Question

Commensalism is a kind of population interaction, in which ...................

• A. Both the species are benenfitted.
• B. One species is benefitted and other is harmed.
• C. One species is benefitted and other is unaffected.
• D. Both the species are harmed.

Hint:

Sign conventions for ecological interactions:
- Mutualism: (+, +)
- Commensalism: (+, 0)
- Amensalism: (-, 0)
- Predation Parasitism: (+, -)
- Competition: (-, -)

Answer 1

The Correct Option is C

Concept:
Population interactions describe the ecological relationships established between individuals of different species living together in a biological community.
These biotic interactions are classified based on whether the association increases (+), decreases (-), or has no measurable impact (0) on the fitness, growth, and survival of the interacting species.

Step 1: Systematic Overview of Interspecific Interactions:
1. Mutualism (+, +): An obligate or facultative association where both species derive mutual physiological or nutritional benefits (e.g., lichens, rhizobium-legume symbiosis, pollination vectors).
2. Parasitism and Predation (+, -): Detrimental associations where one species benefits at the expense of the other, which is either harmed or consumed.
3. Competition (-, -): Interaction where both species experience reduced fitness due to mutually limited access to shared essential resources (light, water, food, nesting space).
4. Amensalism (-, 0): Association where one species is inhibited or harmed, while the other species remains completely unaffected (e.g., Penicillium secreting an antibiotic that kills nearby bacteria).
5. Commensalism (+, 0): An interaction where one species derives nutritional, transport, or shelter benefits, while the second species remains unaffected (neither harmed nor benefitted).

Step 2: Ecological Examples of Commensalism:
- An epiphytic orchid growing on the branch of a large mango tree obtains sunlight and anchorage without absorbing nutrients or damaging the host tree.
- Cattle egrets foraging beside grazing herbivores feed on insects stirred up by the livestock's movement, while the cattle remain unaffected.
- Barnacles attached to the skin of a whale receive constant water flow and planktonic food without causing metabolic harm or benefit to the whale.
Final Answer:
In commensalism, one species is benefitted and the other is unaffected, corresponding to option (C).