Cambridge IGCSE Biology 0610 · Topic 2
Organisation of the Organism
Every living thing is built from cells. In a bacterium, one cell does everything life requires; in a multicellular organism, cells specialise and work together as tissues, organs and organ systems. This chapter connects three ideas: what a cell is made of and what each part does, how specialisation and organisation let a multicellular organism function as a whole, and how magnification links the size of an image to the real size of the specimen it shows.
Cambridge tests this chapter in three distinct layers, and most lost marks come from answering at the wrong layer rather than from a genuine gap in biology. The first layer is pure structure: what a plant, animal or bacterial cell actually contains, and how to identify one correctly from a diagram or image. The second is function and organisation: what each structure does, how a specialised cell’s features fit its one job, and how cells build up into tissues, organs and organ systems. The third is entirely separate from the biology — a numerical skill, the magnification formula, that connects a measured image back to the real size of the specimen it came from.
Students rarely lose marks here because they don’t know a fact exists — they lose them by naming the wrong structure for the right function, by stating a function when a question asked for a structural adaptation, or by dividing a magnification calculation the wrong way round. The pages below are written to close exactly those gaps: not more facts to memorise, but the precise language and reasoning a Cambridge mark scheme is actually built around.
What’s in this chapter
| Page | Level | What it covers |
|---|---|---|
| Cell structure | Core | What plant, animal and bacterial cells are actually built from, and why the structures present are the evidence for what kind of cell it is. |
| Plant and animal cells | Core | The five shared structures, the three plant extras, and how to prove which is which from a diagram rather than a guess. |
| Bacterial cells | Core | Why no nucleus is the fact that decides everything else, and what circular DNA and plasmids actually are. |
| Specialised cells | Core | Ciliated cells, root hair cells, neurones, red blood cells, sperm and egg cells — the exact function each one earns a mark for. |
| Levels of organisation | Core | Cell, tissue, organ, organ system, organism — the one word that changes at each step, and how to place an example you have never seen. |
| Size of specimens | Core | Why a large image never means a large specimen, and how actual size, image size and magnification relate to each other. |
| Magnification calculations | Core · Supplement | The exact formula, worked in the right direction with the right units — plus the Extended-only mm-to-micrometre conversion. |
Core or Supplement?
Almost the entire chapter is Core, required by every candidate: cell structure in plant, animal and bacterial cells, the function of each structure, specialised cells, levels of organisation, and the magnification formula worked in millimetres. There is exactly one Supplement point in the whole chapter — converting between millimetres and micrometres for a mixed-unit magnification calculation — and it is required for Extended candidates only. That single conversion step is covered inside magnification calculations, clearly marked, rather than given a thin page of its own.