1.4 Invertebrates

Please Write: Animals with an external skeleton (exoskeleton) or no skeleton at all are called invertebrates.

Animals with an exoskeleton include:

• Insects

• Spiders

• Lobsters

Animals with no skeleton at all include:

• Slugs

• Jellyfish

• Sea Urchins

• Starfish 

Please Write:

Invertebrates are groups into six main groups of phylum. 

Characteristics used to classify invertebrates include:

- Hard shell/cover

- Tentacles

- Spiny skin

Refer to the dichotomous key table below to see how invertebrate organisms can be classified.

• segmented bodies

• paired and jointed legs

• exoskeleton

• Examples: insect, spider, centipede

Anthropods

• spongy body with holes

• found in water, attached to rocks

• Examples: Breadcrumb Sponge, Glass Sponge

Poriferans

• soft, hollow body

• live in water

• tentacles

• Examples: coral, sea jelly

Cnidarians

Nematodes, platyhelminths and annelids

• soft, long body

• can be segmented, flat or round

• Examples: Leech, Flatworm

​Please Write:

soft body

usually have a protective shell

Examples: snail, octopus, oyster

​​Molluscs

rough, spiny skin

arms radiate from centre of body

found in the sea

Examples: Sea urchin, Brittle star

Echinoderms

Please Write

We can also represent this information in a dichotomous key table