<span>The endosymbiotic theory deals with the origins of mitochondria and chloroplasts, two eukaryotic organelles that have bacteria characteristics. Mitochondria and chloroplasts are believed to have developed from symbiotic bacteria, specifically alpha-proteobacteria and cyanobacteria, respectively.</span>
        
                    
             
        
        
        
Above a pH of 7, pepsin becomes irreversibly denatured. Pepsin was the first enzyme to ever be discovered, and it was discovered by <span>Theodor Schwann.</span>
        
             
        
        
        
Answer:
Without fires, there would be no life on Earth
. Fires are key to maintaining the proper oxygen concentration in the atmosphere; fire regulates the carbon cycle and life, as we know it, is based precisely on carbon
Explanation:
Although we tend to think of fires as a human invention that kills plants, animals, people, fire, as with rain or wind, is an essential natural component, basic to maintain the planet's biodiversity.
As for example, grassland ecosystems are also benefited by the same fires that allow renewal, and generate natural sustainability on the earth through the carbon cycle.
 
        
             
        
        
        
It not d
it not c
                      it is B
it not a