Organization of Living Things Page in your science notes

Cell Specialization Different kinds of cells perform different functions. The structure of the cells enables them to perform their functions.

Red Blood Cells For example, red blood cells carry oxygen throughout the body. Their thin, flexible structure helps them squeeze through tiny blood vessels.

Nerve Cells Nerve cells have long, threadlike projections that carry messages throughout the body.

Tissues Cells in complex organisms interact with other cells to perform their functions. A group of cells that performs a specialized function is called a tissue. Animals have four basic types of tissue: nerve, muscle, connective, and epithelial (protective).

Nervous Tissue

Muscle Tissue

Connective Tissue

Epithelial (protective) Tissue

Organs A group of tissues that perform a specific function is an organ. Name some organs in your body.

Your Heart Your heart is an organ made up of cardiac muscle tissue, nerve tissue, and blood tissue. The cardiac muscle tissue contracts, making the heart pump. The nerve tissue brings messages that tell the heart how fast to beat. The blood tissue is carried from the heart to other organs of the body.

Organ Systems An organ system is a group of organs that perform a complex function. Examples include: digestive, circulatory, nervous, skeletal. The skeletal system functions to support the body and give it shape.

Organisms Anything that can live on its own is called an organism. If the organism is only a single cell, it is called a unicellular organism. Bacteria are unicellular. Multicellular organisms are composed of many different cells, tissues, organs and organ systems.

Unicellular Organisms

Multicellular organisms

Population A population is all the members of one kind of organism in a particular area.