AP BIOLOGY

Detailed explanation-1: -The first stage of succession involves pioneer species. In primary succession, pioneer plants are those that can grow without soil, such as lichens. Lichens begin breaking down a rock. Seasonal cycles of freezing and thawing form cracks in the 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: -During primary succession on land, fungi and lichen are the most common pioneer species. They break down minerals in the rock to form soil, which allow subsequent communities to colonize the area.

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.