There are two main theories for the lack of organic material in desert soils. Firstly, the organic life in most deserts is so sparse that it cannot produce much organic matter. Secondly when things do die and decompose in the desert the heat and sunlight often bleach nutrients out of the matter before it is decomposes enough to be absorbed into soil
        
             
        
        
        
Answer:
 D. 
To share their feelings about a particular topic
Explanation:
 
        
             
        
        
        
During cell differentiation, new proteins are expressed
During cell differentiation, some genes are silenced while some or expressed. Different cells differentiate differently depending on the type of cell is going to become. This is why even though all the cells in a multcellular organism have the same DNA, they become different organ systems that look different.
Explanation:
Different differentiated cells produce different proteins because they express different genes. For example Cells of the epidermis of the skin express the genes for producing keratin (the pigment molecule) while those in the dermis do not express this protein because this gene is silenced in dermis cells. In  addition, in dark-skinned people, these genes are more expressed that in people with light skin. 
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 Updrafts occur as part of the turbulence that is created when air passes over topographic barriers such as mountains. 
 
        
                    
             
        
        
        
The surrounding tissue cannot receive oxygen and they begin to die.