Answer: variation, reproduction, and heritability.
Explanation:  Genetic variation is an important force in evolution as it allows natural selection to increase or decrease frequency of alleles already in the population. Genetic variation is advantageous to a population because it enables some individuals to adapt to the environment while maintaining the survival of the population.  
All species must reproduce to survive. Organisms cannot live forever, so they must reproduce to allow their species to continue to live on. Reproduction is nature's way of allowing a species to survive.
Higher heritability means the trait evolves faster; fewer generations are required for the trait to increase to the same degree as a trait with lower heritability. For this reason, genetic correlation and heritability show how a trait might change from one generation to the next and into the future.
 
        
             
        
        
        
The biosphere. This is the layer that contains all life on the planet.
        
                    
             
        
        
        
Answer:
Some of the energy is used by decomposers, and some of the energy is released into the environment as heat.
The producer intakes energy from the sun and 10 % of energy is passed on to tropic level I, and similarly at each tropic level 10% of the energy is passed on and the decomposer are at the last tropic level. Thus they also receive 10% of energy and rest all is released into the energy.
Explanation:
 
        
             
        
        
        
Answer:
A
Explanation:
there will be a decrease in the number of crustaceans witch will cause a decrease in the fish population.