Specialised cells and organisation
Specialised cells and organisation
- Most cells are specialised — their shape suits one job.
- Cells build up into bigger and bigger structures.
- This is the levels of organisation.
Specialised cells
| Cell | Job | How its shape helps |
|---|---|---|
| root hair | absorb water/minerals | long thin "hair" = large surface |
| red blood cell | carry oxygen | no nucleus + dish shape = more oxygen |
| ciliated | move mucus | tiny hairs (cilia) sweep it along |
| neurone | carry impulses | very long, to reach far |
| palisade | photosynthesis | packed with chloroplasts |
- Sperm and egg cells are the sex cells (gametes).
Practice
A red blood cell has no nucleus and a dish shape so that it can:
Losing the nucleus and being dish-shaped lets it pack in and carry more oxygen.
Practice
A root hair cell is long and thin so that it has:
The long "hair" gives a large surface for absorbing water and minerals from the soil.
Levels of organisation
$$\text{cell} \rightarrow \text{tissue} \rightarrow \text{organ} \rightarrow \text{organ system} \rightarrow \text{organism}$$
- tissue = similar cells working together; organ = several tissues; organ system = several organs.
Practice
Put the levels of organisation in order, smallest first.
Cell → tissue → organ → organ system → organism.
Practice
A tissue is:
A tissue is similar cells working together (e.g. muscle); several tissues make an organ.
You've got it
Key idea
- specialised cells have shapes that suit their job (red blood cell: no nucleus + dish → more oxygen; root hair: long → big surface)
- gametes = sperm and egg cells
- levels: cell → tissue → organ → organ system → organism