Biology — NEET Complete Yearwise Papers MCQs with Solutions
Free NEET Complete Yearwise Papers Biology MCQs with step-by-step solutions (99 questions). Part of NEET 2023 Paper. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Biology · medium · theory
In angiosperm, the haploid, diploid and triploid structures of a fertilized embryo sac sequentially are:
A. Synergids, Primary endosperm nucleus and zygote
B. Antipodals, synergids, and primary endosperm nucleus
C. Synergids, Zygote and Primary endosperm nucleus ✓ Correct
D. Synergids, antipodals and Polar nuclei
Solution: Synergids are cells of the gametophyte, so they are HAPLOID.
The zygote is formed by the fusion of two gametes, so it is DIPLOID.
The primary endosperm nucleus is formed by the fusion of the diploid secondary nucleus with a male gamete, so it is TRIPLOID.
Q2 — Biology · medium · theory
Movement and accumulation of ions across a membrane against their concentration gradient can be explained by
A. Osmosis
B. Facilitated Diffusion
C. Passive Transport
D. Active Transport ✓ Correct
Solution: Moving a solute AGAINST its concentration gradient — from lower to higher concentration — needs energy, and only active transport supplies it (using ATP through membrane pumps).
Osmosis, facilitated diffusion and passive transport all run DOWN the gradient and require no energy.
Q3 — Biology · medium · theory
Large, colourful, fragrant flowers with nectar are seen in
A. Insect pollinated plants ✓ Correct
B. Bird pollinated plants
C. Bat pollinated plants
D. Wind pollinated plants
Solution: Large, colourful, fragrant flowers that offer nectar are advertising themselves to biotic pollinators — the classic entomophilous (insect-pollinated) syndrome.
Wind-pollinated flowers, by contrast, are small, dull and produce no nectar at all.
Q4 — Biology · medium · theory
The phenomenon of pleiotropism refers to
A. Presence of several alleles of a single gene controlling a single crossover
B. Presence of two alleles, each of the two genes controlling a single trait
C. A single gene affecting multiple phenotypic expression ✓ Correct
D. More than two genes affecting a single character
Solution: A gene that affects several, apparently unrelated, phenotypic traits is called a pleiotropic gene, and the phenomenon is pleiotropism.
Phenylketonuria is the standard example — one mutated gene produces mental retardation, reduced hair pigmentation and reduced skin pigmentation.
Q5 — Biology · medium · theory
Which hormone promotes internode/petiole elongation in deep water rice?
A. GA₃
B. Kinetin
C. Ethylene ✓ Correct
D. 2,4-D
Solution: Ethylene promotes rapid internode and petiole elongation in deep-water rice plants, which helps the leaves and upper parts of the shoot stay above water.
Q6 — Biology · medium · theory
Among 'The Evil Quartet', which one is considered the most important cause driving extinction of species?
A. Habitat loss and fragmentation ✓ Correct
B. Over exploitation for economic gain
C. Alien species invasions
D. Co-extinctions
Solution: 'The Evil Quartet' names the four major causes of biodiversity loss, and habitat loss and fragmentation is the MOST important of them — the single largest cause driving animals and plants to extinction.
Q7 — Biology · medium · theory
Upon exposure to UV radiation, DNA stained with ethidium bromide will show
A. Bright red colour
B. Bright blue colour
C. Bright yellow colour
D. Bright orange colour ✓ Correct
Solution: In recombinant DNA technology the separated DNA fragments are invisible until stained. After staining with ethidium bromide and exposing the gel to UV radiation, the DNA shows up as bright ORANGE coloured bands.
Q8 — Biology · medium · theory
Which micronutrient is required for splitting of water molecule during photosynthesis?
A. Manganese ✓ Correct
B. Molybdenum
C. Magnesium
D. Copper
Solution: Manganese plays the major role in the photolysis of water, which liberates oxygen during photosynthesis.
Molybdenum is involved in nitrogen metabolism, magnesium activates enzymes of photosynthesis and respiration, and copper is essential for overall metabolism.
Q9 — Biology · medium · theory
Axile placentation is observed in
A. Mustard, Cucumber and Primrose
B. China rose, Beans and Lupin
C. Tomato, Dianthus and Pea
D. China rose, Petunia and Lemon ✓ Correct
Solution: China rose, tomato, Petunia and lemon all show axile placentation.
The distractors mix in other types: Dianthus and Primrose show free central placentation; pea, lupin and beans show marginal; and cucumber and mustard show parietal.
Q10 — Biology · medium · theory
The process of appearance of recombination nodules occurs at which sub stage of prophase I in meiosis?
A. Zygotene
B. Pachytene ✓ Correct
C. Diplotene
D. Diakinesis
Solution: Recombination nodules appear on the bivalents during PACHYTENE, and it is there that crossing over between non-sister chromatids takes place, catalysed by recombinase.
Q11 — Biology · medium · theory
The reaction centre in PS II has an absorption maxima at
A. 680 nm ✓ Correct
B. 700 nm
C. 660 nm
D. 780 nm
Solution: In photosystem II the reaction centre chlorophyll a has an absorption maximum at 680 nm, which is why it is called P680.
(In photosystem I the peak is at 700 nm — P700.)
Q12 — Biology · medium · theory
Unequivocal proof that DNA is the genetic material was first proposed by
A. Frederick Griffith
B. Alfred Hershey and Martha Chase ✓ Correct
C. Avery, Macleod and McCarty
D. Wilkins and Franklin
Solution: The UNEQUIVOCAL proof came from the Hershey-Chase experiment with bacteriophages.
Griffith demonstrated transformation but did not identify the material; Avery, MacLeod and McCarty gave the biochemical characterisation of the transforming principle; and Wilkins and Franklin produced the X-ray diffraction data.
Q13 — Biology · medium · theory
Among eukaryotes, replication of DNA takes place in:
A. M phase
B. S phase ✓ Correct
C. $G_1$ phase
D. $G_2$ phase
Solution: DNA replication takes place in the S (synthesis) phase of the cell cycle. The amount of DNA per cell doubles, though the chromosome number stays the same.
Most of the cell organelles duplicate during $G_1$.
Q14 — Biology · medium · theory
In tissue culture experiments, leaf mesophyll cells are put in a culture medium to form callus. This phenomenon may be called as
A. Differentiation
B. Dedifferentiation ✓ Correct
C. Development
D. Senescence
Solution: Dedifferentiation is the phenomenon by which living differentiated plant cells, which have lost the capacity to divide, regain that capacity under certain conditions.
Mesophyll cells forming a callus in culture is exactly that.
Q15 — Biology · medium · theory
Cellulose does not form blue colour with Iodine because
A. It is a disaccharide
B. It is a helical molecule
C. It does not contain complex helices and hence cannot hold iodine molecules ✓ Correct
D. It breaks down when iodine reacts with it
Solution: Starch forms the blue colour because its helical secondary structure holds iodine molecules inside the helix.
Cellulose has no complex helices, so it cannot hold iodine and gives no blue colour. (It is a polysaccharide, not a disaccharide, so option (a) is wrong too.)
Q16 — Biology · medium · theory
Spraying of which of the following phytohormone on juvenile conifers helps hastening the maturity period, that leads early seed production?
A. Indole-3-butyric Acid
B. Gibberellic Acid ✓ Correct
C. Zeatin
D. Abscisic Acid
Solution: Spraying juvenile conifers with gibberellins hastens the maturity period, so the trees begin producing seed earlier.
Q17 — Biology · medium · theory
Given below are two statements:
Statement I: The forces generated by transpiration can lift a xylem-sized column of water over 130 meters height.
Statement II: Transpiration cools leaf surfaces sometimes 10 to 15 degrees by evaporative cooling.
In the light of the above statements, choose the most appropriate answer from the options given below:
A. Both Statement I and Statement II are correct ✓ Correct
B. Both Statement I and Statement II are incorrect
C. Statement I is correct but Statement II is incorrect
D. Statement I is incorrect but Statement II is correct
Solution: Both are correct. Measurements show that the forces generated by transpiration can create pressures sufficient to lift a xylem-sized column of water up to 130 metres high.
And transpiration does cool leaf surfaces, sometimes by 10 to 15 degrees, through evaporative cooling.
Q18 — Biology · medium · theory
Family Fabaceae differs from Solanaceae and Liliaceae. With respect to the stamens, pick out the characteristics specific to family Fabaceae but not found in Solanaceae or Liliaceae.
A. Diadelphous and Dithecous anthers ✓ Correct
B. Polyadelphous and epipetalous stamens
C. Monoadelphous and Monothecous anthers
D. Epiphyllous and Dithecous anthers
Solution: Fabaceae — diadelphous stamens with dithecous anthers.
Solanaceae — polyandrous, epipetalous stamens with dithecous anthers.
Liliaceae — polyandrous, epiphyllous stamens with dithecous anthers.
So it is the DIADELPHOUS condition that is specific to Fabaceae.
Q19 — Biology · medium · theory
Expressed Sequence Tags (ESTs) refers to
A. All genes that are expressed as RNA. ✓ Correct
B. All genes that are expressed as proteins.
C. All genes whether expressed or unexpressed.
D. Certain important expressed genes
Solution: The Expressed Sequence Tags approach focuses on identifying all the genes that are expressed as RNA. (The alternative, sequence annotation, sequences the whole genome and then assigns functions to the different regions.)
Q20 — Biology · medium · theory
Identify the correct statements:
A. Detrivores perform fragmentation.
B. The humus is further degraded by some microbes during mineralization.
C. Water soluble inorganic nutrients go down into the soil and get precipitated by a process called leaching.
D. The detritus food chain begins with living organisms.
E. Earthworms break down detritus into smaller particles by a process called catabolism.
Choose the correct answer from the options given below:
A. A, B, C only ✓ Correct
B. B, C, D only
C. C, D, E only
D. D, E, A only
Solution: D is wrong: the detritus food chain begins with DETRITUS — dead organic matter — not with living organisms.
E is wrong in its last word: earthworms break detritus into smaller particles by FRAGMENTATION. Catabolism is the breakdown of detritus into simpler inorganic substances by saprotrophic bacteria and fungi.
A, B and C are all correct.
Q21 — Biology · medium · theory
The thickness of ozone in a column of air in the atmosphere is measured in terms of:
A. Dobson units ✓ Correct
B. Decibels
C. Decameter
D. Kilobase
Solution: The thickness of ozone in a column of air from the ground to the top of the atmosphere is measured in Dobson units (DU).
(Decibels measure sound, and kilobases measure DNA length.)
Q22 — Biology · medium · theory
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:
Assertion A: Late wood has fewer xylary elements with narrow vessels.
Reason R: Cambium is less active in winters.
In the light of the above statements, choose the correct answer from the options given below:
A. Both A and R are true and R is the correct explanation of A ✓ Correct
B. Both A and R are true but R is NOT the correct explanation of A
C. A is true but R is false
D. A is false but R is true
Solution: In winter the cambium is less active, and so it forms fewer xylary elements with narrower vessels. That wood is called autumn wood or late wood.
So both statements are true and the reduced cambial activity is precisely the reason for the character of late wood.
Q23 — Biology · medium · theory
Which of the following stages of meiosis involves division of centromere?
A. Metaphase I
B. Metaphase II
C. Anaphase II ✓ Correct
D. Telophase
Solution: Splitting of the centromere occurs during anaphase of mitosis, and during ANAPHASE II of meiosis.
In metaphase the chromosomes merely align at the equator, and in telophase they have already reached the poles.
Q24 — Biology · medium · theory
The historic Convention on Biological Diversity, 'The Earth Summit' was held in Rio de Janeiro in the year
A. 1985
B. 1992 ✓ Correct
C. 1986
D. 2002
Solution: The Earth Summit — the historic Convention on Biological Diversity — was held in Rio de Janeiro in 1992. It called upon all nations to take appropriate measures for the conservation of biodiversity and the sustainable utilisation of its benefits.
(The World Summit on Sustainable Development, in Johannesburg, was 2002.)
Q25 — Biology · medium · numerical
How many ATP and NADPH₂ are required for the synthesis of one molecule of Glucose during Calvin cycle?
A. 12 ATP and 12 NADPH₂
B. 18 ATP and 12 NADPH₂ ✓ Correct
C. 12 ATP and 16 NADPH₂
D. 18 ATP and 16 NADPH₂
Solution: For every CO₂ molecule entering the Calvin cycle, 3 ATP and 2 NADPH₂ are required.
Making one molecule of glucose needs 6 turns of the cycle:
$6 \times 3 = 18$ ATP and $6 \times 2 = 12$ NADPH₂
Q26 — Biology · medium · theory
In the equation $GPP - R = NPP$, GPP is Gross Primary Productivity and NPP is Net Primary Productivity. R here is ________.
A. Photosynthetically active radiation
B. Respiratory quotient
C. Respiratory loss ✓ Correct
D. Reproductive allocation
Solution: A considerable amount of the gross primary productivity is used up by plants in respiration.
Gross primary productivity minus the respiration losses (R) gives the net primary productivity — so R is the respiratory loss.
Q27 — Biology · medium · theory
During the purification process for recombinant DNA technology, addition of chilled ethanol precipitates out
A. RNA
B. DNA ✓ Correct
C. Histones
D. Polysaccharides
Solution: During isolation of the genetic material, the purified DNA finally precipitates out after the addition of chilled ethanol — it can be seen as fine threads suspended in the suspension.
RNA is removed beforehand by ribonuclease and proteins by protease, so neither is what precipitates here.
Q28 — Biology · medium · theory
What is the role of RNA polymerase III in the process of transcription in Eukaryotes?
A. Transcription of rRNAs (28S, 18S and 5.8S)
B. Transcription of tRNA, 5S rRNA and snRNA ✓ Correct
C. Transcription of precursor of mRNA
D. Transcription of only snRNAs
Solution: Eukaryotes have three nuclear RNA polymerases with a clear division of labour:
RNA polymerase I — 28S, 18S and 5.8S rRNAs
RNA polymerase II — hnRNA, the precursor of mRNA
RNA polymerase III — tRNA, 5S rRNA and snRNAs
Q29 — Biology · medium · theory
What is the function of tassels in the corn cob?
A. To attract insects
B. To trap pollen grains ✓ Correct
C. To disperse pollen grains
D. To protect seeds
Solution: The tassels of a corn cob are the long, hairy styles and stigmas. They wave in the wind and trap the pollen grains — the classic wind-pollination adaptation.
Q30 — Biology · medium · theory
Identify the pair of heterosporous pteridophytes among the following:
A. Lycopodium and Selaginella
B. Selaginella and Salvinia ✓ Correct
C. Psilotum and Salvinia
D. Equisetum and Salvinia
Solution: Selaginella and Salvinia are the two heterosporous pteridophytes — they produce two different kinds of spores, macrospores and microspores.
Psilotum, Lycopodium and Equisetum are all homosporous.