Olympiad Test: Microorganisms - 1 - Class 8 MCQ

Microorganisms can be grouped as:

1. Bacteria and fungi


2. Viruses


3. Algae and protozoa


4. All of these

Explanation:
Microorganisms are organisms that are too small to be seen with the naked eye. They play a crucial role in various ecological processes and can be classified into different groups based on their characteristics and features. The given answer, option D, states that microorganisms can be grouped as all of the mentioned categories, which is correct.
Here is a breakdown of the different groups of microorganisms:
1. Bacteria and fungi:
- Bacteria are single-celled microorganisms that have a simple cellular structure. They can be found in various environments and have diverse metabolic capabilities.
- Fungi are eukaryotic microorganisms that include yeasts, molds, and mushrooms. They obtain nutrients by absorbing organic matter from their surroundings.
2. Viruses:
- Viruses are non-living infectious agents that can only replicate inside host cells. They consist of genetic material (DNA or RNA) surrounded by a protein coat and sometimes an outer envelope. Viruses cause a wide range of diseases in plants, animals, and humans.
3. Algae and protozoa:
- Algae are photosynthetic microorganisms that can be found in aquatic environments. They convert sunlight into energy through photosynthesis and play a crucial role in oxygen production and nutrient cycling.
- Protozoa are single-celled eukaryotic microorganisms that are commonly found in water and soil. They are heterotrophic, meaning they obtain nutrients by ingesting other organisms. Protozoa play important roles in nutrient recycling and are also known to cause diseases.
Conclusion:
Microorganisms can be grouped into various categories, including bacteria, fungi, viruses, algae, and protozoa. These groups have distinct characteristics and functions, and they collectively encompass the diverse world of microorganisms.

Explanation:
To determine which micro-organism cannot be classified as either living or non-living, we need to understand the characteristics of each option:
A: Fungi
- Fungi are living micro-organisms.
- They are eukaryotic organisms that obtain nutrients by absorbing them from their surroundings.
B: Viruses
- Viruses are non-living micro-organisms.
- They are composed of genetic material (DNA or RNA) surrounded by a protein coat.
- Viruses require a host cell to reproduce and carry out metabolic processes.
C: Bacteria
- Bacteria are living micro-organisms.
- They are single-celled prokaryotic organisms that can reproduce independently.
D: Protozoa
- Protozoa are living micro-organisms.
- They are eukaryotic organisms that are typically single-celled and can move independently.
Based on the characteristics mentioned above, the micro-organism that cannot be classified as either living or non-living is Viruses (option B). Viruses exhibit some characteristics of living organisms, such as having genetic material, but they lack the ability to carry out essential life processes without a host cell. Therefore, they are considered non-living entities.

The correct answer is A: Virus.
Explanation:
- Fungus: A fungus is a eukaryotic organism that includes yeasts, molds, and mushrooms. Fungi obtain nutrients by absorbing them from their surroundings. They reproduce through spores.
- Virus: A virus is a microscopic infectious agent that replicates only inside the living cells of an organism. Unlike fungi, viruses are not classified as living organisms because they lack the cellular machinery needed for metabolism and reproduction.
- Yeast: Yeasts are single-celled fungi that reproduce asexually by budding. They are commonly used in baking and brewing.
- Mushroom: Mushrooms are the fruiting bodies of certain types of fungi. They typically have a stalk and a cap and are often found in forests or cultivated for culinary purposes.
- Mould: Moulds are a type of fungus that grows in multicellular filaments called hyphae. They reproduce by producing spores and are commonly found in damp environments.
Summary:
In summary, the organism that is not a fungus is a virus.

The answer is C: Algae
Explanation:
Photosynthesis is the process by which organisms convert light energy into chemical energy in the form of glucose. This process occurs in the chloroplasts of cells and requires sunlight, water, and carbon dioxide.
Algae are a diverse group of eukaryotic organisms that can perform photosynthesis. They can be found in various aquatic environments including freshwater, marine, and even damp soil. Algae are capable of producing their own food through photosynthesis and are considered primary producers in many ecosystems.
Key Points:
- Algae make their own food through photosynthesis.
- They are eukaryotic organisms.
- Algae can be found in various aquatic environments.
- They are considered primary producers in many ecosystems.

Sponginess of bread is because of
There are several factors that contribute to the sponginess of bread. However, none of them are related to bread or orange mold. The correct answer is D: None of these.
Some of the main factors that affect the sponginess of bread include:
1. Yeast: Yeast is responsible for the fermentation process in bread making. It produces carbon dioxide gas, which gets trapped in the dough, creating air pockets and giving the bread its spongy texture.
2. Gluten: Gluten is a protein found in wheat flour. When mixed with water, gluten forms a network that gives bread its structure and elasticity. This network traps the carbon dioxide produced by the yeast, resulting in a spongy texture.
3. Leavening agents: Besides yeast, other leavening agents such as baking powder or baking soda can also be used to make bread rise. These agents release carbon dioxide when they react with moisture and heat, contributing to the sponginess of bread.
4. Kneading: The process of kneading bread dough develops gluten and helps distribute the yeast and air bubbles evenly throughout the dough. Proper kneading is essential to achieve the desired sponginess in the final bread.
5. Baking temperature and time: The baking temperature and time play a crucial role in the sponginess of bread. If the bread is underbaked, it may have a dense texture, while overbaking can result in a dry and tough crumb.
In conclusion, the sponginess of bread is primarily influenced by factors such as yeast, gluten, leavening agents, kneading, and baking temperature/time. Mold growth or freshness of the bread does not directly affect its sponginess.

The responsible factors for making bread soft and lighter are:
Sugar and salt:
- Sugar acts as a food source for yeast and helps in fermentation.
- Salt strengthens the gluten structure, which contributes to the bread's texture and rise.
Co₂ gas given off during fermentation of sugar:
- Yeast consumes sugar and releases carbon dioxide gas during fermentation.
- The gas gets trapped in the dough, causing it to rise and create air pockets, making the bread lighter and softer.
Alcohol released during fermentation of sugar:
- Yeast also produces alcohol as a byproduct of fermentation.
- The alcohol evaporates during baking, leaving behind small air pockets, contributing to the bread's lightness.
Finely grounded:
- This is not directly responsible for making bread soft and lighter.
- Finely ground ingredients can help in better distribution and incorporation into the dough, resulting in a more uniform texture.
Overall, the combination of sugar and salt, along with the carbon dioxide gas and alcohol produced during fermentation, contributes to the softness and lightness of bread.

Food Preservation Techniques:
There are various techniques used in food preservation to prevent spoilage and extend the shelf life of food products. Among these techniques, the most commonly used method is the application of heat. Heat treatment helps in killing or inactivating the microorganisms present in the food, thus preventing their growth and the associated spoilage.
The Technique Used in Food Preservation:
The technique used in food preservation is the application of heat to kill or inactivate the microorganisms. This technique can be further explained as follows:
1. Killing the Microbes:
- The application of heat kills the microorganisms by destroying their cellular structure and enzymes.
- High temperatures, such as boiling or pasteurization, are used to kill the microbes.
- This method is effective in preserving food as it eliminates the microorganisms that cause spoilage and foodborne illnesses.
- It is commonly used in canning and pasteurization processes.
2. Making Them Inactive:
- Heat treatment can also make the microorganisms inactive by denaturing their enzymes and proteins.
- This process prevents the microbes from growing and reproducing, thus inhibiting spoilage.
- Lower temperatures, such as refrigeration or freezing, are used to make the microbes inactive.
- This method is commonly used for preserving perishable foods such as meat, dairy products, and fruits.
3. Combination of Killing and Inactivation:
- In many food preservation processes, a combination of killing and inactivation techniques is employed.
- This ensures that both the existing microorganisms are killed, and the remaining ones are made inactive.
- By using a combination of techniques, the shelf life of the preserved food can be significantly extended.
Conclusion:
In food preservation, the technique used involves killing the microbes and making them inactive. The application of heat is the primary method to achieve these objectives. By using high temperatures, microorganisms can be killed, while lower temperatures can make them inactive. These techniques help in preventing spoilage and extending the shelf life of food products.

Introduction: In this question, we are asked to identify the micro-organism that does not have a regular cell structure. Let's analyze each option and determine the correct answer.

Analysis:

A: Viruses:

• Viruses are microscopic infectious agents that are much smaller than cells.


• They do not have a regular cell structure as they lack cellular organelles like nucleus, mitochondria, etc.


• Instead, they consist of genetic material (DNA or RNA) enclosed in a protein coat called a capsid.

B: Bacteria:

• Bacteria are single-celled micro-organisms that have a well-defined cell structure.


• They have a cell wall, cell membrane, cytoplasm, and genetic material in the form of DNA.

C: Protozoa:

• Protozoa are single-celled eukaryotic micro-organisms.


• They have a well-defined cell structure with a cell membrane, nucleus, and other organelles.


• Protozoa can be classified into various groups based on their cell structure and mode of locomotion.

D: Algae:

• Algae are photosynthetic organisms that can be unicellular or multicellular.


• They have a regular cell structure with a cell wall, cell membrane, chloroplasts, and other organelles.

Conclusion:

After analyzing each option, we can conclude that the micro-organism that does not have a regular cell structure is Viruses (Option A).

Explanation:
When observing a drop of greenish pond water under a microscope, several characteristics can be observed. Here is a detailed explanation of each option and why option C, microorganisms, is the correct answer:
1. Option A: Green color creatures
- This option suggests that the greenish pond water contains organisms that are themselves green in color.
- While it is possible for some organisms to appear green, it is not a definitive characteristic of all organisms in the water.
- Therefore, this option is not the correct answer.
2. Option B: Green water color
- This option suggests that the greenish color of the water is the main characteristic observed under the microscope.
- While the water may indeed have a greenish tint, it does not provide information about the specific organisms present.
- Therefore, this option is not the correct answer.
3. Option C: Microorganisms
- This option suggests that the greenish pond water contains microorganisms, which is the most accurate and comprehensive answer.
- Microorganisms are tiny living organisms that can only be seen under a microscope.
- The greenish color of the water is likely due to the presence of algae or other photosynthetic organisms, which are considered microorganisms.
- Therefore, option C is the correct answer.
4. Option D: None of these
- This option suggests that none of the previous options accurately describe the characteristics of the greenish pond water.
- However, since option C accurately describes the presence of microorganisms, this option is not correct.
Overall, when observing a drop of greenish pond water under a microscope, the most accurate description is that it contains microorganisms. These microorganisms may include algae or other photosynthetic organisms, which contribute to the greenish color of the water.

Answer:

The organisms that are found as both unicellular and multicellular are:

• Bacteria: Bacteria can exist as single-celled organisms or form colonies and biofilms, which are multicellular structures.


• Algae: Algae can range from single-celled organisms to large multicellular forms.

However, the organisms listed below are not found as both unicellular and multicellular:

• Viruses: Viruses are not considered to be living organisms and consist of genetic material enclosed in a protein coat. They can only replicate within host cells.


• Moulds: Moulds are multicellular fungi that exist as filamentous structures composed of hyphae. They do not have a unicellular form.

Therefore, the correct answer is b. Algae.