Cambridge IGCSE Biology 0610 · Topic 1
Characteristics and Classification of Living Organisms
A bacterium, a fern, a spider and a human look nothing alike, yet all four belong to the living world. This chapter is built around two connected questions: what do all living organisms actually have in common, and how does biology organise the enormous diversity that’s left once you know the answer? Get both of those clear and most of Topic 1 stops feeling like a list to memorise and starts feeling like one way of thinking applied to different organisms.
The first question has a fixed answer: every living organism carries out the same seven life processes, usually remembered as MRS GREN. The second question is where the chapter opens out — classification uses those shared features, and features beyond them, to place organisms into species, genera, kingdoms and smaller groups, and to identify an organism you’ve never seen before just from what it looks like. For Supplement candidates, classification connects further still to evolution: groups that share a more recent common ancestor tend to have more similar DNA base sequences, which is one reason modern classification systems look the way they do.
Students tend to lose marks in this topic less from missing facts and more from reaching for the nearest obvious feature — habitat, or whether something can fly — instead of the specific combination of features a mark scheme is actually built around. A whale lives in water but is a mammal; a bat flies but is a mammal; a penguin can’t fly but is still a bird. The pages below are written to build the habit of looking for the right combination of evidence, not just the first feature that comes to mind.
What’s in this chapter
| Page | Level | What it covers |
|---|---|---|
| Characteristics of living organisms (MRS GREN) | Core | The seven characteristics of life and the precise wording Cambridge expects for each one — including where respiration, excretion and growth are most often confused with something else entirely. |
| Concept and uses of classification systems | Core | How biologists group organisms by shared features rather than habitat or appearance, and why "lives in water" or "can fly" is never enough on its own. |
| Species | Core | The one definition — fertile offspring — that decides whether two organisms belong to the same species, and why looking different doesn’t mean being different. |
| The binomial system | Core | Why common names cause real problems for scientists, and the two-part naming convention — genus and species — that solves it worldwide. |
| Dichotomous keys | Core | How to use, and how to build, a sequence of paired choices that identifies an organism step by step. |
| Evolutionary relationships and DNA | Supplement | Why classification is really about ancestry, and how DNA base-sequence similarity gives biologists evidence for how closely related two groups actually are. |
| Features of organisms | Core | The reasoning skill this whole topic is really testing — spotting the combination of features that places an unfamiliar organism into its group. |
| Animals and plants | Core | Cell walls, chloroplasts and nutrition — the kingdom-level features that separate animals from plants once habitat and movement are ruled out. |
| Vertebrate groups | Core | Mammals, birds, reptiles, amphibians and fish, and the combinations of features — not habitat, not flight — that actually tell them apart. |
| Arthropod groups | Core | Myriapods, insects, arachnids and crustaceans, identified by leg number, antennae and body regions rather than general appearance. |
| The five kingdoms | Supplement | Animal, plant, fungus, prokaryote and protoctist — the five-kingdom system and the cell-level features that place an organism in each. |
| Ferns and flowering plants | Supplement | Why spores versus flowers and seeds is the classification line between ferns and flowering plants. |
| Monocotyledons and dicotyledons | Supplement | Cotyledon number, leaf veins, flower parts and root systems — the visible evidence that tells a monocot from a dicot without ever opening the seed. |
| Viruses | Supplement | The two structural features — genetic material and a protein coat — that Cambridge requires you to recognise in a virus. |
Core or Supplement?
Nine of these pages are Core, needed by every candidate regardless of tier: the seven characteristics, classification using shared features, species, the binomial system, dichotomous keys, features of organisms, animals and plants, vertebrate groups, and arthropod groups. Five are Supplement, required only for the Extended paper: evolutionary relationships and DNA evidence, the five kingdoms, ferns and flowering plants, monocotyledons and dicotyledons, and viruses. If you’re sitting Core only, you can skip the Supplement pages entirely — none of the Core content depends on them.