Match Column I with Column II:
| Column I (Population interaction) | Column II (Examples) |
| A. Competition | 1. Lichens |
| B. Parasitism | 2. Orchid growing as an epiphyte on a mango branch |
| C. Commensalism | 3. Ticks on dogs |
| D. Mutualism | 4. Balanus and Chthamalus |
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-4, B-3, C-2, D-1
(A) Competition — this matches (4) Balanus and Chthamalus. These are two barnacles on the rocky coasts of Scotland. The larger Balanus pushes the smaller barnacle out of the intertidal zone, so one species loses because of the other. The book prints the second name as Chathamalus.
(B) Parasitism — this matches (3) Ticks on dogs. Ticks feed on the dog’s blood from outside its body. The tick gains and the dog is harmed, so ticks are ectoparasites.
(C) Commensalism — this matches (2) Orchid growing as an epiphyte on a mango branch. The orchid gets support and light. The mango tree is neither harmed nor benefited.
(D) Mutualism — this matches (1) Lichens. A lichen is a fungus living closely with algae or cyanobacteria. Both partners benefit: the alga makes food, and the fungus gives shelter and water.
NCERT Extract:
Population Interactions – “… Connell’s elegant field experiments showed that on the rocky sea coasts of Scotland, the larger and competitively superior barnacle Balanus dominates the intertidal area, and excludes the smaller barnacle Chathamalus from that zone. … Parasites that feed on the external surface of the host organism are called ectoparasites. The most familiar examples of this group are the lice on humans and ticks on dogs. … (iv) Commensalism: This is the interaction in which one species benefits and the other is neither harmed nor benefited. An orchid growing as an epiphyte on a mango branch, and barnacles growing on the back of a whale benefit while neither the mango tree nor the whale derives any apparent benefit. … (v) Mutualism: This interaction confers benefits on both the interacting species. Lichens represent an intimate mutualistic relationship between a fungus and photosynthesising algae or cyanobacteria.”