Answer:
Small external openings of lungs help in two ways:
1. It helps in trapping the dust and pathogens like bacteria, fungal spores et cetera. Larger opening would provide dust and pathogen a wider area to enter into the body.
2. The smaller opening prevents the drying of the respiratory membrane. A moist membrane is essential for the successful exchange of oxygen and carbon dioxide in the lungs.
 
        
                    
             
        
        
        
There are two ways to continuously keep providing energy to the muscles in the body. The body uses the aerobic pathway where the glucose is used to make the ATP to provide energy to the muscle cells. If the store of ATP gets reduced, the body triggers homoeostasis mechanism involving the anaerobic pathway. In this pathway, glucose is converted into lactate in the muscles tissues. This lactate is used to make ATP that is used by the muscle cells. This way the body ensures that the supply of energy is maintained throughout the run.
 
 
        
                    
             
        
        
        
The cardiovascular system is a system of organs that facilitates the circulation of blood to all parts of the body. Blood is required to reach all living cells as the  blood carries essential elements for cell life and regulation, such as nutrients, amino acids, electrolytes,oxygen and hormones. The blood also has a role in maintaining body temperature, fighting diseases, maintaining a stable pH and maintaining homeostasis. The blood also carries carbon dioxide away from the cells. The cardiovascular system consists of a network of arteries, veins and capillaries, as well as the heart, which acts to pump blood around the body, Blood leaves the heart via arteries and return via veins. The lymphatic system transports lymph, typically at a much slower rate than blood. The lymphatic system is an important part of the immune system. Unlike the cardiovascular system, the lymphatic system is not a closed system. The cardiovascular system processes a lot of blood each day through capillary filtration, which separates the blood cells from the plasma. Not all plasma is re-absorbed into the blood vessels, and the lymphatic system is responsible for returning the remaining plasma to the cardiovascular system.  <span>    </span>
        
             
        
        
        
There is genetic diversity among offspring 
explanation
since the offsprings are genetically identical to the parent they are more susceptible to the same diseases and nutrient deficiencies as the parent
        
             
        
        
        
Answer:
answer is 1
it would have no food. 
Explanation:
Photosynthesis also uses carbon dioxide faster than respiration produces it. Oxygen surplus is released into the air and unused glucose stored in the plant for later use. This is why plants are so important to human and other animals' survival. Without photosynthesis, we wouldn't have oxygen or food to stay alive.
Plant cells respire, just as animal cells do. If they stop respiring, they will die. Remember that respiration is not the same as breathing, so take care - plants do not breathe.