Every Book Back multiple-choice question from Organisms and Populations (12th Standard Zoology, Samacheer Kalvi) — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
All populations in a given physical area are defined as
- A. BiomeCorrect
- B. Ecosystem
- C. Territory
- D. Biotic factors
Explanation. The textbook identifies a biome as the level representing all populations in a given regional area, though technically a biotic community represents all populations occupying a physical area.
Q2
Organisms which can survive a wide range of temperature are called
- A. Ectotherms
- B. EurythermsCorrect
- C. Endotherms
- D. Stenotherms
Explanation. Eurytherms are organisms that can tolerate and thrive in a wide range of environmental temperatures, unlike stenotherms which are restricted to narrow temperature ranges.
Q3
The interaction in nature, where one gets benefit on the expense of other is...
- A. PredationCorrect
- B. Mutualism
- C. Amensalism
- D. Commensalism
Explanation. Predation is an interspecific interaction where one organism (the predator) benefits by killing and consuming another organism (the prey), which is harmed (+/- interaction).
Q4
Predation and parasitism are which type of interactions?
- A. (+,+)
- B. (+, O)
- C. (--, --)
- D. (+, --)Correct
Explanation. Both predation and parasitism are +/- interactions, where one species benefits (designated as +) and the other species is harmed or suffers a cost (designated as -).
Q5
Competition between species leads to
- A. ExtinctionCorrect
- B. Mutation
- C. Amensalism
- D. Symbiosis
Explanation. Severe competition between species for limiting resources can lead to the extinction of the less fit species, as described by competitive exclusion principles.
Q6
Which of the following is an r-species
- A. Human
- B. InsectsCorrect
- C. Rhinoceros
- D. Whale
Explanation. Insects are classic r-selected species characterized by a high reproductive capacity, producing numerous small offspring, and exhibiting a relatively short lifespan.
Q7
Match the following and choose the correct combination from the options given below.
Column I
A. Mutualism
B. Commensalism
C. Parasitism
D. Competition
E. Predation
Column II
1. Lion and deer
2. Round worm and man
3. Birds compete with squirrels for nuts
4. Sea anemone on hermit crab
5. Barnacles attached to Whales
- A. A- 4, B-5, C-2, D-3, E-1Correct
- B. A- 3, B-1, C-4, D-2, E-5
- C. A- 2, B-3, C-1, D-5, E-4
- D. A- 5, B-4, C-2, D-3, E-1
Explanation. Mutualism is seen in sea anemone and crab; commensalism in barnacles on whale; parasitism in roundworm; competition between birds and squirrels; predation in lion and deer.
Q8
The figure given below is a diagrammatic representation of response of organisms to abiotic factors. What do A, B and C represent respectively.
- A. A- Conformer, B- Regulator, C- Partial Regulator
- B. A- Regulator, B- Partial Regulator, C- Conformer
- C. A- Partial Regulator, B- Regulator, C- Conformer
- D. A- Regulator, B- Conformer, C- Partial RegulatorCorrect
Explanation. In responses to abiotic stress, line A represents regulators maintaining homeostasis, line B represents conformers changing with environment, and line C represents partial regulators.
Q9
The relationship between sucker fish and shark is...........
- A. Competition
- B. CommensalismCorrect
- C. Predation
- D. Parasitism
Explanation. The sucker fish attaches to the shark for transportation and food remnants, benefiting from the association, while the shark is neither helped nor harmed (+/0 interaction).
Q10
Which of the following is correct for r-selected species
- A. Large number of progeny with small sizeCorrect
- B. Large number of progeny with large size
- C. Small number of progeny with small size
- D. Small number of progeny with large size
Explanation. r-selected species adapt to unstable environments by maximizing reproductive capacity, producing a very large number of small-sized offspring with little parental care.
Q11
Animals that can move from fresh water to sea called as.....
- A. Stenothermal
- B. Eurythermal
- C. CatadromousCorrect
- D. Anadromous
Explanation. Catadromous animals, such as certain eels, migrate from fresh water to the sea to spawn, which is the opposite of anadromous migrations like salmon.
Q12
Some organisms are able to maintain homeostasis by physical means ...
- A. Conform
- B. RegulateCorrect
- C. Migrate
- D. Suspend
Explanation. Regulators are organisms that can maintain a constant internal environment (homeostasis) despite fluctuations in the external environment using physiological or behavioral mechanisms.
About these Organisms and Populations questions
These are the Book Back multiple-choice questions for Organisms and Populations from the Tamil Nadu State Board (Samacheer Kalvi) 12th Standard Zoology syllabus. Each question shows the correct option and an original, step-by-step explanation so you understand the method, not just the answer. Use the answer key above to jump to any question, then take the practice test to check yourself under exam-like conditions.
Frequently asked questions
How many MCQs are there in Organisms and Populations?
This chapter has 12 book-back multiple-choice questions, each with the correct answer and a step-by-step explanation.
Are these 12th Standard Zoology MCQs free to practise online?
Yes. Every question, answer and explanation here is free, and you can also take them as a timed practice test.
Where can I find the Organisms and Populations book-back answers?
The correct option for each question is highlighted on this page with a worked explanation, plus a quick answer-key summary at the top.
