ANIMAL KINGDOM: INVERTEBRATES

INVERTEBRATES​

Invertebrate animals are those which do not have a backbone. Even so, some have an external skeleton or exoskeleton, a rigid structure that protects their body and helps them to move.

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INVERTEBRATES​: CHARACTERISTICS

​Invertebrates have some characteristics that are specific:

• Exoskeleton: this is an external structure that protects their body. Depending on the type of invertebrate, this may be

  • Calcium plates: when it is formed by calcium plates. ECHINODERMS (STARFISH).

  • Shell: a rigid shell that protects their body. This is the case of GASTROPODS (snails, limpets) and CEPHALOPODS (squid)

  • Chitin: this consists of an articulated shell and is characteristic of ARTHROPODS (spiders and crabs).

INVERTEBRATES​: CHARACTERISTICS

• Symmetry: invertebrates have different types of symmetry:

  • SIMMETRYC:

    • Bilateral symmetry: as with vertebrate animals, the bodies of some invertebrate animals can be divided into two symmetrical halves. WORMS, MOLLUSCS, ARTHROPODS.

    • Radial symmetry: the body has a central axis which is divided into equal parts by several planes. ECHINODERMS: STARFISH, JELLYFISH

  • WITHOUT SYMEMETRY or ASSYMETRIC: animals with

    no simmetry like SPONGES.​

INVERTEBRATES​: CHARACTERISTICS

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• Tentacles: these are long, flexible arms that may have suckers. OCTOPUS, JELLYFISH

• Antennae: some invertebrates have them on the head and they act as sensors. INSECTS, CRUSTACEANS

• Wings: these are membranes that allow insects to fly. INSECTS

• ​Segmentation: this is when the body is made up of repeating units. WORMS, ARTHROPODS (PRAWNS)

HOMEWORK​

Here you have a picture of a living being. Answer the next questions related to it:

a) Is it an invertebrate? Why?

b) Does it have exoskeleton? If it has, which type of exoskeleton does it have?

c) What type of symmetry does it have?

d) Does it have tentacles, antennae, wings or segmentation? Justify your answer.