Organism and populations chapter 12 MCQ Question and Answer

Organisms and populations class 12 chapter 13 MCQ Question and Answer

Organisms and populations class 12 MCQ these are very Important MCQ taken from NCERT Book Practice these and enhance your knowledge and get more marks in your Exams.

Organisms and populations class 12 MCQ

Question:1. Which of the following is a biotic component of an ecosystem?

  1. a. Water
  2. b. Soil
  3. c. Plants
  4. d. Sunlight

Question:2. What is the primary function of the ozone layer in the atmosphere?

  1. a. Absorbing ultraviolet radiation
  2. b. Enhancing photosynthesis
  3. c. Trapping greenhouse gases
  4. d. Regulating temperature

Question:3. In a population, what does the term ‘biotic potential’ refer to?

  1. a. Maximum growth rate under optimal conditions
  2. b. Number of individuals at a given time
  3. c. Interactions with other species
  4. d. Adaptations to the environment

Question:4. What is a keystone species in an ecosystem?

  1. a. A dominant predator
  2. b. A species crucial for maintaining ecosystem balance
  3. c. An invasive species
  4. d. A species with limited ecological impact

Question:5. Which ecological pyramid represents the energy flow in an ecosystem?

  1. a. Pyramid of Numbers
  2. b. Pyramid of Biomass
  3. c. Pyramid of Energy
  4. d. Pyramid of Productivity

Question:6. What is the primary role of decomposers in an ecosystem?

  1. a. Produce oxygen
  2. b. Break down organic matter
  3. c. Synthesize food
  4. d. Enhance nutrient cycling

Question:7. What is the process of converting atmospheric nitrogen into ammonia called?

  1. a. Denitrification
  2. b. Nitrification
  3. c. Nitrogen fixation
  4. d. Ammonification

Question:8 8. Which level of ecological organization includes both living and non-living components?

  1. a. Community
  2. b. Ecosystem
  3. c. Population
  4. d. Species

Question: 9. What is the term for the maximum number of individuals a habitat can support sustainably?

  1. a. Biotic potential
  2. b. Carrying capacity
  3. c. Ecological niche
  4. d. Population density

Question:10. Which biome is characterized by permafrost and low-growing vegetation?

  1. a. Tundra
  2. b. Taiga
  3. c. Tropical Rainforest
  4. d. Desert

Question: 11. What is the primary factor influencing the distribution of oceanic organisms in different zones?

  1. a. Salinity
  2. b. Temperature
  3. c. Pressure
  4. d. Sunlight penetration

Question:12. What is the main source of energy for most ecosystems on Earth?

  1. a. Wind
  2. b. Geothermal heat
  3. c. Sunlight
  4. d. Nuclear energy

Question: 13. Which ecological interaction benefits one species while not affecting the other?

  1. a. Mutualism
  2. b. Commensalism
  3. c. Parasitism
  4. d. Predation

Question:14. What is the term for a group of individuals of the same species occupying a specific area?

  1. a. Community
  2. b. Population
  3. c. Ecosystem
  4. d. Habitat

Question:15. Which gas is a major component of the Earth’s atmosphere?

  1. a. Carbon dioxide
  2. b. Methane
  3. c. Oxygen
  4. d. Nitrogen

Question: 16. What is the role of pioneer species in ecological succession?

  1. a. Establishing the climax community
  2. b. Facilitating the growth of other species
  3. c. Enhancing biodiversity
  4. d. Preventing soil erosion

Question:17. Which term describes the variety of species in a given habitat or ecosystem?

  1. a. Biodiversity
  2. b. Population density
  3. c. Ecological niche
  4. d. Carrying capacity

Question:18. What is a limiting factor for the growth of a population?

  1. a. Abiotic potential
  2. b. Carrying capacity
  3. c. Biotic potential
  4. d. Keystone species

Question:19. What is the primary source of energy for producers in an aquatic ecosystem?

  1. a. Sunlight
  2. b. Organic matter
  3. c. Geothermal heat
  4. d. Chemical reactions

Question:20. Which biome is characterized by dense vegetation, high precipitation, and high biodiversity?

  1. a. Desert
  2. b. Tropical Rainforest
  3. c. Grassland
  4. d. Temperate Deciduous Forest

Question:21. What is the process of converting ammonia into nitrate ions called?

  1. a. Nitrification
  2. b. Denitrification
  3. c. Nitrogen fixation
  4. d. Ammonification

Question:22. Which component of an ecosystem represents non-living factors such as sunlight and temperature?

  1. a. Biotic factors
  2. b. Abiotic factors
  3. c. Producers
  4. d. Consumers

Question: 23. What term describes the specific role or function of a species in an ecosystem?

  1. a. Carrying capacity
  2. b. Ecological niche
  3. c. Mutualism
  4. d. Habitat

Question:24. What is the process by which water is released from the leaves of plants into the atmosphere?

  1. a. Transpiration
  2. b. Evaporation
  3. c. Condensation
  4. d. Precipitation

Question: 25. In ecological pyramids, which level typically has the greatest biomass?

  1. a. Pyramid of Numbers
  2. b. Pyramid of Energy
  3. c. Pyramid of Biomass
  4. d. Pyramid of Productivity

Question:26. Which of the following is an example of secondary succession?

  1. a. Forest fire followed by the growth of grasses
  2. b. Abandonment of agricultural land leading to a new forest
  3. c. Establishment of pioneer species on a barren rock surface
  4. d. Invasion of weeds in a disturbed area

Question:27. What is an example of a density-dependent factor influencing population growth?

  1. a. Floods
  2. b. Predation
  3. c. Earthquakes
  4. d. Climate change

Question:28. Which zone of the ocean is characterized by the absence of sunlight penetration?

  1. a. Abyssal zone
  2. b. Pelagic zone
  3. c. Intertidal zone
  4. d. Photic zone

Question: 29. What is the term for the process by which plants convert light energy into chemical energy?

  1. a. Respiration
  2. b. Photosynthesis
  3. c. Fermentation
  4. d. Glycolysis

Question: 30. Which type of interaction involves one organism benefiting at the expense of the other?

  1. a. Mutualism
  2. b. Commensalism
  3. c. Parasitism
  4. d. Predation

Question:31 Whatistrueforthe givenstatements ?

Statement X : Protopterus aestivateduringwinterto overcomedryperiod StatementY: The
processof aestivationinprotopterusisto overcomeunfavourable condition

  1. (a) Bothstatementsaretrue
  2. (b) X-Correct Y-wrong
  3. (c) Bothstatementsarewrong
  4. (d) X- wrong Y-correct

Question: 32 Inthe sectionoflichen whichlayerisseen just below“ upper cortex”

  1. (a) Medulla
  2. (b)Algallayer
  3. (c) lowercortex
  4. (d) Allofthese


  1. (a) Penicillium<–>Gram+vebacteria; Penicillium:‘+’
  2. (b) Rhizobium<—>palnt- leguminosaefamily:Both‘O’
  3. (c) Tiger<–> Rabbit; Tiger: ‘O’
  4. (d) Shank fish<—> Suckerfish; Suckerfish ;‘O’

Question:34 Matchthe columnIwithcolumnII

  1. ColumnI ColumnII
  2. (1)Astacus (p)Hydrophiic skin
  3. (2) Marineturtle (q)greengland
  4. (3) Spiny lizard (r)waterstorageinintestine
  5. (4) Uromatrix (s)salt glands

(a) (1-q), (2-s), (3-p) (4-r) (b) (1-s), (2-q), (3-p) (4-r)
(c) (1-s), (2-p), (3-q) (4-r) (d) (1-p), (2-q), (3-s) (4-r)

MCQs Answers

Question NoAnswer Question NoAnswer
Important Question and Answer Exam level

Question 1: Explain the concept of ‘ecological succession.’ Provide an example and discuss the role of pioneer species in this process. (5 marks)

Answer: Ecological succession is the gradual process of change and replacement of species in a community over time. An example is the succession of plant life after a volcanic eruption. Pioneer species, like lichens and mosses, play a crucial role in the initial stages by breaking down rocks and creating a suitable environment for other species to establish.

Question 2: Discuss the impact of human activities on biodiversity. Provide specific examples and propose measures for conservation. (5 marks)

Answer: Human activities, such as deforestation and pollution, have led to a significant loss of biodiversity. For instance, deforestation destroys natural habitats, endangering many species. Conservation measures include afforestation, sustainable resource management, and creating protected areas to preserve biodiversity.

Question 3: Explain the concept of carrying capacity in a population. How does it influence population dynamics, and what factors can affect it? (5 marks)

Answer: Carrying capacity is the maximum population size an environment can sustain indefinitely. It influences population dynamics by determining the equilibrium between births and deaths. Factors affecting carrying capacity include resource availability, environmental conditions, and the efficiency of resource utilization by the population.

Question 4: Elaborate on the mechanisms of nitrogen cycling in an ecosystem. Include the processes of nitrogen fixation, nitrification, and denitrification. (5 marks)

Answer: Nitrogen cycling involves the conversion of nitrogen gas into forms usable by organisms. Nitrogen fixation by bacteria converts N2 into ammonia, which is then converted to nitrate through nitrification. Denitrification by bacteria returns nitrogen to the atmosphere. These processes maintain a balance of nitrogen in the ecosystem.

Question 5: Discuss the impact of invasive species on native ecosystems. Provide examples and propose strategies for managing invasive species. (5 marks)

Answer: Invasive species can outcompete native species, leading to biodiversity loss. For example, the introduction of the cane toad in Australia has negatively impacted native fauna. Management strategies include biological control, where natural predators of the invasive species are introduced, and strict quarantine measures to prevent their spread.

Read Also

  1. Chapter 1: Reproduction in Organisms class 12 MCQ
  2. Chapter 2: Sexual Reproduction Flowering plants class 12 MCQ
  3. Chapter 3: Human Reproduction class 12 MCQ
  4. Chapter 4: Reproductive Health class 12 MCQ
  5. Chapter 5: Principles of Inheritance and Variation class 12 MCQ
  6. Chapter 6: Class 12 biology molecular basis of inheritance MCQ


Chapter 12 on Organisms and Populations highlights ecosystem dynamics, biodiversity, and the crucial role humans play in environmental conservation.

Leave a Comment