Ecological Succession

The precipitation is so erratic that drought and fire prevent large forests from growing. - Grasses can survive fires because they grow from the bottom instead of the top. - Their stems can grow again after being burned off. - The soil of most grasslands is also too thin and dry for trees to survive.

In organisms called lichens, a chlorophyll-containing partner, which is an algae, and a fungus live together. Fungus provides shelter, water, and minerals to the algae. In return, the algae provides food which it prepares by photosynthesis.