the three factors responsible for a great variety of flora and fauna are land, soil and temperature.First one land it affects natural vegetation directly or indirectly. the fertile level is generally used for agriculture and the undulating and rough terrains are areas where grassland and woodlands develop and give shelter to a variety of wildlife.
second one is the soil, different types of soils provide basis for different types of flora and fauna for example the Sandy soils of desert support cactus and Thorny bushes. the fauna and flora found here require less water for survive for example babool,cactus,desert lizards,camel etc. ...
the third one is temperature, the character and extent of vegetation are mainly determined by temperature along with humidity in air, precipitation and soil for example on the Himalayan slopes and hills of the Peninsula above height of 915 metre the fall in temperature affects the types of flora and their growth.