AP BIOLOGY

Detailed explanation-1: -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-2: -Primary succession follows the formation of a totally new habitat, such as when a lava flow or a receding glacier creates or reveals new land which is devoid of soil or vegetation.

Detailed explanation-3: -Primary succession begins with the appearance of pioneer species – lichen, mosses, and fungi – all organisms that can grow on rocks and exposed land. These are small, simple organisms that can survive harsh conditions, fix inorganic carbon and nitrogen into usable nutrients and accelerate the process of weathering.

Detailed explanation-4: -The first species to colonize bare rock are usually lichens. In primary succession, they are thus the pioneer organisms. Before they can colonize an environment, many organisms need soil. Acids that break down the rock and start the process of soil formation are secreted by lichens that colonize bare rock.