A free-living, sexually immature form in some animal life cycles that may
differ from the adult in morphology, nutrition, and habitat.
The transformation of a larva into an adult.
An animal that lacks a backbone.
A chordate animal with a backbone. Vertebrates include lampreys,
chondricthyans, ray-finned fishes, lobe-finned fish, amphibans, reptiles (including
birds), and mammals.
An arrangement of body parts such that an organism can be
divided equally by a single cut passing longitudally through it. A bilaterally
symmertrical organism has mirror-image right and left sides.
An arrangement of the body parts of an organism like pieces
of a pie around an imaginary central axis. Any slice passing longitudinally
through a radically symmetrical organism’s central axis divides it into mirror-
A body cavity completely lined with mesoderm.
A body cavity that is in direct contach with the wall of the
The concentration of a nervous system at the anterior (head) end.
11. 2-ended Gut:
12. Sac-like Gut:
Subdivision along the length of an animal body into a series of
repeated parts called segements.
The body of a spinge resembles a trhich-walled sac perforated with
holes. (porifera means “pore-bearer” in Latin.) Water is drawn through the pores
into a centrqal cavity, then flows out through a large opening.
Flatworms, phylum Platyheliminthes (from the Greek
, worm), are the simplest of the bilaterians.
A soft-bodied animal characterized by a muscflar foot, mantle, mantle
cavity, and radula; includes gastropods (snails and slugs), bivalbes (clams,
oysters, and scallops), and cephalopods (squids and octopuses).
An animal characterized by cnidocytes, radical symmetry, a
gastrovascular cavity, and a polyp and medusa. Cnidarians include the hydras,
jellyfishes, sea aneomones, corals, and related animals.
A roundworm, characterized by a pseudocoelom, a cylindrical,
wormlike body form, and a tough cuticle.
A segmented body resembling a series of fused rings is the hallmark of
phylum Annelida (from the Latin
Member of a phylum of slow-moving or sessile marine animals
characterized by a rough or spiny skin, a water vascular system. An endoskeleton,
and radical summetry in adults. Echinoderms including sea stars, sea urchins, and
A flagellated feeding cell found in sponges. Also called a collar cell’
it has a collar-like ring that traps food paticles around the base of flageillum.