31 Years NEET Previous Year Questions: Biological Classification

R.H Whittaker in 1969 proposed five kingdom classification. In this system the arrangement of five kingdoms is based on following three criteria:

• The complexity of cell structure i.e prokaryote and eukaryote. 
• The complexity of the organism's body- unicellular and multicellular. 
• The mode of obtaining nutrition - autotrophs and heterotrophs.
• Phylogenetic relationship.

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 perception power of human beings. 

Archaebacteria differ from other bacteria in having a different cell wall structure. They lack peptidoglyan in cell wall and possess a monolayer of branched fatty acids attached to glycerol by ether bonds in their cell membranes. 

TMV (Tobacco Mosaic Virus) is a rodshaped 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 property. 

• All viruses are nucleoprotein (Nucleic acid + Protein) in the structure. The nucleic acid (DNA and RNA) is 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 capsomere.

Motile bacteria have thin filamentous extensions from their cell wall called flagella. 

• Alternaria is a genus of ascomycete fungi. Alternaria species are known as major plant pathogens. They are also common allergens in humans, growing indoors and causing hay fever or hypersensitivity reactions that sometimes lead to asthma.
• Mucor is a microbial genus of approximately 6 species of moulds commonly found in soil, digestive systems, plant surfaces and rotten vegetable matter. Mucor mucedo uses asexual reproduction. During sexual reproduction, compatible strains form short, specialized hyphae called as gametangia.
• Agaricus is a genus of mushrooms containing both edible and poisonous species, with possibly over 300 members worldwide. The genus includes the common button mushroom (Agaricus bisporus) and the field mushroom (Agaricus campestris), the dominant cultivated mushrooms of the West.
• Phytophthora is a genus of plant-damaging Oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, as well as environmental damage in natural ecosystems. Phytophthora spp. are mostly pathogens of dicotyledons, and are relatively host-specific parasites.

Thus, the correct answer is option A.

Anabaena is a cyanobacteria which lack a true nucleus because of absence of nuclear membrane.

 In a prokaryotic cell, nuclear envelope is not found. It means genetic material (DNA) is not enclosed by any envelope and lies in direct contact with the cytoplasm.

Class- deuteromycetes contains imperfect fungi which play role in decomposition of organic wastes.

Fimbriae are small bristle-like fibres sprouting out of the cell. In some bacteria, they are known to help is attachment to rocks in streams and also to the host tissues.

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

• Brown algae is also known as phaeophyceae. It is a group of marine multi cellular algae, hits 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 ans swollen part contains of egg. It is found in Bryophytes (eg: ferns and mosses), gymnosperms (eg: cycads and conifers), and Pteridophyta (eg: azolla).
• Gymnosperms doesn't have double fertilization, the endosperm is haploid and are formed by the repeated division of haploid megaspores and later develops into female gametophyte with haploid chromosomes.
• Mucor belongs to the Kingdom Fungi and division zygomycota. Zygomycota have sexual spores called zygo- spores and most of them lack flagella.

So, the correct answer is option A.

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

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 a 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.

So, the correct answer is 'Morels and truffles are poisonous mushrooms'.

Lichens cannot grow in the place where sulpher dioxide, pollutant is available in the environment. 

Viroids, the smallest known pathogens, are naked, circular, single-stranded RNA molecules that do not encode protein yet replicate autonomously when introduced into host plants. Viroids only infect plants; some cause economically important diseases of crop plants, while others appear to be benign. 

• A cell wall is a rigid structural layer, which provides protection and structural support to the cells.
• The composition of cell walls varies from species to genera.
• In the case of fungi, the cell wall is composed of strong covalent linkages of chitin, glucans and glycoproteins.
• Alternatively, in case of land plants, the cell wall is composed of cellulose and hemicellulose and Archean cell walls have peptidoglycans.

Eubacteria are the True bacteria.

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

Kingdom Protista 

• Unicellular eukaryotic.
• Mostly aquatic.
• Well define 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.