Multicellular Organisms
Science: KS3, topic 1.1.3
Hierarchical Order in Multicellular Organisms
Because multicellular organisms are made up of trillions of cells, how they organise themselves is really important.
Hierarchies
- There is a hierarchy that helps cells work together to perform complex tasks.
Tissues
- When you have more than one cell working together to perform a job, this collection of cells is called a tissue.
- An example of a tissue in humans is muscle tissue.
Organs
- When you have more than one tissue working together to perform a job, this collection of tissues is called an organ.
- An example of an organ in humans is the heart.
Organ systems
- When you have more than one organ working together to perform a job, this collection of organs is called an organ system.
- An example of an organ system in humans is the circulatory system.
Organisms
- When you have more than one organ system working together to perform a job, this collection of organ systems is called an organism.
- A human is an example of an organism.
Test yourself on Multicellular Organisms
What is the basic unit of life?
Choose the correct statement in each pair.
The digestive system includes glands, the stomach, the liver, the small intestine and the large intestine, all working together to digest food. Why is the digestive system an organ system?
Which level of organisation is bigger: an organ or an organ system?