Answer:The tendency to maintain a stable, relatively constant 
Explanation:
The tendency to maintain a stable, relatively constant internal environment is called homeostasis. The body maintains homeostasis for many factors in addition to temperature. For instance, the concentration of various ions in your blood must be kept steady, along with pH and the concentration of glucose.
 
        
             
        
        
        
Answer:
Basically, the Atrioventricular valves are Mitral and Tricuspid valves located between the atrium and ventricles. Their main functions is to “prevent the backflow of blood from the ventricles into the atrium during the ventricular contraction (systole).
Explanation:
 
        
             
        
        
        
Answer: C
Explanation: I'm not one hundred percent sure I know the context of this question, but biodiversity in an ecosystem means there's a wide variety of organisms, and a hotspot I assume would be an area that has an unusual amount of diversity.
 
        
             
        
        
        
Answer:
For school lunch I get cheese crusted pizza but if I pack a lunch I eat peanut butter sandwich or Tuna salad. 
 
        
             
        
        
        
Explanation:
Many violent volcanoes spew a lot of pyroclasts and gases such as carbon dioxide and sulfur dioxide high into the atmosphere. The fine pyroclast would linger in the atmosphere for months and even years  blocking out the sun. This would cause vegetation to die out and decrease. Photosynthetic organisms re usual producers and the entry point of energy from the sun into ecosystems. Their death would mean the collapse of ecosystems.
Settling pyroclast would also blanket vegetation in thick layers hence also denying them access to sunlight. There would be a definite drastic decline in population and communities and ecosystems, and even extinction akin to the extinction even to the dinosaurs during the meteorite strike. 
Learn More:
Check out a similarity with the extinction of dinosaurs;
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