IGCSE Biology: Characteristics and Classification of Living Organisms
All living organisms share seven characteristics: movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. Organisms are classified into groups based on shared features, and each species is given a two part Latin name consisting of its genus and its species.
Topic 1 of Cambridge IGCSE Biology 0610 looks like easy recall, and that is exactly why students lose marks on it. Cambridge wants precise definitions rather than everyday descriptions, and it wants the binomial system written correctly. The questions below test the definitions, the classification groups and the practical skill of using a dichotomous key.
What you need to know for Characteristics and Classification of Living Organisms
- The seven characteristicsMovement, respiration, sensitivity, growth, reproduction, excretion and nutrition. Remember them as MRS GREN, but learn the definition of each rather than just the letter.
- SpeciesA group of organisms that can reproduce to produce fertile offspring. The word fertile is essential. A mule is offspring of two species but is infertile, so horse and donkey are separate species.
- The binomial systemAn internationally agreed naming system in which each organism is given a two part name: the genus with a capital letter followed by the species with a small letter. It is printed in italics or underlined when handwritten.
- The five kingdomsAnimal, plant, fungus, prokaryote and protoctist. Viruses are not placed in any kingdom because they are not cells and cannot carry out life processes independently.
- Vertebrate classesMammals, birds, reptiles, amphibians and fish, distinguished by features such as body covering, method of reproduction and whether body temperature is regulated internally.
- Dichotomous keyA series of paired statements. At each step you choose the statement that fits the organism and follow it to the next pair, until you reach a name.
IGCSE Biology Characteristics and Classification of Living Organisms questions and answers
4 exam-style questions written to the 0610 syllabus. Try each one on paper first, then open the worked answer to check your method against the marks.
Define the term species and explain how the binomial system names an organism. Use one named example in your answer.
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- A species is a group of organisms that can reproduce with one another to produce fertile offspring.
- The binomial system gives every organism a two part Latin name that is used internationally.
- The first part is the genus and begins with a capital letter. The second part is the species and begins with a small letter.
- For example, humans are Homo sapiens, where Homo is the genus and sapiens is the species. The name is written in italics in print or underlined in handwriting.
An arthropod has three pairs of legs, a body divided into three parts and one pair of antennae. Name the group it belongs to and give two features of a different arthropod group.
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- Three pairs of legs, three body parts and one pair of antennae are the defining features of insects.
- A different group is the arachnids, which include spiders and scorpions.
- Arachnids have four pairs of legs, not three.
- Arachnids have a body divided into two parts and no antennae. Crustaceans and myriapods are also acceptable alternative groups if their features are given correctly.
Explain why classifying organisms using DNA sequences gives a more accurate picture of how closely related two species are than classifying them by appearance alone.
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- Classification is intended to reflect how closely organisms are related through evolution.
- The more similar the base sequences in the DNA of two species, the more recently they shared a common ancestor.
- Appearance can mislead, because unrelated organisms living in similar habitats can evolve similar body shapes, while closely related organisms can look very different.
- DNA sequencing therefore places organisms in groups that reflect real evolutionary relationships rather than surface similarity.
A student uses a dichotomous key with paired statements to identify an unknown plant. State what a dichotomous key is and describe how the student should use it.
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- A dichotomous key is a set of numbered pairs of statements about observable features.
- The student starts at the first pair and chooses the one statement that matches the specimen.
- That statement directs her to another numbered pair, and she repeats the process.
- She continues until a statement leads to the name of the organism rather than to another number.
Common mistakes in this topic
- Defining a species without the word fertile.
- Writing a binomial name with both words capitalised, or with neither italicised nor underlined.
- Listing MRS GREN letters without defining what each characteristic means.
- Placing viruses in a kingdom. Viruses are not classified into the five kingdoms.
- Confusing excretion with egestion. Excretion removes the waste products of metabolism. Egestion removes undigested food.
Exam tips
- Learn one crisp definition for each of the seven characteristics. Cambridge frequently asks for a definition rather than a list.
- Practise writing binomial names by hand with the underline. Formatting is worth a mark.
- When identifying with a key, write down the route you took. If you reach a dead end you can retrace it.
- For kingdom questions, learn one distinguishing cell feature per kingdom rather than lists of examples.
- For arthropods, learn leg number and body sections as a table. Every arthropod question turns on those two facts.
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Characteristics and Classification of Living Organisms FAQs
What are the seven characteristics of living organisms?
Movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. Cambridge expects a definition of each: for example sensitivity is the ability to detect and respond to changes in the internal or external environment, and excretion is the removal of the toxic waste products of metabolism.
How do I write a binomial name correctly?
Write the genus first with a capital letter, then the species with a small letter. Italicise the whole name in typed work or underline it in handwriting. For example, Panthera leo for a lion. Marks are given for the format as well as the name.
Why are viruses not placed in any kingdom?
Viruses are not made of cells. They have no cytoplasm, no cell membrane of their own and no ability to respire, grow or reproduce without invading a host cell. Because the five kingdom system classifies cellular organisms, viruses sit outside it.
What is the difference between a genus and a species?
A genus is a group of closely related species that share many features. A species is a single group within that genus whose members can reproduce to produce fertile offspring. In Homo sapiens, Homo is the genus and sapiens is the species.
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Written to the published Cambridge IGCSE Biology (0610) syllabus. Check your school entry code and syllabus year, because Core and Extended candidates are assessed on different content. Last reviewed 2026-08-12.