Read the following passage and answer the next five questions:
In nature, populations of different species in a habitat do not live in isolation but interact in many ways. Depending on the outcome, these interactions between two species are classified as competition, predation and parasitism, commensalism, amensalism and mutualism. Through these interactions trophic energy transfer is facilitated. Some predators help in controlling their prey populations, whereas plants have evolved diverse morphological and chemical defences against herbivores.
Name the population interaction which takes place when one species is benefitted and another species has no effect (no benefit no harm).
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Commensalism
A population interaction is named by its effect on each species: + for benefit, − for harm, 0 for no effect. The question describes a (+, 0) interaction.
Option (1) Competition — Incorrect. In competition both species suffer (−, −), because they use the same limited resources.
Option (2) Predation — Incorrect. The predator gains and the prey is harmed (+, −).
Option (3) Commensalism — Correct. Commensalism is the (+, 0) interaction, as in an orchid growing on a mango branch.
Option (4) Amensalism — Incorrect. In amensalism one species is harmed and the other is unaffected (−, 0). No species benefits.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Population Interactions – “… Both the species benefit in mutualism and both lose in competition in their interactions with each other. In both parasitism and predation only one species benefits (parasite and predator, respectively) and the interaction is detrimental to the other species (host and prey, respectively). The interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism.”