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Using keysScientists use keys to identify unknown plants or animals. A key is a series of questions, each with two possible answers. The answers lead you to the next question or will identify the unknown creature. It’s all very clever, as you’ll find out when you give it a try …

My name is:

____________ ____________ ____________ ____________ ____________

1 If the person is a boy, go to number 2 If the person is a girl, go to number 4

2 If he is wearing glasses, his name is Thabo If he is not wearing glasses, go to number 3

3 If he is wearing a cap, his name is Tozi If he is not wearing a cap, his name is Jannie

4 If she is wearing earrings, her name is Angela If she is not wearing earrings, her name is Jane

Let’s find out their names by using a dichotomous key.

You have to choose one of two answers each time. That’s why it’s

called a dichotomous key.

Name:

Classifying organisms: pg1 of 6

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How good are you?

1. ____________________ 2. ____________________ 3. ____________________

4. ____________________ 5. ____________________ 6. ____________________

1 If its hind legs are pointed and have hair, it is a Diving Beetle If all its legs end in 2 claws, go to 2

2 If its wing cases are very small, it is a Rove Beetle If its wing cases are large, go to 3

3 If it has large jaws, it is a Stag Beetle If its jaws are small or not shown in the drawing, go to 4

4 If its antennae have brush-like tufts of hair at the tip, it is a Cockchafer Beetle If its antennae are not like the above, go to 5

5 If its antennae are longer than its body, it is a Long-horned Beetle If its antennae are shorter than its body, it is a Weevil Beetle

1 32 4 5 6

These are the parts you must

know to be able to use the key

head

jaws

claw

wing caseleg

antenna

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Sorting living things out

Because there are so many varied (different) plants and animals, scientists need to keep dividing them into smaller groups to identify them. They look for differences and similarities to put the plants and animals into groups.

ANIMAL GROUPS

All the animals in the world can be put into one of two groups:1) Vertebrates or2) Invertebrates

Vertebrates are animals with a backbone

FISH• Breathe with gills• Lay eggs in water• Have fins and scales• Body temperature changes

AMPHIBIANS• Born with gills then develop lungs• Lay eggs in water or damp places• Damp, scaleless skin• Body temperature changes

REPTILES• Breathe with lungs• Lay eggs on land• Dry, scaly skin• Body temperature changes

BIRDS• Breathe with lungs• Lay eggs with hard shells• Feathers• Steady body temperature

MAMMALS• Breathe with lungs• Babies born live• Body hair or fur• Steady body temperature• Feed babies milk

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YES

YES

YES

MILLIPEDE

HAS IT GOT HARD WING CASES? HAS IT GOT 8 LEGS?

HAS IT GOT MORE THAN 20 LEGS?

SPIDER

NO

NO

NO

WOODLOUSE

Use this key to identify which group each of these animals is in:

a. b. c. d. e.

1 Does it have fins? YES ……. It’s a FISH NO ……. Go to 2

2 Does it have feathers? YES ……. It’s a BIRD NO ……. Go to 3

3 Does it have fur or hair? YES ……. It’s a MAMMAL NO ……. Go to 4

4 Does it have dry, scaly skin? YES …… it’s a REPTILE NO ……. It’s an AMPHIBIAN

a _____________________ b _____________________

c _____________________ d _____________________

e _____________________

The key can also be shown as a branched pattern. Just follow the line. Try this one.

HAS IT GOT 6 LEGS?

ab

cd

e

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Invertebrates are animals with no backbone

Invertebrates are also divided into groups. Each group shares similar characteristics. Here are just three of the many groups:

INSECTS

ARACHNIDS

MOLLUSCS

NO

WOODLOUSE

crab

six legs

eight legs

three body parts

two body parts

slimy foot

some have a shell

worm

centipede

butterfly

spider wasp

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Use the numbered key to classify the invertebrates in the pictures below. Write the answers next to the appropriate letter.

Clue 1: Has an external skeleton Go to clue 2 Has no external skeleton Go to clue 5

Clue 2: Body divided into segments Go to clue 3 Body not divided into segments Go to clue 5

Clue 3: Body divided into 3 parts Insect Body divided into 2 parts Go to clue 4

Clue 4: Has 4 pairs of jointed legs Spider Has 5 or more pairs of jointed legs Crustacean

Clue 5: Soft body covered with a chalky shell Mollusc Soft body divided into segments Worm

A _________________ B __________________ C ___________________

D _________________ E __________________ F ____________________

G_________________ H__________________

A

D

EF

G

H

BC