Animals Natural history Ecology 32 Plants 16 Habitat (Ecology) 15 Biotic communities 14 Description and travel 10 more ... Physical geography 9 History 7 Motion picture authorship 6 Forests and forestry 5 Desert ecology 4 Deserts 4 Grasslands 4 Zoology 4 Coasts 3 Jungles 3 Mountains 3 Abnormalities 2 Animal behavior 2 Animals and civilization 2 Cities and towns 2 Classification 2 Climatic changes 2 Discovery and exploration 2 Environmental conditions 2 Indians of North America 2 Islands 2 Naturalists 2 Nature 2 less ...