Animal Form and Function - porifera, cnidaria, platyhelminthes

Ectoderm

covering the surface of the embryo, gives rise to the skin and in some cases cetnral nervous system

endoderm

innermost layer, lines developing digestive tube, or archenteron, and forms lining of the digestive tract and organs derived from it, such as the liver and lungs of vertebrates.

Mesoderm

develops into the muscles and most other organs between the digestive tube and the outer covering of the animal.

coelom

body cavity - hydrostatic pressure, cushioning, organs can develop independently from body wall

diploblastic

2 germ layers - endoderm and ectoderm (radiata)

triploblastic

3 germ layers - endoderm, ectoderm and mesoderm (bilateria)

acoelomate

no body cavity e.g. platyhelminthes

pseudocoelomate

coelom not completely bordered by mesoderm. cavity is not separated from digestive tube (endoderm) e.g. nematodes, rotifera

coelomate

cavity is entirely surrounded by mesoderm, most of Bilateria

protostomia

blastopore becomes mouth

spiral cleavage

deuterostomia

blastopore becomes anus

radial cleavage

Ostia

where water is drawn into in porifera

osculum

water exists through here in porifera

asconoid, syconoid, leuconoid

the 3 forms of porifera, based on choanocyte location

dimorphic

has 2 types of body plans e.g. polyp and medusa in cnidaria

statocysts

a small organ of balance and orientation in some aquatic invertebrates, consisting of a sensory vesicle or cell containing statoliths

manubrium

mouth tube in medua form of cnidaria

choanocyte

A flagellated collar cell that generates water currents and captures food particles by phagocytosis.

parazoa

A group of animals that lack true tissues and organs (e.g., sponges)

pinacocyte

A flattened cell forming the outer surface (pinacoderm) of the sponge.

spongocoel

The central cavity of a sponge through which water flows before exiting the osculum

Cnidae

Specialised stinging organelles unique to cnidarians (e.g., jellyfish, corals, hydra) used for defence and capturing prey.
They are contained within cnidocyte cells

cnidocyte

A specialised stinging cell found in cnidarians that contains a cnida (usually a nematocyst) used to capture prey or defend the organism.

nematocyst

The most common type of cnida, consisting of a capsule containing a coiled, barbed thread that rapidly everts and injects toxins when triggered.

Cnidocil

A hair-like sensory trigger on a cnidocyte.
When stimulated (mechanically or chemically), it triggers discharge of the nematocyst.

pharynx

sucks in food in a platyhelminthes

diverticulum

keeps food statioanry in a platyhelminthes for extracellular digestion

Direct life cycle

A life cycle where a parasite requires only one host species to complete its development.

Indirect life cycle

A life cycle where a parasite requires one or more intermediate hosts before reaching the final host.

Dual gland adhesive organ

A temporary attachment structure in some flatworms consisting of adhesive glands and releasing glands that allow attachment and detachment from surfaces.

Opisthaptor

A posterior attachment organ in monogenean flatworms used to anchor to the host (usually fish).

Protonephridia

A simple excretory system consisting of flame cells and tubules used for osmoregulation and waste removal.

Scolex

The head region of a tapeworm that contains hooks or suckers used for attachment to the host intestine.

flame cells

flagella of this cell beats and dras innterstitial fluid into tubule to filter solutes

monoecious

individuals that possess both functional male and female reproductive organs

dioecous

species with distinct, separate male and female individuals, each producing only one type of gamete (sperm or eggs)