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All questions of Biological Classification for NEET Exam

The five kingdom classification was proposed by
a)Hutchinson
b)Bentham and Hooker
c)Engler and Prantl
d)Whittaker
Correct answer is 'D'. Can you explain this answer?

Rohit Shah answered
The first major break from the Linnean model came from Thomas Whittaker. In 1969 Whittaker proposed a "five kingdom" system in which three kingdoms were added to the animals and plants: Monera (bacteria), Protista, and Fungi.

Classification given by Bentham and Hooker is
  • a)
    artificial
  • b)
    natural
  • c)
    phylogenetic
  • d)
    numerical.
Correct answer is option 'B'. Can you explain this answer?

Geetika Shah answered
Classification given by Bentham and Hooker is Natural System. Monocots were placed after dicots, closely related families were seperated, gymnosperms were placed between dicots and monocots.

Identify the virus in figure given below
  • a)
    HIV
  • b)
    Retrovirus
  • c)
    Bacteriophage
  • d)
    TMV
Correct answer is option 'C'. Can you explain this answer?

Sarthak Verma answered
A bacteriophage is a type of virus that infects bacteria. In fact, the word "bacteriophage" literally means "bacteria eater," because bacteriophages destroy their host cells. All bacteriophages are composed of a nucleic acid molecule that is surrounded by a protein structure.

Identify from the following, the only taxonomic category that has a real existence.
  • a)
    Phylum
  • b)
    Species
  • c)
    Genus
  • d)
    Kingdom
Correct answer is option 'B'. Can you explain this answer?

Explanation:

Archaebacteria are microorganisms that belong to the domain Archaea. They are prokaryotic organisms, meaning they lack a true nucleus and other membrane-bound organelles that are common in eukaryotic cells. Archaebacteria are known to survive in extreme environmental conditions that would be lethal for most other organisms. This is due to several factors, but the most important one is their rigid cell wall.

Rigid Cell Wall:

Archaebacteria have a unique cell wall composition that is different from that found in other bacteria. Their cell walls are made up of a complex polysaccharide called pseudomurein, which is more resistant to heat, acids, and other harsh environmental conditions than the peptidoglycan found in other bacterial cell walls. This rigid cell wall provides the archaebacteria with a protective barrier that helps them to withstand extreme temperatures, pH levels, and pressures.

Other Factors:

Apart from the rigid cell wall, there are several other factors that contribute to the ability of archaebacteria to survive in extreme environments. These include:

1. Unique metabolic pathways: Archaebacteria have evolved unique metabolic pathways that allow them to extract energy and nutrients from the environment in which they live. These pathways allow them to survive in environments that would be toxic to other organisms.

2. Resistance to radiation: Some archaebacteria are known to be resistant to high levels of radiation, which allows them to survive in environments such as hot springs and deep-sea hydrothermal vents.

3. Adaptability: Archaebacteria are highly adaptable and can adjust their metabolism and other cellular processes in response to changes in their environment. This allows them to survive and thrive in a wide range of conditions.

Conclusion:

In conclusion, archaebacteria can survive in extreme conditions because of their unique cell wall composition, as well as other factors such as their metabolic pathways, radiation resistance, and adaptability. Their ability to survive in extreme environments makes them important models for studying the origin and evolution of life on Earth.

Which is the possible region of respiration in bacteria
  • a)
    Mitochondria
  • b)
    Cell wall
  • c)
    Nucleoid
  • d)
    Mesosome
Correct answer is option 'D'. Can you explain this answer?

Anjana Sharma answered
Mesosomes or chondrioids are folded invaginations in the plasma membrane of bacteria that are produced by the chemical fixation techniques used to prepare samples for electron microscopy.
Bacteria have a cell wall, a simple nuclear body without a nuclear membrane, ribosomes and mesosomes in the cytoplasm, and sometimes granules of reserve material, but no endoplasmic reticulum or organelles such as mitochondria or chloroplasts. 

All eukaryotic unicellular organisms belong to
  • a)
    Monera
  • b)
    Fungi 
  • c)
    Protista
  • d)
    Bacteria
Correct answer is option 'C'. Can you explain this answer?

Monera are unicellular and prokaryotic , fungi are multicellular and eukaryotic then bacteria is taken under Monera . and protista are unicellular eukaryotic..

In five kingdom of classification, Whittaker assigned eukaryotes to
  • a)
    Only two of five kingdoms
  • b)
    All five kingdoms
  • c)
    Only three of five kingdoms
  • d)
    Only four of five kingdoms
Correct answer is option 'D'. Can you explain this answer?

Krishna Iyer answered
  • In Whittaker’s five kingdom of classification, kingdom protista, kingdom fungi, kingdom plantae and kingdom animalia are eukaryotic organisms.
  • The kingdom monera includes prokaryotic organisms.

Can you explain the answer of this question below:
All prokaryotic, unicellular organisms are included under kingdom
A:Fungi
B:Monera
C:Protista
D:Animalia
The answer is b.

Krishna Iyer answered
  • Monera is a kingdom that contains unicellular organisms with a prokaryotic (is a unicellular organism that lacks a membrane- bound nucleus, mitocondria, or any other membrane- bound organelle.) cell organization, like bacteria.
  • They are single- celled organisms with no true nuclear membrane. The taxon Monera was first proposed as a phylum by Ernst Haeckel in 1866. 

Which one is important in nutrient recycle and act as decomposer and mineralisers of the biosphere?
  • a)
    Bacteria:- Chemosynthetic autotrophic bacteria
    Fungi:- ascomycetes, Phycomycetes
  • b)
    Bacteria:- Photosynthetic autotrophic bacteria
    Fungi:- Basidiomycetes, deuteromycetes
  • c)
    Bacteria:- Heterotrophic bacteria
    Fungi:- Phycomycetes, Basidiomycetes
  • d)
    Bacteria:- Heterotrophic bacteria
    Fungi:- ascomycetes, deuteromycetes
Correct answer is option 'C'. Can you explain this answer?

Rajeev Saxena answered
Heterotrophic bacteria are most abundant in nature. The majority are important decomposers.
Commonly known as sac-fungi, the ascomycetes are mostly multicellular, e.g., Penicillium, or rarelyunicellular, e.g., yeast (Saccharomyces). They are saprophytic, decomposers, parasitic or coprophilous (growing on dung).
Some members of deuteromycetes are saprophytes or parasites while a large number of them are decomposers of litter and help in mineral cycling. Some examples are Alternaria, Colletotrichum and Trichoderma.

In which class of fungi the mushroom belongs to?
  • a)
    Ascomycetes
  • b)
    Basidiomycetes
  • c)
    Deuteromycetes
  • d)
    Phycomycetes
Correct answer is option 'B'. Can you explain this answer?

Rahul Bansal answered
  • Mushrooms are the commonly known form of Basidiomycetes, called bracket fungi or puffballs.
  • They grow in soil, on logs and tree stumps and in living plant bodies as parasites, e.g., rusts and smuts.

Hence, the correct option is B
NCERT Reference: Topic Basidiomycetes” of chapter "Biological Classification" of NCERT.

Causes of water bloom is :-
  • a)
    Green algae
  • b)
    Blue green algae
  • c)
    Bacteria
  • d)
    Hydrilla
Correct answer is option 'B'. Can you explain this answer?

These are a result of blue-green algae, which are actually bacteria (cyanobacteria). Some algal blooms are the result of an excess of nutrients (particularly phosphorus and nitrogen) in waters and higher concentrations of these nutrients in water cause increased growth of algae and green plants.

Halophiles, methanogens and thermoacidophils are
  • a)
    Cyanobacteria
  • b)
    Eubacteria
  • c)
    Actinomycetes
  • d)
    Archaebacteria
Correct answer is 'D'. Can you explain this answer?

Lavanya Menon answered
Methanogens , Halophiles , Thermoacidophils , all belong to ARCHAEBACTERIA. They are primitive organisms which means they were the first to inhabit earth . They are often called LIVING FOSSILS. Methanogens are found in Rumen of cattles , Halophiles are found in salt lakes , Thermoacidophils are found in hot sulphur springs and Archaebacteria are found in some of the harsh climatic conditions where no other life form could survive.

The cell wall of fungi consist of
  • a)
    Cellulose
  • b)
    Chitin
  • c)
    Glycopeptides
  • d)
    Starch
Correct answer is option 'B'. Can you explain this answer?

Om Desai answered
  • Chitin is a long-chain N-acetylglucosamine polymer and is a glucose derivative.
  • This polysaccharide is a primary component of cell walls in the fungi, arthropod exoskeletons such as crustaceans and insects, mollusc's radula, cephalopod beaks, and fish.
  • The cell wall of plants are made up of cellulose.

The asexual reproduction in fungi takes place by
  • a)
    endospore
  • b)
    gametangia
  • c)
    exospores
  • d)
    conidiospore
Correct answer is option 'D'. Can you explain this answer?

Prisha Bajaj answered
Asexual Reproduction in Fungi by Conidiophores:

Asexual reproduction is a type of reproduction in which offspring arise from a single organism, and inherit the genes of that parent only. Fungi reproduce both sexually and asexually. Asexual reproduction in fungi takes place through conidiophores.

Conidiophores:

Conidiophores are specialized structures that produce conidia or conidiospores. These are asexually produced spores that develop on the surface of the conidiophore. Conidiophores are produced by many different types of fungi, including both molds and yeasts.

How Conidiophores work:

Conidiophores are produced by the mycelium of the fungus. They are typically found in clusters, and can grow to be several millimeters in length. The conidiophore is composed of several cells, including a basal cell, a stalk cell, and a terminal cell. The terminal cell is where the conidia are produced.

The conidia are formed by a process called conidiation. This process involves the development of a small bud on the surface of the terminal cell. As the bud grows, it becomes surrounded by a protective layer of cells, which eventually break apart to release the conidiospore.

Advantages of Asexual Reproduction:

Asexual reproduction has several advantages for fungi. First, it allows for rapid reproduction, since no mating is required. This is particularly important in environments where conditions are favorable for growth, but may not be stable over a long period of time.

Second, asexual reproduction allows for the production of large numbers of offspring that are genetically identical to the parent. This can be advantageous in environments where the parent organism is well adapted to the local conditions, since the offspring will also be well adapted.

Third, asexual reproduction allows for the spread of fungi over long distances, since the conidia can be carried by wind or other means.

Conclusion:

In conclusion, the asexual reproduction in fungi takes place by conidiophores. These specialized structures produce conidia or conidiospores, which are asexually produced spores that develop on the surface of the conidiophore. This type of reproduction has several advantages for fungi, including rapid reproduction, large numbers of offspring, and the ability to spread over long distances.

Photosynthetic prokaryotic organism is:-
  • a)
    Rhizobium
  • b)
    Nostoc
  • c)
    Pseudomonas
  • d)
    Staphylococcus
Correct answer is option 'B'. Can you explain this answer?

Raghav Bansal answered
Nostoc, is genus of blue-green algae with cells arranged in beadlike chains that are grouped together in a gelatinous mass. Like most blue-green algae,Nostoc contains two pigments, blue phycocyanin and red phycoerythrin, as well as chlorophyll, and has the ability to fix nitrogen in specialized cells called heterocysts. This makes them photosynthetic.

Most common method of reproduction in prokaryotes :-
  • a) 
    Budding
  • b) 
    Binary fission
  • c) 
    Transduction
  • d) 
    Conjugation
Correct answer is option 'B'. Can you explain this answer?

Sushil Kumar answered
Binary fission ("division in half") is a kind of asexual reproduction. It is the most common form of reproduction in prokaryotes such as bacteria. It occurs in some single-celled Eukaryotes like the Amoeba and the Paramoecium. In binary fission, DNA replication and segregation occur simultaneously.

Which system of classification was developed during Linnaeus time?
  • a)
    Five kingdom of classification
  • b)
    Three kingdom of classification
  • c)
    Four kingdom of classificaition
  • d)
    Two kingdom of classification
Correct answer is option 'D'. Can you explain this answer?

Dipika Das answered
In Linnaeus' time a TwoKingdomsystem of classification with Plantaeand Animaliakingdoms was developed that included all plants and animals respectively. This system was used till very recently.

HIV attack :-
  • a)
    Epithelial cell
  • b)
    Sex cell  germinal cells
  • c)
    B - lymphocytes
  • d)
    T4 - lymphocytes
Correct answer is option 'D'. Can you explain this answer?

Hitakshi Tamta answered
HIV attack and destroy T4 - lymphocytes also known as CD4 cells, are white blood cells that fight infection and play an important role in your immune system. If too many CD4 cells are lost, your immune system will have trouble fighting off infections. Even a minor infection such as cold can be much more severe because the body has difficulty responding to new infections.

The primitive prokaryotes responsible for the production of biogas from the dung of ruminant animals, include the 
  • a)
    thermoacidophiles
  • b)
    methanogens
  • c)
    eubacteria
  • d)
    halophiles
Correct answer is option 'B'. Can you explain this answer?

Mulinti Omkr answered
Thermoacidophiles are the bacteria that survives in hot springs because of branched chain lipids in the cell membranes
the primitive prokaryotes responsible for the production of biogas from the dung of ruminant animals include the methanogens
halophiles are the bacteria that can live in the saline habitats

Mumps are caused by :-
  • a)
    Bacteria
  • b)
    Virus
  • c)
    Rhizopus
  • d)
    Animals
Correct answer is option 'B'. Can you explain this answer?

Rajeev Saxena answered
Mumps
 is a contagious disease 
caused
 by a virus that passes from one person to another through saliva, nasal secretions, and close personal contact. The condition primarily affects the salivary glands, also called the parotid glands. These glands are responsible for producing saliva.

Which of the following organisms have been placed under kingdom Protista?
  • a)
    Chrysophytes and dinoflagellates
  • b)
    Euglenoids
  • c)
    Slime moulds and protozoans
  • d)
    All of these
Correct answer is option 'D'. Can you explain this answer?

Mira Joshi answered
The kingdom protista has been  broadly divided into three main groups:
(i) Photosynthetic Protists (Protistan Algae) e.g., Dinoflagellates, Chrysophytes and Euglenoids
(ii) Consumer-Decomposer Protists(Slime Moulds)
(iii) Protozoan Protists
Euglenoids are Euglena like unicellular glagellates which posess pellicle instead of cell wall. Chrysophytes include diatoms and desmids. They  belong to the division Chrysophyta/Bacillariophyta. The dinoflagellates belong to division Pyrrophyta and class Dinophyceae. Slime moulds possess the characters of both animals and fungi and , therefore they are commonly called fungus-animals.

Arranging organism on the basis of their shared similar or derived characters that differ from ancestral character is called
a)Homogram
b)Monogram
c)Histogram
d)Cladogram
Correct answer is 'D'. Can you explain this answer?

Rajat Kapoor answered
Arranging organisms on the basis of their shared similar or derived characters that differ from ancestral characters, will produce a phylogenetic tree called cladogram. Depending upon the type of system of classification, organisms are classified into two kingdoms or three kingdoms, four kingdoms, five kingdoms and now into six kingdoms.

Coenocytic means _______
  • a)
    sharing of common cytoplasm
  • b)
    removal of plasma membrane
  • c)
    sharing of common nucleus
  • d)
    sharing of common hyphael wall
Correct answer is option 'A'. Can you explain this answer?

Srestha Bose answered
Coenocytic means sharing of common cytoplasm. This term is commonly used to describe a type of cell or organism that does not have distinct cell boundaries or compartments. Instead, coenocytic cells contain multiple nuclei within a single, continuous cytoplasmic mass.

Explanation:
Coenocytic cells are typically found in fungi, algae, and some types of plants. In these organisms, individual cells may fuse together during development to form a single, multinucleate cell. This single cell may then develop into a larger structure or organism, such as a fungus or alga.

Some key characteristics of coenocytic cells include:

- Lack of cell walls: Coenocytic cells do not have distinct cell walls separating them from neighboring cells. Instead, they are connected by a network of cytoplasmic strands.
- Multiple nuclei: Because coenocytic cells contain multiple nuclei within a single cytoplasmic mass, they are often referred to as multinucleate.
- Large size: Without the constraints of cell walls, coenocytic cells can grow to very large sizes. Some fungi, for example, can form structures that are many meters in length.

Overall, the term "coenocytic" refers to a unique type of cell organization that is characterized by the sharing of cytoplasmic material between multiple nuclei.

Nitrogen fixation in legume roots is performed by:
  • a)
    Autotrophic bacteria
  • b)
    Heterotrophic bacteria
  • c)
    Viruses
  • d)
    Protozoa
Correct answer is option 'E'. Can you explain this answer?

Nitrogen Fixation in Legume Roots
Nitrogen fixation is a crucial biological process that converts atmospheric nitrogen (N2) into ammonia (NH3), a form usable by plants. In legumes, this process primarily occurs in symbiotic relationships with specific bacteria.
Key Players in Nitrogen Fixation:
- Rhizobium Bacteria: The primary bacteria involved in nitrogen fixation in legume roots are from the genus Rhizobium. These are heterotrophic bacteria that thrive in the root nodules of legumes.
- Symbiotic Relationship: Legumes, such as peas, beans, and lentils, form nodules on their roots where these bacteria reside. The plant provides carbohydrates and a suitable environment for the bacteria, while the bacteria convert nitrogen gas from the atmosphere into ammonia.
- Mutual Benefits: This mutualistic relationship benefits both partners. The bacteria gain nutrients and a habitat, while legumes receive essential nitrogen, which is vital for their growth and development.
Process of Nitrogen Fixation:
- Root Nodule Formation: When legumes are exposed to Rhizobium, the bacteria invade the root hairs, leading to nodule formation.
- Nitrogen Conversion: Within these nodules, the Rhizobium bacteria utilize the enzyme nitrogenase to convert atmospheric nitrogen into ammonia, which the plant can then assimilate.
- Impact on Soil Fertility: This process not only supports the growth of legumes but also enhances soil fertility, benefiting subsequent crops planted in the same soil.
Conclusion:
In summary, nitrogen fixation in legume roots is primarily performed by heterotrophic bacteria, specifically Rhizobium, establishing a vital symbiotic relationship that plays a significant role in agriculture and ecosystem health.

TMV contains :-
a. Single stranded RNA
b. ds-RNA
c. ds-DNA
d. ss-DNA
Correct answer is option 'A'. Can you explain this answer?

Rajeev Saxena answered
Tobacco mosaic virus (TMV) is a positive-sense single stranded RNA virus, genus tobamovirus that infects a wide range of plants, especially tobacco and other members of the family Solanaceae. The infection causes characteristic patterns, such as "mosaic"-like mottling and discoloration on the leaves (hence the name).

The protein coat of the virus is called :-
  • a)
    Capsule
  • b)
    Pellicle
  • c)
    Capsid
  • d)
    Prion
Correct answer is option 'C'. Can you explain this answer?

Anjali Iyer answered
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic material of the virus.

A distinction between unicellular and multicellular is not possible in case of
  • a)
    Algae
  • b)
    Plantae
  • c)
    Protozoa
  • d)
    Animalia
Correct answer is option 'A'. Can you explain this answer?

Roshni Basak answered
Unicellular vs Multicellular

Unicellular organisms are those that are composed of a single cell, while multicellular organisms are those that are made up of multiple cells.

Algae

Algae are a diverse group of aquatic organisms that can be found in a variety of environments, from freshwater to saltwater. They can be either unicellular or multicellular, depending on the species.

Plantae

Plants, which belong to the kingdom Plantae, are multicellular organisms that are capable of photosynthesis. They are made up of a variety of specialized cells that work together to carry out the functions necessary for growth and survival.

Protozoa

Protozoa are a group of unicellular eukaryotic organisms that are found in a variety of environments, including water, soil, and the digestive tracts of animals. They are capable of a wide range of metabolic activities, including photosynthesis, and are an important part of many ecosystems.

Animalia

Animals, which belong to the kingdom Animalia, are multicellular organisms that are capable of movement and are characterized by a wide range of specialized tissues and organs. They are found in a variety of environments, from the depths of the ocean to the highest mountains.

Why is the answer A?

The answer to this question is A because algae can be either unicellular or multicellular. Some species of algae, such as Chlamydomonas, are unicellular, while others, such as kelp, are multicellular. Therefore, it is not possible to make a clear distinction between unicellular and multicellular when it comes to algae.

Which of the following is incorrect about Cyanobacteria?
  • a)
    They are photoautotrophs
  • b)
    They lack heterocysts
  • c)
    They often form blooms in polluted water bodies
  • d)
    They have chlorophyll similar to green plants
Correct answer is option 'B'. Can you explain this answer?

Lead Academy answered
Cyanobacteria are indeed photoautotrophs, meaning they can perform photosynthesis to produce their own food using light energy.
While some Cyanobacteria lack heterocysts, others have specialized cells called heterocysts that are involved in nitrogen fixation.
Cyanobacteria often form blooms in polluted water bodies. These blooms can occur when excess nutrients like phosphorus and nitrogen are present, leading to rapid Cyanobacteria growth.
Cyanobacteria have chlorophyll, like green plants, but it is not precisely the same as the chlorophyll found in green plants. They have chlorophyll a, which is similar to the chlorophyll found in higher plants, but they also have other pigments, such as phycocyanin and phycoerythrin, which can give them a bluish-green or red color.
So, the statement that Cyanobacteria have chlorophyll similar to green plants is incorrect because their chlorophyll is similar but not identical.

Bacteria reproduce by ___________
  • a)
    Sexual reproduction and asexual reproduction
  • b)
    Asexual reproduction
  • c)
    Spores
  • d)
    Sexual reproduction
Correct answer is option 'A'. Can you explain this answer?

  • Bacteria reproduce either by asexual reproduction or sometimes adopt sexual mode of reproduction.
  • In sexual reproduction they mainly adopt conjugation in which DNA transfer takes place from one bacterium to other.
  • In asexual reproduction they undergo binary fission.

Which of the following pairs include photosynthetic and saprophytic organisms respectively?
  • a)
    Monocot and dicot
  • b)
    Algae and fungi
  • c)
    Mosses and ferns
  • d)
    Ferns and gymnosperms
Correct answer is option 'B'. Can you explain this answer?

Ciel Knowledge answered
Correct option is B.
  • Photosynthetic organisms, also known as photoautotrophs, are organisms that are capable of photosynthesis. Some of these organisms include higher plants, some protists (algae and euglena), and cyanobacteria.
  • A saprophytic organism is also referred to as a saprotroph, is any organism that feeds and grows on dead organisms. Such as fungi.

What is mycorrhiza?
  • a)
    A type of bacteria
  • b)
    A fungal infection in plants
     
  • c)
    A symbiotic association between fungi and plant roots
  • d)
    A method of asexual reproduction in fungi
Correct answer is option 'C'. Can you explain this answer?

Answer: C

Solution: Mycorrhiza refers to a symbiotic association between fungi and the roots of a plant. In this relationship, the fungus enhances the plant's nutrient and water absorption capabilities, while the plant provides the fungus with carbohydrates produced through photosynthesis. This mutually beneficial relationship is crucial for the health of many ecosystems, making Option C the correct answer.

Which one is not a member of kingdom Protista?
  • a)
    Slime molds
  • b)
    Euglenoids
  • c)
    Phycomycetes
  • d)
    Protozoa
Correct answer is option 'C'. Can you explain this answer?

Rajat Roy answered
Kingdom Protista includes unicellular, eukaryotic organisms only. Phycomycetes is a subdivision of fungus which are multicellular. Protozoa, slime molds and euglenoids are part of kingdom Protista.

Interferons are synthesized in response to
[CBSE-2001]
  • a)
    Mycoplasma
  • b)
    Bacteria
  • c)
    Viruses
  • d)
    Fungi
Correct answer is option 'C'. Can you explain this answer?

Pragati Pillai answered
**Interferons and their synthesis in response to viruses**

**Introduction:**
Interferons are a group of small proteins that play a crucial role in the immune response against viral infections. They are synthesized and released by host cells in response to viral invasion. Interferons act as signaling molecules, allowing cells to communicate with each other and coordinate their antiviral defenses.

**Synthesis of Interferons:**
Interferons are synthesized in response to viral infections by infected host cells. The synthesis of interferons is triggered by the detection of viral components or the activation of specific cellular pathways involved in antiviral defense.

**Viral Infections and Interferon Synthesis:**
When a virus infects a host cell, it releases its genetic material (either DNA or RNA) into the host cell. The viral genetic material is recognized by specific cellular sensors called pattern recognition receptors (PRRs), which are present in the host cell cytoplasm or on the cell surface.

**Activation of Cellular Pathways:**
The recognition of viral genetic material by PRRs activates specific cellular pathways, such as the Toll-like receptor (TLR) pathway or the retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) pathway. These pathways lead to the activation of transcription factors, such as interferon regulatory factors (IRFs) and nuclear factor kappa B (NF-κB).

**Transcription and Translation of Interferons:**
The activated transcription factors bind to specific DNA sequences in the promoter regions of interferon genes, leading to their transcription. The transcribed interferon mRNA is then translated into interferon protein in the cytoplasm.

**Release and Action of Interferons:**
Once synthesized, interferons are released by the infected host cell and bind to specific receptors on neighboring cells. This binding activates a signaling cascade within the recipient cells, leading to the induction of antiviral defense mechanisms. These mechanisms include the upregulation of genes involved in the inhibition of viral replication and the activation of immune cells, such as natural killer (NK) cells and macrophages, to eliminate virus-infected cells.

**Conclusion:**
In summary, interferons are synthesized in response to viral infections. The detection of viral genetic material by cellular sensors triggers specific cellular pathways, leading to the synthesis and release of interferons. These interferons then act as signaling molecules, coordinating the immune response against viral infections.

Read the following statements regarding methanogens and select the correct option.
(i) They are included in the group Archaebacteria.
(ii) They are responsible for the production of biogas in gobar gas plants.
(iii) They live in hot sulphur springs.
(iv) They are strictly anaerobic.
  • a)
    Statements (i), (ii) and (iv) are correct
  • b)
    Statements (i) and (ii) are correct
  • c)
    Statements (ii), (iii) and (iv) are correct
  • d)
    All statements are correct
Correct answer is option 'B'. Can you explain this answer?

Mira Joshi answered
Archaebacteria differ from other bacteria in having a different cell wall structure and this feature is responsible for their survival in extreme conditions. Methanogens are present in the gut of several ruminant animals such as cows and buffaloes and they are responsible for the production of methane (biogas) from the dung of these animals. Methanogens are obligate anaerobes.
So the correct option is "Statement(i) and (ii) are correct".

Which scientist demonstrated that viruses could be crystallized and that these crystals consisted largely of proteins?
  • a)
    Dmitri Ivanowsky
  • b)
    M.W. Beijerinek
  • c)
    W.M. Stanley
  • d)
    Louis Pasteur
Correct answer is option 'C'. Can you explain this answer?

Ciel Knowledge answered
W.M. Stanley demonstrated that viruses could be crystallized, with these crystals primarily consisting of proteins. This groundbreaking discovery provided insights into the structural composition of viruses and their behavior outside their specific host cells. Stanley's work significantly contributed to the understanding of viruses as obligate parasites and highlighted the importance of their proteinaceous nature in their biological activities.

Which of the following is the only group of organisms capable of using inorganic compounds as source of energy :–
  • a)
    Eucaryotes
  • b)
    Procaryotes
  • c)
    Both the above
  • d)
    None of the above
Correct answer is option 'C'. Can you explain this answer?

Nandini Patel answered
On the basis of their energy source, organisms are classified as organotrophic and lithotrophs. Most prokaryotes and all non-phototrophic eukaryotes use organic compounds as their energy source and thus, are referred to as organotrophs. They oxidise organic compounds during cellular respiration and the produced oxygen as a byproduct. But some Cyanobacteria and Archaea use inorganic compounds as an electron donor in electron transport chain and are referred to as lithotrophs, none of the eukaryotes falls in this category. Virus act as non-living outside the cell. It becomes active when it enters the host cell and derives the cellular protein from the host.

Which of the following is incorrect about Cyanobacteria?
  • a)
    They are photoautotrophs.
  • b)
    They lack  heterocysts.
  • c)
    They often form blooms in polluted water bodies.
  • d)
    They have chlorophyll A similar to green plants.
Correct answer is option 'B'. Can you explain this answer?

Cyanobacteria and Heterocysts

Cyanobacteria, also known as blue-green algae, are a group of prokaryotic organisms that are found in various aquatic and terrestrial environments. They are photosynthetic and use sunlight to produce energy and organic compounds.

Heterocysts are specialized cells that some cyanobacteria have. They are able to fix atmospheric nitrogen into a form that can be used by the cell. Heterocysts are important for cyanobacteria because, unlike other organisms, they cannot take up nitrogen from the soil. Therefore, they need to be able to produce their own nitrogen.

The incorrect statement about cyanobacteria is option B, which states that they lack heterocysts. In fact, some cyanobacteria do have heterocysts, which are specialized cells that are able to fix atmospheric nitrogen. However, not all cyanobacteria have heterocysts.

Therefore, the correct statement about cyanobacteria is:
- They are photoautotrophs, meaning they use sunlight to produce energy and organic compounds.
- They often form blooms in polluted water bodies, which can be harmful to other organisms in the ecosystem.
- They have chlorophyll A similar to green plants, which allows them to capture sunlight for photosynthesis.
- Some cyanobacteria have heterocysts, specialized cells that are able to fix atmospheric nitrogen.

Which among the following are incorrect about Phycomycetes?
  • a)
    Phycomycetes are aseptate fungi and are coenocytic
  • b)
    Phycomycetes are also called as algal fungi
  • c)
    Zygospores are formed due to isogamous fertilization and zoospores are formed due to anisogamous fertilization
  • d)
    Phycomycetes are also called as conjugation fungi
Correct answer is option 'C'. Can you explain this answer?

Geetika Shah answered
Zygospores are formed either due to isogamous or anisogamous fertilization. Zoospores and aplanospores are motile and non-motile spores produced due to asexual mode respectively. Phycomycetes are aseptate fungi and are coenocytic. Phycomycetes are also called as algal fungi or conjugation fungi.

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