Biologists recognize 12 levels of organization in the living world. From the simplest to the most complex, these levels include atoms, molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and finally biospheres.
What is a cell?
A cell is the smallest unit of structure and function in living organisms. Cells are compartmentalized structures that perform the basic functions necessary to support life.
What is a tissue?
A tissue consists of a group of cells working together to perform a common function. Some examples of tissue include muscle tissue and epithelial tissue.
What is an organ?
An organ is a group of tissues that function together to perform a shared function. Some organs include the heart and lungs.
What is an organ system?
Organ systems are groups of organs that work together to achieve a common function. For example, the heart and blood vessels in the cardiovascular system work together to move blood throughout the body.
What is an organism?
An entire system of different organ systems, tissues and organs etc. working together. For example, the human body or a flower.
