Simple Invertebrates. Sponges, jellyfish and coral, flatworms, roundworms, and segmented worms too!. Phylum Platyhelminthes (Flatworms). More complex than sponges and cnidarians. Organisms with long, flat body. Clearly defined head with mouth. Some have senses, a few even have eyespots.
Sponges, jellyfish and coral, flatworms, roundworms, and segmented worms too!
Asexually-regeneration & fission
3 tissue layers
headhas hooks that attach to the host
can grow up to
18 feet long!
Humans can get liver fluke by eating raw or uncooked fish that contains the parasite.
Hookworm eggs are passed in the feces of an infected person.
Hookworm infection is mainly acquired by walking barefoot on contaminated soil.
A medusa is free-swimming.
Most are solitary.
Their opening is on the bottom of their body.
Polyps are like an upside down medusa.
Their opening is on the top of their body.
Coral polyps are tiny and live in huge colonies of thousands.
Corals build their “home” as the colony grows larger and larger.Medusae vs. Polyps
Most jellyfish are harmless to people, although not so to small fish and other marine organims.
One teaspoon of garden soil may contain as many as 10,000 tiny nematodes (roundworms) in it!