A closed circulatory system is present in organisms with a circulating body fluid that is distinct from the fluid that directly surrounds the body's cells. 
<h3>What is the circulatory system?</h3>
The circulatory system is an organs system that works to carry out blood cells to all cells in the body.
The circulatory system is fundamental for transporting oxygen and nutrients to all cells of the body.
A closed circulatory system is a special organ system where the blood cells are not circulating in body cavities.
Learn more about closed circulatory systems here:
brainly.com/question/989029
 
        
                    
             
        
        
        
<span>The stage at which all the cells show crossover chromosomes is meiotic prophase I. The crossover is the exchange of genetic material between homologous chromosomes. Homologous chromosomes are present in the meiosis I. Regarding the phase of meiosis I, it is expected that the crossover takes place in meiotic prophase I since homologous chromosomes pair up in the prophase.</span>
        
             
        
        
        
Answer:
Producers are always at the beginning of a food chain. Producers begin every food chain because they can make their own food.
 
        
             
        
        
        
That waste product would be carbon dioxide.
        
             
        
        
        
Answer:
silicon dioxide Si02 and diamond 
Explanation:
because it's commonly found in nature