NEB Class 11 · Past paper
The complete NEB Class 11 2066 exam paper for Biology, all 38 questions with solved model answers.
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What do you understand by taxonomy?
Taxonomy is the branch of biology that deals with the identification, nomenclature and classification of organisms into ordered groups (taxa) on the basis of their similarities and differences.
How is biology inter related with other sciences?
Biology draws on other sciences: physics (biophysics, working of eye/muscles), chemistry (biochemistry, metabolism), mathematics (biostatistics), and geology (palaeontology). Thus biology is interdisciplinary and depends on allied scienc...
Give the zoological name of (i) Jelly fish and (ii) Pigeon.
(i) Jelly fish = Aurelia aurita (ii) Pigeon = Columba livia
Who proposed recapitulation theory?
The recapitulation theory (biogenetic law, "ontogeny repeats phylogeny") was proposed by Ernst Haeckel.
Mention the number of valves in auriculo-ventricular aperture.
The auriculo-ventricular aperture of the frog heart is guarded by an auriculo-ventricular valve made of two (bicuspid) flaps/cusps.
What is pellicle?
The pellicle is the thin, firm yet flexible outer living covering of Paramecium lying just outside the plasma membrane; it maintains the definite body shape while allowing movement.
Name the boring organ of Earthworm.
The prostomium (a small lobe overhanging the mouth) acts as the boring/burrowing organ of the earthworm.
Define adaptation.
Adaptation is the structural, physiological or behavioural adjustment of an organism that fits it to survive and reproduce successfully in its particular environment.
Write the full form of IUCN.
IUCN = International Union for Conservation of Nature (and Natural Resources).
What is taxis?
Taxis is a directional locomotory response of a free-moving organism towards (positive) or away from (negative) an external stimulus such as light (phototaxis) or chemicals (chemotaxis).
Point out the drawbacks of "Lamarckism".
Drawbacks of Lamarck's theory (inheritance of acquired characters): - Acquired characters are not inherited because they affect only somatic cells, not the germ cells (Weismann's germplasm theory; his mice-tail experiment cut tails for m...
List the significances of conjugation in Paramecium.
Significances of conjugation in Paramecium: - It is a form of sexual reproduction that brings about recombination/reshuffling of genetic material between two individuals, giving variation. - It rejuvenates the animal by reorganising the ...
Describe pre-erythrocytic schizogony of malarial parasites.
In pre-erythrocytic schizogony, the sporozoites injected by the bite of an infected female Anopheles reach the liver through blood. Each sporozoite enters a liver (hepatic) cell, rounds up and grows into a cryptozoite/schizont. Its nucle...
How do flatworms and round worms differ in body cavity, digestive tract and excretory organs?
Feature Flatworms (Platyhelminthes) Round worms (Nematoda) --------- Body cavity Acoelomate (no body cavity) Pseudocoelomate (false coelom) Digestive tract Incomplete (single opening; mouth but no anus), or absent Complete (mouth and anu...
Draw a well labelled diagram of T.S. of earthworm passing through the intestinal region.
The section is roughly circular. From outside in: cuticle - epidermis - circular muscle - longitudinal muscle - coelomic epithelium - coelom. The intestine lies centrally, its dorsal wall folded inward to form the typhlosole (increases a...
Discuss the control measures of water pollution.
Control measures of water pollution: - Treat sewage and industrial effluents (sedimentation, filtration, biological treatment) before discharge into water bodies. - Restrict use of fertilizers and pesticides in catchments to reduce eutro...
Write short notes on fish migration.
Fish migration is the periodic mass movement of fishes from one place to another for feeding, breeding or in response to environmental change. Types: - Diadromous migration between fresh and salt water: anadromous (sea to river to breed,...
Write an essay on "evolution of man".
Human evolution (from primate ancestors to Homo sapiens) proceeded through the following main stages: - Dryopithecus (~25 million yrs): common ancestor of apes and man; arboreal, ape-like. - Ramapithecus: first man-like primate; probably...
Give an illustrated account of the excretory system of Earthworm. OR Describe the structure of lung of Frog and discuss its working mechanism.
Excretory system of earthworm: Excretion is carried out by coiled tubular structures called nephridia (metanephridia). Three types occur: (i) Septal nephridia on the walls of septa from the 15th segment backward, opening into the intesti...
Define adventitious root.
An adventitious root is a root that develops from any part of the plant other than the radicle, e.g. from stem nodes, leaves or other tissues (as in grasses, banyan prop roots).
What do you mean by cytokinesis?
Cytokinesis is the division of the cytoplasm of a cell that follows nuclear division (karyokinesis), partitioning the parent cell into two daughter cells.
What do you understand by binomial nomenclature?
Binomial nomenclature (given by Carolus Linnaeus) is the system of naming each organism by two Latin words: the genus (capitalised) followed by the species, both italicised, e.g. Homo sapiens.
What is incipient nucleus?
An incipient nucleus (nucleoid) is the false/primitive nucleus of a prokaryotic cell: a naked mass of circular DNA not bounded by a nuclear membrane, as in bacteria and blue-green algae.
What is sporangium?
A sporangium is a sac-like structure in which spores are produced and enclosed, e.g. the sporangia on the fern sporophyll.
Mention abiotic factors.
Abiotic factors are the non-living physical and chemical components of an environment, e.g. light, temperature, water, air, humidity, soil, pH and minerals.
What is lichen?
A lichen is a composite organism formed by the symbiotic association of a fungus (mycobiont) and an alga/cyanobacterium (phycobiont), living together as a single thallus.
What is food chain?
A food chain is the linear sequence through which food energy is transferred from producers to a series of consumers by eating and being eaten, e.g. grass - grasshopper - frog - snake.
What do you mean by micronutrients?
Micronutrients are essential mineral elements required by plants in very small (trace) amounts, e.g. iron, manganese, zinc, copper, boron, molybdenum and chlorine.
Define aestivation.
Aestivation is the mode of arrangement of sepals or petals in a floral bud with respect to one another, e.g. valvate, twisted (contorted), imbricate.
Differentiate between saturated and unsaturated fatty acids.
Saturated fatty acid Unsaturated fatty acid ------ Carbon chain has only single bonds ($C-C$) Chain has one or more double bonds ($C=C$) Carbon atoms are fully saturated with hydrogen Fewer hydrogen atoms (unsaturated) Usually solid at r...
Describe the plastids.
Plastids are double-membrane-bound organelles found only in plant cells. Types: - Chloroplast (green, contains chlorophyll; site of photosynthesis). - Chromoplast (coloured other than green; gives colour to flowers and fruits). - Leucopl...
Describe the process of crossing over in meiosis.
Crossing over is the mutual exchange of segments between the non-sister chromatids of homologous chromosomes during pachytene of prophase I of meiosis. The homologues pair (synapsis) to form bivalents; the non-sister chromatids come in c...
Describe the structure of Yeast.
Yeast (Saccharomyces) is a unicellular ascomycete fungus. Each cell is oval/spherical, bounded by a cell wall (of chitin and glucan) and plasma membrane. The cytoplasm contains a single nucleus, mitochondria, ribosomes, a large vacuole, ...
Describe the scalariform conjugation in Spirogyra.
In scalariform (ladder-like) conjugation two filaments of Spirogyra lie side by side. Papillae (conjugation tubes) grow out from opposite cells of the two filaments and fuse to form a conjugation tube, so the paired tubes look like the r...
Describe the male cone of Pinus.
The male cone (staminate strobilus) of Pinus is a small, oval, catkin-like cone borne in clusters at the base of long shoots. It has a central axis bearing spirally arranged microsporophylls (stamens). Each microsporophyll bears two micr...
Differentiate between prokaryotic and eukaryotic cell.
Prokaryotic cell Eukaryotic cell ------ Nucleus is not membrane-bound (nucleoid) True membrane-bound nucleus present Membrane-bound organelles absent Mitochondria, ER, Golgi, plastids etc. present Ribosomes are 70S Ribosomes are 80S (70S...
Describe the life cycle of Dryopteris showing alternation of generation. OR Describe the family Cruciferae with necessary diagrams and give two examples of economic value of this family.
Life cycle of Dryopteris (fern): The fern plant is the dominant diploid (2n) sporophyte with roots, rhizome and pinnate leaves (fronds). The lower surface of fertile fronds bears sori, each a cluster of sporangia covered by an indusium. ...
Define ecosystem and discuss the main components of ecosystem.
An ecosystem is a self-regulating natural unit in which the living organisms (biotic community) interact with one another and with their non-living (abiotic) surroundings, exchanging matter and energy.
Main components:
Abiotic components - the non-living part:
Biotic components - the living part:
Energy flows one way (sun -> producers -> consumers -> decomposers) while nutrients are recycled, keeping the ecosystem in balance.
Saturated fatty acid Unsaturated fatty acid ------ Carbon chain has only single bonds () Chain has one or more double bonds () Carbon atoms are fully saturated with hydrogen Fewer hydrogen atoms (unsaturated) Usually solid at r...