Chordates and Animal Body Plans Overview

Notochord

Flexible, rod-like structure; supports the body.

Dorsal Nerve Cord

Hollow cord above the notochord.

Pharyngeal Slits

Openings near the throat used for filter feeding or respiration.

Postanal Tail

Tail extending beyond the anus.

Chordate Symmetry

All chordates show bilateral symmetry, with clear anterior (head), posterior (tail), dorsal (back), and ventral (belly) sides.

Vertebrates

Have a backbone (e.g., mammals, fish, amphibians).

Invertebrate Chordates

Chordates without a backbone, including tunicates and lancelets.

Tunicates

Look like sponges as adults; lose most chordate features.

Lancelets

Fish-like, retain all chordate features throughout life.

Nutrition in Animals

All animals are heterotrophs (ingest food).

Cell Structure in Animals

Eukaryotic and multicellular; lack cell walls; cells held together by collagen.

Reproduction in Animals

Most reproduce sexually and are diploid.

Zygote Development

Zygote develops into a blastula, which undergoes gastrulation.

Hox Genes

Possess Hox genes that control body patterning (head → tail).

Asymmetry

No symmetry (e.g., sponges).

Radial Symmetry

Body arranged around a central axis (e.g., cnidarians).

Bilateral Symmetry

Two-sided symmetry (e.g., worms, insects, vertebrates).

Diploblastic

2 layers (ectoderm & endoderm) - e.g., cnidarians.

Triploblastic

3 layers (ectoderm, endoderm, mesoderm) - most animals.

Coelom

True body cavity from mesoderm.

Coelomates

Animals with a true coelom (e.g., annelids, arthropods).

Pseudocoelom

Cavity from mesoderm + endoderm.

Protostomes

Mouth develops first (e.g., mollusks, arthropods).

Deuterostomes

Anus develops first (e.g., echinoderms, chordates).

Porifera

No true tissues or organs; sessile, filter feeders.

Cnidaria

Radial symmetry, soft-bodied, carnivorous; specialized tissues & stinging cells (cnidocytes).

Platyhelminthes

Bilateral symmetry, unsegmented, flat body; cephalization, one digestive opening.

Nematoda

Cylindrical, unsegmented worms with a complete digestive tract.

Annelida

Segmented bodies, closed circulatory system, complete digestive tract.

Arthropoda

Exoskeleton made of chitin; jointed appendages, segmented bodies.

Echinodermata

Radial symmetry (adults), endoskeleton, water vascular system.