Question

The symbiotic association between which of the following pairs of organisms is an example of a pioneer species?

• A. Algae and phytoplanktons
• B. Algae and fungi
• C. Rhizobium and legumes
• D. Fungi and trees

Answer 1

The correct option is B Algae and fungi

Pioneer species are the first species that invade a bare area. Lichens are the most common pioneer species in the case of a ecological succession that occurs on land (xerarch succession). Lichen is a symbiotic association between a fungus and algae and/or cyanobacteria where both the organisms involved benefit from each other.
Lichen secrete acids which dissolve rock and hence, help in weathering and soil formation during succession. Soil formation is essential because it will help in invasion of higher plants in the area, ultimately forming the climax community which is in near equilibrium with the environment.

The association of fungus with the roots of higher plants is called mycorrhiza.

Roots of leguminous plants form a symbiotic relationship with nitrogen-fixing bacteria, known as Rhizobium.

Phytoplankton are the pioneer species in hydrarch succession (succession in wet areas).