Arthropoda and the external skeleton
Jointed limbs and a hard outer covering.
Insects in the sun
Crabs, spiders and insects live even in dry, exposed places.
What do you think helps their bodies survive there?
What this lesson covers
The idea
Arthropods have jointed appendages and segmented bodies with specialised segments; their hard external skeleton protects them, reduces water loss and supports powerful muscles, letting them survive dry, exposed environments.
Insects in the sun
Crabs, spiders and insects live even in dry, exposed places.
What do you think helps their bodies survive there?
- A hard outer covering that reduces water loss
- A soft, thin skin
- Pores in the body
Features of an arthropod
Open each tab.
A strong outer covering
The hard external skeleton does three jobs: it protects, it reduces loss of water and it supports powerful muscles. This lets arthropods live where it is dry and exposed.
Arthropods have jointed appendages and segmented bodies with specialised segments; their hard external skeleton protects them, reduces water loss and supports powerful muscles, letting them survive dry, exposed environments.
Notes
Arthropods have jointed appendages, segmented bodies and a hard external skeleton that protects, reduces water loss and supports powerful muscles.
Check yourself
What does arthropod mean, from arthro and poda?
Which animals are arthropods?
Which is a defining structural feature of arthropods?
What do arthropods gain from the outer covering?
- Pore-bearer. Pore-bearers are the Porifera.
- Spiny skin. Echinodermata means spiny skin.
- Jointed limbs or appendages — correct. Yes!
- Insects, crabs and spiders — correct. Yes!
- Snails, squids and octopuses. These are molluscs.
- Hydra, jellyfish and corals. These are cnidarians.
- A hard internal skeleton of calcium carbonate. This describes echinoderms.
- A hard external skeleton — correct. Yes!
- A single opening. A single opening is found in cnidarians and flatworms.
- Water flowing through pores. This is how sponges get food and oxygen.
- A nerve cord and segments. The book gives protection, reduced water loss and support for muscles as the gains of the outer covering.
- Protection, less water loss and support for powerful muscles — correct. Yes!