• Sponges have eukaryotic cells with cell membranes
• They are a collection of cells organized into an organism with
no tissues or symmetry
• Sponges have cells lining the gastrovascular cavity that
individually take in food by sifting particles from the water, so
they are filter feeders
• Substances are circulated via the water
• Cells release waste by diffusion
• No real response to environment
• Do not move
• Reproduction asexual by budding or gemmules
• Sexual by releasing sperm into the water which fertilizes eggs
inside the sponge
• The simplest phylum of animals
• Eukaryotic cells
• radial symmetry
• They are unique due to stinging cells (nematocysts) that
paralyze prey
• Circulation and excretion by diffusion through body wall
• Respond to environment by some specialized sensory cells,
nerve net,
• Sea anemones can creep and burrow, some use water and
gastrovascular cavity as a hydrostatic skeleton
• Alternate between sexual (external fertilization) and asexual
by budding
• Groups: Hydra, corals, sea anemones, jellyfish
• Ecological role: build reefs vital to coastal ecosystems which
are some of the most productive on earth
• Flatworms have eukaryotic cells
• Flatworms are unique because they have no coelom
(acoelomates) and have a one opening gastrovascular cavity
• 3 germ layers
• Circulation by diffusion, gas exchange (respiration) by diffusion
• Excretion-some have flame cells that remove excess water and
nitrogenous wastes
• Response-ganglia (groups of nerve cells) connected by nerve
cords with eyespots and specialized sensory cells
• Movement by cilia and muscle cells in free-living forms
• Two types of feeding-some are parasitic, feeding on
predigested food by the host or blood
• Free-living forms like the planarian suck food into pharynx and
undigested waste out the same opening
• Reproduction-free-living forms hermaphrodites and can
reproduce sexually or asexually
• Parasitic sexual or asexual by fission
• Ecological role-parasites or free-living scavengers
• Groups: Trematodes-parasitic flukes
• Cestodes-Tapeworms
• Turbellarians- planarians, free-living scavengers