Invertebrates Over 90% of animals are invertebrates!

Characteristics of invertebrates They are multicellular. They are eukaryotes. They are heterotrophs. They don’t have a cell wall. They can move. Most are organised in a way called symmetrical. Sponges and coral are not symmetrical. Most have nervous and muscle tissue. Even sponges can move when they are larvae.

Symmetry This means one can draw a line down the middle of the animal and the two sides will be similar like mirror images. bilateral symmetry radial symmetry

Invertebrate Phyla Porifera Annelida Cnidaria Mollusca Echinodermata Arthropod

Common names for the phyla

Phylum Porifera sponges The sponges we use in The bathtub can be naturally harversted or artificially made. Found in marine environment. The most primitive of the invertebrates. They are mobile only in the larvae stage. They are filter feeders.

Phylum Cnidaria stinging cell animals Found in marine environment Have specialised stinging cells which they use to stun their prey. Use tentacles to sweep in prey.

Phylum Annelida Live on land as well as under water Have muscles Have a long, slender body Segmented body – many body parts duplicated in each segment

Phylum Echinodermata Found in marine environment Needle like spines used for protection Radial symmetry

Phylum Mollusca Soft bodied Most have a protective shell Many have a muscular foot for movement

Phylum Arthropoda Includes incredibly diverse groups such as: insects, crustaceans, spiders, scorpions, and centipedes. bilateral symmetry, segmented bodies each body segment bears a pair of jointed appendages movement controlled by complex muscular system body covered by an exoskeleton

spiders and insects are both part of the phylum Arthropoda What’s the difference between a spider and an insect?

Spiders body divided in 2 segments: cephalothorax, abdomen; 4 pairs of appendages; 4 eyes; no antennea Insects: body divided in 3 segments: head, thorax, abdomen; 3 pairs of appendages; have antennea; some have wings