Zoology: Animal Structure, Physiology and Diversity
Core concepts
Know the major animal phyla and their key features: Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata, Chordata. Understand body symmetry, coelom types, segmentation, and developmental patterns. Know vertebrate classes and their adaptations: fish, amphibians, reptiles, birds, mammals. Know organ systems comparatively: digestive, circulatory (open vs closed), respiratory (gills, lungs, tracheae), excretory (nephridia, Malpighian tubules, kidneys), and nervous systems.
Traps
Arthropods have an open circulatory system; annelids and chordates have closed systems. Echinoderms are deuterostomes despite radial symmetry as adults. Amphibians need water for reproduction; reptiles have amniotic eggs. Not all animals with radial symmetry are simple. Do not confuse a coelom (true body cavity) with a pseudocoelom. Insects use tracheae, not lungs.
Worked example / rule of thumb
Rule of thumb: "symmetry, coelom, segmentation, and development define the phylum." Worked example: an animal with bilateral symmetry, a true coelom, segmentation, and a closed circulatory system fits Annelida. If a question describes jointed appendages and an exoskeleton, answer Arthropoda, with open circulation and Malpighian tubules for excretion.