Animal Biology: Body Plans, Invertebrate & Vertebrate Phyla

Ectoderm

Outer layer (skin, nervous system)

Mesoderm

Middle layer (muscles, circulatory system)

Endoderm

Inner layer (digestive tract)

Diploblastic

2 layers (ectoderm + endoderm) → Cnidaria, Ctenophora

Triploblastic

3 layers (ectoderm, mesoderm, endoderm) → most other animals

Asymmetry

No symmetry (sponges)

Radial Symmetry

Body parts arranged around central axis (Cnidaria)

Bilateral Symmetry

Mirror-image halves (Platyhelminthes onward)

Acoelomate

No body cavity (Platyhelminthes)

Pseudocoelomate

Cavity not fully lined by mesoderm (Nematoda, Rotifera)

Coelomate (Eucoelomate)

Cavity fully lined by mesoderm (Mollusca, Annelida, Chordata)

Protostome

Blastopore becomes mouth (Mollusca, Annelida, Arthropoda)

Deuterostome

Blastopore becomes anus (Echinodermata, Chordata)

Porifera

Phylum of sponges

Cnidocytes

Stinging cells in Cnidaria

Nematocysts

Organelles within cnidocytes

Planaria

Non-parasitic flatworms in class Turbellaria

Rotifera

Pseudocoelomate, triploblastic with ciliated crown for feeding

Nematoda

Roundworms, pseudocoelomate, triploblastic

Mollusca

Protostomes, eucoelomates with shared features like mantle and radula

Annelida

Segmented worms, coelomate, triploblastic

Arthropoda

Triploblastic, coelomate, protostome with jointed appendages

Echinodermata

Deuterostomes with radial symmetry as adults

Agnatha

Jawless fish (lampreys, hagfish)

Chondrichthyes

Cartilaginous fish (sharks, rays)

Osteichthyes

Bony fish with swim bladder

Amphibia

Frogs, salamanders with moist skin and 3-chambered heart

Reptilia

Amniotic egg, dry skin

Aves

Birds with feathers and endothermic metabolism

Mammalia

Hair, mammary glands, endothermic; includes monotremes, marsupials, placentals

Cloaca

Common opening for excretory and reproductive systems in birds, reptiles, amphibians