Animal Phyla Notes

Sponges are the simplest animals.
Asymmetrical.
No tissues.
Acoelomate.
Skeleton made of spicules.
Filter plankton from sea water.
- Water flows in through pores and out through the osculum.
Adults are sessile (don’t move).
Larva can swim until they find a location to live and grow.
Asexual reproduction: Fragmentation.
Sexual reproduction: Sperm swims to egg in sponge; larva swims to new location.
Evolutionary advance: Multicellularity.

Includes jellyfish, corals, and sea anemones.
Radial symmetry.
Diploblastic.
Acoelomate.
Hydrostatic skeleton.
Predators that capture prey with tentacles covered with stinging cells (cnidocytes).
Two-way gut (one opening).
Cnidocytes contain nematocysts.
Medusa are free-floating.
Polyps are sessile.
Asexual reproduction: Budding.
Sexual reproduction: External - all larva are free swimming.
Evolutionary advances:
- Tissues.
- Symmetry (radial).

Flatworms (e.g., tapeworms, planaria).
Bilateral symmetry.
Triploblastic.
Acoelomate.
Two-way gut (one opening called a pharynx located on ventral side in the middle).
Muscles found in mesoderm aid in movement.
Nerves grouped at anterior end lead to forward movement (cephalization).
Asexual reproduction: Fragmentation.
Sexual reproduction: Many are hermaphroditic (common in parasites).
Regeneration in Planaria.
Evolutionary advances:
- Three tissue layers.
- Bilateral symmetry.
- Cephalization.

Roundworms (e.g., Heartworms).
Bilateral symmetry.
Triploblastic.
Pseudocoelomate.
One-way gut (2 openings) allows organisms to eat more and increase activity level.
Pseudocoelom allows for better coordination of muscles.
Usually reproduce sexually.
Evolutionary advances:
- Pseudocoelom.
- One-way feeding.
Elephantiasis is caused by a type of roundworm blocking the lymphatic system, causing limbs to swell.

Includes cephalopods (octopuses), gastropods (snails), and bivalves (clams).
Bilateral symmetry.
Triploblastic.
Coelomate.
One-way gut (2 openings).
Most have a radula which scrapes food from rocks and plants.
Some filter feed.
Gastropods (snails) glide along surfaces.
Cephalopods (octopus) use siphons/suckers & hydrostatic pressure.
Bivalves (clams) can move or can be sessile.
Sexes usually separate.
Aquatic mollusks fertilize externally.
Terrestrial mollusks fertilize internally.
Evolutionary advances:
- True coelom isolates internal organs from body wall movements, which allows increase locomotion and organ complexity.

Segmented worms (earthworms; leeches).
Bilateral symmetry.
Triploblastic.
Coelomate.
Segments.
One-way gut (2 openings).
Some are sanguivorous (blood-sucking parasites).
Characteristic peristaltic (involuntary muscle) movement caused by complex muscle coordination.
Asexual reproduction: Fragmentation.
Sexual reproduction: Some are hermaphroditic while others have separate sexes.
Evolutionary Advances
- Segmentation - repeated body sections that contain complex sets of body structures.

Includes crustaceans, spiders, & insects.
Bilateral symmetry.
Triploblastic.
Coelomate.
Segments.
Jointed, waterproof exoskeleton made of chitin.
Completely differentiated one-way gut (2 openings).
Can be carnivores, herbivores, detritivores, filter feeders and/or parasites.
Joints permit powerful and complex movements.
Adapted to water, land, and air.
External fertilization is prominent.
Some metamorphosize.
Evolutionary advances/unique characteristics:
- Jointed Appendages
- Exoskeleton

Includes sea urchins, sea stars, and sea cucumbers.
Bilateral symmetry as larva; radial symmetry as adults.
Triploblastic.
Coelomate.
One-way gut (2 openings).
Eject stomach from mouth and digest food externally – then suck in food.
Tube feet controlled by internal water pressure system allow them to crawl along surfaces.
Asexual reproduction: Fragmentation.
Sexual reproduction: External fertilization.
Evolutionary Advances/unique characteristic
- Tube feet