NEB Class 11 · Past paper
The complete NEB Class 11 2068 exam paper for Biology, all 38 questions with solved model answers.
Tap a question to open its answer.
What is prokaryotic cell?
A prokaryotic cell is a primitive cell that lacks a true membrane-bound nucleus and membrane-bound organelles, its genetic material lying free as a nucleoid, e.g. bacteria and blue-green algae.
Define cell wall.
A cell wall is the rigid, non-living, outermost protective covering of plant cells, fungi and bacteria; in plants it is made mainly of cellulose and gives shape, support and protection.
What is cyclosis?
Cyclosis is the streaming (rotational or circulatory) movement of cytoplasm within a living cell, which helps in distributing nutrients and organelles.
Define binomial nomenclature.
Binomial nomenclature is the system of naming organisms by two Latin words - the genus and the species - introduced by Carolus Linnaeus, e.g. Mangifera indica.
What is coenocytic?
A coenocytic structure is a multinucleate mass of cytoplasm formed by repeated nuclear division without cell wall/cytoplasmic division, e.g. the hyphae of Rhizopus and Vaucheria.
Define thallophytes.
Thallophytes are simple, primitive plants whose body is a thallus not differentiated into true root, stem and leaves, and which lack vascular tissue, e.g. algae and fungi.
What is rhizoids?
Rhizoids are fine, thread-like, root-like outgrowths that anchor lower plants (mosses, ferns, fungi) to the substratum and help in absorption of water and minerals.
Define abiotic factor.
Abiotic factors are the non-living physical and chemical components of the environment that affect organisms, e.g. light, temperature, water, air, soil and minerals.
Define food chain.
A food chain is the sequence of transfer of food energy from producers to a series of consumers through eating and being eaten, e.g. phytoplankton -> zooplankton -> fish.
What is acid rain?
Acid rain is precipitation (rain, snow, fog) made abnormally acidic (pH < 5.6) by dissolved oxides of sulphur and nitrogen (forming H2SO4 and HNO3) released from burning fossil fuels.
Describe the fatty acids.
Fatty acids are long-chain aliphatic carboxylic acids ($R-COOH$) that are the building blocks of fats/lipids. They may be saturated (only single C-C bonds, e.g. palmitic, stearic acid; solid) or unsaturated (one or more C=C double bonds,...
Discuss the structure of golgi complex.
The Golgi complex (dictyosome) is a stack of 3-10 flattened, membrane-bound sacs (cisternae) arranged parallel and slightly curved, associated with small vesicles and vacuoles. It has two faces: the convex cis (forming) face towards the ...
Describe the process of mitosis.
Mitosis is an equational nuclear division producing two genetically identical daughter cells. Karyokinesis occurs in four phases: - Prophase: chromosomes condense and become visible; nuclear membrane and nucleolus disappear; spindle begi...
Elaborate the economic importance of fungi.
Economic importance of fungi:
Describe the scalariform conjugation in Spirogyra.
In scalariform (ladder-like) conjugation, two Spirogyra filaments lie parallel; conjugation tubes grow out from the opposite cells of the two filaments and fuse, so the joined tubes resemble the rungs of a ladder. The protoplast of each ...
Discuss the carbon cycle in nature.
The carbon cycle is the circulation of carbon between the atmosphere, living organisms and the earth. - CO2 of the air is fixed by green plants during photosynthesis into organic food. - Carbon passes to animals through food chains. - Re...
Describe the importance of structure of endoplasmic reticulum.
The endoplasmic reticulum (ER) is a network of membrane-bound tubules, vesicles and cisternae in the cytoplasm connecting the nuclear membrane with the plasma membrane. Rough ER (RER) bears ribosomes and is important in protein synthesis...
Describe the life cycle of Fern with alternation of generation. OR Describe the Cruciferae with necessary diagrams and give two examples of economic value of this family.
Life cycle of fern (alternation of generations): The dominant fern plant is the diploid sporophyte (2n) with rhizome, roots and fronds. Fertile fronds bear sori of sporangia on their underside. Spore mother cells in the sporangium undergo meiosis to form haploid spores (n). A spore germinates into a small green heart-shaped prothallus (gametophyte, n) bearing antheridia (biflagellate antherozoids) and archegonia (eggs). With water, fertilisation forms a diploid zygote (2n) that grows into a new sporophyte. Thus a gametophyte generation (n) alternates with a sporophyte generation (2n).
OR - Family Cruciferae (Brassicaceae): herbs with cruciform flowers; flower bisexual, actinomorphic; sepals 4 (2+2), petals 4 (cross-shaped), stamens 6 tetradynamous (4 long + 2 short), bicarpellary syncarpous superior ovary, unilocular becoming bilocular by a false septum (replum); fruit a siliqua/silicula. Floral formula: $\oplus$ ♂ $K_{2+2} , C_4 , A_{2+4} , \underline{G}_{(2)}$. Economic value: mustard Brassica campestris (oil), cabbage/cauliflower Brassica oleracea (vegetable).
floral-diagram-mustard
What is ecosystem? Describe in detail about the pond ecosystem.
An ecosystem is a natural unit in which living organisms interact with one another and with their non-living environment through exchange of matter and energy. A pond is a good example of a small, self-sufficient freshwater ecosystem.
Abiotic components: water, dissolved oxygen and CO2, light, temperature, and inorganic (nitrates, phosphates) and organic nutrients.
Biotic components:
Energy flows from sun -> producers -> consumers -> decomposers, while nutrients are recycled, keeping the pond in a self-regulating balance.
Define molecular biology.
Molecular biology is the branch of biology that studies life at the molecular level, especially the structure and function of biomolecules like DNA, RNA and proteins and how they control cellular activities.
Name the branch of biology with the study of fossils.
The study of fossils is called Palaeontology.
How was the earth formed?
The earth is believed to have formed about 4.6 billion years ago from a hot, spinning cloud of gas and dust (nebula) that condensed and cooled; the molten mass gradually solidified, and water vapour condensed to form the oceans.
Who wrote the book "Origin of Species"?
The book "On the Origin of Species" (1859) was written by Charles Darwin.
What do you understand by taxonomic hierarchy?
A taxonomic hierarchy is the arrangement of organisms into successive ranks or categories in a definite order - Kingdom, Phylum, Class, Order, Family, Genus, Species - from the largest to the smallest group.
What is Ostium?
An ostium is an aperture or opening; in the frog heart, the sino-auricular ostium (guarded by a valve) is the opening through which blood passes from the sinus venosus into the right auricle.
What do you mean by speciation?
Speciation is the evolutionary process by which new species arise from pre-existing ones, usually through variation, isolation (geographic/reproductive) and natural selection.
Name two wildlife reserves of Nepal.
Two wildlife reserves of Nepal: Koshi Tappu Wildlife Reserve and Shuklaphanta Wildlife Reserve (also Parsa).
Give the difference between reflex action and taxis.
A reflex action is an automatic, involuntary response of a part of the body to a stimulus, mediated by the nervous system (e.g. withdrawal of hand from a hot object). Taxis is a directed locomotory movement of the whole organism towards ...
Define the term nature conservation.
Nature conservation is the wise, planned protection, management and sustainable use of natural resources (forests, wildlife, soil, water) so that they are preserved for present and future generations.
Describe the process of binary fission in Paramecium.
Binary fission is the common asexual reproduction of Paramecium, occurring in favourable conditions. It is transverse: the micronucleus divides by mitosis and the macronucleus by amitosis; a constriction appears across the middle of the ...
Draw a well labeled diagram of T.S. of earthworm through Pharynx.
Model answer for this question is being prepared.
Write short note on hibernation and aestivation.
Hibernation (winter sleep): a state of dormancy/inactivity in which some animals pass the cold winter by lowering metabolism, e.g. the frog buries itself in mud and remains inactive. Aestivation (summer sleep): a state of dormancy by whi...
Write short note on teeth of frog.
The frog has small, backwardly directed teeth that are homodont (all alike), polyphyodont (replaced many times) and acrodont (attached to the surface of the bone). They occur on the upper jaw (maxillary teeth) and on the roof of the mouth as vomerine teeth; the lower jaw is toothless. The teeth are not used for chewing but only to hold slippery prey and prevent its escape.
Write short note on the "use and disuse of organ".
The theory of use and disuse of organs is a part of Lamarckism. It states that an organ that is used constantly becomes better developed and stronger, while an organ that is not used gradually weakens and degenerates, and these changes a...
Discuss the effects of water pollution.
Effects of water pollution: - Water-borne diseases in humans (cholera, typhoid, dysentery, jaundice) from contaminated drinking water. - Death of aquatic life: toxic effluents and oxygen depletion kill fish and other organisms. - Eutroph...
Write short note on migratory behavior of fishes.
Many fishes undertake regular migration for feeding and especially for breeding. Anadromous fishes (e.g. salmon, hilsa) migrate from the sea into rivers to spawn, while catadromous fishes (e.g. eel) migrate from fresh water to the sea to breed. They are guided by cues such as water temperature, currents, chemical signals (smell) and light. Migration helps them find suitable spawning grounds, food and favourable conditions, ensuring survival of the species.
Describe the structure of lung and explain the working mechanism in frog. OR What is schizogony? Illustrate it with reference to the life cycle of Plasmodium vivax.
Lung of frog and its working: Each lung is a thin-walled, elastic, hollow ovoid sac whose inner wall is folded into a network of ridges (alveoli) richly supplied with blood capillaries, giving a large surface for gaseous exchange. The tw...
Discuss briefly the evolution of human being from his early ancestor to modern man.
Evolution of man (progressive stages): - Dryopithecus (~25 mya): ape-like common ancestor of apes and man, arboreal. - Ramapithecus: first near-human, probably semi-erect, small canines. - Australopithecus (~4 mya, Africa): bipedal, brai...
Fatty acids are long-chain aliphatic carboxylic acids () that are the building blocks of fats/lipids. They may be saturated (only single C-C bonds, e.g. palmitic, stearic acid; solid) or unsaturated (one or more C=C double bonds,...
Life cycle of fern (alternation of generations): The dominant fern plant is the diploid sporophyte (2n) with rhizome, roots and fronds. Fertile fronds bear sori of sporangia on their underside. Spore mother cells in the sporangium undergo meiosis to form haploid spores (n). A spore germinates into a small green heart-shaped prothallus (gametophyte, n) bearing antheridia (biflagellate antherozoids) and archegonia (eggs). With water, fertilisation forms a diploid zygote (2n) that grows into a new sporophyte. Thus a gametophyte generation (n) alternates with a sporophyte generation (2n).
OR - Family Cruciferae (Brassicaceae): herbs with cruciform flowers; flower bisexual, actinomorphic; sepals 4 (2+2), petals 4 (cross-shaped), stamens 6 tetradynamous (4 long + 2 short), bicarpellary syncarpous superior ovary, unilocular becoming bilocular by a false septum (replum); fruit a siliqua/silicula. Floral formula: ♂ . Economic value: mustard Brassica campestris (oil), cabbage/cauliflower Brassica oleracea (vegetable).