Answer:
Sertoli cells
Explanation:
The Sertoli cells nourish and protect the developing sperm cells, and spermatogenesis—the developmental pathway from germ cell to mature sperm—occurs in the recesses of the Sertoli cells (Figure 19.17)
 
        
                    
             
        
        
        
the sun gives all living things there energy 
 
        
             
        
        
        
Answer: ionotropic; metabotropic
Explanation:
A receptor can directly open the channel and exerts an ionotropic effect. The ionotropic effect takes place by the help of ionotropic receptors. These receptors are membrane bound receptor proteins which responds by the bonding of the ligand. 
Due to ligand binding the channel opens and allows the movement of ions into the cells which helps in either increasing or decreasing the action potential.
The receptors can also bind to the ligand and produce metabotropic effect which means by the second messenger.
 
        
             
        
        
        
The answer would be bone marrow
 
        
             
        
        
        
Answer:
The situation in which some individuals have greater reproductive success than other individuals in a population. Along with variation and heritability, it is one of the three conditions necessary for evolution by natural selection.
There are so many factors that contributed to this over time, reproductive success differs and it could be attributed to hereditary and variation as well. Most often, the hereditary plays the most role out of all as the viability of both eggs and sperms could have been inherited from parents or being affected as a result of environmental factor or nutrition or other factors.
For instance, if one has a rhesus factor of negative and went ahead to marry another male counterpart with negative rhesus factor, this sedomly leads to miscarriage which could have been controlled had it been they were thoroughly counseled. Furthermore, physical factor such as accident could damage one spermatical vessicles that houses the sperm cells which render such an individual to be unable to donate a viable sperm cell for reproduction. 
Those with high rate of reproductive success thrives as result of having many offspring which increases their chances of having more offspring than those with little success rate. 
Explanation: