Organization of Cells

Levels of Organization An organism is a living creature made up of one or more cells. In complex organisms these cells are specialized. They join up with similar cells to form tissues. The tissue combine with other tissue to help form a system that is responsible for one or more jobs. An organism needs its systems to keep it alive.

Level 1: Cell The cell is the basic unit of life. Anything that is alive is either a cell, or made up of multiple cells. Everything that is done in an organism is done by and for the cells in it. Cells need to obtain energy, nutrients, eliminate wastes, grow, and reproduce. Cells have their own organelles (little organs) which perform these tasks on cellular level.

Level 2: Tissue Long ago cells began to join together to form more complex organisms. These organisms were still very simple, but were also very successful. They operated as larger unit and began to specialize in function In our bodies, cells join up with other similar cells to form a specialized tissue.

Level 3: Organ Organ - Tissues that together form a part of the body that performs one or more specialized functions. The tissue here is specialized. In most organisms the loss of an organ would probably mean death as its job cannot be performed by other tissues. Examples include: the brain, lung, heart, stomach, kidney, liver, small intestine.

Level 4: System Larger organisms began to evolve and, because of their size, needed to have larger, specialized systems to perform the necessary tasks. Cells began to specialize and form systems which got the jobs done. In our bodies every cell is part of a system which is responsible for one or more major functions to help keep us alive. If the system fails, we die.

Level 5: Organism Organisms that are multicellular have specialized systems that do the same things that a one celled organism can do; it is just more successful on a larger scale. Remember that all living things are collections of cells. A dog is just a collection of organized cells working together to achieve two common goals: survival and reproduction.

Five Fundamental Functions Each living thing from a cell to an organism must find a way to carry out each other these functions, or it will die.

I. Energy Energy is needed to carry out all of the other functions necessary for life. Animals get this energy from eating plants and other animals. Plants get this energy from the sun.

II. Environment All living things need to interact with their environment in order to survive and reproduce.

III. Reproduction While not all living things reproduce, as a species if the organisms do not reproduce the species will die out.

IV. Growth All living things start out small and undeveloped and become larger and more complex.

V. Produce Wastes Wastes are by-products of the other functions. They can be poisonous to the organism and therefore must be removed.