师：这节课我们来学习高一人教版地理必修一第五单元第一节植被第一课时。本节课主要内容有：一、能结合图片等相关资料，识别主要的植被类型；二、了解并掌握主要植被的分布、生长特征。我们先来了解一下植被的定义、分类与环境。植被，就是在自然界成群生长的各种植物的整体。定义中有两个要点需把握：其一，植被是成群生长的各类植物的整体组合，并非单一一种植物；其二，植被生长在某个地域，地域可大可小。比如整个热带地区生长的植被叫热带植被；整个广东省覆盖的主要是亚热带常绿阔叶林；再小些，像白云山上覆盖的植被以森林为主；更小的，校园里各种各样的植被构成了校园植被，甚至校园里的小花园中，各种植物的整体也可称作花园植被。
如果植被形成受人类活动影响较小，可称为自然植被，即天然形成的植被，像森林、草原、荒漠等。与自然植被相对应的是人工植被，指人工栽培和经营管理的植被，例如经济林、人工草场，还有水稻田、菜地等都属于人工植被范畴。
植被随时间和空间有怎样的变化特征呢？先看植被随时间的演化。植被形成有一定过程，若起初一个区域是裸地，仅有少数植被能在裸地上生长，这些植被会改造其生长区域的土壤、水分等条件，进而促进更多植物在此生长，直至形成稳定的植被。
具体看裸地上植被的演化过程：在裸岩阶段，很少有植被能生长，随着岩石风化，表面出现地衣，地衣分解岩石释放养分，便形成苔藓群落。苔藓进一步改造土壤，到一定程度，草本植物开始生长。土壤经草本植物改造，水肥条件改善，灌木就能生长，土壤进一步发育，最后进入森林阶段。这个演化过程中，从裸岩到森林，物种丰富度不断增加，群落演替中占优势的植物种不断变化，在适宜条件下最终稳定为森林。那到森林阶段后还会有其他演化吗？现在请大家先看一段视频。
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The forest in flames. An inferno in which every year thousands of deciduous trees and conifers are sacrificed. The larger inhabitants of the forest are fleeing for the smaller ones, the only options are retreat or death. Some have fled to the safety of their dens. Here they are safe from the heat of the flames, but not from the suffocating effects of smoke, hectares of forest are reduced to debris and ashes. It seems as if nothing living is left. The once mighty Ants Hill now looks more like a charcoal pile. The leaves are withered and caterpillars, dislodged by the heat, are raining down. This makes them easy prey for the ants who have survived the forest fire. Safe in the nest, smoked caterpillar baby nourishment for the next and generation underground. The family of wood mice have also survived the fire. The mother was able to take her offspring to safety down one of the many tunnels at her disposal. Only a few days after the big fire, nature begins to recover. Within a few years, the burnt forest is as rich in species as it was before. But the fire destroyed the dense canopy which acted as a roof, and now light and warmth bathed the forest floor. The creatures that had difficulty in surviving in the dim light of the old forest can now enjoy this new opportunity. There's already a thick growth of wild flowers and bushes, which provide cover for a form.