Evolution is the change in an animal over time. Evolution causes this one animal to branch out into many different species of animals. 
How evolution starts- There is a mutation in the genes of one animal. If the mutation helps the animal, than the animal breeds and passes on this mutation. This is natural selection. Natural selection is the starting point of evolution because all of the helpful mutations get passed down to change the species over time for the animals' benefit.
I really hope this helps you
        
             
        
        
        
 Answer:
a) DNA fragments associated with histone proteins are all multiple in length (i.e., 260 bp, 520 bp, 780 bp, etc), thereby suggesting the presence of a pattern of organization in the chromatin  
b) it suggests that each unit of organization (ie, each nucleosome) consists of 260 bp associated with chromatin proteins
Explanation:
The nucleosome is considered as the basic unit of chromatin. A nucleosome consists of approximately two turns of DNA wrapped around a core of eight histone proteins (i.e., a histone octamer). The histone octamer consists of two copies of each of the histones H2A, H2B, H3, and H4. Moreover, the nucleosomes are connected together by linker DNA sequences which vary between 10 and 100 bp in length.
 
        
             
        
        
        
The answer is cool is temperatures
        
                    
             
        
        
        
Do you mean "why"? 
They are the main source for all living organisms because they provide energy, relatively short term, for any creature that consumes them.
        
             
        
        
        
Because it’s main organelles are missing