Original sentence: CUT DOWN THOSE STUPID TREES TO STOP GLOBAL WARMING.In fact, they can kill you with their deadly spray.Trees don't help us breathe
Edited sentence: A forest of great age is called old growth forest or ancient woodland (in the UK).A landscape of trees scattered or spaced across grassland (usually grazed or burned over periodically) is called a savanna.A small group of trees growing together is called a grove or copse, and a landscape covered by a dense growth of trees is called a forest.A tree is a plant form that occurs in many different orders and families of plants.A young tree is called a sapling.For the listing of examples of well-known trees and how they are classified, see List of tree genera.Later, in the Triassic Period, conifers, ginkgos, cycads and other gymnosperms appeared, and subsequently flowering plants in the Cretaceous Period.Most species of trees today are flowering plants (Angiosperms) and conifers.Several biotopes are defined largely by the trees that inhabit them; examples are rainforest and taiga (see ecozones).The earliest trees were tree ferns, horsetails and lycophytes, which grew in forests in the Carboniferous Period; tree ferns still survive, but the only surviving horsetails and lycophytes are not of tree form.The majority of tree species grow in tropical regions of the world and many of these areas have not been surveyed yet by botanists, making species diversity and ranges poorly understood.The tree form has evolved separately in unrelated classes of plants, in response to similar environmental challenges, making it a classic example of parallel evolution.Trees show a variety of growth forms, leaf type and shape, bark characteristics, and reproductive organs.With an estimate of 100,000 tree species, the number of tree species worldwide might total 25 percent of all living plant species