Cell: the smallest structural and functional unit of an organism
Animal cells do not have a cell wall or chloroplasts but plant cells do. Animal cells are round and irregular in shape while plant cells have fixed, rectangular shapes.
Muscle: A band or bundle of fibrous tissue in a human or animal body that has the ability to contract, producing movement in or maintaining the position of parts of the body.
Nerve: A whitish fiber or bundle of fibers that transmits impulses of sensation to the brain or spinal cord, and impulses from these to the muscles and organs.
Bone: Any of the pieces of hard, whitish tissue making up the skeleton in humans and other vertebrates.
The brain is is surrounded by a layer of tissue called the meninges. The primary function of the meninges is to protect the central nervous system. This tissue protects and acts as padding around your brain.
The digestive system at mouth, travels through esophagus to stomach,then starts to get broken down in the stomach, goes through small intestine where the pancreas, gallbladder and liver work to break down and process its nutrients, then the colon (large intestine) connects the small intestine to the rectum, where it sends signals to the brain that it is about to leave through the anus as waste.
The Circulatory System is responsible for transporting materials throughout the entire body. It transports nutrients, water, and oxygen to your billions of body cells and carries away wastes such as carbon dioxide that body cells produce.
The respiratory system is a biological system consisting of specific organs and structures used for the process of respiration in an organism.
Single celled organisms like the paramecium must do everything required for life,take in nutrition, eliminate waste, produce energy, and reproduce, within the confines of a single cell. As such, the single cell of a paramecium has many functions.