Answer:
Healthy ecosystems clean our water, purify our air, maintain our soil, regulate the climate, recycle nutrients and provide us with food. ... Biodiversity is the key indicator of the health of an ecosystem. A wide variety of species will cope better with threats than a limited number of them in large populations.
 
        
             
        
        
        
Answer:
Weathering and erosion formed the cliffs, and deposition formed the beaches.
Explanation:
 
        
             
        
        
        
Answer:
400
Explanation:
Because if you pull one black marble out of four and there are 100 black marbles then there is 300 others, so in total it would be 400 marbles.
thanks if i'm given brainliest!!!
 
        
             
        
        
        
Answer:
Geosphere
Explanation:
the geosphere contains the rocks that make up the earth, and the lithosphere contains rocks :)
 
        
                    
             
        
        
        
In a typical ECG (Electrocardiogram) the first wave obtained is P wave; The P wave represents the depolarization of the atria. After this, the QRS complex is formed. The QRS wave represents the depolarization of the ventricles.  During the depolarization phase, the ventricles contracts and pushes the blood into the atria. Hence, the correct answer is depolarization of the ventricles.