NEB Class 11 · Past paper
The complete NEB Class 11 2069 exam paper for Biology, all 38 questions with solved model answers.
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What is the message of Steward's experiment?
Steward's experiment (on carrot phloem cells growing into whole plants in culture) demonstrated cellular totipotency - that a single differentiated plant cell retains the full genetic capacity to regenerate into a complete plant.
What do you mean by RER and SER?
RER (Rough Endoplasmic Reticulum) bears ribosomes on its surface and is involved in protein synthesis and transport. SER (Smooth Endoplasmic Reticulum) lacks ribosomes and functions in the synthesis of lipids and steroids and in detoxification.
Define suicidal bag.
The lysosome is called the suicidal bag of the cell because it contains powerful hydrolytic (digestive) enzymes that can, on rupture, digest the cell's own components (autolysis).
What does it mean by taxonomy?
Taxonomy is the science of identification, naming (nomenclature) and classification of living organisms into ordered groups based on their similarities and differences.
Write the name of bacteria on the basis of its shape.
On the basis of shape, bacteria are named: Coccus (spherical), Bacillus (rod-shaped), Spirillum (spiral) and Vibrio (comma-shaped).
Define the function of leaf.
The main functions of the leaf are photosynthesis (manufacture of food), transpiration (loss of water vapour through stomata) and gaseous exchange (respiration).
Mention about sori.
A sorus (plural sori) is a cluster of sporangia borne on the lower surface of a fertile fern frond, often protected by a flap called the indusium.
How do you mean autoecology?
Autecology is the branch of ecology that studies the relationship of a single species (individual organism) with its environment.
State about predation.
Predation is a biological interaction in which one organism (the predator) kills and feeds on another organism (the prey), e.g. a snake eating a frog. It regulates prey populations.
Elaborate climax community.
A climax community is the final, stable and self-perpetuating community that develops at the end of ecological succession, in equilibrium with the prevailing climate and environment (e.g. a mature forest).
Differentiate between DNA and RNA.
DNA RNA ------ Sugar is deoxyribose Sugar is ribose Usually double-stranded helix Usually single-stranded Nitrogen bases A, T, G, C (thymine) A, U, G, C (uracil in place of thymine) Occurs mainly in the nucleus (chromosomes) Occurs in nu...
Describe the structure and functions of plastid.
Plastids are double-membrane organelles of plant cells. Types: chloroplasts (green, with chlorophyll, in grana-stroma organisation), chromoplasts (coloured, in flowers/fruits) and leucoplasts (colourless, storage). A chloroplast has oute...
Describe the process of meiosis I.
Meiosis I is the reductional division that halves the chromosome number. Its stages:
Thus one diploid cell gives two haploid cells, providing genetic variation through crossing over and independent assortment.
Describe the structure of Spirogyra.
Spirogyra is a green, filamentous freshwater alga whose unbranched filament is made of a single row of cylindrical cells joined end to end. Each cell has a cellulose cell wall with a mucilage sheath, a peripheral cytoplasm, a large centr...
Importance of nitrogen cycle in nature.
Importance of the nitrogen cycle: - It makes atmospheric nitrogen available to plants in usable form (nitrates) through nitrogen fixation by bacteria (Rhizobium, Nostoc) and lightning. - It supplies nitrogen needed for building proteins ...
Consequences of deforestation.
Consequences of deforestation: - Soil erosion, landslides and floods due to loss of protective vegetation cover. - Loss of biodiversity/wildlife habitat and extinction of species. - Climatic change: rise in atmospheric CO2, global warmin...
Distribution of Pinus and its importance.
Distribution: Pinus is a gymnosperm widely distributed in the temperate and hilly regions; in Nepal it grows on the mid-hills and mountains (e.g. Pinus roxburghii, Pinus wallichiana) at about 1000-3000 m altitude.
Importance: it yields valuable softwood timber for construction and furniture, resin/turpentine, paper pulp, and edible seeds in some species; pine forests also protect watersheds and are grown as ornamentals.
Describe the structure and lifecycle of Marchantia in detail. OR Describe the family Solanaceae with necessary diagrams and give two examples of economic value of this family.
Marchantia (liverwort): The plant body is a green, dorsiventral, dichotomously branched thallus (gametophyte, n) attached to soil by rhizoids and scales; its upper surface shows rhomboidal areas with air pores and gemma cups for vegetati...
Define succession and describe the process of succession in detail.
Ecological succession is the orderly, gradual and progressive replacement of one biotic community by another in an area until a stable climax community is established.
Process (stages):
Succession starting on a bare lifeless area is primary (e.g. on rock - xerarch; in water - hydrarch), while that on a previously inhabited but disturbed area is secondary.
Define the term Herpetology.
Herpetology is the branch of zoology that deals with the study of reptiles and amphibians.
Give a reason to show the relation of zoology with chemistry.
Zoology is related to chemistry because life processes in animals - digestion, respiration, metabolism and the action of enzymes and hormones - are essentially chemical reactions, studied as biochemistry.
What is recapitulation theory?
The recapitulation theory (biogenetic law) of Ernst Haeckel states that "ontogeny repeats phylogeny", i.e. the developmental (embryonic) stages of an organism briefly repeat the evolutionary history of its ancestors.
What do you know about primordial soup?
The primordial (primitive) soup is the hot, dilute mixture of simple organic molecules (amino acids, sugars) believed to have accumulated in the early oceans, from which the first life is thought to have originated (Oparin-Haldane hypoth...
Write the scientific name of a vertebrate having long, flexible neck and webbed toes.
A vertebrate having a long, flexible neck and webbed toes is the swan/duck; e.g. the domestic duck Anas platyrhynchos.
Name the excretory organs of flatworms.
The excretory organs of flatworms (Platyhelminthes) are flame cells (protonephridia/solenocytes).
When do female anopheles mosquitos become infectious?
A female Anopheles mosquito becomes infective when the sporozoites of Plasmodium have developed and migrated to its salivary glands; on biting, it then transmits the parasite to man.
What is smog?
Smog is a thick, harmful haze formed near the ground by the mixing of smoke and fog (or by photochemical reaction of vehicular pollutants in sunlight); it reduces visibility and causes respiratory problems.
What do you mean by arboreal adaptation?
Arboreal adaptation refers to the structural and behavioural modifications that fit an animal for living on trees, e.g. grasping (prehensile) limbs and tail, opposable digits and sharp claws, as in monkeys and squirrels.
Define Buffer zone.
A buffer zone is the peripheral area surrounding a national park or protected area where regulated human use of resources is allowed, so as to reduce conflict and act as a protective barrier for the core protected area.
Write short note on Miller-Urey Experiment.
The Miller-Urey experiment (1953) tested the origin of life (chemical evolution). Stanley Miller and Harold Urey passed electric sparks (simulating lightning) through a mixture of gases believed to make up the primitive atmosphere - methane (CH4), ammonia (NH3), hydrogen (H2) and water vapour - in a closed apparatus. After some days they obtained simple organic compounds including amino acids (like glycine and alanine). This supported the Oparin-Haldane hypothesis that life's building blocks could form spontaneously from simple molecules under early-earth conditions.
Give any six important characters of Phylum Mollusca.
Six important characters of Phylum Mollusca: 1. Body is soft, unsegmented, and usually divided into head, muscular foot and visceral mass. 2. Body is covered by a soft fold of skin called the mantle, which often secretes a calcareous she...
Draw a neatly labeled diagram of T.S. of ileum of frog (no description required).
Model answer for this question is being prepared.
Describe the process of cocoon formation in Pheretima.
In Pheretima, after copulation and mutual exchange of sperm (stored in spermathecae), the clitellum (glandular girdle over segments 14-16) secretes a tough cocoon (cocoon membrane). The clitellar cells also secrete albumen into it. The c...
Describe erythrocytic schizogony of Plasmodium.
In erythrocytic schizogony, the merozoites released from the liver enter red blood cells (RBCs). Inside the RBC a merozoite becomes a rounded trophozoite with a vacuole (the signet-ring stage); it grows, feeds on haemoglobin (leaving hae...
Discuss the effects of air pollution.
Effects of air pollution: - Respiratory and health problems in humans (asthma, bronchitis, lung cancer) and eye/throat irritation. - Acid rain from SO2 and NOx damages plants, soil, buildings and aquatic life. - Global warming from green...
Discuss the causes of extinction of wildlife.
Causes of extinction of wildlife: - Habitat destruction due to deforestation, urbanisation and agriculture. - Over-hunting, poaching and illegal trade for skin, horn, ivory and meat. - Environmental pollution and use of pesticides. - Int...
Give an account of the structure of heart of Frog. OR Describe the nephridial system of Pheretima.
Heart of frog: The frog heart is three-chambered - two auricles (right and left) and one ventricle - enclosed in a two-layered pericardium. On the dorsal side lies a triangular sinus venosus that receives deoxygenated blood from the body...
Discuss the modern synthetic theory of evolution.
The modern synthetic theory (Neo-Darwinism) explains evolution by combining Darwin's natural selection with genetics and population biology. It regards evolution as a change in gene (allele) frequency in a population over generations, br...