31 Years NEET Previous Year Questions: Biological Classification - 1

• Some of the organisms can fix atmospheric nitrogen in specialised cells called heterocysts, e.g., Nostoc and Anabaena.
• Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes.
• Fusion of protoplasms between two motile or non-motile gametes is called plasmogamy.
• Fusion of two nuclei is called karyogamy.

Hence, the correct option is D

NCERT Reference: Page no. 22 of topic “2.3 KINGDOM FUNGI” of chapter 2 of NCERT

• Viroids have free RNA without protein coat.
• Potato spindle tuber disease is a disease caused by viroids.

Hence, the correct option is D

NCERT Reference: Page no. 27 of chapter 2 of NCERT

• The cyanobacteria are unicellular, colonial or filamentous, freshwater/marine or terrestrial algae.
• The colonies are generally surrounded by a gelatinous sheath. They often form blooms in polluted water bodies.
• Some of these organisms can fix atmospheric nitrogen in specialised cells called heterocysts, e.g. Nostoc and Anabaena.

Fig: Nostoc showing Heterocyst

Hence, the correct option is B

NCERT Reference: Page no. 19 of topic “2.1.2 Eubacteria” of chapter 2 of NCERT

• Halophiles can be found in hypersaline environments which are widely distributed in various geographical areas on Earth, such as saline lakes, salt pans, salt marshes, or saline soils.
• Thermoacidophiles can be found in hot springs and solfataric environments, within deep-sea vents, or in other environments of geothermal activity. These are microorganisms that are both thermophilic and acidophilic, i.e., they can grow under conditions of high temperature and low pH.
• Methanogens are a group of microorganisms that can produce methane as a byproduct of their metabolism. They hold an important place in the digestive system of ruminants.
• Cyanobacteria, also called blue-green algae, are microscopic organisms found naturally in all types of water. These single-celled organisms live in fresh, brackish (combined salt and fresh water), and marine water.

Hence, the correct option is A

NCERT Reference: Page no. 19 of topic “2.1.1 Archaebacteria” of chapter 2 of NCERT

• Infective constituent of the virus is not the protein coat, but the nucleic acid, either DNA or RNA
• In general, viruses that infect plants have single stranded RNA and viruses that infect animals have either single or double stranded RNA or double stranded DNA.

Hence, the correct option is D

NCERT Reference: Page no. 26 (last paragraph) of chapter 2 of NCERT

• In modern medicine certain infectious neurological diseases were found to be transmitted by an agent consisting of abnormally folded protein. The agent was similar in size to viruses.
• These agents were called prions. The most notable diseases caused by prions are bovine spongiform encephalopathy (BSE) commonly called mad cow disease in cattle.

Hence, the correct option is B

NCERT Reference: Page no. 27 of “Prions” of chapter 2 of NCERT

• In Agaricus, (member of Basidiomycetes), basidium commonly produces four microspores or basidiospores exogenously. 
  
• Neurospora (member of Ascomycetes) produces ascospores, endogenously inside the fruiting body, ascus.
• Alternaria (member of Deuteromycetes) does not produce any sexual spores.
• Saccharomyces (member of Ascomycetes) produces ascospores endogenously.

Hence, the correct option is C

NCERT Reference: Page no. 24 of topic “2.3.3 Basidiomycetes” of chapter 2 of NCERT

• An organism that does not possess a true nucleus (nucleus with nuclear membrane) and membrane-bounded organelles are called as prokaryotes. 
• Monerans are prokaryotes. Eg. bacteria (Mycobacterium), cyanobacteria (Nostoc and Oscillatoria). 
• Saccharomyces belong to Kingdom Fungi which possess a true nucleus and membrane-bounded organelles i.e., eukaryotic. 

Fig: Saccharomyces

Hence, the correct option is A

NCERT Reference: Page no. 23 of topic “2.3.2 Ascomycetes” of chapter 2 of NCERT

All unicellular eukaryotic organisms like diatoms, desmids (chrysophytes), euglenoids, dinoflagellates and slime mould are included in Protista. 

Characteristics of Kingdom Protista:

• Unicellular eukaryotic.
• Mostly aquatic.
• Well defined nucleus present.
• Various membrane bound organelles  present.
• Flagella and cilia, if present have  (9+2) pattern of microtubular stands.
• Reproduction is asexual and sexual.
• Autotrophic, parasitic and heterotrophic.

Hence, the correct option is B

NCERT Reference: Page no. 20 of topic “2.2 KINGDOM PROTISTA” of chapter 2 NCERT

• A biological kingdom composed of prokaryotes (especially bacteria) is Monera. As such, it is made up of cells that are single-celled and without a true nucleus.

Now, let us find the solution from the options:

• Typically, Cyanobacteria receive their energy via oxygen photosynthesis, which creates oxygen gas in the Earth's atmosphere. Cyanobacteria are also named Blue-green algae. They are bacteria which are photosynthetic. Thus, option A is not the correct option.
• Single-celled biflagellates with two specialized flagella are golden algae. The pigment fucoxanthin and the use of oil droplets as a nutritional reserve define them. Desmids are sometimes referred to as golden algae. Thus, option B is not the correct option.
• Eubacteria are single-celled prokaryotic microorganisms which have a variety of features and are present in all regions of the world in diverse environments. Bacteria have two domains, namely archaea and Eubacteria. True bacteria, too, are named Eubacteria. They've got rigid walls of cells and flagella.
• Algal fungi are also named Phycomycetes. They have distinctive coenocytic aseptate hyphae. Thus, option D is not the correct option.

Hence, the correct option is C

NCERT Reference: Page no. 19 of topic “2.1.2 Eubacteria” of chapter 2 of NCERT

• The cell wall is an outermost, rigid layer that provides support to the cell.
• The presence of a cell wall is a characteristic feature of plants, fungi and bacteria. It is absent in animals.
• The fungi are the group of eukaryotic cells that are saprotrophic in nature and include yeasts, mushrooms and moulds.
• The cell wall of fungus is mainly made up of chitin, glycans and glycoproteins. It provides rigidity and shape to the cell and helps in ion exchange and metabolism.
• Chitin is a homo-polysaccharide which is made up of N-acetyl glucosamine (NAG).
• The peptidoglycan is the major component of the cell wall of bacteria. In Gram-positive bacteria, a thick layer of peptidoglycan and teichoic acid is present in the cell wall, due to which it is unable to get the pink colour of safranin dye. It appears violet in colour. In Gram-negative bacteria, a thin layer of peptidoglycan layer is present in the cell wall, due to which it gets the pink colour of safranin dye. It appears pink in colour.
• Cellulose is the major component of the cell wall of plants and algae. Cellulose is a homopolysaccharide of the glucose molecule. It is the most abundant organic molecule on earth. It is digested by a cellulase enzyme.
• The hemicellulose is a heteropolysaccharide, made up of galactose, mannose and arabinose. It is present in the cell wall of plants and acts as cementing in ground substance.

Hence, the correct option is A

NCERT Reference: Page no. 22 of topic “2.3 KINGDOM FUNGI” of chapter 2 of NCERT

• Viroids are infectious, nonprotein‐coding, highly structured small circular low-molecular-weight ribonucleic acids (RNAs) able to replicate autonomously and induce diseases in higher plants. 
• Viroids are single-stranded covalently closed circular RNA molecules existing as highly base-paired rod-like structures.

Hence, the correct option is D

NCERT Reference: Page no. 27 of chapter 2 of NCERT

• Lichens are very good pollution indicators. They cannot grow in the place where sulphur dioxide, pollutant is available in the environment. 
• Whereas Conifers, Algae and Fungi do not act as pollution indicators.

Fig: Lichens as Air pollution indicators

Hence, the correct option is D

NCERT Reference: Page no. 27 of chapter 2 of NCERT

A. Neurospora has a short life cycle and hence, it is used in genetical and biochemical studies. Hence, statement A is correct.

B. Morels or Morchella, commonly known as a sponge mushroom produces fruiting body basidiocarp which is edible. Truffles are the ascomycetes which also produce edible fruiting bodies. Hence, statement B is incorrect.

C. Yeast is a unicellular i.e. single-celled and non-mycelial saprophytic fungus. In anaerobic conditions, yeast converts sugar into alcohol with the release of carbon dioxide and some energy. Due to this, yeast is used in the fermentation process. Hence, statement C is correct.

D. Penicillium is a saprophytic fungus belonging to Ascomycetes. The mycelium is profusely branched and septate. Cells are thin-walled with many nuclei in them. Thus, it is multicellular. Penicillin is an antibiotic produced from Penicillium. Hence, statement D is correct.

Hence, the correct option is B

NCERT Reference: Page no. 24 of topic “2.3.2 Ascomycetes” of chapter 2 of NCERT

• In chrysophytes, the cell walls form two thin overlapping shells holding together.
• The body of Diatoms appears like a soap box due to overlapping shells. 

Fig: Chrysophytes

Hence, the correct option is D

NCERT Reference: Page no. 20 of topic “2.2.1 Chrysophytes” of chapter 2 of NCERT

Let us find the correct answer from the following,

Option A: Alternaria belongs to Deuteromycetes, which are also known as imperfect fungi since they reproduce through asexual reproduction or vegetative reproduction. Deuteromycetes reproduce by asexual spores known as conidia. Some members of deuteromycete are parasitic and saprophytes, while a majority of them are decomposers of litter and they help in mineral cycling. Alternaria lack sexual reproduction. Therefore, this is the correct option.

Option B: Mucor is a type of fungus seen in soil and plant leaves. They belongs to the category of phycomycetes and they undergoes asexual reproduction by zoospores or aplanospores. Other examples for phycomycetes are Rhizopus and Albugo. Therefore, this is the incorrect option.

Option C: Agaricus, which is also known as mushroom, belongs to basidiomycetes. They grow on soil, logs and tree stumps. Asexual spores are absent, but vegetative reproduction is common in them.These are saprophytic fungi and are not parasitic. Ustillago and Puccinia are other examples for basidiomycetes. Therefore, this is the incorrect option.

Option D: Phytophthora belongs to algal fungi, also known as phycomycetes. These are mostly found in aquatic habitats. They have coenocytic and septate mycelium. Therefore, this is the incorrect option.

Hence, the correct option is A

NCERT Reference: Page no. 24 of topic “2.3.4 Deuteromycetes” of chapter 2 of NCERT

• Anabaena is a cyanobacteria which lacks a true nucleus because of the absence of a nuclear membrane.
• Vaucheria, Volvox, and Mucor have domain Eukaryota while Anabaena has domain Prokaryota. Eukaryotes have membrane-bound well-defined nucleus whereas Prokaryotes do not have a membrane-bound nucleus because, in them, the genetic material lies freely in the cytoplasm. 

Hence, the correct option is D

NCERT Reference: Page no. 19 of topic “2.1.2 Eubacteria” of chapter 2 of NCERT

• Deuteromycetes are the imperfect fungi which include all those fungi in which the sexual stage is either absent or not known.
• Some of the members are saprophytes or parasites while most of them are decomposers of litter and help in the cycling of minerals. E.g., Colletotrichum, Helminthosporium, etc.

Hence, the correct option is D

NCERT Reference: Page no. 24 of topic “2.3.4 Deuteromycetes” of chapter 2 of NCERT

• Mucor belongs to the Kingdom Fungi and division zygomycota. Zygomycota have sexual spores called zygo- spores and most of them lack flagella.
• Gymnosperms don't have double fertilization, the endosperm is haploid and is formed by the repeated division of haploid megaspores and later develops into female gametophyte with haploid chromosomes.
• Brown algae are also known as Phaeophyceae. It is a group of marine multi-cellular algae, which play a critical role in marine environments. Its brown color is due to the presence of pigment fucoxanthin. It also consist of pigment chlorophyll a and c.
• Archegonia is the female reproductive part of flask-shaped structure. It contains of neck and swollen base, where neck consist of one or more layers of cells and swollen part contains of egg. It is found in Bryophytes (eg: ferns and mosses), gymnosperms (eg: cycads and conifers), and Pteridophyta (eg: azolla).

Hence, the correct option is A
NCERT Reference: Page no. 23 of topic “2.3.1 Phycomycetes”of chapter 2 of NCERT

The kingdom Monera possesses unicellular organisms (e.g - bacteria) having no nuclear membrane.

Hence, the correct option is C

NCERT Reference: Page no. 18 of chapter 2 of NCERT

The main principle for analysis by R.H. Whittaker include:

1. Complexity of cell structure (eukaryotic or prokaryotic)
2. Body organisation(unicellular or multicellular)
3. Thallus organisation
4. Mode of nutrition (autotrophs or heterotrophs)
5. Reproduction (sexual or asexual)
6. Phylogenetic relationships

And therefore presence or absence of a well-defined nucleus is not the basis for R.H. Whittaker's classification. 

Hence, the correct option is A

NCERT Reference: Page no. 17 “TABLE 2.1 Characteristics of the Five Kingdoms” of chapter 2 of NCERT

• Several mushrooms such as Amanita muscaria, Psilocybe mexicana and Panaeolus spp. secrete hallucinogenic substances like psilocybin and psilocin.
• These substances may destroy brain cells and the perception power of human beings. 

Amanita Muscaria:

• 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.
• Their cell walls are made of a variety of polymers, but do not contain peptidoglycan unlike eubacteria.
• Lipids of their cytoplasmic membranes are ether-linked, unlike eubacteria which contain glycerol ester lipids in their cell membrane.

Hence, the correct option is A

NCERT Reference: Page no. 19 of topic “2.1.1 Archaebacteria” of chapter 2 of NCERT

• TMV (Tobacco Mosaic Virus) is a rod shaped virus.
• The rod has a core which contains helically coiled single-stranded RNA.
• There is a protective covering of protein called capsid around the infective part.
• Capsid consists of small subunits called capsomeres and has antigenic properties. 

Hence, the correct option is B

NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2 of NCERT

• A virus is a small collection of genetic code, either DNA or RNA, surrounded by a protein coat. A virus cannot replicate alone. Viruses must infect cells and use components of the host cell to make copies of themselves.
• All viruses are nucleoproteins (Nucleic acid + Protein) in the structure. The nucleic acid (DNA and RNA) is the genetic material.
• In a particular virus, either DNA or RNA is genetic material never both are present in a virus.
• Single-stranded RNA or ssRNA - Tobacco mosaic virus (TMV) Virus envelope is known as capsid. The capsid is composed of protein subunits called capsomeres.

Hence, the correct option is A

NCERT Reference: Page no. 26 of topic “2.6 VIRUSES, VIROIDS, PRIONS AND LICHENS” of chapter 2 of NCERT