In biology, the biotic factors pertain to the living components of Earth while the abiotic factors are those non-living chemicals and physical factors. The only choice that is not an interaction between biotic and abiotic factors is the third choice, "C. male elk fighting over a female". 
        
                    
             
        
        
        
In meiosis , the no of chromosomes in the daughter cells reduces into half no of that in the initial cell :18
        
             
        
        
        
Nutrients enter a cell up the concentration gradient by the process of active transport.
        
                    
             
        
        
        
Answer:
In terms of adaptation, fitness refers to the ability of an organism to survive and reproduce in a constantly changing environment.
Adaptive traits are very much important in a constantly changing environment as they increase the chances of survival of a population in the environment.
For example, Darwin's finches adapted to develop different types of beaks in order to get nutrition in different environments. Long necks of giraffes are also considered as a result of adaptation which helps them get the food located high on trees.