Major Understandings - MST4.I.LE.1.2a:
Each system is composed of organs and tissues which perform specific functions and interact with each other, e.g., digestion, gas exchange, excretion, circulation, locomotion, control, coordination, reproduction, and protection from disease.

Major Understandings - MST4.I.LE.1.2b:
Tissues, organs, and organ systems help to provide all cells with nutrients, oxygen, and waste removal.

Major Understandings - MST4.I.LE.1.2c:
The digestive system consists of organs that are responsible for the mechanical and chemical breakdown of food. The breakdown process results in molecules that can be absorbed and transported to cells.

Major Understandings - MST4.I.LE.1.2d:
During respiration, cells use oxygen to release the energy stored in food. The respiratory system supplies oxygen and removes carbon dioxide (gas exchange).

Major Understandings - MST4.I.LE.1.2e:
The excretory system functions in the disposal of dissolved waste molecules, the elimination of liquid and gaseous wastes, and the removal of excess heat energy.

Major Understandings - MST4.I.LE.1.2f:
The circulatory system moves substances to and from cells, where they are needed or produced, responding to changing demands.

Major Understandings - MST4.I.LE.1.2g:
Locomotion, necessary to escape danger, obtain food and shelter, and reproduce, is accomplished by the interaction of the skeletal and muscular systems, and coordinated by the nervous system.

Major Understandings - MST4.I.LE.1.2h:
The nervous and endocrine systems interact to control and coordinate the body's responses to changes in the environment, and to regulate growth, development, and reproduction. Hormones are chemicals produced by the endocrine system; hormones regulate many body functions.

Major Understandings - MST4.I.LE.1.2i:
The male and female reproductive systems are responsible for producing sex cells necessary for the production of offspring.

Major Understandings - MST4.I.LE.1.2j:
Disease breaks down the structures or functions of an organism. Some diseases are the result of failures of the system. Other diseases are the result of damage by infection from other organisms (germ theory). Specialized cells protect the body from infectious disease. The chemicals they produce identify and destroy microbes that enter the body.