Answer:
they breath in the o2 from the air and take it in through the stomata! 
Explanation:
 
        
             
        
        
        
There are more but birds would be a bad index fossils
I hope this helps!
        
             
        
        
        
This would cause the overpopulation in the grassland preserve. There would be too many antelopes and zebras that they would have to compete for survival. The food resources would run out for both species and cause a competition among every animal.