NEB Class 11 · Past paper
The complete NEB Class 11 2067 exam paper for Biology, all 37 questions with solved model answers.
Tap a question to open its answer.
Write two peculiar characters of class Aves.
Two peculiar characters of class Aves: (i) body is covered with feathers and the fore-limbs are modified into wings for flight; (ii) presence of a beak without teeth and pneumatic (hollow) bones that make the body light for flying.
Give classification of Earthworm.
Earthworm (Pheretima posthuma): Kingdom Animalia, Phylum Annelida, Class Oligochaeta, Order Haplotaxida, Genus Pheretima.
What are homologous organs?
Homologous organs are organs of different animals that have the same basic structure and embryonic origin but perform different functions, e.g. the forelimb of man, wing of bird and flipper of whale. They indicate divergent evolution.
The opening of pulmonary veins are devoid of valves. Why?
The pulmonary veins open into the left auricle carrying oxygenated blood; since the blood flows forward into the auricle without any risk of back-flow at this point, valves are not required at their openings.
Define Physiology.
Physiology is the branch of biology that deals with the study of the functions and vital processes of organisms and their parts (organs, tissues and cells).
Mention the functions of Trichocyst in Paramecium.
Trichocysts of Paramecium are spindle-shaped bodies below the pellicle that discharge sticky threads used mainly for defence/offence and for anchorage during feeding.
Which human ancestor invented fire?
Homo erectus (e.g. Peking man, Sinanthropus) is credited with the discovery and use of fire.
Who coined the term Biology?
The term Biology was coined by Lamarck and Treviranus (independently, 1802). (Aristotle is called the Father of Biology.)
What do you understand by wild life?
Wildlife refers to all the non-domesticated (wild) animals and plants living naturally in their own habitats without human interference.
What is the gist of Lamarckism?
The gist of Lamarckism is the inheritance of acquired characters: environment and use/disuse of organs cause changes in an organism during its life, and these acquired characters are passed on to the offspring, leading to evolution.
Describe the general characters of class Mammalia.
General characters of class Mammalia: - Body covered with hair; skin has sweat and sebaceous glands. - Females possess mammary glands that secrete milk to nourish the young. - Warm-blooded (homeothermic); heart four-chambered; RBCs non-n...
Earthworms are friends of farmers. Justify.
Earthworms are called friends of farmers because: - Their burrowing aerates and loosens the soil, improving drainage and root penetration. - They feed on dead organic matter and their castings enrich the soil with humus and nutrients (ni...
Draw a well labeled diagram of the arterial system of frog (no description required).
Model answer for this question is being prepared.
Write short note on taxis.
Taxis is a directed locomotory movement of a free-living organism in response to an external stimulus. It is positive when the movement is towards the stimulus and negative when away. Types by stimulus include phototaxis (light), chemotaxis (chemicals), thermotaxis (temperature) and geotaxis (gravity), e.g. Euglena moving towards light. Taxis helps organisms seek favourable conditions (food, light) and avoid harmful ones.
Discuss the control of depletion of wild life in Nepal.
Measures to control depletion of wildlife in Nepal: - Establish and protect national parks, wildlife reserves and conservation areas (e.g. Chitwan, Bardia, Sagarmatha). - Enforce laws against poaching, illegal hunting and trade in wildli...
The benefits of animal migration.
Benefits of animal migration: - Enables animals to reach areas with abundant food and to escape food scarcity. - Provides favourable climate and shelter, escaping extreme cold or heat. - Ensures suitable breeding/spawning grounds for suc...
Describe the reproductive system of Frog with suitable diagram. OR Describe the structure and function of septal nephridia of Earthworm.
Reproductive system of frog (sexes separate): Male: a pair of testes attached to the kidneys by mesorchium; fine vasa efferentia carry sperms from each testis into the kidney and then through the ureter (urinogenital duct) to the cloaca....
Discuss the Neo Darwinism along with the drawbacks of theory of Natural Selection.
Neo-Darwinism (modern synthetic theory): It is a modified form of Darwinism that combines Darwin's natural selection with the findings of genetics (Mendelism), mutation and population biology. Its main factors are: - Gene/genetic variati...
Define cellular totipotency.
Cellular totipotency is the inherent ability of a single living plant cell to divide, grow and develop into a complete organism under suitable conditions.
What is plasmodesmata?
Plasmodesmata are fine cytoplasmic threads that pass through the pores in adjacent plant cell walls, connecting the protoplasts of neighbouring cells and allowing communication and transport between them.
Write the function of plasma membrane.
The plasma membrane is selectively permeable and regulates the entry and exit of substances into and out of the cell, thereby maintaining the internal environment of the cell.
What do you mean by heterocyst?
A heterocyst is a specialised, thick-walled, colourless enlarged cell found in some filamentous blue-green algae (e.g. Nostoc, Anabaena) that is the site of nitrogen fixation.
Why lichen is called a dual organism?
A lichen is called a dual (composite) organism because its body is formed by the symbiotic association of two different organisms: a fungus (mycobiont) and an alga or cyanobacterium (phycobiont).
What is zygospore?
A zygospore is a thick-walled, diploid resting spore formed by the fusion of two gametes/protoplasts (e.g. in the conjugation of Spirogyra or in Rhizopus), which germinates under favourable conditions.
Give one example of each: (i) Vascular seedless plant (ii) Vascular seeded plant.
(i) Vascular seedless plant: fern (Dryopteris) (ii) Vascular seeded plant: pine (Pinus) (or any angiosperm/gymnosperm).
What is chiasmata?
Chiasmata (singular chiasma) are the X-shaped points of contact between non-sister chromatids of homologous chromosomes where crossing over (exchange of segments) occurs during prophase I of meiosis.
Write the meaning of sporophyll with its types.
A sporophyll is a leaf-like structure that bears sporangia (spores). Types: microsporophyll (bears microsporangia/microspores) and megasporophyll (bears megasporangia/megaspores).
Define a perianth.
A perianth is the outer, sterile whorl(s) of a flower when the calyx and corolla are not distinguishable; its members are called tepals, e.g. in lily.
Define protein and highlight its role as an important biomolecule.
Proteins are complex nitrogenous macromolecules made of amino acids joined by peptide bonds. Roles as biomolecules:
Thus proteins are essential for growth, repair, catalysis and regulation of life processes.
Describe the process of amitosis and mention its significance.
Amitosis is the simplest, direct cell division without the formation of spindle or chromosomes. The nucleus elongates and constricts in the middle to divide into two, followed by constriction of the cytoplasm (cytokinesis), forming two d...
Describe the structure and function of chloroplast.
The chloroplast is a green, double-membrane plastid. Between the two membranes and enclosing a matrix called the stroma, it has a system of flattened sacs, the thylakoids, stacked to form grana interconnected by stroma lamellae. The thylakoid membranes contain chlorophyll; the stroma contains enzymes, DNA, ribosomes and starch grains. Function: it is the site of photosynthesis - the light reactions occur on the grana and the dark (Calvin) reactions in the stroma, converting light energy into chemical energy (food).
Describe the structure of fern prothallus.
The prothallus is the independent, green, haploid gametophyte of the fern. It is a small, heart-shaped, dorsiventral thallus attached to the soil by rhizoids on its lower surface. The same lower surface bears the sex organs: antheridia (...
Describe the structure of megasporophyll of Cycas.
The megasporophyll of Cycas is a leaf-like, brown, spirally arranged structure crowded at the stem apex (not forming a compact cone). It has a lower stalk, a middle region bearing a row of ovules (2-8) along its margins, and an upper pin...
What are the physical constraints of a mountain ecosystem?
Physical constraints of a mountain ecosystem: - Low temperature and severe cold that decreases with altitude. - Low atmospheric pressure and thin air (low oxygen). - High wind velocity and intense solar/UV radiation. - Steep, rocky slope...
Justify with appropriate reasons that viruses are living beings.
Viruses can be regarded as living because: - They possess genetic material (DNA or RNA) and can reproduce/multiply inside a host cell. - They show host specificity and can mutate, giving rise to new strains (heritable variation). - They ...
Describe the distinguishing characteristics of family Solanaceae with floral diagram and floral formula, and give scientific names of any two plants of this family. OR Explain the alternation of generations based on the life cycle of Funaria.
Family Solanaceae: mostly herbs and shrubs with alternate leaves; inflorescence often a cyme. Floral characters: flower bisexual, actinomorphic, hypogynous; calyx 5, gamosepalous, persistent; corolla 5, gamopetalous (rotate/campanulate);...
Define ecosystem and describe food chain, trophic level and ecological pyramids of a grassland ecosystem.
An ecosystem is a functional unit where the biotic community interacts with the abiotic environment, exchanging energy and matter.
Food chain (grassland): the transfer of food energy through a series of organisms by eating and being eaten, e.g. grass -> grasshopper -> frog -> snake -> hawk.
Trophic levels: the successive feeding steps in a food chain -
Ecological pyramids graphically show the relationship between trophic levels:
bio-ecological-pyramid