Biology MCQs

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Biology MCQs

Practice complete Biology MCQs covering Introduction to Biology, Cell Biology, Cell Structure, Cell Division, Biomolecules, Plant Physiology, Human Physiology, Genetics, Evolution, Biotechnology, Ecology, Classification of Living Organisms, Plant Kingdom, Animal Kingdom, Microbiology, Human Diseases, Nutrition, Reproduction, Environmental Biology, and all other important topics. Includes chapter-wise and exam-oriented multiple-choice questions with detailed answers and explanations for JKSSB, SSC, Banking, Railway, UPSC, CUET, NEET, State PSCs, and other competitive exams.

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Page 101 of 103
Question #2001
The network of membrane-bound tubules involved in transport and synthesis is:
A. Endoplasmic reticulum
B. Golgi apparatus
C. Lysosomes
D. Mitochondria
Discuss
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Correct Answer: Option A

Explanation:
ER is a continuous membrane system; rough ER has ribosomes for protein synthesis, smooth ER for lipid synthesis and detoxification. Golgi modifies and packages.
This question belongs to: Science Biology
Question #2002
In which phase of mitosis do chromosomes align at the equator?
A. Metaphase
B. Telophase
C. Prophase
D. Anaphase
Discuss
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Correct Answer: Option A

Explanation:
During metaphase, chromosomes are maximally condensed and attach to spindle fibers at the kinetochores, aligning at the metaphase plate.
This question belongs to: Science Biology
Question #2003
Cytokinesis in plant cells occurs by:
A. Cleavage
B. Furrowing
C. Cell plate formation
D. Budding
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Correct Answer: Option C

Explanation:
Due to the rigid cell wall, plant cells form a cell plate at the equator, which develops into a new cell wall separating daughter cells. Animal cells form a cleavage furrow.
This question belongs to: Science Biology
Question #2004
The element present in the center of the chlorophyll molecule is:
A. Cobalt
B. Magnesium
C. Calcium
D. Iron
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Correct Answer: Option B

Explanation:
Magnesium (Mg²⁺) is the central atom in the porphyrin ring of chlorophyll, crucial for light absorption. Iron is in hemoglobin.
This question belongs to: Science Biology
Question #2005
Which plant tissue is responsible for transport of organic nutrients?
A. Phloem
B. Epidermis
C. Xylem
D. Collenchyma
Discuss
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Correct Answer: Option A

Explanation:
Phloem transports organic solutes (mainly sucrose) from source to sink. Xylem transports water and minerals. Phloem is composed of sieve tubes and companion cells.
This question belongs to: Science Biology
Question #2006
The openings on the leaf surface for gas exchange are called:
A. Cuticles
B. Hydathodes
C. Lenticels
D. Stomata
Discuss
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Correct Answer: Option D

Explanation:
Stomata are pores flanked by guard cells that regulate gas exchange and transpiration. Lenticels are on bark, hydathodes for guttation.
This question belongs to: Science Biology
Question #2007
The process of water loss as vapor from leaves is:
A. Guttation
B. Translocation
C. Evaporation
D. Transpiration
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Correct Answer: Option D

Explanation:
Transpiration mainly occurs through stomata and drives the transpiration pull for water movement. Guttation is liquid loss, evaporation from free surface.
This question belongs to: Science Biology
Question #2008
The hormone responsible for apical dominance in plants is:
A. Auxin
B. Gibberellin
C. Ethylene
D. Cytokinin
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Correct Answer: Option A

Explanation:
Auxin produced at the shoot apex inhibits lateral bud growth, a phenomenon called apical dominance. Removing the tip promotes branching.
This question belongs to: Science Biology
Question #2009
The gaseous plant hormone is:
A. Cytokinin
B. Auxin
C. Gibberellin
D. Ethylene
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Correct Answer: Option D

Explanation:
Ethylene (C₂H₄) is a gaseous hormone that promotes fruit ripening, senescence, and abscission. It is the only gaseous plant hormone.
This question belongs to: Science Biology
Question #2010
The primary product of photosynthesis is:
A. Glucose
B. ATP
C. NADPH
D. Oxygen
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Correct Answer: Option A

Explanation:
The Calvin cycle fixes CO₂ into glucose, which is the primary organic product of photosynthesis. Oxygen is a byproduct of water splitting.
This question belongs to: Science Biology
Question #2011
Double fertilization is a characteristic feature of:
A. Pteridophytes
B. Gymnosperms
C. Angiosperms
D. Bryophytes
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Correct Answer: Option C

Explanation:
In angiosperms, one sperm fertilizes the egg (zygote) and the other fuses with two polar nuclei (triploid endosperm). This double fertilization is unique.
This question belongs to: Science Biology
Question #2012
Which of the following is a nitrogen-fixing bacterium in legume roots?
A. Lactobacillus
B. Nitrosomonas
C. Rhizobium
D. Azotobacter
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Correct Answer: Option C

Explanation:
Rhizobium species form symbiotic root nodules in legumes and fix atmospheric nitrogen into ammonia. Azotobacter is free-living, Nitrosomonas nitrifies, Lactobacillus ferments.
This question belongs to: Science Biology
Question #2013
The food chain starts with:
A. Decomposers
B. Producers
C. Primary consumers
D. Secondary consumers
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Correct Answer: Option B

Explanation:
Producers (green plants, algae, cyanobacteria) form the first trophic level, converting solar energy into biomass. Consumers depend on them.
This question belongs to: Science Biology
Question #2014
In a food chain, herbivores are called:
A. Primary consumers
B. Tertiary consumers
C. Producers
D. Secondary consumers
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Correct Answer: Option A

Explanation:
Herbivores feed directly on producers, occupying the second trophic level. Carnivores that eat herbivores are secondary consumers.
This question belongs to: Science Biology
Question #2015
Which gas is the main cause of global warming?
A. Oxygen
B. Carbon dioxide
C. Nitrogen
D. Hydrogen
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Correct Answer: Option B

Explanation:
CO₂ is the primary greenhouse gas, along with methane and water vapor, trapping heat and leading to global warming and climate change.
This question belongs to: Science Biology
Question #2016
The ozone layer is located in which layer of the atmosphere?
A. Mesosphere
B. Troposphere
C. Thermosphere
D. Stratosphere
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Correct Answer: Option D

Explanation:
The ozone layer is in the stratosphere (15-35 km altitude), absorbing harmful UV-B and UV-C radiation. CFCs cause its depletion.
This question belongs to: Science Biology
Question #2017
Which of the following is a renewable natural resource?
A. Coal
B. Petroleum
C. Solar energy
D. Natural gas
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Correct Answer: Option C

Explanation:
Solar energy is renewable and inexhaustible. Coal, petroleum, and natural gas are fossil fuels, which are non-renewable and finite.
This question belongs to: Science Biology
Question #2018
The Chipko movement was primarily for the conservation of:
A. Soil
B. Wildlife
C. Forests
D. Water
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Correct Answer: Option C

Explanation:
The Chipko movement (1970s, Uttarakhand) involved hugging trees to prevent them from being felled, promoting forest conservation.
This question belongs to: Science Biology
Question #2019
A network of interconnected food chains is called a:
A. Trophic level
B. Ecological niche
C. Food web
D. Food pyramid
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Correct Answer: Option C

Explanation:
A food web represents complex feeding relationships in an ecosystem, showing how multiple food chains are linked. Food chain is linear.
This question belongs to: Science Biology
Question #2020
The ultimate source of energy for most ecosystems is:
A. Sun
B. Water
C. Soil
D. Wind
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Correct Answer: Option A

Explanation:
Solar energy is converted to chemical energy by photosynthesis, driving nearly all ecosystems. Only deep-sea vents rely on chemosynthesis.
This question belongs to: Science Biology

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