All Free Biology MCQs with Answers

2511. Chrysophytes, Euglenoids, Dinoflagellates and Slime moulds are included in the Kingdom:

• A. Fungi
• B. Animalia
• C. Monera
• D. Protista

Explanation: Certainly, let me explain the classification of these microorganisms:1. **Fungi**: None of the mentioned organisms belong to the Fungi kingdom. Fungi are a separate kingdom that includes organisms like mushrooms, yeasts, and molds. They are characterized by their cell walls made of chitin and their mode of nutrition, which is typically absorptive.2. **Animalia**: Chrysophytes, Euglenoids, Dinoflagellates, and Slime molds are not part of the Animalia kingdom. Animals are multicellular, heterotrophic organisms that exhibit a wide range of characteristics, including the ability to move and a lack of cell walls.3. **Monera**: The Monera kingdom, which is now considered obsolete, included unicellular prokaryotic organisms like bacteria. The organisms you mentioned are eukaryotic and thus do not fall under the Monera category.4. **Protista**: The Protista kingdom is where you'll find Chrysophytes, Euglenoids, Dinoflagellates, and Slime molds. These are all eukaryotic microorganisms that don't fit neatly into the categories of animals, plants, or fungi. Protists are a diverse group, and they can be unicellular or multicellular, photosynthetic or heterotrophic. This kingdom is often considered a "catch-all" for eukaryotes that don't fit elsewhere in the classification system.So, the correct answer is **Protista** for Chrysophytes, Euglenoids, Dinoflagellates, and Slime molds.

2512. The imperfect fungi which are decomposers of litter and help in mineral cycling belong to:

• A. Phycomycetes
• B. Ascomycetes
• C. Deuteromycetes
• D. Basidiomycetes

Explanation: Imperfect fungi that are decomposers of litter and play a role in mineral cycling can belong to various fungal groups. Let me explain each of the options you provided:1. **Phycomycetes:** - Phycomycetes are commonly referred to as water molds and belong to the phylum Zygomycota.While some Zygomycetes are parasitic, many can act as saprophytes, decomposing dead organic matter, including litter, and participating in mineral cycling.2. **Ascomycetes:** - Ascomycetes are a diverse group of fungi that include the morels, truffles, and yeast, among others. Some ascomycetes, such as those in the genus Penicillium, are well-known decomposers of organic material and play a significant role in breaking down litter and recycling nutrients.3. **Deuteromycete (anamorphic fungi):** - Deuteromycetes, also known as fungi imperfecti, are fungi that do not have a known sexual reproductive stage and have been classified based on their asexual structures. Some deuteromycetes are decomposers and can contribute to the decomposition of litter, although their classification is based on the absence of a sexual reproductive cycle.4. **Basidiomycetes:** - Basidiomycetes are a diverse group that includes mushrooms, toadstools, and bracket fungi. Many basidiomycetes are involved in the decomposition of organic matter, particularly in forest ecosystems. They help break down litter and recycle nutrients.It's important to note that while these groups may contain species with decomposer roles, the specific ecological functions of fungi can vary within each group, and they are not limited to a single ecological niche. Fungi play a crucial role in nutrient cycling and decomposition processes in various ecosystems.

2513. In which group of organisms the cell walls form two thin overlapping shells which fit together?

• A. Dinoflagellates
• B. Slime moulds
• C. Chrysophytes
• D. Euglenoids

Explanation: Dinoflagellates:Dinoflagellates are a group of protists, specifically algae. They are unicellular organisms.The cell walls of dinoflagellates are made of cellulose plates, which can form two thin overlapping shells. These plates fit together, creating a protective armor-like structure around the cell. Slime Moulds:Slime molds are not known for having cell walls with two thin overlapping shells that fit together.Slime molds are unique organisms that can exist as both single-celled amoeboid forms and multicellular plasmodial forms, but their cell walls do not exhibit the specific structure mentioned. Chrysophytes:Chrysophytes are a group of algae, and they typically have cell walls made of silica scales.These silica scales can overlap but are not as well-known for forming two thin shells that fit together like the description in the question. Euglenoids:Euglenoids are a group of unicellular protists.They have flexible cell walls made of protein strips beneath the cell membrane. These protein strips do not form two thin overlapping shells that fit together.In summary, among the options given, the group of organisms where cell walls form two thin overlapping shells that fit together is Dinoflagellates.

2514. Pick up the wrong statement.

• A. Some fungi are edible.
• B. Nuclear membrane is present in Monera.
• C. Cell wall is absent in Animalia.
• D. Protists have photosynthetic and heterotrophic modes of nutrition.

Explanation: The wrong statement is:2. Nuclear membrane is present in Monera.Explanation for each statement:1. Some fungi are edible: This statement is correct. Many fungi are edible, and they are commonly consumed by humans in various culinary dishes.2. Nuclear membrane is present in Monera: This statement is incorrect. Monera is an outdated biological kingdom that included prokaryotic organisms such as bacteria. These organisms do not have a true nucleus with a nuclear membrane. The correct term for organisms with a nuclear membrane is "Eukaryota."3. Cell wall is absent in Animalia: This statement is correct. Animalia is a kingdom of organisms, and one of the defining characteristics of animals is the absence of a cell wall. Animals have cell membranes but lack the rigid cell walls found in organisms like plants and fungi.4. Protists have photosynthetic and heterotrophic modes of nutrition: This statement is correct. Protists are a diverse group of eukaryotic microorganisms, and they can exhibit various modes of nutrition. Some protists are photosynthetic, like algae, while others are heterotrophic, meaning they obtain nutrients by consuming other organisms or organic matter. Some protists can even switch between these modes depending on environmental conditions.Kingdom Monera consists of prokaryotic organisms, characterised by absence of nuclear envelope around nucleus and absence of membranebound cell organelles.

2515. Choose the wrong statement.

• A. Morels and truffles are poisonous mushrooms.
• B. Yeast is unicellular and useful in fermentation.
• C. Penicillium is multicellular and produces antibiotics.
• D. Neurospora is used in the study of biochemical genetics.

Explanation: The wrong statement is: "Morels and truffles are poisonous mushrooms."Explanation of each statement:1. Morels and truffles are poisonous mushrooms. - This statement is incorrect. Morels and truffles are not poisonous mushrooms. In fact, they are highly prized and sought after in the culinary world for their unique flavors and aromas.2. Yeast is unicellular and useful in fermentation. - This statement is correct. Yeast is a type of fungus that is unicellular and is commonly used in the fermentation process for making bread, beer, and other fermented products.3. Penicillium is multicellular and produces antibiotics. - This statement is correct. Penicillium is a genus of fungi, and it is typically multicellular. However, it is famous for producing antibiotics, particularly penicillin, which was a groundbreaking discovery in the field of medicine.4. Neurospora is used in the study of biochemical genetics. - This statement is correct. Neurospora is a genus of fungi that has been extensively used in genetic research, particularly in the study of biochemical genetics. It has played a significant role in advancing our understanding of gene function and regulation.

2516. True nucleus is present in:

• A. Vaucheria
• B. Volvox
• C. Anabaena
• D. Mucor

Explanation: True nucleus is absent in Vaucheria, Anabaena, and Mucor. 1. Vaucheria: Vaucheria is a multicellular green alga belonging to the class Xanthophyceae. It lacks a true nucleus because it has a unique type of nucleus known as a coenocytic nucleus. In coenocytic organisms, the nuclear material is not enclosed within a membrane-bound nucleus.2. Anabaena: Anabaena is a genus of filamentous cyanobacteria (blue-green algae) that also lacks a true nucleus. Like many prokaryotes, cyanobacteria have a nucleoid region where their genetic material is located, but it is not enclosed within a membrane-bound nucleus.3. Mucor: Mucor is a genus of fungi, and like other fungi, it lacks a true nucleus. Fungi have a different type of nucleus compared to eukaryotic cells, known as a nucleoid, where the genetic material is not enclosed within a nuclear membrane.Volvox, on the other hand, is a green alga that possesses a true nucleus. It belongs to the Chlorophyta group of green algae, which are eukaryotic organisms with well-defined, membrane-bound nuclei.In summary, the absence of a true nucleus is a characteristic of coenocytic algae (Vaucheria), prokaryotic organisms (Anabaena), and fungi (Mucor), while organisms like Volvox have true nuclei enclosed within nuclear membranes.

2517. Five kingdom system of classification suggested by R.H. Whittaker is not based on:

• A. Presence or absence of a well defined nucleus
• B. Mode of reproduction
• C. Mode of nutrition
• D. Complexity of body organisation

Explanation: R.H. Whittaker considered complexity of cell structure and structural (body) organisation, mode of nutrition, ecological life style and phylogenetic relationships for the five kingdom system of classification.

2518. Which of the following shows coiled RNA strand and capsomeres?

• A. Polio virus
• B. Tobacco mosaic virus
• C. Measles virus
• D. Retrovirus

Explanation: So, in this context, the Tobacco Mosaic Virus fits the description you provided.Tobacco mosaic virus is a RNA virus that causes tobacco mosaic disease. It has single stranded coiled RNA molecule as its genetic material a part of which hangs outside the protein coat. Protein coat consists of approximately 2130 capsomeres which are helically arranged to form a hollow cylinder of about 4 nm diameter.

2519. Viruses have

• A. DNA enclosed in a protein coat
• B. Prokaryotic nucleus
• C. Single chromosome
• D. Both DNA and RNA.

Explanation: Sure, I can explain each of these options:1. **DNA enclosed in a protein coat**: - This describes the structure of many viruses. Viruses are genetic entities that can contain either DNA or RNA as their genetic material. This genetic material is enclosed in a protein coat called a capsid. Some viruses also have an outer lipid envelope derived from the host cell's membrane.2. **Prokaryotic nucleus**: - Viruses do not have a nucleus, and they are not classified as prokaryotic or eukaryotic because they are not considered living organisms. Instead, they are considered obligate intracellular parasites, relying on host cells to replicate.3. **Single chromosome**: - Viruses typically have a single chromosome (either DNA or RNA), which carries the genetic information necessary for their replication. However, the term "chromosome" is more commonly associated with the genetic material found in living cells rather than viruses.4. **Both DNA and RNA**: - Some viruses have DNA as their genetic material (DNA viruses), while others have RNA as their genetic material (RNA viruses). They do not contain both DNA and RNA simultaneously. The choice of DNA or RNA depends on the specific type of virus.So, the most accurate statement about viruses is that they contain genetic material (either DNA or RNA) enclosed in a protein coat, and they lack a prokaryotic or eukaryotic nucleus.Viruses are nucleoprotein entities which are able to utilize synthetic machinery of a living cell of the host organism for its multiplication which does not involve growth and division. They have either RNA or DNA as genetic material and a protein coat.

2520. Archaebacteria differ from eubacteria in

• A. Cell membrane structure
• B. Mode of nutrition
• C. Cell shape
• D. Mode of reproduction

Explanation: The archaebacteria are the 'ancient' bacteria that include extremophiles like methanogens, halophiles and thermophiles. They represent some of the most ancient of life forms that persist today. They have both eubacterial and eukaryotic characters besides the features unique to them. Their mode of reproduction, nutrition and cell shape and size resembles a typical eubacteria. Lipids of their cytoplasmic membranes are ether linked unlike eubacteria which contain glycerol ester lipids in their cell membrane.Archaebacteria have unique cell membrane structures that are distinct from the typical phospholipid bilayer found in eubacteria. They often have ether-linked lipids in their cell membranes, whereas eubacteria have ester-linked lipids. This distinction is important because it impacts the stability and function of the cell membrane in different environmental conditions.