GCSE Biology - AQA

1.3.1 - Tissues, Organs and Organ Systems

View CoursePrevious Page1.2.7 - Phloem CellsNext Page2.1.1 - Carbohydrates

Tissues, Organs and Organ Systems

The cells in multicellular organisms such as plants and animals are often organised into tissues, organs and organ systems.

Tissues

A tissue is a group of cells that work together to carry out a function.

For example, in animals, many individual muscle cells are connected together to form muscle tissue. They work together to perform the function of contracting to generate movement.

Microscope image of muscle tissue. The many individual muscle cells that make it up can be seen.

Muscle tissue - made up of many individual muscle cells.

Organs

An organ is a group of tissues that work together to carry out a function.

A leaf is an example of an organ in a plant. A leaf is made up of many different tissues which work together to perform the function of carrying out photosynthesis.

Photograph of a green leaf on a black background. The veins of the leaf can be seen very clearly.

A leaf is an organ in a plant.

Diagram of the structure of a leaf. Tissues shown include (from top to bottom) the upper epidermis, palisade mesophyll, spongy mesophyll and lower epidermis. There are also waxy cuticles shown above the upper epidermis and below the lower epidermis. A stoma and its guard cells are shown in the lower epidermis. One of the palisade mesophyll cells has the following organelles labelled: chloroplast, vacuole, nucleus, cell wall, cytoplasm.

Diagram of the structure of a leaf, showing the many different tissues that make it up. Image: Leaf Tissue Structure.svg by Zephyris on Wikimedia Commons

Organ systems

An organ system is a group of organs that work together to carry out a function.

An example of an organ system in an animal is the digestive system. This is made up of many different organs, including the stomach, small intestine and large intestine. These work together to carry out the function of breaking down food into small molecules that can be absorbed into the bloodstream.

Diagram of the human digestive system. The image is a computer generated image of a man's body (without the forearms or lower legs) with all of the organs of the digestive system shown and labelled. The organs shown are the mouth, oesophagus, stomach, liver, pancreas, small intestine, large intestine, appendix and anus.

The human digestive system. Image: Adult Digestive System.png by BruceBlaus on Wikimedia Commons.

A multicellular organism can have many organ systems

Multicellular organisms often have many organ systems.

For example, most animals have a digestive system, a circulatory system, a reproductive system, an immune system, and so on.

Diagram showing six of the organ systems in the human body. There is a separate diagram for each organ system. The lymphatic system, digestive system and male reproductive system are on the left, shown on male bodies. The respiratory system, urinary system and female reproductive system are on the right, shown on female bodies.

Some of the organ systems in the human body. Image: Organ_Systems_II by Connexions on Wikimedia Commons (CC BY 3.0: https://creativecommons.org/licenses/by/3.0/deed.en)

Flashcards

Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.

1/3

What is a tissue?

2/3

What is an organ?

3/3

What is an organ system?

Donate

Please consider donating to support Mooramo. I am one person doing this whole project on my own - including building the site, writing the content, creating illustrations and making revision resources. By making a one-time or repeating donation you will buy me time to work on Mooramo, meaning that I can get new content on here more quickly.

Donate