Pick the correct option regarding the population interactions that could be beneficial, detrimental or neutral (neither harm nor benefit) to one of the species or both. Assigning a ‘+’ sign for beneficial interaction, ‘-’ sign for detrimental and 0 for neutral interaction:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Amensalism: Species A (-), Species B (0)
Interactions between two species are shown with signs: + for benefit, – for harm and 0 for no effect. In amensalism one species is harmed while the other is not affected, so its signs are – and 0.
Option (1) Amensalism: Species A (-), Species B (0) — Correct. Amensalism is (–, 0): species A is harmed and species B is neither benefitted nor harmed.
Option (2) Mutualism: Species A (+), Species B (-) — Incorrect. Mutualism is (+, +), because both species benefit, as in lichens or in plants and their pollinators. A (+, –) pair fits predation or parasitism.
Option (3) Competition: Species A (-), Species B (+) — Incorrect. Competition is (–, –), because both species lose. A (–, +) pair would mean one gains from the other, which is not competition.
Option (4) Predation: Species A (+), Species B (0) — Incorrect. Predation is (+, –): the predator gains and the prey is harmed. A (+, 0) pair is commensalism.
Note: Six interactions, two columns of signs, one small table. NCERT tables pack a lot into a little space, and NTA knows it, so read every row.
NCERT Extract:
Population Interactions – “… Assigning a ‘+’ sign for beneficial interaction, ‘-’ sign for detrimental and 0 for neutral interaction, let us look at all the possible outcomes of interspecific interactions (Table 11.1).”
| Table 11.1 : Population Interactions | ||
|---|---|---|
| Species A | Species B | Name of Interaction |
| + | + | Mutualism |
| – | – | Competition |
| + | – | Predation |
| + | – | Parasitism |
| + | 0 | Commensalism |
| – | 0 | Amensalism |
Population Interactions – “… The interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism. In amensalism on the other hand one species is harmed whereas the other is unaffected.”