NEET Biology Biological Classification MCQs Set 14

Answer: (a) Bacteria

Explanation:
1. Nitrogen fixation, ammonification, nitrification and denitrification are all carried out by bacteria.
2. Legumes only host nitrogen-fixing bacteria.

Teacher's Note:
1. Cyanobacteria also fix nitrogen.
2. Fungi do not take part in these steps.

Answer: (a) Peptidoglycan

Explanation:
1. Archaebacteria have no peptidoglycan in the cell wall; they have pseudomurein or other polymers.
2. They do have DNA and ribosomes and unusual branched lipids.

Teacher's Note:
1. Peptidoglycan is typical of eubacteria.
2. Archaebacteria live in extreme habitats.

Answer: (b) Water bloom

Explanation:
1. Excess growth of cyanobacteria forms a water bloom.
2. It uses up oxygen and some forms release toxins that kill fish.

Teacher's Note:
1. Blooms need nutrient-rich water.
2. BGA usually raise soil fertility.

Answer: (c) Both aerobic respiration and cell wall formation

Explanation:
1. Mesosomes are infoldings of the plasma membrane.
2. They help in respiration, cell wall formation, DNA replication and distribution to daughter cells.

Teacher's Note:
1. They resemble mitochondria in function.
2. They increase the surface area of the membrane.

Answer: (a) Oxygenic

Explanation:
1. Cyanobacteria have chlorophyll a and photosystems I and II.
2. They split water and release oxygen.

Teacher's Note:
1. Purple and green sulphur bacteria are anoxygenic.
2. Cyanobacteria made the early atmosphere oxygen-rich.

Answer: (b) Protista

Explanation:
1. Protists are eukaryotes, mostly unicellular, and they connect prokaryotes with multicellular plants, fungi and animals.
2. So Protista is the link.

Teacher's Note:
1. They have a true nucleus.
2. They show many body plans.

Answer: (a) Bacteria

Explanation:
1. Prokaryotes lack mitochondria, so the respiratory chain sits on the plasma membrane and mesosomes.
2. Algae and fungi are eukaryotes and have mitochondria.

Teacher's Note:
1. Cyanobacteria use the thylakoid membrane.
2. Eukaryotes use mitochondria.

Answer: (b) Soil

Explanation:
1. Soil holds the largest number and variety of bacteria.
2. Air has the fewest.

Teacher's Note:
1. A gram of fertile soil holds millions.
2. Many are decomposers.

Answer: (b) Chemoautotrophs

Explanation:
1. Chemoautotrophs oxidise inorganic substances like ammonia, nitrite or sulphur for energy.
2. They fix carbon dioxide using that energy.

Teacher's Note:
1. Nitrosomonas and Nitrobacter are examples.
2. Photoautotrophs use light.

Answer: (c) Extra-chromosomal genetic material of bacteria

Explanation:
1. Plasmids are small circular DNA molecules separate from the bacterial chromosome.
2. They are not essential for survival but may carry genes like antibiotic resistance.

Teacher's Note:
1. They are used as vectors in genetic engineering.
2. The F plasmid controls conjugation.

Answer: (b) Aerobic bacteria

Explanation:
1. Aerobic bacteria such as Acetobacter oxidise the ethanol in wine to acetic acid.
2. This makes the wine sour like vinegar.

Teacher's Note:
1. Oxygen is needed for the souring.
2. Fermentation to alcohol is by yeast.

Answer: (d) Rhodospirillum

Explanation:
1. Rhodospirillum is a photosynthetic purple non-sulphur bacterium that fixes carbon dioxide.
2. The other three are heterotrophs.

Teacher's Note:
1. Photosynthetic bacteria do not release oxygen.
2. Rhizobium fixes nitrogen.

Answer: (b) Cell wall

Explanation:
1. Gram positive walls have a thick peptidoglycan layer and take up the crystal violet stain.
2. Gram negative walls have a thin peptidoglycan layer with an outer membrane and lose the stain.

Teacher's Note:
1. Gram stain was devised by H. C. Gram.
2. Staining depends on the wall.

Answer: (c) Lipid and protein

Explanation:
1. Like other membranes, the bacterial plasma membrane is a lipid bilayer with proteins.
2. Cellulose and chitin are wall materials of other groups.

Teacher's Note:
1. Bacterial walls have peptidoglycan.
2. Mesosomes are infoldings of the membrane.

Answer: (c) Bacteria

Explanation:
1. Bacteria fix nitrogen and decompose organic matter, returning nutrients to the soil.
2. Bacteriophages are viruses and do not improve fertility.

Teacher's Note:
1. Nitrifying and nitrogen fixing bacteria are key.
2. Decomposers recycle minerals.

Answer: (a) Nitrogen-fixing bacteria

Explanation:
1. Nitrogen fixers convert atmospheric nitrogen into ammonia and add it to the soil.
2. Denitrifiers do the reverse and reduce fertility.

Teacher's Note:
1. Rhizobium and Azotobacter are examples.
2. Denitrification returns nitrogen to the air.

Answer: (d) Distilled water

Explanation:
1. Bacteria occur in soil, polar ice and the sea.
2. Distilled water has no nutrients to support them.

Teacher's Note:
1. Bacteria are nearly everywhere.
2. They live even in hot springs.

Answer: (b) Pyrrophyta

Explanation:
1. Dinoflagellates (Pyrrophyta) have a cell wall of stiff cellulose plates.
2. They have two flagella, one in a transverse groove and one longitudinal.

Teacher's Note:
1. Dinoflagellates are marine.
2. Euglenoids have a flexible pellicle.

Answer: (c) Diatoms

Explanation:
1. Diatoms store food as oil and leucosin (chrysolaminarin).
2. Euglenoids store paramylon.

Teacher's Note:
1. Diatom walls are silica.
2. Dinoflagellates store starch.

Answer: (c) They have highly siliceous walls

Explanation:
1. Diatom frustules are made of silica, which resists decay.
2. They therefore persist as deposits.

Teacher's Note:
1. Diatomaceous earth is formed from the walls.
2. Frustules have two overlapping halves.

Answer: (c) Diatoms

Explanation:
1. Kieselguhr (diatomaceous earth) is the accumulation of diatom cell walls.
2. It is gritty and heat resistant.

Teacher's Note:
1. Used in filters, polishing and insulation.
2. Also called diatomite.

Answer: (b) Chrysophyta

Explanation:
1. Diatoms belong to Chrysophyta.
2. Their silica walls form diatomite.

Teacher's Note:
1. Myxophyceae are blue-green algae.
2. Phaeophyceae are brown algae.

Answer: (c) Cell wall

Explanation:
1. Diatoms have a two-piece siliceous cell wall (frustule), which is their unique feature.
2. Their photosynthesis is oxygenic.

Teacher's Note:
1. The frustule has fine patterns.
2. Walls fit like a soap box.

Answer: (c) Slime moulds

Explanation:
1. Slime moulds feed on decaying organic matter.
2. The others are photosynthetic.

Teacher's Note:
1. Slime moulds form plasmodia.
2. They are saprophytic.

Answer: (a) Diatoms

Explanation:
1. Auxospores, silica frustules and oil/leucosin storage are features of diatoms.
2. The other groups do not have these.

Teacher's Note:
1. Auxospores restore cell size in diatoms.
2. Diatoms are Chrysophyta.

Answer: (b) Euglenoids

Explanation:
1. Euglenoids store food as paramylon, a starch-like carbohydrate.
2. Diatoms store oils and leucosin.

Teacher's Note:
1. Euglenoids have a pellicle.
2. They have two flagella.

Answer: (b) Protista

Explanation:
1. Euglena is photosynthetic in light and feeds on organic matter in the dark.
2. It is a protist.

Teacher's Note:
1. Such mixotrophs make classification difficult.
2. Euglenoids are protists.

Answer: (a) Pyrrophyta

Explanation:
1. Dinoflagellates are called fire algae.
2. They are placed in Pyrrophyta.

Teacher's Note:
1. Pyrrophyta means fire plants.
2. Noctiluca and Gonyaulax are examples.