Good Science Victorian Curriculum Year 7

CHAPTER 2: CLASSIFICATION
Keys identify a set of important
characteristics
3 Investigation 2.2
Supermarket
classification key
The most important part of designing a key is deciding which
characteristics it uses to identify organisms.
The characteristics chosen for a key depend on the organisms to
be classified. It makes sense for the first steps of a key to be easily
observable features; for example, whether an organism has a
backbone. When the classification becomes more specific, such as
classifying different species of an animal, the key will need more detail;
for example, whether an insect has spots on its wings.
The largest group of animals on Earth are the arthropods. Arthropoda
means ‘jointed feet’, and all arthropods have legs with joints as well as
an exoskeleton, which is outside their bodies.
Table 2.1 shows the five classes (sub-groups) of arthropod, and the
physical characteristics by which they are grouped. Can you develop
a key that would allow you to identify the class of any arthropod?
Table 2.1 The five classes of arthropod
Class Characteristics Examples
Insects 3 body parts (head, thorax, abdomen)
6 legs (3 pairs)
Fly, mosquito,
dragonfly
0, 1 or 2 pairs of wings
1 pair of antennae
Crustaceans 3 body parts (head, thorax, abdomen)
10 legs (5 pairs)
Crab, lobster,
prawn
No wings
2 pairs of antennae
Arachnids 2 body parts (cephalothorax, abdomen)
8 legs (4 pairs)
Spider, tick,
scorpion
No wings
No antennae
Centipedes Many body segments
Centipede
1 pair of legs on each segment
Flat body cross-section
No wings
1 pair of antennae
Millipedes Many body segments
2 pairs of legs on each segment
Rounded body cross-section
No wings
1 pair of antennae
Millipede
Why do different keys include different characteristics?
KEY SKILL
Identifying and
managing relevant
risks
Go to page 143
CHECKPOINT 2.2
1 Explain the role of a
classification key.
2 Describe some structural
features of humans that might
be used to classify them.
3 Explain the difference between
a branching key and a
dichotomous key.
4 While exploring the Amazon
rainforest, you find a previously
undiscovered species of
arthropod. It’s bright pink, has
10 spiky legs, a head, thorax
and abdomen, and it cannot
fly. What class would you put
it into?
5 Create a branching key that
can be used to classify all
the different shoes worn by
students in your class.
DESIGN AND
TECHNOLOGIES
6 Design a simple key to identify
organisms in a local habitat
of your choice. Use the
SmartArt tool in PowerPoint
or another suitable tool to
present your key.
SUCCESS CRITERIA
I can name at least two
types of classification key.
I can create a simple key
of my own to classify objects
or organisms.
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