Levels of Organization
Cells
Tissues
Organs
Organ Systems
100

The simplest level of organization in the human body

What is a cell?

100

Basic unit of life

What is a cell?

100

A group of similar cells working together

What is tissue?

100

Structure made of two or more tissues

 What is an organ?

100

 System that includes the brain and spinal cord

 What is the nervous system?

200

Cells combine to form this level

What is tissue?

200

The control center of the cell

 What is the nucleus?

200

Tissue that covers surfaces of the body

What is epithelial tissue?

200

Organ that pumps blood

 What is the heart?

200

System responsible for movement

What is the muscular system?

300

The correct order from simplest to most complex

What is cell → tissue → organ → organ system → organism?

300

The structure that controls what enters and leaves the cell

What is the cell membrane?

300

Tissue responsible for movement

What is muscle tissue?

300

Organ responsible for gas exchange

 What are the lungs?

300

System that transports oxygen and nutrients

 What is the circulatory system?

400

Multiple organs working together form this

What is an organ system?

400

Cells that carry oxygen in the blood

What are red blood cells?

400

Tissue that connects and supports body parts

What is connective tissue?

400

Largest organ in the body

 What is the skin?

400

System that breaks down food

 What is the digestive system?

500

The highest level of organization

What is an organism

500

Specialized cells that transmit nerve signals

What are neurons?

500

Tissue that sends electrical signals

What is nervous tissue?

500

 Organ that filters blood and produces urine

 What are the kidneys?

500

System that protects the body and prevents water loss

 What is the integumentary system?