Biodiversity

(d) Their RNA is of high molecular weight

Viroids are free RNA with no protein coat, smaller than viruses, and infectious (e.g. potato spindle tuber disease). Their RNA is of low molecular weight, so (d) is the wrong statement.

(c) Vexillum

In a papilionaceous corolla (pea, Fabaceae) the large posterior petal is the standard or vexillum, two lateral petals are wings (alae), and two fused anterior petals form the keel (carina). Pappus is a modified calyx in Asteraceae and corona is an outgrowth in Calotropis/Passiflora.

(a) Liliaceae

Liliaceae has a tricarpellary, syncarpous, superior ovary with axile placentation. Solanaceae is bicarpellary, Fabaceae is monocarpellary, and Poaceae has a monocarpellary one-seeded ovary.

(a) Chitin

Most fungal cell walls are made of chitin (N-acetylglucosamine polymer) along with glucans. Peptidoglycan is bacterial, and cellulose is the main wall component in plants (and some oomycetes), not typical fungi.

(b) Golden algae are also called desmids.

Golden algae (chrysophytes) are the diatoms and golden-brown algae, whereas desmids are a separate group of green algae, so this statement is wrong. Cyanobacteria are indeed called blue-green algae, and Phycomycetes are called algal fungi. Note that (c) is also loosely worded, since eubacteria are the "true" bacteria, but (b) is the clearly incorrect statement and the one given as the answer.

(c) Sequoia is one of the tallest trees

The coast redwood Sequoia sempervirens is among the tallest trees in the world. Gymnosperms are all heterosporous, so (a) is wrong. Salvinia is a pteridophyte (a water fern), so (b) is wrong. Gymnosperm leaves, such as the needles of conifers, are well adapted to extremes of climate, so (d) is wrong.

(d) Water

In bryophytes and pteridophytes the male gametes (antherozoids) are flagellated and swim to the egg through a film of water. This is why these groups need water for fertilisation. Wind, insects and birds are pollen vectors in seed plants.

(a) Biological names can be written in any language

This is contrary to the rules. The ICN and ICZN require scientific names to be in Latin (or latinised) form and italicised, or underlined when handwritten. The first word is the genus and the second the specific epithet, so (b), (c) and (d) are all correct rules.

(b) Protista

Chrysophytes (diatoms and golden algae), euglenoids, dinoflagellates and slime moulds are all unicellular, eukaryotic organisms placed in Kingdom Protista in Whittaker's five-kingdom system. Monera has only prokaryotes, Fungi are heterotrophic absorptive organisms, and Animalia are multicellular animals.

(c) Methanogens

Methanogens are archaebacteria that live in the anaerobic gut of ruminants such as cattle, and they produce methane (biogas) from the dung. Halophiles live in salty places and thermoacidophiles in hot, acidic habitats. Eubacteria are the true bacteria and are not the primitive group in question.

(c) Mucor has biflagellate zoospores

Mucor is a Zygomycete that reproduces by non-motile sporangiospores and zygospores; biflagellate zoospores are found in aquatic fungi (Oomycetes, Chytrids). The other statements are correct: brown algae have chlorophyll a, c and fucoxanthin, archegonia occur in bryophytes, pteridophytes and gymnosperms, and gymnosperm endosperm is haploid.

(d) Morels and truffles are poisonous mushrooms

Morels (Morchella) and truffles are edible, prized ascomycete fungi, not poisonous ones. The other statements are true: yeast ferments, Penicillium is multicellular and produces penicillin, and Neurospora is used for biochemical genetics.

(d) Mycoplasma

Mycoplasma is the smallest prokaryote and lacks a cell wall, which makes it pleomorphic. Nostoc (peptidoglycan wall), Aspergillus (chitin) and Funaria (cellulose) all have cell walls.

(b) Chrysophytes

Diatoms, the main chrysophytes, have siliceous cell walls in two thin overlapping halves that fit together like a soap box. Dinoflagellates have cellulose plates, euglenoids have a flexible pellicle, and slime moulds have no such wall.

(b) Photosynthesis

Chromatophores are membranous vesicles in photosynthetic bacteria (e.g. purple bacteria) that carry the photosynthetic pigments. They carry out photosynthesis, not respiration, growth or movement.

(b) The viroids were discovered by D.J. Ivanowski

Viroids were discovered by T.O. Diener in 1971; Ivanowski showed in 1892 that tobacco mosaic agent passes through filters. The other statements are correct: TMV and AIDS are viral, Stanley crystallised TMV, and Beijerinck coined contagium vivum fluidum.

(c) Fimbriae

Fimbriae are small bristle-like fibres on the cell surface of some bacteria that help them attach to rocks in streams and to host tissues. Holdfast and rhizoids are algal/fungal anchorage structures, and mesosomes are membrane infoldings involved in respiration and division.

(b) Deuteromycetes

Deuteromycetes (imperfect fungi) have no known sexual stage; many are saprophytes that decompose litter and recycle minerals, e.g. Alternaria, Trichoderma. Ascomycetes, Basidiomycetes and Phycomycetes have known sexual reproduction, so they are not called imperfect.

(a) Nuclear membrane is present in Monera

Monera are prokaryotes and lack a membrane-bound nucleus, so (a) is wrong. Animalia lack cell walls, Protista include photosynthetic and heterotrophic forms, and some fungi (mushrooms) are edible.

(d) Presence or absence of a well defined nucleus

Whittaker's five kingdoms used cell structure (prokaryote vs eukaryote is only used to separate Monera), body organisation, mode of nutrition and reproduction, and phylogenetic relationships. The official key treats the well-defined nucleus as the option that is not a basis of his scheme. Note that the question is loosely worded, since the other three criteria are clearly used by Whittaker, so go with the key.

(a) Tobacco mosaic virus

TMV is a helical rod: a single-stranded RNA coiled inside a helical protein coat of capsomeres. Measles and polio viruses are not described this way in NCERT, and a retrovirus is an enveloped RNA virus with reverse transcriptase.

(c) Mesosomes

Mesosomes are infoldings of the bacterial plasma membrane that carry respiratory enzymes, so they do the job of mitochondria and also help in cell wall formation and DNA replication. Ribosomes make protein and the nucleoid holds the DNA.

(a) Sea-fan (Gorgonia)

Gorgonia is an animal (a cnidarian coral) and animal cells have no cell wall. Saccharomyces has a chitin wall, and cyanobacteria (blue-green algae) have a peptidoglycan wall.

(d) Rhodospirillum

Anoxygenic photosynthesis uses H$_2$S or other donors instead of water, so no O$_2$ is released. This is done by purple and green photosynthetic bacteria such as Rhodospirillum. Spirogyra, Chlamydomonas and Ulva are green algae that split water and release oxygen (oxygenic).

(a) Chlorella

Chlorella is a unicellular green alga rich in protein and is used as a food supplement, including by space travellers. Spirogyra and Ulothrix are not used as food, and Polysiphonia is a red alga not used as a human food source (Porphyra and Laminaria are the usual edible examples).

(b) Upper antheridium and lower oogonium.

In Chara the male structure (globule, antheridium) lies below and the female structure (nucule, oogonium) lies above it at the node, and both are on the same (monoecious) plant. So (a), (c) and (d) are correct, while the statement with the antheridium above and the oogonium below is wrong.

(a) Amanita muscaria

Amanita muscaria (fly agaric) contains the hallucinogenic and toxic compounds muscimol and ibotenic acid. Neurospora is a genetic research organism, Ustilago is a smut pathogen and Morchella esculenta (morel) is an edible fungus.

(d) DNA enclosed in a protein coat

A virus is a nucleoprotein particle: its genome (either DNA or RNA, never both) is enclosed in a protein coat called the capsid. Viruses have no nucleus or chromosome, so (a) and (b) are wrong, and (c) is wrong because a virus has only one type of nucleic acid.

(d) Cell membrane structure

Archaebacteria have cell membranes with branched, ether-linked lipids (in some, lipid monolayers), unlike the ester-linked lipid bilayer of eubacteria; this helps them survive extreme conditions. Both groups show similar cell shapes, varied nutrition and binary fission, so (a), (b) and (c) are not distinguishing features.

(c) Sphagnum

Sphagnum, a moss, grows in bogs and its dead remains build up as peat, which is used as fuel and as a packing and soil material for its water holding capacity. Riccia, Funaria and Marchantia do not form peat.

(c) Spirogyra

Spirogyra shows isogamy by conjugation, where non-flagellated (amoeboid) gametes of equal size fuse through a conjugation tube. Ulothrix and Ectocarpus have flagellated isogametes, and Sargassum is oogamous.

(b) Lilium

In angiosperms like Lilium, the male gametophyte is the pollen grain, which at shedding has just two cells (a vegetative cell and a generative cell). Pinus pollen has four cells (two prothallial, one generative and one tube cell), while Funaria and Pteris have many-celled male gametophytes or antheridia-bearing plants.

(a) flagella

Motile bacteria move by flagella, which are thin filaments made of flagellin protein that rotate. Pili and fimbriae are for attachment and conjugation, not movement, and bacteria do not have cilia.

(c) In Oomycetes female gamete is smaller and motile, while male gamete is larger and non-motile

In oomycetes the female gamete (oosphere) is larger and non-motile, and the male gamete is smaller and motile, so the statement is reversed. The other statements are correct: Chlamydomonas shows isogamy and anisogamy, and Fucus is oogamous.

(c) A museum has collection of photographs of plants and animals.

A museum holds preserved plant and animal specimens (and dried or mounted material), not photographs. Photograph collections are not a taxonomic aid in NCERT. The other three statements are correct.

(b) Spirogyra

Spirogyra shows isogamy through non-flagellated gametes (conjugation, amoeboid gametes). Chlamydomonas has flagellated isogametes, Volvox and Fucus are oogamous.

(b) Cycas

Cycas has coralloid roots that harbour cyanobacteria (Anabaena, Nostoc) in association. Pinus has mycorrhiza on its roots; Equisetum and Psilotum do not have a cyanobacterial association.

(c) Three

(A) true, since gametophytes of liverworts, mosses and ferns are free-living. (B) true. (C) true, as Fucus, Volvox and Albugo are oogamous. (D) false, since the moss sporophyte is more elaborate than the liverwort one. (E) false, since Pinus is monoecious. That is three correct statements.

(d) Chromatophores

In some cyanobacteria the pigments sit on membranous extensions of the cell called chromatophores, which are the equivalent of thylakoids. Heterocysts are nitrogen-fixing cells, and pneumatophores are aerial roots of mangroves.

(d) Upper oogonium and lower antheridium on the same plant

In monoecious Chara the sex organs are borne on the same plant with the oogonium (female) above and the antheridium (male) below at a node. Antheridiophores and archegoniophores belong to liverworts, stamens and carpels to flowers.

(a) Archaebacteria

Deep sea water has no light, so cyanobacteria cannot live there. Archaebacteria such as thermophiles and methanogens live in extreme habitats like deep sea hydrothermal vents, so they are the likely ones.

(c) Fungi

Fungi are the most species-rich group among those listed (about 1.5 million estimated, with over 70,000 described). Algae, lichens, and mosses and ferns have far fewer species.

(a) Archaebacteria

Halophilic archaebacteria (with thermophiles and methanogens) live in extreme habitats such as salt pans and saline lakes. Their unusual cell wall and membrane lipids let them survive these conditions. Eubacteria, cyanobacteria and mycobacteria are not typical of extreme salinity.

(b) Rhodospirillum – Mycorrhiza

Rhodospirillum is a free-living photosynthetic nitrogen-fixing bacterium, not a mycorrhiza. Mycorrhiza is a fungus-root association. The other pairs are correct: Frankia fixes nitrogen in Alnus, Anabaena is a nitrogen-fixing cyanobacterium, and Rhizobium nodulates legumes such as alfalfa.

(c) Mycoplasma

Mycoplasmas are the smallest living cells. They lack a cell wall, can live without oxygen, and are pathogenic to both plants and animals. Bacillus, Pseudomonas and Nostoc all have cell walls.

(b) Volvox

Volvox is a colonial green alga with a hollow spherical colony of flagellated cells. Chlorella is unicellular, while Ulothrix and Spirogyra are filamentous.

(d) RNA molecules without protein coat

Viroids are free RNA molecules of low molecular weight and have no protein coat. Viruses always have a protein coat (capsid) around their nucleic acid, which may be DNA or RNA.

(a) Pinus – Dioecious

Pinus is monoecious, with male and female cones on the same tree, so the pairing is the mismatch. Cycas is dioecious. Salvinia is heterosporous and Equisetum is homosporous.

(c) Haplodiplontic, Diplontic

Ectocarpus has a haplodiplontic life cycle with alternation of haploid and diploid multicellular phases. Fucus is diplontic: the plant body is diploid and only the gametes are haploid.

(d) Chlamydomonas

In zygotic meiosis the zygote divides by meiosis to give haploid cells. This is seen in haplontic organisms like Chlamydomonas. Fucus has gametic meiosis, and Marchantia and Funaria show sporic meiosis.

(d) Glycocalyx

The glycocalyx is the outermost slime layer or capsule of a bacterial cell. It is gelatinous and sticky, and helps bacteria adhere to surfaces. The cell wall gives shape and rigidity, and bacteria have no nuclear membrane.

(a) Saccharomyces

Saccharomyces is a yeast, a unicellular fungus and therefore a eukaryote. Mycobacterium is a bacterium, while Nostoc and Oscillatoria are cyanobacteria, all of which are prokaryotes.

(a) Ovules are not enclosed by ovary wall in gymnosperms

Gymnosperms have naked seeds because their ovules are exposed, with no ovary wall. Selaginella and Salvinia are both heterosporous, horsetails (Equisetum) are pteridophytes, and Cycas has an unbranched stem while Cedrus is branched.

(c) Pseudopodia are locomotory and feeding structures in Sporozoans

Sporozoans (e.g. Plasmodium) have no locomotory structures; pseudopodia are found in amoeboid protozoans. The other statements are true: fungi and plants have cell walls, mushrooms are basidiomycetes, and Monera lack mitochondria.

(a) Uniflagellate gametes – Polysiphonia

Polysiphonia is a red alga, and red algae have no flagellated stages at all; their gametes are non-motile. The other pairs are right: brown algae have biflagellate zoospores, Marchantia has gemma cups, and Chlorella is unicellular.

(d) a-(iii), b-(iv), c-(i), d-(ii)

A herbarium stores dried, pressed, mounted plant specimens; a key is a booklet of contrasting characters used for identification; a museum holds preserved plants and animals; a catalogue is a methodical list of species in an area with brief descriptions.

(d) Pinus

Pinus pollen grains have two air bladders (wings) that aid wind dispersal. Mustard and mango are angiosperms without winged pollen, and Cycas pollen is not winged.

(c) Agaricus

Agaricus is a basidiomycete: after karyogamy and meiosis in the basidium, four basidiospores form exogenously on it. In Neurospora (and other ascomycetes) the ascospores form endogenously inside the ascus, and Alternaria and Saccharomyces are not of the exogenous basidiospore type.

(a) Pteridophytes

In heterosporous pteridophytes (Selaginella, Salvinia), the female gametophyte is retained on the parent sporophyte and the zygote develops into a young embryo there. This is considered a precursor to the seed habit. Bryophytes do not retain the gametophyte in this way as the sporophyte depends on the gametophyte, and gymnosperms are a later stage in evolution.

(d) it has obligate association with mycorrhizae.

Pinus seeds need a mycorrhizal fungus to germinate and establish, because the fungus helps absorb water and minerals such as phosphorus. The association is obligate, and the other reasons given are not the cause.

(a) Infective constituent in viruses is the protein coat.

The infective part of a virus is its nucleic acid (genome), not the protein coat. The coat only protects the genome and helps it enter the host, as the Hershey-Chase and Fraenkel-Conrat work shows. The other statements are correct: prions are misfolded proteins, viroids are free RNA without a coat, and viruses are obligate parasites.

(b) Yeasts have filamentous bodies with long thread-like hyphae.

Yeasts are unicellular fungi and do not form long hyphae. The other statements are correct: conidia form exogenously and ascospores endogenously, morels and truffles are edible ascomycetes, and Claviceps gives ergot alkaloids and LSD.

(b) (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)

A saprophyte decomposes dead organic matter. A parasite lives on a living host. A lichen is a symbiosis of an alga (or cyanobacterium) with a fungus. Mycorrhiza is a symbiosis of a fungus with plant roots. Only option (b) gives all four matches.

(d) Mangifera indica Linn.

The genus name is capitalised and the species name is not, and both are italicised or underlined. The author citation is written in abbreviated, non-italic form after the name. Linnaeus is cited as "Linn." (so "Car. Linn." is wrong), and "Indica" in capitals is wrong. Option (a) leaves out the author citation.

(d) Amylopectin and glycogen

Floridean starch is the reserve food of red algae. It is highly branched, like amylopectin and glycogen. Mannitol and algin, and laminarin, are reserve or structural products of brown algae. Cellulose is unbranched.

(b) Chlorella and Spirulina

Chlorella (green alga) and Spirulina (cyanobacterium, also called blue-green alga) are unicellular. Volvox is colonial and Anabaena is filamentous. Laminaria and Sargassum are brown algae, and Gelidium and Gracilaria are red algae, and all of these are multicellular.

(d) They have free RNA without protein coat

Viroids, discovered by T. O. Diener, are infectious agents made only of low molecular weight, free RNA with no capsid. Viruses have a protein coat, and no known viroid has DNA, so (a), (b) and (c) are wrong.

(b) Equisetum

Equisetum is a pteridophyte whose sporophyte bears spore-producing strobili (cones). Marchantia is a liverwort, and Salvinia and Pteris bear sporocarps and sori respectively, not strobili.

(d) Diadelphous and Dithecous anthers

Fabaceae has diadelphous stamens (9+1) with dithecous anthers. Solanaceae has epipetalous stamens and Liliaceae has epiphyllous stamens, so diadelphous is specific to Fabaceae. Monothecous anthers occur in Malvaceae, not here.

(a) Selaginella and Salvinia

Selaginella and Salvinia produce two kinds of spores (micro- and megaspores) and are heterosporous. Psilotum, Equisetum and Lycopodium are homosporous, which rules out the other options.

(d) Both A and R are correct and R is correct explanation of A

In mosses the spore germinates directly into a creeping, green, branched protonema, the first stage of the gametophyte. The spores come from the capsule of the sporophyte, so R explains A.

(b) A is true but R is false

Gymnosperm pollen is released from microsporangia and carried by air currents, so A is true. R is false because the pollen tube is formed and carries male gametes to the archegonia, so pollen tube is present, not absent.