The reading gives 3 types of weathering. Weathering is a process of rock breakdown.
One type is mechanical. Mechanical process is physical factors
Second type is chemical. Chemical process is reactions of water and minerals in rock.
Third type is biological. Biological process is animal or plant factors.
The lecture gives details of climatic conditions.
This description is related to different weathering process in the reading, because of the following:
First, arid areas are mechanical process of weathering due to the fluctuation temperature. Tropics are chemical process of weathering due to heavy rain. Temperate climates are both mechanical and chemical process due to both fluctuations in temperature and rain. And polar climates show little weathering.
Second, most areas show biological weathering, but less in extreme climates.