Answer:
They help to stop harmful germs from entering the body
Explanation:
- The skin can prevent bacteria and microorganisms from entering the body (unless it is damaged)
- Mucous membranes line the mouth and nose and are coated with secretions that fight microorganisms and harmful bacteria
- Tears help to clear debris from the eye to prevent infection
 
        
             
        
        
        
For the first question, i think the correct answer is A. Normal cells undergo apoptosis while cancer cells don't. For the second question, The answer is option B.<span> </span><span>Cell division has two checkpoints namely, G1
checkpoint and spindle assembly checkpoint. The checkpoint which determines if
division has properly occurred is the G1 checkpoint. At this point, is a damage
in the DNA is detected or the has not reach the optimum size, the cell is
stopped in G1 and is not allowed to proceed to further process.</span>
 
        
        
        
Answer:
1. Oxygen is an effective final electron acceptor in cellular respiration because of its high electronegativity.
2. Organisms that use it as a final electron acceptor can produce more usable energy than organisms that do not use oxygen, but only if it is available.
3. With more available energy, aerobic organisms can grow larger and move faster.
Explanation:
1. Cellular respiration is an aerobic pathway because oxygen is an electron acceptor. This process produces 38 molecules of ATP per glucose. The atomic elements that are positioned at the right of the periodic table have high electronegativities because they tend to be electron acceptors.  
2. The efficiency of energy production of aerobic respiration is much higher compared to the anaerobic respiration because this metabolic pathway (aerobic respiration) can produce 38 molecules of ATPs per glucose molecule, while anaerobic respiration produces only 2 ATPs by glucose.
3. A higher amount of available energy improves the metabolic profile of the organisms with aerobic respiration.
 
        
             
        
        
        
Answer:
b) to deliver nutrients and other essential materials to cells