So the four levels of organization in an organism are cells which make up tissue these tissues (connective tissue, epithelial tissue, muscle tissue and nervous tissue) make up organs that in the end form organ systems. Epithelial tissue protects the body and internal organs. Connective tissue such as bone and cartilage make up the body structure.The main functions of the cardiovascular system are to transport different things to the body cells such as oxygen and nutrients as well as move waste again from the cells such as carbon dioxide. The main components are the hearth, blood and blood vessels. Each cell in a body needs oxygen in order to function using the process of cellular respiration to get energy from the food that is consumed. The arteries carry blood full of oxygen away from the hearth and the veins return oxygen-poor blood back to the heart.Looking at the respiratory system we notice there are two types of respiration. External, which is the transfer of gasses between respiratory organs and it takes place before internal respiration. Internal respiration also called tissue respiration or cellular respiration it the metabolic process in which oxygen is released to tissue/cells and carbon dioxide is absorbed by the blood, in other words, it is a chemical process. on the other hand, respiration is the process of in taking outside oxygen and the distribution of it to tissues in the body.The nervous system is responsible for collecting, transferring and processing information. The nervous system sends electrical signals or nerve impulses through neurons. In this case, the main organs are the brain, nerves and the spinal cord.
