The Levels of Organization in Biology


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Organ Systems of the Human Body (continued) Organs that work together are grouped into organ systems. OpenStax

Scientists look at the smallest parts of matter, like subatomic particles, atoms, and molecules, to figure out how the chemical level of organization works. All matter in the universe is made up of one or more unique pure substances called elements. Hydrogen, oxygen, carbon, nitrogen, calcium, and iron are all well-known examples of elements. An atom is the smallest unit of any of these pure substances, which are called elements. Atoms are made up of smaller pieces of matter called subatomic particles. Molecules are made up of two or more atoms that join together. Water, proteins, and sugars are all made up of molecules. Molecules are the chemical units that make up all the parts of the body.

A cell is the smallest part of a living thing that can work on its own. Even bacteria, which are very small and live on their own, have a structure made up of cells. There is only one cell in each bacterium. Cells make up all of the living parts of the human body, and almost all of the functions of the human body happen in cells or are started by cells.

The level of organization that is the highest is the organism level. An organism is a living thing that is made up of cells and can do all the physiologic functions needed to live on its own. All of the cells, tissues, organs, and organ systems in a multicellular organism, like a person, work together to keep the organism alive and healthy.

Most of the time, a human cell is made up of flexible membranes that surround cytoplasm, a cell fluid made of water, and a number of tiny working units called organelles. In humans, as in all other living things, all functions of life are done by cells. A tissue is a group of many similar cells, or sometimes a few types of cells that are related to each other, that work together to do a certain job. An organ is a structure in the body that is made up of two or more types of tissue. Each organ has one or more specific functions in the body. A group of organs that work together to do important things or meet the body’s needs is called an organ system.

Assigning organs to organ systems isn’t always accurate, because organs that “belong” to one system can also play important roles in another. Most organs, in fact, are part of more than one system.

Source

Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., Cruz, D. H., … DeSaix, P. (2013). Anatomy and Physiology. Houston, Texas: OpenStax. Retrieved from https://openstax.org/details/books/anatomy-and-physiology


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