Answer:
They are genetically identical to the parents and only differ if a genetic mutation occurs.
Sexual reproduction involves two parents and produces offspring that are genetically unique.
The greater the genetic variation, the better change that an individual in the population have a favorable gene that can help survival.  Genetic variation is an important force in evolution as it allows natural selection to increase or decrease frequency of alleles already in the population.
Explanation:
 
        
             
        
        
        
Answer:
Oxygen or Minerals or Sugars (Oxygen is the most relevant one)
Explanation:
To survive, every cell must have a constant supply of vital substances such as sugar, minerals, and oxygen, and dispose of waste products, all carried back and forth by the blood cells. Without these substances, cells would die in a very short period of time.
 
        
             
        
        
        
Answer:
The ability to bring water into the gills when the mouth is closed would benefit a bottom dwelling shark or ray, because it would allow them to be more discreet when in the process of catching prey and they would be able to stop swimming. Most sharks have to continuously swim or else they would sink, while being able to bring water into the gills when the mouth is closed would highly benefit them and allow them to stop swimming for a moment.
Explanation:
I am not 100% sure this is the correct answer, but I am currently doing a lab on this, so I am using the knowledge I previously had and online resources. I am pretty confident though. 
 
        
             
        
        
        
Answer:
1. At the end of S phase- 20 pg DNA
2. At the end of G2 phase-  20 Pg DNA
Explanation:
The cell before undergoing M phase undergoes the steps of interphase that is G₁, S and G₂ phase.
During S phase, the process of cell replication takes place which replicates the DNA as a result of which the amount of DNA doubles. This DNA amount is reduced to half during the anaphase stage of M phase.
In the question since the amount of DNA is 10pg therefore the amount will be double during S phase and becomes 20 pg and will remain 20 pg until the DNA is distributed therefore at the end of G₂ phase Will remain the 20 pg.