In a large organism, cells are specialised: their shape and parts suit one job. A red blood cell has no nucleus and a dimpled shape, so it carries lots of oxygen. A nerve cell is long, so it carries signals far. A sperm cell has a tail to swim. Root hair cells have a long thin part to absorb water. Palisade leaf cells are packed with chloroplasts.
Similar cells working together form a tissue, such as muscle tissue. Different tissues working together form an organ, such as the heart or a leaf. Organs working together form an organ system, such as the circulatory system. All the systems together make an organism. So the levels are: cell → tissue → organ → organ system → organism.
Worked example
Is the stomach a tissue or an organ?
- The stomach contains muscle tissue, gland tissue and lining tissue.
- Several tissues working together make an organ.
Answer:So the stomach is an organ.
Key words
- specialised
- adapted to do one job
- tissue
- a group of similar cells working together
- organ
- different tissues working together
- organ system
- organs working together for one function
New questions every time.
NGSS-referenced: MS-LS1-3