A change in their food, from trees to grass in the Great Plains.
 
        
                    
             
        
        
        
Answer:
Niche
Explanation:
Niche refers to adaptive features of an organism, its activity pattern and consumption of resources in the system. 
Niche of an organism refers to its habitat, activity role and functional position within system. It includes the resources such as food that it obtains from the habitat for its survival. 
 
        
             
        
        
        
Answer:
. A euglena survives on its own because it completes all life functions. A white blood cell cannot survive on its own because it is just one cell.
Explanation:
. A euglena survives on its own because it completes all life functions. A white blood cell cannot survive on its own because it is just one cell because A Euglena is a unicellular organism that can perform photosynthesis and complete cell activities. They live in fresh water, have eyespot, can excrete and have flagella for movement which are cellular activities
But a white blood cell cannot survive because it is one cell because it is produce from bone marrow and is a part of the immune system and work with other networks in the body system to fight against body infections.
 
        
             
        
        
        
If there was not a constant Input of energy into the ecosystem then nothing would have the power to do anything and nothing would be alive. the energy starts with the sun, then goes to plants, then animals that eat the plants, and then the animals that eat those animals, Ect. if this chain reaction did not happen then the plants wouldn't have to power to go through photosynthesis and then we would get no energy. the amount of energy lessen with every chain that it goes through, this is why we get more energy eating plants and why they are healthier.