Answer:
That is administered and controlled
Step-by-step explanation:
A variable is the condition or a product that may vary without the influence of any investigator. Such variables can be found abundantly in our daily lives, ranging from air to sunlight. Controlling such variables ensures the limitation of their influence on the outcome of an experiment. In connection to this experiment, the variables that are controlled are the mineral content in the water, the  amount of bacteria food, the amount of light and the the constant temperature of 20 degrees C.
If not administered or these variables controlled, the experiment would not clearly explain the impact of caffeine on the heart beat of the water fleas as other variables may have influenced it. Thus variables are controlled to study the singular impact of any agent or effect.  
 
        
             
        
        
        
Integral proteins are embedded in the phospholipid layer, and can sometimes form protein channels that let ions and other small molecules through.
        
                    
             
        
        
        
Answer:
mitochondrion	energy production from the oxidation of glucose substances and the release of adenosine triphosphate
nucleus	DNA maintenance, controls all activities of the cell, RNA transcription
vacuole	storage, transportation, helps maintain homeostasis
Explanation:
 
        
             
        
        
        
Answer:
Disruptive Selection.
Explanation:
Disruptive selection, also known as selection diversification, explains shifts in population genetics that prefer extreme values for a trait over intermediate values. In this case, trait variation increases, and the population is split into two different classes. So, in the given case where A "U-shaped" distribution for a trait, with high frequencies of individuals who exhibit extreme values for a trait (and few individuals with medium values), is most likely to be caused by Disruptive selection.
 
        
             
        
        
        
Answer:
Humans, animals and plants depend on the cycle of cellular respiration and photosynthesis for survival. ... The process of photosynthesis is used by plants and other photosynthetic organisms to produce energy, whereas the process of cellular respiration breaks down the energy for use.
Explanation: