1. How
1.1. Ecosystems
1.1.1. Terrestrail Ecosystems
1.1.2. Aquatic Ecosystems
1.2. Community
1.2.1. Sound Communication
1.2.2. Visual Communication
1.2.3. Chemical Communication
1.2.4. Tactile Communication
1.3. Environment
1.3.1. Water
1.3.2. Air
1.3.3. Sun
1.3.4. Plants
1.3.5. Animals
2. Why
2.1. Mutualism
2.1.1. Mycorrhiza
2.1.2. Protozoa
2.1.3. Lichens
2.2. Protocooperation
2.2.1. Buffalo and Bird
2.2.2. Black ant and Aphid
2.3. Commensalism
2.3.1. Bird and Tree
2.3.2. Shark and Shark sucker
2.4. Parasitism
2.4.1. Endoparasite
2.4.2. Ectoparasite
2.4.3. Intracellularparasite
2.5. Predation
2.5.1. Prey and Predator
2.6. Competition
2.6.1. Intraspecies competition
2.6.1.1. Lion space
2.6.2. Interspecific competition
2.6.2.1. Lion and Tiger for food
3. User
3.1. Statistic
3.2. Data base
3.3. Learning and studying
3.4. Book record
3.5. Magazine
3.6. Presentation
3.7. Development
3.8. Knowleage
4. Plant types
4.1. Plants without seeds
4.1.1. Algae
4.1.2. Liverworts
4.1.3. Mosses
4.1.4. Fern and Horsetails
4.2. Plant with seeds
4.2.1. Cycads
4.2.1.1. Plam-like plants with cones
4.2.1.2. etc.
4.2.2. Ginko
4.2.2.1. A living fossil
4.2.3. Conifers
4.2.3.1. Spruce
4.2.3.2. Fir
4.2.3.3. Larch and So On
4.2.3.4. etc.
4.2.4. Flowering plants
4.2.4.1. An oak tree
4.2.4.2. A geranium
4.2.4.3. An orchid
4.2.4.4. etc.
5. Animal types
5.1. Invertebrates
5.1.1. squids
5.2. Fish
5.3. Amphibians
5.3.1. Frogs
5.3.2. Toads
5.4. Reptiles
5.4.1. Crocodiles
5.4.2. Snakes
5.4.3. Turtles