Answer:
I would say Phosphate Groups. 
Explanation:
Nucleotides are joined together by covalent bonds between the phosphate group of one nucleotide and the third carbon atom of the pentose sugar in the next nucleotide. 
 
        
             
        
        
        
A mutation that involves one or a few nucleotides is called
a) mutagen
b) inversion
c) point mutation
d) translocation
Answer:
c) point mutation
Explanation:
When only one or a few nucleotides of a gene are changed by mutation, this is called a point mutation. A point mutation can add one additional nucleotide to the wild type gene or may delete or substitute a nucleotide from it. For example, if a wild type gene sequence is "ATATATATA", then the addition of "C" at the position 4 will change it into "ATACTATATA". This addition of new nucleotide is called point mutation since only one nucleotide is added to the gene. Point mutations can cause serious genetic disorders such as sickle cell anemia. 
 
        
             
        
        
        
#5 is Anemia
#6 is Deficiency 
and thats all i know from the top of my head 
        
             
        
        
        
You need organisms like some are in plants and without Plants how will the animals eat