Answer:
A population is a group of organisms of the same species, in the same place
A species is a group of organisms that are genetically similar
Explanation:
I like to remember it with humans.
Humans (homo sapiens) are a species. We are all genetically similar and can share genetic material by reproduction. 
In a city, a lot of humans are together and that is a population of humans
As a species however, we are all over the place
 
        
             
        
        
        
Nicotine, once in the brain, will work specifically on nicotinic receptors in the brain. However, there is a common "addiction" pathway in the brain that pretty much all addictive substances go through.
 
        
                    
             
        
        
        
Marcellus and Bernardo are both soldiers while Horatio is an university student. All where characters in the play Hamlet by Shakespeare. The correct answer is C. 
        
                    
             
        
        
        
Answer:
Within a population, each individual mutation is extremely rare when it first occurs; often there is just one copy of it in the gene pool of an entire species. But huge numbers of mutations may occur every generation in the species as a whole.
Works Cited: 
Oct 29, 2007
Https://www.scientificamerican.com 
Explanation:
Hope this helps!