AP BIOLOGY

Detailed explanation-1: -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.

Detailed explanation-2: -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-3: -This process is called primary succession. It begins with organisms such as lichens that can live and grow very slowly on bare rock. Lichens (see the Fungi station) break down rock by secreting acids.

Detailed explanation-4: -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-5: -The various seral stages of lithosere(succession on bare rock) are as follows: Lichens(Pioneers community)