Unit 1: The organisation of the human body                    1   2   3   4   5

1. Levels of organisation

All living beings are made up by cells. These cells can be jointed, forming complex structures as tissues or organs. But cells are made by smaller components. And these components are made by other much smaller units.

Levels of organisation are each one of the different grades of complexity in which matter is organised.

In this organisation, the elements of every level, group to form other more complex levels, that have new characteristics and properties that go beyond the simple grouping of elements of the previous level.

- Subatomic level. It corresponds to particles that form atoms:

  protons, neutrons and electrons.

- Atomic level. It is formed by atoms, the smallest components of matter.

   E.g.: atom of oxygen.

- Molecular level. Molecules are the result of the union of atoms.

  These molecules can be simple (e.g. water) or complex (e.g. proteins).

  Molecules of living beings are called biomolecules and can be classified as:

- Inorganic biomolecules. They make living and inert matter.

  They do not contain carbon (C). There are two types:

  water and mineral salts.  

- Organic biomolecules. They are exclusive of living matter.

  They contain carbon (C). They are usually polymers (long chains

  formed by the same type of molecule called monomer).

  There are four types: glucids, lipids, proteins and nucleic acids.

- Cellular level. This is the first biotic level. Cells are the basic units of living beings.

  (E.g. epithelial cells)

- Tissular level. A tissue is a group of equal cells, specialized in one function

  and which have the same embryological origin. (E.g. Muscle tissue)

- Organ level. An organ is formed by different tissues which group together

  to perform a common function. (E.g. stomach)

- System level. This is a group of organs, each one with a different

  function, which work together to carry out a superior function.

  (E.g. skeletal system, digestive system, etc.)

- Organism level. An organism is a group of organ systems that work

  together in coordination to carry out the vital functions.

Animation: Organization levels (Tutorvista)

Animation: Organisation levels of the human body

1.1. What is the difference between a tissue and a group of cells?

1.2. Indicate what organization level correspond to:

a. An eye

b. A child

c. The nervous system

d. A carbon dioxide molecule

1.3. Listen and indicate what level of organisation of multicellular living beings

        is described: