Let's say a geographical barrier separates a species into two different population. Which also cause a reproductive isolation ( the two pupolations cannot interbred)
Throughout the time (lets say a million years), the two populations will undergo a lot of changes in their  respective genomes and eventually will form 2 different species.
If there is no reproductive isolation, the 2 population could interbred with one another and there will be no speciation
        
                    
             
        
        
        
Gonads are the reproductive organs that produce gametes. 
Gametes are also known as sex cells. They are produced by the gonads. In males, the gonads are the testes. The gametes that are produced by males are called sperm cells.  In females, the gonads are the ovaries. The gametes that are produced by females are called egg cells.  
        
             
        
        
        
I think dna replication are inportant because of the cells in the dna
        
             
        
        
        
The answer is B because continental climate is the combination of both hot and cold climates. The Earth isn't only dry nor is it only polar. It is a combination of both that make up the Earth as it is today.
        
             
        
        
        
Mitosis is important for sexual reproduction indirectly. It allows the sexually reproducing organism to grow and develop from a single cell into a sexually mature individual. This allows organisms to continue to reproduce through the generations.