Which trophic level contains the organisms that are the source of chemical energy used in an ecosystem?

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.

im not intirely sure but i think the anwser is d relative humidity