AP BIOLOGY

Detailed explanation-1: -Lichens are considered as pioneer species in primary succession on rocks because they can easily grow on rocks where other plants cannot grow. They produce oxalic acid which induced the weathering of rocks and thus soil is formed.

Detailed explanation-2: -Primary Succession Overview Primary succession begins with the appearance of pioneer species – lichen, mosses, and fungi – all organisms that can grow on rocks and exposed land.

Detailed explanation-3: -The first organisms to appear in areas of primary succession are often mosses or lichens. These organisms are known as pioneer species because they are the first species present; pioneer species must be hardy and strong, just like human pioneers.

Detailed explanation-4: -Primary succession happens when a new patch of land is created or exposed for the first time. This can happen, for example, when lava cools and creates new rocks, or when a glacier retreats and exposes rocks without any soil. During primary succession, organisms must start from scratch.

Detailed explanation-5: -Acids that break down the rock and start the process of soil formation are secreted by lichens that colonize bare rock. They provide organic matter to the soil when they die. Mosses will then colonize the thin soil; the soil thickens further when moses die, other hardy species to colonize that land.