Classification keys (branching)

Using yes/no questions to identify living things with a branching key

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Try each question. If you're stuck, leave it and come back. The answer key is on the last page.

1
What is a classification key used for? A) To identify a living thing by answering questions about it B) To list every living thing on Earth C) To draw a picture of an animal D) To measure the size of a plant
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True or false? Each question in a branching (binary) key has only two possible answers, usually yes or no. A) True B) False
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Question 1 asks 'Does it have feathers?' If you answer 'yes', what kind of animal is it? A) A bird B) A fish C) A mammal D) An insect
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4
What is a classification key? A) A tool with yes/no questions to help identify living things B) A type of door key C) A key to a science laboratory D) A piece of equipment
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A key asks: 'Does it have legs?' You answer 'no'. Which animal could it lead to next? A) Snake B) Cat C) Bird D) Spider
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Why should each question in a key only have two possible answers? A) So the group splits cleanly in two at every step B) So the key is colourful C) So children can read it D) So animals have only two features
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7
A key has these questions to identify an animal: bird, beetle or worm. Put them in a sensible order. Put these in order: Does it have a backbone?, Does it have feathers?, Does it have wings?
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Put these questions in a sensible order for a key to identify a worm, a fly, a fish and a bird. Put these in order: Does it have a backbone?, Does it have wings?, Does it live in water?
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Order these key questions from most general to most specific to identify trees. Put these in order: Is it a tree?, Does it have broad leaves?, Are the leaves shaped like a hand (lobed)?
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Use this key. Question 1: 'Does it have wings?' Yes - go to Q2. No - it's a snake. Q2: 'Does it have feathers?' Yes - bird. No - insect. Put the steps to identify a SPARROW in order. Put these in order: Q1: Does it have wings? - Yes, Q2: Does it have feathers? - Yes, Answer: bird
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Answer key

Classification keys (branching) · for parents and teachers

1
To identify a living thing by answering questions about it
A classification key uses a series of questions to identify a living thing by separating it from others step by step.
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True
True. Branching (binary) keys ask yes/no questions. Each answer takes you down one branch towards the correct organism.
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A bird
Feathers are unique to birds. So a 'yes' answer to that question identifies the animal as a bird straight away.
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A tool with yes/no questions to help identify living things
A classification key uses yes/no questions about features to help identify a living thing.
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Snake
A snake has no legs, so 'no' would take you towards the snake. Cats, birds and spiders all have legs.
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So the group splits cleanly in two at every step
Binary (yes/no) questions guarantee that each step splits the remaining organisms into two clear groups, with no overlap.
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Does it have a backbone?, Does it have feathers?, Does it have wings?
A good key starts with broad features (backbone) and finishes with specific ones (feathers, wings) to narrow down to one animal.
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Does it have a backbone?, Does it have wings?, Does it live in water?
A good key starts with a big general feature (backbone), then uses more specific features (wings, where it lives) to narrow down.
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Is it a tree?, Does it have broad leaves?, Are the leaves shaped like a hand (lobed)?
Good keys start with broad features (is it a tree?) and end with very specific ones (exact leaf shape) to narrow down to one species.
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Q1: Does it have wings? - Yes, Q2: Does it have feathers? - Yes, Answer: bird
Step by step you eliminate the wrong groups: yes to wings (not a snake), yes to feathers (not an insect), so the answer is bird.