Animals

Protostomes

Animals characterized by bilaterally symmetrical body plans, spiral cleavage, and the mouth developing from the blastula.

Key adaptations of Protostomes

Cephalization, central nervous system (CNS), coelom, and tube-within-a-tube body plan.

Lophotrochozoa

A major lineage of protostomes that includes Phyla Platyhelminthes, Annelida, and Mollusca.

Platyhelminthes

Flatworms that are mostly parasitic, lack a coelom, and can reproduce sexually or asexually.

Annelida

Segmented worms that possess a closed circulatory system; includes earthworms and leeches.

Mollusca

Soft-bodied animals that are diverse with open or closed circulatory systems; examples include snails and octopuses.

Ecdysozoa

A major lineage of protostomes that includes Nematoda (roundworms) and Arthropoda (insects, crustaceans, and spiders).

Nematoda

Roundworms characterized by a molted cuticle and a pseudocoelom; can be parasitic or free-living.

Arthropoda

Animals with segmented bodies, an exoskeleton, and an open circulatory system; includes insects, crustaceans, and spiders.

Deuterostomes

Animals characterized by radial cleavage, enterocoelom, and the anus developing first from the blastopore.

Key phyla of Deuterostomes

Echinodermata, Hemichordata, and Chordata.

Echinodermata

Phylum including sea stars and sea urchins, featuring radial symmetry and a water vascular system.

Chordata

Phylum characterized by a notochord, dorsal nerve cord, pharyngeal slits, and a post-anal tail.

Cephalochordata

Subphylum of Chordata including lancelets that are burrowers with a notochord.

Urochordata

Subphylum of Chordata including tunicates, which are sessile as adults and have a gelatinous tunic.

Vertebrata

Subphylum of Chordata characterized by vertebrates, an internal skeleton, and a closed circulatory system.

Key features in vertebrate evolution

Innovations such as jaws, bony skeleton, limbs for land, and the amniotic egg.

Acoelomate

Animals lacking a body cavity; for example, flatworms.

Pseudocoelomate

Animals with a partially lined body cavity.

Coelomate

Animals with a fully lined body cavity.

Diploblastic

Animals with two germ layers (ectoderm and endoderm), characteristic of basal phyla.

Triploblastic

Animals with three germ layers (ectoderm, mesoderm, and endoderm), characteristic of bilaterians.

Asymmetry

No symmetry in body structure, as seen in sponges.

Bilateral symmetry

A body plan divided into mirror-image halves, associated with mobility and cephalization.

Radial symmetry

Body parts arranged around a central axis, suitable for sedentary or free-floating lifestyles.

Porifera

Phylum of sponges, characterized by asymmetrical body structure and suspension feeding.

Ctenophora

Phylum known as comb jellies, featuring gelatinous bodies with ciliary 'combs' for movement.

Cnidaria

Phylum that includes hydras, jellyfish, corals, and anemones, known for their radial symmetry and tentacles.

Placozoa

Simplest animal structure that reproduces asexually by division and absorbs nutrients through secreted enzymes.

Acoelomorpha

Small, unsegmented flatworms that lack coelom and have a simple nervous system.