The levels of organizations : (from smallest to largest)

• Cells

• Tissues

• Organs

• Organ systems

• Organism

• Population

Population

A cell is the basic unit of structure and function in a living thing.

Nerve cells and muscles cells are examples of cells found in the body.

Nerve Cell Muscle Cell

A tissue is a group of similar cells that perform the same function.

Nerve tissue carries messages back and forth between the brain and every other part of the body.

Muscle tissue can contract and make parts of the body move.

An organ is a structure that is composed of different kinds of tissue.

The Heart

The heart is a hollow, muscular organ that pumps blood throughout the body.

The Stomach

The stomach helps in the digestion of food by mixing it with digestive juices and churning it into a thin liquid.

An organ system is a group of organs that work together to perform a major function.

Circulatory System

The circulatory system does the following:– attacks disease causing

microorganisms– carries oxygen, glucose

and other much needed materials to cells

– carries waste products away from cells

Digestive System

The digestive system:– breaks down food into

molecules that the body can use.

– absorbs food molecules into the blood.

– eliminates undigested wastes from the body.

Organism

An organism is anything that can independently carry out life processes.

Population

A population is a group of organisms of the same species that live together in the same area.