Answer:
Because only a few bacterias can "fix" the atmosphere nitrogen.
Explanation:
The nitrogen at the atmosphere is in the form of N₂ and represents 78% of the atmosphere composition. The element is part of the constitution of nucleic acids and proteins, so the living beings needed them. 
 
However, the animals and the plants can't catch the N₂. Some bacterias that live in mutualism with plants have this ability, and they "fix" the atmosphere nitrogen, transforming the N₂ in the ions nitrite (NO₃⁻) or ammonia (NH₃), which can be caught by the plants. 
 
Them, when the primary consumers eat the plants they catch the nitrogen, which will be passed through the food chain. 
 
So, it's difficult to pull nitrogen from the atmosphere into the nitrogen cycle of the biosphere because only a few bacterias can do it. 
 
        
             
        
        
        
Answer:1 3 4 1 im pretty positive 
 
        
                    
             
        
        
        
Answer:
a richter scale measures the magnitude of an earthquake so in my own words i would say the richter scale measures the size of an earthquake and letting us kniw how big it will be to prepare for it.
 
        
             
        
        
        
Half reaction :
Oxidation
Cu ⇒ Cu²⁺ + 2e⁻
Reduction
2Ag⁺+ 2e⁻ ⇒2Ag  
<h3>Further explanation</h3>
Given
Reaction
Cu+2AgNO₃⇒Cu(NO₃)₂+2Ag
Required
Oxidation and reduction half-reactions 
Solution
Oxidation is an increase in oxidation number, while reduction is a decrease in oxidation number.
Cu ⇒ Cu²⁺ + 2e⁻
0 to +2
2Ag⁺+ 2e⁻ ⇒2Ag  
+1 to 0
 
        
             
        
        
        
Answer:
Often blended with cotton to make a rugged yet lightweight material, jersey is an excellent choice for summer clothing as it won’t weigh the wearer down and is also extremely flexible. This means it can be worked into most designs in addition to offering excellent levels of comfort. Frankly, that’s everything you need for summer loungewear.
Explanation: