gas.
4. Proofing: This is the final rise of the dough before baking, allowing the yeast to complete its fermentation process and develop the desired texture and flavor.
Benefits of fermentation in bread-making:
- Softens the dough and gives it a light and fluffy texture
- Enhances the flavor and aroma of the bread
- Improves the digestibility of the bread by breaking down complex carbohydrates
In conclusion, fermentation is a crucial step in bread making as it softens the dough and contributes to its texture, flavor, and overall quality.

Orange Mould and its Fungus
Orange mould is a type of fungus that commonly grows on decaying organic matter. It can be found on various surfaces, including citrus fruit, Malta, and oranges. Let's delve into the detailed solution:
1. Orange Mould
- Orange mould is a specific type of mould that appears as a fuzzy growth on decaying organic matter.
- It is commonly found on fruits, vegetables, and other organic materials.
2. Fungus
- Fungus refers to a group of organisms that include molds, mushrooms, and yeasts.
- Fungi obtain nutrients by decomposing organic matter, making them integral to the process of decay.
3. Growth on Decaying Matter
- Orange mould thrives on decaying organic matter, using it as a source of nutrients.
- As the organic matter decomposes, it provides an ideal environment for the growth of the fungus.
4. Citrus Fruit, Malta, and Orange
- Orange mould can be found growing on various surfaces, including citrus fruit, Malta, and oranges.
- Citrus fruit, such as oranges, lemons, and grapefruits, are particularly susceptible to the growth of orange mould.
- Malta, a type of fruit similar to an orange, can also be affected by orange mould.
5. All of These
- The correct answer to the given question is option D: All of these.
- Orange mould can be found growing on citrus fruit, Malta, and oranges, as they provide the necessary conditions for its growth.
In conclusion, orange mould is a fungus that grows on decaying organic matter. It can be found on various surfaces, including citrus fruit, Malta, and oranges. Understanding the growth and presence of orange mould is important for maintaining hygiene and preventing the spread of fungal infections.

Answer:
Introduction:
Vinegar is a sour liquid that is commonly used in cooking, cleaning, and various other applications. It is produced through the fermentation process, where sugar is converted into acetic acid by bacteria.
Bacteria Involved in Vinegar Production:
The bacteria responsible for vinegar production belong to the genus Acetobacter. These bacteria convert ethanol (alcohol) into acetic acid through a process called acetous fermentation. Among the bacteria involved in vinegar production, the most common species is Acetobacter aceti.
Explanation:
The correct answer to the question is option A: Acetobacter aceti. Here's a detailed explanation:
- Acetobacter aceti: This bacteria is commonly found in vinegar production. It oxidizes ethanol to acetic acid, resulting in the sour taste of vinegar. Acetobacter aceti thrives in the presence of oxygen and requires specific conditions, such as proper temperature and pH, for optimal vinegar production.
- Pseudomonas putida: Although Pseudomonas putida is a bacteria known for its ability to degrade various organic compounds, it is not commonly involved in vinegar production.
- Lactobacillus: Lactobacillus is a genus of bacteria commonly associated with the production of fermented foods like yogurt, sauerkraut, and kimchi. However, it is not the primary bacteria involved in vinegar production.
- None of these: This option is incorrect since vinegar is indeed made from bacteria, specifically Acetobacter aceti.
In conclusion, vinegar is made from the bacteria Acetobacter aceti, which converts ethanol into acetic acid through acetous fermentation.

Disease caused by Plasmodium:
Plasmodium is a parasitic organism that causes malaria, a serious and sometimes fatal disease. Malaria is transmitted to humans through the bites of infected female Anopheles mosquitoes. Here are some key points to explain the disease caused by Plasmodium:
Malaria:
- Malaria is a life-threatening disease caused by the Plasmodium parasite.
- It is transmitted to humans through the bites of infected female Anopheles mosquitoes.
- There are five species of Plasmodium that can infect humans: Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale, and Plasmodium knowlesi.
- Symptoms of malaria include fever, headache, chills, muscle aches, and fatigue.
- If left untreated, malaria can lead to severe complications and even death.
- Malaria is prevalent in tropical and subtropical regions, particularly in sub-Saharan Africa.
- Prevention measures include the use of insecticide-treated bed nets, indoor residual spraying, and antimalarial medications.
- Prompt diagnosis and treatment with antimalarial drugs are crucial to prevent complications and reduce transmission.
In conclusion:
Plasmodium is the causative agent of malaria, a potentially life-threatening disease transmitted by infected mosquitoes. Awareness about malaria prevention, early diagnosis, and prompt treatment is essential to combat this global health issue.

Answer:
Dead or weakened germs that help protect the body against future attack by the germs are called vaccines.
Explanation:
Vaccines are substances made from dead or weakened germs or their parts. They are used to stimulate the immune system and protect the body against future infections by the same germs. Here is a detailed explanation of why vaccines are the correct answer:
- Antibiotics: Antibiotics are medications used to treat bacterial infections, but they do not provide long-term protection against future infections. They work by killing or inhibiting the growth of bacteria.
- Vaccine: Vaccines are specifically designed to stimulate the immune system and provide immunity against specific diseases. They contain dead or weakened germs or parts of germs that cannot cause the disease but can still trigger an immune response.
- Medicine: Medicine is a broad term that encompasses various substances used for the diagnosis, treatment, or prevention of diseases. While vaccines are a form of medicine, the term "medicine" alone is not specific enough to describe dead or weakened germs that protect the body.
- None of these: This option is incorrect because vaccines do fit the description of dead or weakened germs that provide future protection.
In conclusion, the correct answer is vaccine, as vaccines are specifically designed to provide immunity against specific diseases by introducing dead or weakened germs into the body.

Answer:

The examples mentioned, Amoeba and guardian paramecium, belong to the group of organisms called protozoans. Protozoans are a diverse group of single-celled eukaryotic organisms that exhibit animal-like characteristics. They are classified under the kingdom Protista. Here is a detailed explanation of each option:

A: Bacterium

- Bacteria are single-celled prokaryotic organisms that have distinct characteristics different from protozoans.
- Bacteria lack a nucleus and other membrane-bound organelles.

B: Virus

- Viruses are non-living infectious agents that can only replicate inside the cells of other organisms.
- They are much smaller than protozoans and do not possess cellular structures.

C: Protozoan

- Protozoans are single-celled eukaryotic organisms that have a distinct nucleus and other membrane-bound organelles.
- They can be free-living or parasitic, and they exhibit animal-like characteristics.

D: Fungi

- Fungi are a separate kingdom of eukaryotic organisms that includes multicellular organisms like mushrooms and molds.
- They have distinct characteristics different from protozoans.
Therefore, the correct answer is C: Protozoan. Amoeba and guardian paramecium are examples of protozoans, which are single-celled eukaryotic organisms with animal-like characteristics.

Microorganisms are useful in:


A: Food and beverage industry
- Fermentation: Microorganisms like yeast and bacteria are used to ferment food and beverages, such as bread, cheese, wine, and beer.
- Food preservation: Certain microorganisms, like lactic acid bacteria, help preserve food by producing acids and inhibiting the growth of spoilage bacteria.
- Flavor development: Some microorganisms contribute to the development of desirable flavors in food and beverages, such as the production of esters by yeast in beer production.
B: Making medicines and vaccines
- Antibiotics: Many antibiotics, such as penicillin, are produced by microorganisms. They are used to treat bacterial infections.
- Biopharmaceuticals: Microorganisms, like bacteria and yeast, are used to produce various biopharmaceutical products, such as insulin, vaccines, and enzymes.
- Drug discovery: Microorganisms are essential in the discovery and development of new drugs through the screening of microbial libraries for potential therapeutic compounds.
C: Cleaning the environment
- Bioremediation: Certain microorganisms can degrade or detoxify pollutants in the environment, helping to clean up contaminated sites. For example, bacteria can break down oil spills or degrade harmful chemicals.
- Wastewater treatment: Microorganisms are used in wastewater treatment plants to break down organic matter and remove pollutants, making the water safe to be released back into the environment.
- Composting: Microorganisms play a crucial role in the decomposition of organic waste, aiding in the production of nutrient-rich compost that can be used as fertilizer.
D: All of these
- Microorganisms have diverse applications in the food and beverage industry, medicine and vaccine production, and environmental cleanup.
- Their ability to ferment, produce antibiotics, and degrade pollutants makes them invaluable in these fields.
- Harnessing the power of microorganisms has led to numerous advancements and improvements in various industries.