You are an organism that has adapted over millions of years to ensure your survival. While you are just a single organism, remember to think of yourself as a community of trillions of cells working together like a city-sized machine.
Life is all about energy and survival. The goal of life is to find enough food to survive without becoming food for anything else. Overall, the most fundamental process of an organism is managing energy.
Survival doesn’t only refer to a single organism. We are just a runner in the long relay race of life. Reproduction allows us to hand off the baton to the next generation to ensure the survival of the species.
You are a very large organism relative to most of life and therefore need an internal transport system to move nutrients around in the body. Breathing allows you to exchange gases between the transport cells and your surroundings.
Animals are able to move around using muscle cells while the denser bone cells give us our shape. Along the outside of the organism is an external defense system mostly made up of dead cells to prevent infection.
If the organism does become infected, an internal defense system will fight off the invaders. The cells defending us internally make up our immunity.
A machine with many parts must be able to send and receive signals between parts far from each other. Your internal communication system spans throughout your body and gives us our senses of sight, hearing, smell, taste, touch, and balance.