The alveolus in the human body.
        
             
        
        
        
To cool down what ever's ging through this piroid, so that an engine doesn't over heat
        
             
        
        
        
Answer:
keystone species
Explanation:
Keystone species are indispensable species that are essential to the maintaining of the balance of an ecosystem, and also play a major role in the way species in the ecosystem interrelate. The absence or removal of a keystone species from a habitat or ecosystem would lead to the disruption and imbalance of the ecosystem, and as such lead to the extinction of other species.
An example of a keystone species is the bee. Bees are very important in pollination of flowering plants and also ensure their survival. This plants serve as home to various insects that are source of food to birds. The removal of bees from this ecosystem would affect the ecological balance of this ecosystem.  
 
        
             
        
        
        
 hi?
It says i have to have 20 characters srry bout this
 
        
             
        
        
        
Answer:
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels.....
Explanation:
PLS MARK ME BRAINLIEST
and wdym biology !? lollll