These are the simplest invertebrate animals. AKA sponges.
porifera
Cells that coat the inner cavity, creating a flow of water.
choanocytes
Water, containing waste products, that leaves the central cavity, is released through this hole.
osculum
Cells situated in the external layer of the sponge.
incurrent pores
Cells that form the pores which let the water flow through the porifera.
porocytes
Aquatic animals that have radial symmetry. Their cells are grouped in simple tissues. Some have organs.
cnidarians
Sac-shaped sessile cnidarians are called ________.
polyps
Umbrella-shaped sea cnidarians are called _______.
jellyfish
This type of skeleton allows jellyfish to keep their shape by collecting water inside their cells.
hydrostatic skeleton
Stinging cells with a coiled flagellum that can inject liquid into prey to paralyse them. They are found in the tentacles of jellyfish.
cnidoblasts
The simplest animals that have bilateral symmetry and cephalisation of the nervous system.
flatworms
The concentration of nerve centers at the "head" of the animal's body is known as
filtration
spicules
cephalisation
planariation
Parasites that live in the intestines of many animals (including humans).
tapeworms
