IGCSE Biology: Characteristics and Classification of Living Organisms — Practice Questions

These are original questions written for Marlbridge, in the style and at the standard of the examination. They are not reproduced past-paper questions — examination boards hold copyright in their own papers. Use these alongside the official past papers available free from your board.

Related: Characteristics and Classification revision notes

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Section A

1. Define growth and excretion as characteristics of living organisms. [4]

2. Explain the difference between excretion and egestion, giving an example of each. [4]

3. Define a species. [2]

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Section B

4. The binomial name for the domestic cat is Felis catus.

(a) State which part is the genus and which the species. [1]

(b) State two rules for writing a binomial name. [2]

(c) Explain one advantage of the binomial system. [2]

5. (Supplement) Kingdom features.

(a) State the cell wall material and type of nutrition for plants and for fungi. [4]

(b) State the single feature that distinguishes prokaryotes from protoctists. [1]

6. Four arthropods are examined.

(a) State the three features common to all arthropods. [3]

(b) An organism has eight legs, two body parts and no antennae. Identify its group. [1]

(c) An organism has six legs, three body parts and one pair of antennae. Identify its group. [1]

7. A student constructs a dichotomous key for five leaves.

(a) Explain what is meant by a dichotomous key. [2]

(b) Give two features that would make an unreliable basis for a key, with reasons. [2]

8. A vertebrate has dry, scaly skin, lays eggs with a soft leathery shell on land, and has a body temperature that varies with its surroundings.

(a) Identify the vertebrate group. [1]

(b) Give one feature that would distinguish a bird from this group, and state the corresponding feature in the bird. [2]

9. (Supplement) A flowering plant has flower parts arranged in threes and leaves with parallel veins.

(a) State whether it is a monocotyledon or a dicotyledon, using both pieces of evidence given. [2]

(b) State the number of cotyledons its seed would contain. [1]

(c) A different organism has many pairs of legs, one or two pairs per body segment, and a body made of many segments. Identify its arthropod group. [1]

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Answers

1. Growth — a permanent increase in size and dry mass [1] [1]. Excretion — the removal of the waste products of metabolism and substances in excess of requirements [1] [1]. “Permanent”, “dry mass”, “of metabolism” and “substances in excess of requirements” each carry marks.

2. Excretion removes waste made by the organism’s own chemical reactions [1], e.g. carbon dioxide and urea [1]; egestion removes undigested food that was never absorbed into the body [1], e.g. fibre passed out as faeces [1].

3. A group of organisms with similar characteristics [1] that can interbreed to produce fertile offspring [1]. “Fertile” is essential — a mule proves why.

4. (a) Felis is the genus, catus the species [1].

(b) Genus has a capital letter, species is lower case [1]; both are italicised or underlined [1].

(c) It is a universal system used worldwide [1], avoiding the confusion caused by common names differing between languages and regions [1].

5. (a) Plants: cellulose [1] wall, photosynthesis [1]. Fungi: chitin [1] wall, saprotrophic nutrition [1].

(b) Prokaryotes have no nucleus; protoctists have one [1].

6. (a) A hard exoskeleton [1]; jointed legs [1]; a segmented body [1].

(b) Arachnid [1].

(c) Insect [1].

7. (a) A series of paired, contrasting statements [1]; at each step one is chosen, leading either to the next pair or to an identification [1].

(b) Any two with reasons: colour — it changes with age and season [1]; size — it varies between individuals and is relative rather than absolute [1]. (Also acceptable: behaviour, which is not always observable, or a feature affected by environmental conditions such as light exposure.)

8. (a) Reptile [1]. (b) Any one, with the reptile’s own feature for contrast: birds have feathers, not scales [1] [1]; or birds lay eggs with a hard shell, not a soft leathery one; or birds maintain a constant body temperature, rather than one that varies with the surroundings.

9. (a) Monocotyledon [1]; flower parts in threes and parallel leaf veins are both diagnostic monocotyledon features (dicotyledons have flower parts in fours or fives and branching, net-like veins) [1]. (b) One cotyledon [1]. (c) Myriapod [1].

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Where marks are usually lost

• Defining growth without “permanent” or “dry mass”.
• Calling egestion excretion.
• Omitting “fertile” from the species definition.
• Giving cellulose as the fungal cell wall material.
• Building a key on features that vary with age, season or individual.
• Confusing reptile and bird eggs — reptile shells are soft and leathery, bird shells are hard; getting this backwards is a very common slip.
• Counting flower parts or leaf-vein pattern alone without linking both pieces of evidence to the monocotyledon/dicotyledon conclusion the question asked for.
• Mixing up crustaceans and myriapods — both have “many” legs, but crustaceans are diagnosed by two pairs of antennae (body parts vary, and in some the head and thorax are fused into a cephalothorax), while myriapods have many segments and only one pair of antennae.

Questions 8 and 9 draw on the vertebrate and plant classification tables in the Characteristics and Classification revision notes — material the earlier questions on this page don’t reach, since questions 1-5 and 7 focus on MRS GREN, the five kingdoms and dichotomous keys, and question 6 already covers arthropod classification.