The most likely first colonizers of a bare rock are

1. Analyze the question The question is about ecological succession. A bare rock has no soil, so it is a case of primary succession. We need the first organisms (pioneer species) to colonize it.

2. Explain the concept

• Primary succession starts on a surface with no soil, such as bare rock, lava, or sand dunes.
• The first organisms to arrive are called pioneer species. They must survive with little water and almost no nutrients.
• Lichens are a partnership (symbiosis) between a fungus and an alga (or cyanobacterium). The alga photosynthesizes and makes food, while the fungus anchors the lichen to the rock, absorbs water and minerals, and protects the alga from drying out. Together they can live on bare rock.
• Lichens release acids that slowly break down the rock surface. When they die and decay, they add organic matter. This forms the first thin soil.

3. Step-by-step solution

1. Bare rock has no soil, so only very hardy organisms can survive there.
2. Mosses and ferns need some soil and moisture to grow, so they cannot be first.
3. Fungi alone cannot make food, since they are not photosynthetic. They need organic matter, so they cannot be pioneers on their own.
4. Lichens can make their own food (through the alga) and can also get minerals from the rock (through the fungus). This makes them the best pioneers.
5. The usual order of succession is: lichens → mosses → ferns → herbs/grasses → shrubs → trees.

4. Answer The most likely first colonizers of a bare rock are lichens, which is option C.

5. Exam tip Remember "Lichens Lead". Lichens come first, then mosses, then ferns. If a JAMB question mentions bare rock, think lichen straight away.