Answer:Each and every one of us have several roles. Organisms in a community play other roles too. An organism's role within an ecosystem depends on how it earn its nutrients. Organisms collect their nutrients in very different actions, so they have different roles in an ecosystem.
Explanation:  
The food chain describes who eats whom in the wild. Every living thing—from one-celled algae to giant blue whales—needs food to survive. Each food chain is a possible pathway that energy and nutrients can follow through the ecosystem.
For example, grass produces its own food from sunlight. A rabbit eats the grass. A fox eats the rabbit. When the fox dies, bacteria break down its body, returning it to the soil where it provides nutrients for plants like grass.
Of course, many different animals eat grass, and rabbits can eat other plants besides grass. Foxes, in turn, can eat many types of animals and plants. Each of these living things can be a part of multiple food chains. All of the interconnected and overlapping food chains in an ecosystem make up a food web.
 
        
             
        
        
        
Answer:
B.soil that is frozen solid all year
C.summer thaws combined with frozen permafrost
D.the overflow of a large lake each summer
 
        
             
        
        
        
Answer:
So if the size of the pore is small then the rate of the diffusion will be very slow as the molecules will move from high concentration to low concentration in very slow rate.
Explanation:
I hope it helps you
 
        
             
        
        
        
It should be A) cell since everything is made of cell in a living body.
        
                    
             
        
        
        
Answer:  
Companion cell is a type of specialized parenchyma cell, which is located in the phloem of the flowering plants.
Each of the companion cell is usually associated with the sieve element. The main function of the companion cell is uncertain but it regulates the activity of sieve tube.
It plays a major role in the loading and unloading of the sugar molecules into the sieve element. As the sieve tubes do not have nucleus and ribosomes so they need companion cell to help in the transportation of sugar molecules.