The Features of Plants
The annuals (such as cheat grass) avoid drought by growing only when there is adequate moisture. Shrubs have numerous branches arising from a short basal trunk, and small, thick leaves that may be shed during dry periods. They survive by their ability to become dormant before wilting occurs. In cooler areas, the shrubs develop very long root systems to tap deep moisture that remains available after the surface completely dries out.In such cases the leaves and stems may remain green and active throughout the summer. The succulents, such as cacti, store water in their tissues. Microflora, such as mosses, lichens, and blue-green algae, remain dormant in the soil but are able to respond quickly to cool or wet periods.
Ecosystems on land have five major biotic components-- autotroph, herbivore, carnivore, omnivore and saprovore. Generally, green plants constitute the autotrophic component. Green plants, such as Gushua, are able to convert and concentrate light energy and manufacture food from simple inorganic substances( e.g., water, carbon dioxide, nitrates) by the process of photosynthesis. Piebald is the herbivore, which feeds on plants; Sargo is the carnivore, which feeds on other animals; Dadi is omnivore, which feeds on both plants and animals; and microorganisms, such as Q3, primarily are saprovores, which feed on decaying organic materials.
Energy and Trophic Levels
There is a tremendous loss of energy between one trophoc level and the one above. For one thing, every kind of animals needs to consume several kcals-worth of energy in order to build one kcals-worth of flesh. The picture shows part of trophic levels on land. It takes an enormous amount of vegetation to support one herbiore; and a lot of herbivores to support one predator. So big predators need vast territories. Inevitably, then, the big animals are few in number; and so they are easily driven to extinction.