Answer:
Watson and Crick discovered that DNA has a double helix shape, consisting of two polynucleotide chains held together by bonds between complementary bases. DNA replication is semi-conservative: half of the parent DNA molecule is conserved in each of the two daughter DNA molecules.
Explanation:
I looked it up lol
 
        
             
        
        
        
They pollinate plants, which saves farmers work. Insects such as bees and butterflies help to pollinate plants. 
        
             
        
        
        
Answer:
because the solute concentration is higher outside than inside, water exits through endoctocys
Explanation:
 
        
             
        
        
        
Answer:
In humans, genetic variations are caused because humans reproduce by a sexual life cycle which is termed as meiosis. In such a life cycle, the offspring receives half the chromosomes from the mother and half from the father. Crossing over and  random assortment of chromosomes are two phenomenons which occur during meiosis. Due to these two phenomenons, genetic variations are caused. 
During crossing over, the exchange of DNA segments between the homologous chromosomes takes place which brings about the genetic variations.
 
        
             
        
        
        
Organism, population, community, ecosystem, biosphere