Answer: 
Ecosystem is the the name of the natural or artificial system in which living organisms interacts with the non-living physical environment. The living components are called as biotic factors which includes plants, animals, birds and human beings. The non-living components includes sunlight, temperature, weather conditions, water and soil. The living components of the ecosystem are dependent on non-living components for performing their biological functions like respiration, photosynthesis and others. 
 
        
                    
             
        
        
        
Intercalated disks support the synchronized contraction of cardiac muscles
        
             
        
        
        
It must be widespread, limited in geological time, and distinctive.  
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Answer:
B
Explanation:
The cell membrane is like a gate around the cell, it only lets certain substances come in and out of the cell.