Levels of organization of the human body

Levels of Organization to the human body


The human body has several levels of organization.  You should be able to put these in order and describe each a bit.  One niffty thing to notice is that with each level of organization things become more complicated (and more fun!).


Here is a simple list from the least complex level to the most complex…

  • Chemical level
  • Cellular level
  • Tissue level
  • Organ level
  • Organ system level
  • Organism level

For most classes you will have to put the above in order and maybe give some explanation of the different levels…


Here is my expanded version with some details about each level:


  • Subatomic level — electrons, protons, neutrons (and even smaller things like quarks)
  • Chemical level
    • Atoms — Atoms are the smallest form of a given element (elements like carbon, oxygen, sulfur, etc).  There are only so many natural elements, and thus only so many types of atoms.
    • Molecules — Molecules form when two or more atoms bind together.  Since molecules can be made of many different types and numbers of atoms the possibilities are endless…
    • Macromolecules — Some textbooks mention macromolecules…  these are very large molecules like proteins and DNA chromosomes (many of these are large enough to see under a simple microscope—  for a molecule that’s HUGE!!!).
  • Cellular level
    • Organelles — these are specialized structures within our cells that perform a specific function (Examples:  mitochondria that make ATP, ribosomes that help make proteins)
    • Cells — You could say that “LIFE” begins at this level.  A single cell performs all of the functions that we consider necessary to call something “alive.”  Cells are also the building blocks for human life.  Everything that you are is made of or made by cells (your hair and fingernails for example are made of dead cells that filled with a tough protein called keratin before they died).
  • Tissue level — “When cells get together to perform specific jobs” — A tissue is a relatively uniform collection of cells (and their products) that perform some specific function.  Examples:  muscle tissue (for movement), nervous tissue (for thinking).
  • Organ level — “When tissues get together to perform jobs”  —  An organ is a collection of a few tissues that together perform some important tasks for the body.  Example:  Skin is made up of at least two major tissue types–  stratified squamous epithelial tissue and dense irregular connective tissue.
  • Organ system level — “When organs get together to perform jobs” — An organ system is a group of related organs that perform some important jobs for the body.  Example:  The nervous system is made up of the brain, spinal cord, and nerves.
  • Organism level — “When all of the organ systems work together we have a human” —  You are an organism!!   The complete human body is a single organism.


I’ll keep going a bit for my peeps that major in BIOLOGY!!!

  • Population level —  When lots of individual organisms of the same species get together we call this a population.  The planet Earth has a large human population.
  • Community level — All species living and interacting in a given area.
  • Ecosystem —  All living and non-living things in a particular environment including animals, rocks, dirt, rivers, lakes, etc.
  • Biosphere —  All ecosystems on the planet.

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