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Cellulose is the major component of cell walls of [CBSE AIPMT 2008]
(a) Cellulose does occur in cell walls of Oomycetes (e.g. Pythium) and Hyphochytridiomycetes. The fungal cell wall contains \(80-90 \%\) carbohydrates, the remainder being proteins and lipids. The typical feature of the fungal cell wall is the presence of chitin.
During the formation of bread, it becomes porous due to the release of \(\mathrm{CO}_{2}\) by the action of [CBSE AIPMT 2002]
(a) Strains of Saccharomyces cerevisiae are extensively used for leavening of bread. During fermentation, the yeasts produce alcohol and \(\mathrm{CO}_{2}\) which leaves the bread porous.
Which of the following is the use of lichens in case of pollution? [CBSE AIPMT 1999]
(b) Growth of lichens on trees is inhibited by air pollution. Hence, atmospheric pollution causes a decrease in their populations. So, lichens are biological indicators of pollution.
Mycorrhiza represents [CBSE AIPMT 1994, 96, 2003]
(c) Mycorrhiza \((\) mykes \(=\) mushroom \(+\) rhiza \(=\)root) represents a symbiotic association of fungi with the roots of
higher plant. Mycorrhiza meaning fungus root is an infected root system arising from the rootlets of a seed plant.
In ectomycorrhiza, the ultimate absorbing rootlets of the root system are completely surrounded by a distinct mantle or sheath of fungal tissue. In endomycorrhiza, there is no such sheath. Most of the fungus is within the root and may be intracellular as well as intercellular.
Which of the following statements about inclusion bodies is incorrect? [NEET 2020]
(a) Option (b),(c), and (d) are correct whereas option (a) is incorrect because Inclusion bodies are nuclear or cytoplasmic aggregates of proteins. They represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins. These are not involved in the ingestion of food particles.
Select wrong statement [CBSE AIPMT 2015]
(a) All statements are correct except the statement(a), which can be corrected as Viroids were discovered by TO Diener in 1971 as a new infectious agent that was smaller than a virus.
TO Diener discovered a [CBSE AIPMT 2009]
(a) Viroids are small, circular, single-stranded free infectious RNA molecules that are the smallest known pathogens. The extracellular form of the viroid is naked RNA, i.e. there is no protein capsid of any kind. This RNA molecule contains no protein-encoding genes and therefore, the viroid is totally dependent on the host for its replication. No viroid diseases of animals are known and the precise mechanisms by which viroids cause
plant diseases remain unclear.
Which of the following statements is not true for retroviruses? [CBSE AIPMT 2004]
(a) Retroviruses are so, named because they contain enzyme reverse transcriptase or RNA-dependent DNA polymerase. The genetic material of these viruses is RNA, e.g. Rous Sarcoma Virus.
Viruses are no more ‘alive’ than isolated chromosomes because [CBSE AIPMT 2003]
(a) Viruses are non-cellular obligate parasite. In the free state, they are just like particles. They do not have their own metabolic machinery and use the host’s machinery for multiplication.
Interferons are synthesised in response to [CBSE AIPMT 2001]
(c) Cells infected by virus produce interferon which is an antiviral protein. It spreads to neighboring cells and makes them resistant to virus infections by inhibiting viral growth.
Protista differs from Monera in having [AIIMS]
(d) All single-celled eukaryotes are placed under Protista. Phylogenetically the Kingdom Protista acts as a connecting link between the prokaryotic Kingdom Monera and the complex multicellular kingdoms – Fungi, Plantae and Animalia.
Being eukaryotes, the protistan cell body contains a well defined nucleus and other membrane-bound organelles. It is surrounded by plasmalemma (cell membrane). Cilia and flagella occur in a number of forms. Nucleus has a typical structure-porous nuclear envelope, chromatin, nucleolus, and nucleoplasm. Monerans lack nuclear membrane.
Which of the following statements is correct? [NEET 2021]
(c) Some of the cyanobacteria like Nostoc can fix nitrogen in specialised cells called heterocysts. Fusion of two nuclei is called karyogamy. Organisms that depend on living plants and animals are called parasites.
Match the organisms in column I with habitats in column II.
\(\begin{array}{|l|l|l|l|}
\hline & \text { Column I } & & \text { Column II } \\
\hline \text { A. } & \text { Halophiles } & \text { (i) } & \text { Hot springs } \\
\hline \text { B. } & \text { Thermoacidophiles } & \text { (ii) } & \text { Aquatic environment } \\
\hline \text { C. } & \text { Methanogens } & \text { (iii) } & \text { Guts of ruminants } \\
\hline \text { D. } & \text { Cyanobacteria } & \text { (iv) } & \text { Salty area } \\
\hline
\end{array}\)
Select the correct answer from the options given below. [NEET 2023]
Which of the following are found in extreme saline conditions? [NEET 2022]
(d) Halophiles, a type of archaebacteria, usually occur in extreme saline conditions like salt pans, salt beds, and salt marshes.
Which among the following are the smallest living cells, known without a definite cell wall, pathogenic to plants as well as animals, and can survive without oxygen? [NEET 2024]
(b) Mycoplasmas are the smallest living cells, known without a definite cell wall. They are pathogenic to both plants and animals and can survive without oxygen.
Which of the following is correct about viroids? [NEET 2024]
(b) Viroids are free RNA particles that lack protein coat. They are infectious agents smaller than viruses.
Archaebacteria differ from eubacteria in [AIPMT]
(a) The archaebacteria are the ‘ancient’ bacteria that include extremophiles like methanogens, halophiles, and thermophiles. They represent some of the most ancient 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 resemble 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 linked unlike eubacteria which contain glycerol ester lipids in their cell membrane.
Which of the following statements is incorrect? [NEET 2021]
(d) Infective constituent in the viruses is the genetic material, i.e., either DNA or RNA.
Match column I with column II.
\(\begin{array}{|l|l|l|l|}
\hline & \text { Column I } & & \text { Column II } \\
\hline \text { A. } & \text { Saprophyte } & \text { (i) } & \begin{array}{l}
\text { Symbiotic association of fungi } \\
\text { with plant roots }
\end{array} \\
\hline \text { B. } & \text { Parasite } & \text { (ii) } & \begin{array}{l}
\text { Decomposition of dead organic } \\
\text { materials }
\end{array} \\
\hline \text { C. } & \text { Lichens } & \text { (iii) } & \begin{array}{l}
\text { Living on living plants or } \\
\text { animals }
\end{array} \\
\hline \text { D. } & \text { Mycorrhiza } & \text { (iv) } & \begin{array}{l}
\text { Symbiotic association of algae } \\
\text { and fungi }
\end{array} \\
\hline
\end{array}\)
Choose the correct answer from the options given below. [NEET 2023]
Select the correct combination of the statements (i-iv) regarding the characteristics of certain organisms.
(i) Methanogens are archaebacteria which produce methane in marshy areas.
(ii) Nostoc is a filamentous blue-green alga which fixes atmospheric nitrogen.
(iii) Chemosynthetic autotrophic bacteria synthesise cellulose from glucose.
(iv) Mycoplasma lack a cell wall and can survive without oxygen.
The correct statements are [AIPMT]
(d) Chemosynthetic autotrophic bacteria oxidise various inorganic substances such as nitrates, nitrites, and ammonia and use the released energy for their ATP production. They play a great role in recycling nutrients like nitrogen, phosphorus, iron, and sulphur.
One of the following is not the characteristic feature of cyanobacteria. [AMU]
(a) Cyanobacteria are either unicellular (Chroococcus), colonial (Gloeocapsa, Microcystis), or filamentous (Oscillatoria, Nostoc). The filaments may show false or true branching. Many cyanobacteria grow in abundance in water rich in nutrients. This surface growth is called water bloom. Cyanobacteria forming water blooms release toxins that are harmful to both aquatic fauna and flora. Some filamentous cyanobacteria (e.g., Anabaena, Nostoc, Scytonema, Tolypothrix) have the capacity to fix atmospheric nitrogen. All such cyanobacteria are heterocystous and the heterocysts are the main sites of nitrogen fixation.
Which one of the following is not a plant like protist? [MH CET]
(d) Dinoflagellates and chrysophytes/desmids and diatoms) are photosynthetic protists as they possess chlorophyll pigment. Slime moulds possess the characters of both animal and fungi, commonly called fungus animals. These are consumer decomposer protists that lack any chlorophyll and are incapable of photosynthesising.
Which of the following organisms are known as chief producers in the oceans? [NEET 2024]
(b) Diatoms are the most common form of phytoplankton in the ocean. They have the pigment chlorophyll which helps in photosynthesis. Since they are the primary producers of the aquatic food chain and the marine ecosystem depends on them, they are called chief producers in the oceans.
Ciliates differ from all other protozoans in [NEET 2022]
(d) Ciliates differ from other protozoans in having two types of nuclei: macronucleus and micronucleus (nuclear dimorphism). E.g., Paramecium has macronucleus which controls metabolic activities as well as growth and micronucleus that takes part in reproduction.
Select the wrong statement. [NEET 2022]
(a) Diatoms are marine or freshwater unicellular organisms which have cell walls (frustules) composed of pectin impregnated with silica and consisting of two halves, one overlapping the other. The siliceous frustules of diatoms do not decay easily.
The genetic material in tobacco mosaic virus is [AIIMS]
(b) Tobacco Mosaic Virus (TMV) contains single-stranded RNA (ssRNA) as genetic material.
Viroids differ from viruses in having [NEET 2024]
(c) Viroids are free RNA particles that lack protein coat. They are infectious agents smaller than viruses.
After karyogamy followed by meiosis, spores are produced exogenously in [NEET 2023]
(c) In Agaricus, (member of Basidiomycetes), basidium commonly produces four meiospores or basidiospores exogenously. Neurospora and Saccharomyces (members of Ascomycetes) produce ascospores, endogenously inside the fruiting body, ascus. Alternaria does not produce any sexual spores.
Which of the following statements is incorrect? [NEET 2021]
(a) Yeast is a non-mycelial unicellular ascomycetes fungus.
Select the wrong statement. [NEET 2024]
(c) Pseudopodia are the locomotory organ in amoeboid protozoans, e.g., Amoeba. Flagellated protozoans possess flagella for locomotion, e.g., Trypanosoma. In sporozoans, locomotory organelles (cilia, flagella, pseudopodia, etc.) are absent, e.g., Plasmodium. Ciliated protozoans possess cilia as locomotory organelles, e.g., Paramecium.
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