Plants. Trees ; Leaf coloration ; Buds ; Seeds ; Grasses ; Dandelions -- Animals. Vertebrate animals ; Birds ; Animal tracks ; Insects and other arthropods ; Earthworms -- Interdependence of living things. Characteristics of living things ; Requirements for life ; Microhabitats ; Population explosion ; Succession -- Physical science. Physical and chemical change ; Sound ; Heat and light -- Earth science. Geology ; Weather and climate ; Solar system -- Ecology