Invertebrate Zoology Animals without Backbones

Patterns of the Invertebrate Symmetry- orientation around a central axis Germ Layers- embryonic tissue Deuterosome vs Protostome Body openings and digestion Coelom development

Deuterostomes Indeterminate cleavage blastophore becomes anus/second opening becomes mouth radial cleavage-cells of cleavage are aligned

Protostomes Determinate cleavage in most ( fate fixed early) blastophore develops into a mouth first Spiral cleavage-cells do NOT line up

Symmetry ( a ) radial- can be divided along any plane, through a central axis into roughly equal halves ( b ) bilateral- can be divided down it’s length only one way into similar right and left halves (not shown asymmetry-irregular in shape

Germ Layers 1. Ectoderm- outermost germ layer (forms skin, nerves ) 2. Mesoderm- middle germ layer ( forms muscle, kidney, liver etc.) 3. Endoderm- innermost germ layer ( forms digestive and reproductive tract )

Mesoderm forms as an outpocketing from endoderm ectoderm endoderm

Coelom Coelomate- has a true coelom CAVITY WITHIN A BODY Acoelomate- lacks a true coelom Pseudocoelomate- false body cavity ( no mesodermal connection )

Body Cavity COELOM- true cavity within a body Acoelomate- lacks a true body cavity Pseudocoelomate- has a false body cavity ( cavity develops with no mesodemal connection ) Coelomate- true body cavity developing from out pockets of the mesoderm

SUMMARY GERM LAYERS 1. Ectoderm- outermost germ layer (forms skin, nerves ) 2. Mesoderm- middle germ layer ( forms muscle, kidney, liver etc.) 3. Endoderm- innermost germ layer ( forms digestive and reproductive tract )

BODY SYMMETRY Symmetry- orientation around a central axis ( a ) radial- can be divided along any plane, through a central axis into roughly equal halves ( b ) bilateral- can be divided down it’s length only one way into similar right and left halves (not shown asymmetry-irregular in shape

Invertebrate Phyla

Porifera Parazoa-lacking true tissue Filter feeders- incurrent and excurrent pore ( oscula choanocytes- collar cells that create current amoebocytes- capture food by phagocytosis Spicules- silica or calcium carbonate skeletal structures Spongin- protein in some species for support Hermaphrodites contain both male and female sex organs BEHAVE LIKE A COLONY

Cnidarians Eumetazoan- have true tissues Radial symmetry acoelomate- lack a coelom diploblastic- only two germ layers Alternation of generation polyp- plant like medusa- free swimming ( jelly fish like Digestive traffic-two way, gastrovascular cavity-no separate circulatory/digestive system

Nematocyst- stinging cell

Sea Anemone

Phylum Cnidaria Class Hydrozoa hydra Class Scyphozoa jelly fish Class Anthozoa sea anemone

BUD----- nematocyst

Platyhelminthes Planaria

Nematoda Three germ layers Pseudocoelomate One-way digestive pattern Little need for resp. or digestive system Separate sexes Parasitic and free-living

ectoderm endoderm mesoderm

Rotifera Mostly freshwater Pseudocoelom with several organ systems Crown of cilia around mouth Both sexual and asexual reproduction

S- SYMMETRY assymetry GL-GERM LAYERS none BO-BODY OPENINGS many BC-BODY CAVITIES acoelomate DT-DIGESTIVE TRAFFIC none, filter feeds cells digest CS-CIRCULATORY SYSTEM none, filter water to remove water