Animal Classification General characteristics: heterotrophs mobile – animals can perform rapid, complex movements multicellular cells that make up animals’ bodies are diploid

animals are classified based on: level of organization – i.e. cells, tissue, organs body plan or body shape symmetry – similarity of form or arrangement around a point, around a line, or on either side of a flat plane asymmetric – no symmetry (ex. sponges)

Radial Symmetry body parts are arranged around a central axis, like spokes around the hub of a wheel (ex. jellyfish)

Bilateral Symmetry body is organized along a longitudinal axis, with the right half an approximate mirror image of the left half

Animals are also classified as protostomes and deuterostomes Early pattern of embryological development is different The first opening that will form the digestive system becomes the mouth in protostomes First opening becomes anus in deuterstomes The pattern of cell division up to the 8 cell stage is also different

animals with bilateral symmetry have an anterior end (head), posterior end (tail), dorsal side (back), and a ventral side (belly)

Phylum Porifera Sponges simplest animals – made up of cells working together (not organized into tissues or organs) asymmetrical – no symmetry, irregular body masses made of 2 layers of cells ectoderm – outer layer of cells endoderm – inner layer of cells  separated by mesoglea – jellylike material sponges have a “skeleton” of flexible protein called spongin some have spicules for support – made of CaCO 3 or silica (glass) – also good protection

Sponges

osculum choanocyte amoebocyte pinacocyte pore spicule mesoglea

Sponges are filter feeders – draw water into pores (ostia) food is trapped by choanocytes (collar cells) wastes are released through pores called oscula amoeboid cells carry food from the collar cells to the ectoderm – amoeboid cells move through the mesoglea

sessile – sponges lived attached to rocks in the ocean most are marine – only a few small fresh water species

Sponge Reproduction: Sexual reproduction – shed eggs and sperm into the water fertilized eggs develop into free swimming larvae that swim to a new rock and attach and grow into a new sponge

Sponge Reproduction: Asexual reproduction fragmentation – sponges can break into pieces and each new piece grows into a new sponge Budding – new sponge grows off of adult some can form gemmules – little capsules of amoebocytes encased in protective coats that can withstand harsh conditions (grow into new sponges when living conditions improve)