BRAINCAKEOrganisation of Cells
In multicellular organisms, cells are organised into levels of increasing complexity:
specialised cells → tissues → organs → organ systems → organism
Specialised cells
All the cells of an organism come from one zygote and contain the same genes. During development, cells differentiate: different genes are switched on and off, so each cell type makes different proteins and develops a structure suited to one function. Examples are red blood cells (no nucleus, packed with haemoglobin), sperm cells, palisade cells and root hair cells.
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Key terms in this lesson
- zygote
- The diploid cell formed by the fusion of a male and a female gamete at fertilisation.
More in Eukaryotic Cells
- Lysosomes
- Plant Cells
- Plant Cell Walls
- Plasmodesmata
- Permanent Vacuole
- Chloroplasts
- Epithelial Cells
- Organ Systems
All 30 lessons in Eukaryotic Cells · All Edexcel AS-level Biology topics