CSIR-NET Life Sciences Unit 9 PYQs: Diversity of Life Forms Questions with Solutions

A cell wall of peptidoglycan (murein) is unique to bacteria. Archaeal walls are made of pseudomurein, S-layer proteins or polysaccharides, never peptidoglycan, which is why archaea resist penicillin and lysozyme. Both groups lack a nuclear membrane, usually have one circular chromosome, and organise genes into operons.

In bisporic development the megaspore mother cell’s first meiotic division gives two cells, one of which degenerates. The surviving dyad cell, with two meiotic nuclei, forms the eight-nucleate embryo sac. That is the Allium type. Polygonum is monosporic (the commonest type), Oenothera monosporic and four-nucleate, and Plumbago tetrasporic.

Answer: (1) Cytochrome oxidase I

The standard animal DNA barcode is a 648-bp segment of the mitochondrial cytochrome c oxidase subunit I (COI) gene (Hebert, 2003). It varies enough between species but little within them, and universal primers amplify it. matK and rbcL are the plant barcodes, and ITS is used for fungi.

Answer: (1) female flowers and hermaphrodite flowers on separate individuals.

Gynodioecy: some plants carry only female (pistillate) flowers and others carry hermaphrodite flowers, as in thyme and many Lamiaceae. It is often caused by cytoplasmic male sterility. Separate male and female plants is dioecy. Female and hermaphrodite flowers on the same plant is gynomonoecy, and male and female flowers on the same plant is monoecy.

Answer: (3) Phylogenetic classification

A phylogenetic classification (cladistic) groups organisms by common ancestry, so that each named group is a clade with its ancestor and all its descendants. Linnaean ranks and binomial nomenclature are naming conventions. They can be applied to groups whether or not those groups reflect ancestry.

Answer: (1) Cork cambium

The cork cambium (phellogen) is a secondary lateral meristem. It cuts off phellem (cork) to the outside and phelloderm (secondary cortex) to the inside. The three layers together make the periderm. The fascicular and interfascicular cambia make secondary xylem and phloem.

Answer: (3) southern India and Sri Lanka

The grizzled giant squirrel, Ratufa macroura, lives only in southern India (riverine forests of Tamil Nadu and Kerala, as in the Srivilliputhur sanctuary) and Sri Lanka. North-east India has the black giant squirrel (R. bicolor), and peninsular India also has the Malabar giant squirrel (R. indica).

Answer: (4) Water is conducted by hydroids in all bryophytes.

Bryophytes are homosporous, their life cycle is dominated by the gametophyte, and their antherozoids are biflagellate. Statement 4 is the incorrect one. Hydroids, dead water-conducting cells, occur only in some mosses (Polytrichales and relatives). Liverworts and hornworts have no such conducting strand.

Answer: (3) International Code of Botanical Nomenclature (ICBN)

The International Code of Botanical Nomenclature (ICBN) was renamed the International Code of Nomenclature for algae, fungi, and plants (ICN) by the Melbourne Code, adopted in 2011 and published in 2012. That code also allowed English descriptions instead of Latin and electronic publication of new names.

Answer: (2) Apis dorsata

Apis dorsata, the rock or giant honeybee, is native to the Indian subcontinent and South-east Asia. So are A. cerana indica and A. florea. A. mellifera was introduced from Europe for beekeeping. A. koschevnikovi and A. nigrocincta are found only in Borneo and Sulawesi.

Answer: (4) Lepidoptera

The fall armyworm, Spodoptera frugiperda, is a moth, order Lepidoptera, family Noctuidae. It comes from the Americas and was first recorded in India on maize in Karnataka in 2018, after which it spread across the country. Its caterpillars cause the damage.

Answer: (1) Nymphaeales

APG IV places three lineages at the base of the angiosperm tree, the ANA grade: Amborellales, then Nymphaeales (water lilies), then Austrobaileyales. Amborellales is not among the options, so Nymphaeales is the earliest-diverging group listed. Piperales are magnoliids, Ranunculales are early eudicots, and monocots diverged later.

Answer: (2) Branchiostoma

Paedomorphosis is keeping juvenile or larval features in a sexually mature adult. The axolotl (Ambystoma) and some newts (Triturus) breed with gills, and the larvacean Oikopleura keeps a tadpole-like body plan throughout life. Branchiostoma (amphioxus) goes through a normal larva-to-adult metamorphosis, so it is not paedomorphic.

Answer: (1) Leafless and rootless body with a dichotomously branching stem

Psilotales, the whisk ferns (Psilotum, Tmesipteris), have a leafless, rootless body with a dichotomously branched stem, only tiny enations or scales, and a rhizome with rhizoids and mycorrhiza. Giant fronds belong to tree ferns and Marattiales, whorled scale leaves to horsetails, and microphylls with roots to lycophytes.

Answer: (1) It is found in catfish and facilitates sound transmission from the swim bladder to the inner ear.

Weberian ossicles are a chain of small bones derived from the anterior vertebrae. They link the swim bladder to the inner ear in the Ostariophysi (catfishes, carps, characins), so the swim bladder acts as a sound amplifier and these fish hear unusually well.

Answer: (3) Cyanobacteria (Blue-green algae)

Cyanobacteria are prokaryotes, so the bacteriological code (ICNP) covers them. For historical reasons they are also named as “blue-green algae” under the botanical code (ICN). Authors can therefore publish their genera under either code, an unresolved dual system. Green algae, diatoms and slime moulds are eukaryotes and fall under the ICN only.