Top 100 Biology MCQ Questions with Answers
The 100 most important Biology questions — pulled from our full bank of 200 Biology questions, ranked by how frequently they're asked in real exams. Answers and explanations are shown directly below each question.
1.Animals without a backbone are called:
easy- A.vertebrates
- B.chordates
- C.invertebrates Correct Answer
- D.mammals
Explanation: Insects, worms and molluscs are invertebrates.
Practice more on this topic →2.The largest mammal is the:
easy- A.elephant
- B.hippopotamus
- C.blue whale Correct Answer
- D.giraffe
Explanation: It is also the largest animal known to have lived.
Practice more on this topic →3.Fishes breathe mainly through:
easy- A.lungs
- B.skin only
- C.trachea
- D.gills Correct Answer
Explanation: Gills extract dissolved oxygen from water.
Practice more on this topic →4.Birds are characterised by the presence of:
easy- A.scales
- B.hair
- C.fins
- D.feathers Correct Answer
Explanation: Birds are warm-blooded and lay eggs.
Practice more on this topic →5.A whale is a:
easy- A.mammal Correct Answer
- B.fish
- C.reptile
- D.amphibian
Explanation: It breathes air through lungs and feeds milk to its young.
Practice more on this topic →6.Which of the following is a reptile?
easy- A.crocodile Correct Answer
- B.frog
- C.whale
- D.bat
Explanation: Reptiles have dry scaly skin.
Practice more on this topic →7.The largest phylum of the animal kingdom is:
medium- A.Arthropoda Correct Answer
- B.Mollusca
- C.Chordata
- D.Annelida
Explanation: Insects alone make up the majority of known species.
Practice more on this topic →8.Insects have how many legs?
medium- A.six Correct Answer
- B.four
- C.eight
- D.ten
Explanation: Their body has head, thorax and abdomen.
Practice more on this topic →9.Spiders belong to the class:
medium- A.Insecta
- B.Crustacea
- C.Arachnida Correct Answer
- D.Mammalia
Explanation: They have eight legs.
Practice more on this topic →10.Frogs belong to the class:
medium- A.Reptilia
- B.Amphibia Correct Answer
- C.Pisces
- D.Aves
Explanation: They live both in water and on land.
Practice more on this topic →11.The only mammal capable of true flight is the:
medium- A.flying squirrel
- B.flying fish
- C.bat Correct Answer
- D.ostrich
Explanation: Flying squirrels only glide.
Practice more on this topic →12.Which mammal lays eggs?
medium- A.kangaroo
- B.dolphin
- C.bat
- D.duck-billed platypus Correct Answer
Explanation: It is a monotreme found in Australia.
Practice more on this topic →13.Hydra belongs to the phylum:
medium- A.Porifera
- B.Annelida
- C.Mollusca
- D.Cnidaria (Coelenterata) Correct Answer
Explanation: It has stinging cells called cnidoblasts.
Practice more on this topic →14.Earthworm belongs to the phylum:
medium- A.Annelida Correct Answer
- B.Arthropoda
- C.Mollusca
- D.Platyhelminthes
Explanation: Its body is divided into many ring-like segments.
Practice more on this topic →15.Starfish belongs to the phylum:
medium- A.Mollusca
- B.Arthropoda
- C.Pisces
- D.Echinodermata Correct Answer
Explanation: Echinoderms have spiny skin and radial symmetry.
Practice more on this topic →16.Snails and octopus belong to the phylum:
medium- A.Annelida
- B.Echinodermata
- C.Mollusca Correct Answer
- D.Porifera
Explanation: Molluscs have a soft body, often with a shell.
Practice more on this topic →17.Sponges belong to the phylum:
hard- A.Cnidaria
- B.Porifera Correct Answer
- C.Echinodermata
- D.Annelida
Explanation: Porifera means pore-bearing.
Practice more on this topic →18.A notochord is a characteristic feature of:
hard- A.arthropods
- B.chordates Correct Answer
- C.molluscs
- D.annelids
Explanation: In vertebrates it is replaced by the backbone.
Practice more on this topic →19.Which of the following is a cold-blooded (poikilothermic) animal?
hard- A.sparrow
- B.lizard Correct Answer
- C.dog
- D.whale
Explanation: Its body temperature varies with the surroundings.
Practice more on this topic →20.The fastest land animal is the:
hard- A.lion
- B.cheetah Correct Answer
- C.horse
- D.leopard
Explanation: It can reach about 100 km/h in short bursts.
Practice more on this topic →21.Which gas is released during photosynthesis?
easy- A.oxygen Correct Answer
- B.carbon dioxide
- C.nitrogen
- D.hydrogen
Explanation: Water is split and oxygen is released.
Practice more on this topic →22.Photosynthesis requires sunlight, water and:
easy- A.oxygen
- B.nitrogen
- C.carbon dioxide Correct Answer
- D.ammonia
Explanation: It enters leaves through stomata.
Practice more on this topic →23.Cellular respiration mainly releases:
easy- A.light
- B.sound
- C.energy Correct Answer
- D.magnetism
Explanation: The energy is stored as ATP.
Practice more on this topic →24.The largest gland in the human body is the:
easy- A.pancreas
- B.liver Correct Answer
- C.thyroid
- D.pituitary
Explanation: It also produces bile.
Practice more on this topic →25.The main organs of excretion in humans are the:
easy- A.kidneys Correct Answer
- B.lungs
- C.liver only
- D.stomach
Explanation: They filter urea from the blood.
Practice more on this topic →26.Digestion of starch begins in the:
easy- A.stomach
- B.small intestine
- C.large intestine
- D.mouth Correct Answer
Explanation: Salivary amylase acts on starch.
Practice more on this topic →27.Most of the absorption of digested food takes place in the:
medium- A.small intestine Correct Answer
- B.stomach
- C.large intestine
- D.oesophagus
Explanation: Villi greatly increase the absorbing surface.
Practice more on this topic →28.The enzyme in saliva that digests starch is:
medium- A.pepsin
- B.salivary amylase Correct Answer
- C.lipase
- D.trypsin
Explanation: It converts starch to maltose.
Practice more on this topic →29.Pepsin, secreted in the stomach, digests:
medium- A.fats
- B.starch
- C.vitamins
- D.proteins Correct Answer
Explanation: It works in acidic conditions.
Practice more on this topic →30.Bile, which helps in fat digestion, is stored in the:
medium- A.pancreas
- B.gall bladder Correct Answer
- C.stomach
- D.spleen
Explanation: It is made in the liver.
Practice more on this topic →31.Loss of water vapour from the aerial parts of plants is called:
medium- A.translocation
- B.respiration
- C.guttation
- D.transpiration Correct Answer
Explanation: It mostly occurs through stomata.
Practice more on this topic →32.The human heart has how many chambers?
medium- A.four Correct Answer
- B.two
- C.three
- D.five
Explanation: Two atria and two ventricles.
Practice more on this topic →33.The pigment that carries oxygen in human blood is:
medium- A.chlorophyll
- B.melanin
- C.carotene
- D.haemoglobin Correct Answer
Explanation: It is found in red blood cells.
Practice more on this topic →34.The universal blood donor group is:
medium- A.A
- B.O Correct Answer
- C.B
- D.AB
Explanation: Group AB is the universal recipient.
Practice more on this topic →35.Anaerobic respiration in yeast produces:
medium- A.lactic acid only
- B.ethanol and carbon dioxide Correct Answer
- C.oxygen
- D.water only
Explanation: This is the basis of fermentation in bread and brewing.
Practice more on this topic →36.Red blood cells in adults are produced mainly in the:
medium- A.liver
- B.spleen
- C.bone marrow Correct Answer
- D.kidney
Explanation: Red bone marrow is the site of blood cell formation.
Practice more on this topic →37.ATP is called the:
hard- A.energy currency of the cell Correct Answer
- B.genetic material
- C.structural protein
- D.storage fat
Explanation: Energy is released when it loses a phosphate group.
Practice more on this topic →38.Glycolysis takes place in the:
hard- A.nucleus
- B.mitochondrial matrix
- C.cytoplasm Correct Answer
- D.chloroplast
Explanation: It breaks glucose into two pyruvate molecules.
Practice more on this topic →39.The Krebs cycle takes place in the:
hard- A.cytoplasm
- B.nucleus
- C.mitochondrial matrix Correct Answer
- D.ribosome
Explanation: It is also called the citric acid cycle.
Practice more on this topic →40.The main nitrogenous waste excreted by humans is:
hard- A.uric acid
- B.ammonia
- C.creatinine only
- D.urea Correct Answer
Explanation: Birds excrete uric acid; fishes largely excrete ammonia.
Practice more on this topic →41.The powerhouse of the cell is the:
easy- A.mitochondrion Correct Answer
- B.ribosome
- C.Golgi apparatus
- D.lysosome
Explanation: It produces most of the cell's ATP.
Practice more on this topic →42.The cell was first observed by:
easy- A.Anton van Leeuwenhoek
- B.Robert Brown
- C.Louis Pasteur
- D.Robert Hooke Correct Answer
Explanation: He saw dead cork cells under a microscope in 1665.
Practice more on this topic →43.The cell theory was proposed by:
easy- A.Watson and Crick
- B.Mendel and Darwin
- C.Hooke and Brown
- D.Schleiden and Schwann Correct Answer
Explanation: They stated that all organisms are made of cells.
Practice more on this topic →44.Proteins are synthesised on the:
easy- A.lysosomes
- B.vacuoles
- C.centrioles
- D.ribosomes Correct Answer
Explanation: Ribosomes may lie free or on the rough ER.
Practice more on this topic →45.The plant cell wall is mainly made of:
easy- A.cellulose Correct Answer
- B.chitin
- C.protein
- D.lipid
Explanation: Fungal walls are made of chitin.
Practice more on this topic →46.The control centre of the cell is the:
easy- A.mitochondrion
- B.vacuole
- C.plastid
- D.nucleus Correct Answer
Explanation: It contains the genetic material.
Practice more on this topic →47.Photosynthesis takes place in the:
medium- A.mitochondria
- B.chloroplasts Correct Answer
- C.lysosomes
- D.ribosomes
Explanation: They contain the green pigment chlorophyll.
Practice more on this topic →48.Lysosomes are known as the "suicide bags" of the cell because they:
medium- A.produce energy
- B.store food
- C.contain enzymes that can digest the cell itself Correct Answer
- D.make proteins
Explanation: They release digestive enzymes if the cell is damaged.
Practice more on this topic →49.The Golgi apparatus is mainly involved in:
medium- A.photosynthesis
- B.packaging and secretion of materials Correct Answer
- C.respiration
- D.DNA replication
Explanation: It modifies and ships proteins in vesicles.
Practice more on this topic →50.The endoplasmic reticulum studded with ribosomes is called the:
medium- A.smooth ER
- B.Golgi body
- C.plastid
- D.rough ER Correct Answer
Explanation: Smooth ER lacks ribosomes and makes lipids.
Practice more on this topic →51.Prokaryotic cells lack a:
medium- A.cell wall
- B.ribosome
- C.membrane-bound nucleus Correct Answer
- D.genetic material
Explanation: Bacteria are prokaryotes.
Practice more on this topic →52.The fluid mosaic model of the plasma membrane was proposed by:
medium- A.Singer and Nicolson Correct Answer
- B.Hooke and Brown
- C.Watson and Crick
- D.Mendel and Morgan
Explanation: It was proposed in 1972.
Practice more on this topic →53.The smallest known cell is that of:
medium- A.Amoeba
- B.yeast
- C.Mycoplasma Correct Answer
- D.Spirogyra
Explanation: It is a bacterium without a cell wall.
Practice more on this topic →54.The largest single cell is the:
medium- A.egg of an ostrich Correct Answer
- B.human egg cell
- C.Amoeba
- D.a red blood cell
Explanation: The yolk of the ostrich egg is one cell.
Practice more on this topic →55.The large central vacuole is a feature of:
medium- A.animal cells
- B.bacteria
- C.mature plant cells Correct Answer
- D.red blood cells
Explanation: It maintains turgor and stores substances.
Practice more on this topic →56.Besides the nucleus, DNA is also found in:
medium- A.lysosomes
- B.mitochondria Correct Answer
- C.Golgi body
- D.ribosomes
Explanation: Mitochondria and chloroplasts have their own DNA.
Practice more on this topic →57.The statement "omnis cellula e cellula" is attributed to:
hard- A.Rudolf Virchow Correct Answer
- B.Matthias Schleiden
- C.Robert Hooke
- D.Theodor Schwann
Explanation: It means all cells arise from pre-existing cells.
Practice more on this topic →58.Centrioles are found in:
hard- A.plant cells only
- B.animal cells and help in cell division Correct Answer
- C.bacteria only
- D.red blood cells only
Explanation: They organise the spindle fibres.
Practice more on this topic →59.A normal human body cell has how many chromosomes?
hard- A.23
- B.44
- C.46 Correct Answer
- D.48
Explanation: They exist as 23 pairs.
Practice more on this topic →60.Which organelle is responsible for detoxification and lipid synthesis?
hard- A.rough endoplasmic reticulum
- B.smooth endoplasmic reticulum Correct Answer
- C.centriole
- D.nucleolus
Explanation: It is abundant in liver cells.
Practice more on this topic →61.The control centre of the human nervous system is the:
easy- A.brain Correct Answer
- B.heart
- C.kidney
- D.liver
Explanation: It works with the spinal cord.
Practice more on this topic →62.Insulin is secreted by the:
easy- A.liver
- B.thyroid
- C.adrenal gland
- D.pancreas Correct Answer
Explanation: It lowers blood sugar.
Practice more on this topic →63.The structural and functional unit of the nervous system is the:
easy- A.neuron Correct Answer
- B.nephron
- C.alveolus
- D.sarcomere
Explanation: It carries nerve impulses.
Practice more on this topic →64.Reflex actions are controlled mainly by the:
easy- A.cerebrum
- B.spinal cord Correct Answer
- C.liver
- D.heart
Explanation: This gives a rapid response without waiting for the brain.
Practice more on this topic →65.Thyroxine is secreted by the:
easy- A.thyroid gland Correct Answer
- B.pituitary gland
- C.pancreas
- D.adrenal gland
Explanation: It needs iodine for its synthesis.
Practice more on this topic →66.The emergency hormone that prepares the body for "fight or flight" is:
easy- A.adrenaline Correct Answer
- B.insulin
- C.thyroxine
- D.oestrogen
Explanation: It is secreted by the adrenal glands.
Practice more on this topic →67.Which plant hormone promotes cell elongation and growth?
medium- A.abscisic acid
- B.ethylene
- C.cytokinin
- D.auxin Correct Answer
Explanation: Auxin accumulates on the shaded side of a stem.
Practice more on this topic →68.The hormone that promotes stem elongation and seed germination is:
medium- A.abscisic acid
- B.ethylene
- C.gibberellin Correct Answer
- D.florigen only
Explanation: It breaks seed dormancy.
Practice more on this topic →69.Cell division in plants is promoted by:
medium- A.abscisic acid
- B.ethylene
- C.auxin only
- D.cytokinin Correct Answer
Explanation: It delays senescence of leaves.
Practice more on this topic →70.The gaseous plant hormone that hastens fruit ripening is:
medium- A.auxin
- B.gibberellin
- C.ethylene Correct Answer
- D.cytokinin
Explanation: Raw bananas ripen faster beside ripe ones.
Practice more on this topic →71.The pituitary gland is called the "master gland" because it:
medium- A.is the largest gland
- B.controls the activity of other endocrine glands Correct Answer
- C.is found in the stomach
- D.makes bile
Explanation: It lies at the base of the brain.
Practice more on this topic →72.The part of the brain that maintains balance and posture is the:
medium- A.cerebrum
- B.medulla oblongata
- C.hypothalamus
- D.cerebellum Correct Answer
Explanation: It coordinates voluntary movements.
Practice more on this topic →73.Involuntary actions such as breathing and heartbeat are controlled by the:
medium- A.cerebrum
- B.medulla oblongata Correct Answer
- C.cerebellum
- D.olfactory bulb
Explanation: It connects the brain to the spinal cord.
Practice more on this topic →74.Diabetes mellitus is caused by a deficiency of:
medium- A.thyroxine
- B.insulin Correct Answer
- C.adrenaline
- D.growth hormone
Explanation: Blood glucose then stays high.
Practice more on this topic →75.Goitre is caused by a deficiency of:
medium- A.iodine Correct Answer
- B.iron
- C.calcium
- D.vitamin C
Explanation: The thyroid gland enlarges without enough iodine.
Practice more on this topic →76.Growth of a plant shoot towards light is called:
medium- A.geotropism
- B.phototropism Correct Answer
- C.hydrotropism
- D.thigmotropism
Explanation: Shoots are positively phototropic.
Practice more on this topic →77.The gap between two neurons is called the:
hard- A.axon
- B.dendrite
- C.synapse Correct Answer
- D.node of Ranvier
Explanation: Neurotransmitters cross it.
Practice more on this topic →78.Under-secretion of growth hormone in childhood causes:
hard- A.gigantism
- B.diabetes
- C.dwarfism Correct Answer
- D.goitre
Explanation: Over-secretion causes gigantism.
Practice more on this topic →79.The myelin sheath around axons:
hard- A.digests nerve cells
- B.stores glucose
- C.insulates the axon and speeds up impulse conduction Correct Answer
- D.makes hormones
Explanation: It is made of fatty material.
Practice more on this topic →80.The plant hormone that promotes dormancy and helps in stomatal closure under stress is:
hard- A.auxin
- B.gibberellin
- C.cytokinin
- D.abscisic acid Correct Answer
Explanation: It is known as the stress hormone.
Practice more on this topic →81.The Father of Genetics is:
easy- A.Gregor Mendel Correct Answer
- B.Charles Darwin
- C.Thomas Morgan
- D.Watson
Explanation: He worked on pea plants in the 1860s.
Practice more on this topic →82.Mendel conducted his experiments on:
easy- A.maize
- B.fruit flies
- C.wheat
- D.garden pea plants Correct Answer
Explanation: He studied seven pairs of contrasting traits.
Practice more on this topic →83.The double helix model of DNA was proposed by:
easy- A.Mendel and Morgan
- B.Hooke and Brown
- C.Darwin and Wallace
- D.Watson and Crick Correct Answer
Explanation: They proposed it in 1953.
Practice more on this topic →84.Humans have how many pairs of chromosomes?
easy- A.22
- B.24
- C.46
- D.23 Correct Answer
Explanation: One pair is the sex chromosomes.
Practice more on this topic →85.The theory of natural selection was proposed by:
easy- A.Lamarck
- B.Mendel
- C.Charles Darwin Correct Answer
- D.Pasteur
Explanation: Alfred Russel Wallace independently reached the same idea.
Practice more on this topic →86.Genes are located on the:
easy- A.ribosomes
- B.chromosomes Correct Answer
- C.lysosomes
- D.cell wall
Explanation: They are segments of DNA.
Practice more on this topic →87.In humans, the combination of sex chromosomes in a male is:
medium- A.XY Correct Answer
- B.XX
- C.XO
- D.YY
Explanation: Females are XX.
Practice more on this topic →88.A trait that is expressed even in the heterozygous condition is called:
medium- A.recessive
- B.dominant Correct Answer
- C.hybrid
- D.mutant
Explanation: A dominant trait masks the recessive one in a heterozygote.
Practice more on this topic →89.The phenotypic ratio in the F2 generation of a monohybrid cross is:
medium- A.1:1
- B.9:3:3:1
- C.1:2:1
- D.3:1 Correct Answer
Explanation: The phenotypic ratio is 3:1: three show the dominant trait for every one recessive.
Practice more on this topic →90.Haemophilia is a:
medium- A.dominant autosomal disorder
- B.viral disease
- C.sex-linked recessive disorder Correct Answer
- D.vitamin deficiency
Explanation: It is carried on the X chromosome.
Practice more on this topic →91.Colour blindness is an example of:
medium- A.a bacterial disease
- B.an X-linked recessive disorder Correct Answer
- C.a dominant disorder
- D.a nutritional disorder
Explanation: It is more common in males.
Practice more on this topic →92.Lamarck's theory of evolution is based on the:
medium- A.survival of the fittest
- B.inheritance of acquired characters Correct Answer
- C.mutation only
- D.genetic drift only
Explanation: The long neck of the giraffe was his classic example.
Practice more on this topic →93.Fossils are evidence of:
medium- A.organic evolution Correct Answer
- B.photosynthesis
- C.digestion
- D.pollination
Explanation: They record past life forms in rocks.
Practice more on this topic →94.The forelimbs of a human and the wing of a bat are examples of:
medium- A.analogous organs
- B.vestigial organs
- C.homologous organs Correct Answer
- D.rudimentary organs
Explanation: They share the same basic structure but differ in function.
Practice more on this topic →95.The wings of a bird and an insect are examples of:
medium- A.homologous organs
- B.vestigial organs
- C.analogous organs Correct Answer
- D.genes
Explanation: They perform the same function but have different origins.
Practice more on this topic →96.Darwin's book 'On the Origin of Species' was published in:
medium- A.1859 Correct Answer
- B.1809
- C.1900
- D.1953
Explanation: It set out the theory of natural selection.
Practice more on this topic →97.The phenotypic ratio in the F2 generation of a dihybrid cross is:
hard- A.3:1
- B.1:2:1
- C.1:1:1:1
- D.9:3:3:1 Correct Answer
Explanation: It follows Mendel's law of independent assortment.
Practice more on this topic →98.The nitrogenous base found in RNA but not in DNA is:
hard- A.thymine
- B.uracil Correct Answer
- C.adenine
- D.guanine
Explanation: Uracil replaces thymine in RNA.
Practice more on this topic →99.Down syndrome is caused by:
hard- A.an extra copy of chromosome 21 Correct Answer
- B.a missing X chromosome
- C.a viral infection
- D.a vitamin deficiency
Explanation: It is called trisomy 21.
Practice more on this topic →100.Genetic engineering mainly involves the use of:
hard- A.grafting only
- B.tissue culture only
- C.recombinant DNA technology Correct Answer
- D.cross-pollination only
Explanation: Genes from one organism are inserted into another.
Practice more on this topic →