metazoan terms

radial symmetry

many axis of symmetry
Ex: sea anemone

bilateral symmetry

one cut of symmetry separating organism into a left and right half

Usually tied to cephalization and a complete gut
Ex: humans

pentaradial symmetry

5 pt symmetry
Ex: sea star

asymmetrical symmetry

not symmetrical
Ex: sponge

complete gut

• 1 way

• mouth and anus

incomplete gut

• 2 way gut

blind gut

• food and waste exit the same hole

cephalization

• head vs no head

  • involves concentrating neural cells and morphologies in one area to form a central control area

• associated with bilateral symmetry with exceptions in bivalves and echinoderms

  • echinoderms do not have this; lost this when they ‘changed’ symmetry from bilateral to pentaradial

Metazoan development

zygote 2n) → radial/spiral

cleavage → blastula → gastrula

Identify key features on a dissected bivalve (i.e. mussel)

Know where the foot, radula, mantle, shell, gills, etc. are located

Identify key features on a dissected squid

Know where the inc sac, pen, siphon, mantle, tentacle, etc. are located

Identify key features on a dissected earthworm

Know where the crop, nerve cord, clitellum, etc. are located

ectoderm

outside skin layer

endoderm

inner skin layer

mesoderm

middle skin layer

makes up tissue and exoskeleton

blastula

hollow ball of cells

spicules

needle like structure

skeletal structure of sponges

cnidocytes

specialized stinging cells in cnidarians

ecdysis

molting of outer cuticles

ex: crabs and barnacles

segmentation

division of organisms

body in segments

trocophore larvae

swimming ciliated aquatics

found in water

ex: clams, snails

blastopore becomes mouth

blastopore first becomes the mouth

1 way gut

protostomes

paired setae

hair like bristles used for movement

water vascular system

system for locomotion, digestion

ex: sea stars/urchins

blastopore becomes anus

blastopore forming gut cavity forms anus first

complete gut

(chordata and echinoderm)

notochord

rod found on dorsal side of animals

structural support that’s reduced/lost in adults

found on back of chordates

acoelomate

any animal without a body cavity

ex: flatworm

coelomate

have a body cavity called a coelom with a complete lining called peritoneum derived from mesoderm (one of the three primary tissue layers).

pseudocoelomate

a fluid-filled body cavity located between the mesoderm and endoderm layers. This unique body structure allows for the development of more complex organs and systems compared to those without a body cavity.

clitellum

a thick, saddle-like ring found in the epidermis (skin) of the worm, usually with a light-colored pigment

tagmata

a functional body section of an arthropod formed by the fusion of multiple segments. These specialized regions, such as the head, thorax, and abdomen in insects

chelicerae

the first pair of appendages in chelicerates, such as spiders, scorpions, and mites. They are often specialized as fangs or pincers and are located near the mouth. In spiders, they are used to hold prey and inject venom. 

tube feet

small, flexible, tubular appendages found in echinoderms, like sea stars, sea urchins, and sea cucumbers. These appendages are part of the echinoderm's water vascular system, which uses water pressure to help them move, feed, and breathe

water vascular system

locomotion, but it also plays a vital role in feeding, respiration, and waste removal

in echinoderms

pharyngeal slits

openings in the pharynx that develop into gill arches in bony fish and into the jaw and inner ear in terrestrial animals

in chordates

dorsal hollow nerve cord

in chordates, including vertebrates, is a primary center for coordinating responses to sensory stimuli and controlling motor activities, essentially acting as the central nervous system's foundation. It develops into the brain and spinal cord in vertebrates. 

post anal cord

a tail that extends beyond the anus in chordates. It's a defining characteristic of the phylum Chordata. While all chordates have one, at some point in their development, it is not always present in the adult form. In some chordates, like humans and other great apes, the post-anal tail is reduced to a vestigial coccyx or "tail bone"

ctenidia

a comblike structure, especially a respiratory organ or gill in a mollusk, consisting of an axis with a row of projecting filaments.