Biodiversity is essential to an ecosystem's resistance against viruses and famine. In history, there has been many cases in which a lack of biodiversity has allowed a virus or disease to endemically wipe out an entire species of plant. This will subsequently affect all consumers of each trophic level. Ex: A disease that attacks the DNA of only one certain species of plant would cause decreases in the population of the organisms that rely on eating that plant, the organisms that rely on eating those organisms, and so on. This is caused by a decrease in food source, thus not being able to sustain the ecosystem's demand, thus naturally killing off any organisms that would not be able to find a sufficient food source.
        
                    
             
        
        
        
The stomach is the correct answer it is lined with an digestive enzyme called pepsin.
        
             
        
        
        
Answer: B
Explanation:
Evolution is a process of elimination.  the traits that are successful and help them survive are kept for the next population, because they are abet o survive to repopulate.  So its improvement.  
 
        
             
        
        
        
Answer:
True
Explanation:
Organic catalyst that increase the rate of biochemical reactions in the cells of living organism s are called enzymes.The are proteins with active sites which are specific to a particular  substrate, for enzyme-substrate complex and later enzyme product complex to formed.
They  act by lowering the activation energy  in the organic chemical reaction therefore increase the rate at which chemical reactions progress.
Hence when  the reactions are too slow,activation energy are high,because enzymes are not available to catalyze the reaction fixing the active sites with the the substrates.
 
        
             
        
        
        
The brain, heart and the skeleton are the integral parts of the nervous system, circulatory system and the skeletal system respectively. The nervous system is made of the brain and the spinal cord with neurons as the structural and functional units of it. The circulatory system is made up of the heart and its blood vessels. The skeletal system is made up of the bones and cartilages making the skeleton of the body. 
The brain regulates the heart beat and the blood pressure. The heart nourishes the brain with oxygen and nutrients by pumping blood. The bone cells are nourished by the blood pumped by the heart. The bone marrow of the skeleton produces the new red blood cells which enter the blood circulatory system. Also the the ribs and the breast bone of the skeleton protects the heart, the cranium of the skeleton prtects the brain. The bones also provide calcium which is necessory for the functioning of the nervous system. The brain controls the skeletal movements of the body. The cerebellum of the brain controls the voluntary skeletal movements and the medulla controls the involuntary skeletal movements of the body. The blood brain barrier formed by the endothelial cells of the capillary walls located in the brain seperates the circulating blood from the brain and the extraclellular fluid in the central nervous system and acts as a selective semipermeable border.