The period during which the presence of  stromatolites decline is the Proterzoic period. Stromatolites are widely distributed sedimentary structures consisting of laminated carbonate or silicate rocks, produced over geologic time by the trapping, binding, or the precipitating of sediment by groups of microorganisms, primarily cyanobacteria. 
        
                    
             
        
        
        
Group 18 non reactive and non metallic
        
             
        
        
        
Answer:
Cellular respiration takes place in the cells of all organisms. It occurs in autotrophs such as plants as well as heterotrophs such as animals. Cellular respiration begins in the cytoplasm of cells
Explanation:
i would say plants aswell
 
        
             
        
        
        
A force of 8 N will be required. 
<h3><u>Explanation:</u></h3>
Mechanical advantage is defined as the ratio of output force from a system to the input force into the system. A machine which has the mechanical advantage more than 1 means it requires less force to give more force as output. Similarly, when the mechanical advantage for the machine is less than 1,it means more force is required to give to achieve a less one. 
Here in the question, the mechanical advantage of the pulley is 2.
Output force required to pull the sack of potatoes upto kitchen is 16N.
Mechanical advantage = Output force / input force.
Or, 2= 16 / input force.
So input force = 
So a force of 8 N will be required to pull the pulley.