Nine Animal Phyla

Question 1

Phylum: Cnidarians

Answer 1

Hydra, Jellyfish, Sea Anemone

• radial symmetry
• body plan: polyp (vase shapes, mostly sessile) or medusa (upside down bowl shaped, mostly motile)
• ectoderm and endoderm connected by mesoglea
• has a gastrovascular cavity where extra cellular digestion occurs
• carries out intracellular digestion inside body cells in lysosomes
• no transport system b/c every cell is in direct contact with environment
• has stinging cells, called cnidocytes, containing stingers, called nematocysts

Question 2

Phylum: Platyhelminthes

Answer 2

Flatworms, Tapeworms

• simplest animals with bilateral symmetry
• three cell layers: ectoderm, endoderm, mesoderm
• digestive cavity with one opening for both ingestion and egestion
• no circulatory, digestive, or respiratory systems; exchanges nutrition and wastes through diffusion with environment

Question 3

Phylum: Nematodes

Answer 3

Roundworms

• unsegmented worms with bilateral symmetry, but little sensory apparatus
• only 950 cells, so are commonly used for scientific studies
• some are parasitic

Question 4

Phylum: Annelids

Answer 4

Segmented Worms (earthworms, leeches)

• bilateral symmetry with little sensory apparatus
• digestive tract consists of crop, gizzard, and intestine
• excretory organs are nephridia; for excretion of urea
• closed circulatory system; heart consists of 5 pairs of aortic arches

Question 5

Phylum: Mollusks

Answer 5

Squids, Octopuses, Slugs, Clams, and Snails

• soft body protected by hard calcium containing shell
• open circulatory system with blood filled spaces called hemocoels or sinuses
• three distinct body zones: head-foot, visceral mass, and mantle (secretes shell)
• radula: a moveable, tooth bearing structure; acts like a tongue
• most have gills and nephridia

Question 6

Phylum: Arthropods

Answer 6

Insect (Grasshopper), Crustacea (Shrimp, Crab), and Arachnid (Spider)

• jointed appendages
• segmented into head, throat, abdomen
• more sensory apparatus than annelids, giving them more speed and freedom of movement
• exoskeleton made of chitin
• open circulatory system with tubular heart and hemocoels
• excretory organ is malpighian tubes, waste is uric acid
• air ducts called trachea bring air

Question 7

Phylum: Echinoderms

Answer 7

Sea Stars (Star Fish) and Sea Urchins

• most are sessile or slow moving
• bilateral symmetry as an embryo but revert to radial symmetry as adult
• locomotive structures: tube feet
• water vascular systems
• sexual reproduction; external fertilization
• endoskeleton consisting of calcium plates

Question 8

Phylum: Porifera

Answer 8

Sponges

• sessile
• filters nutrients from water drawn into a central cavity
• two cell layers: ectoderm and endoderm connected by mesoglea
• reproduces asexually by fragmentation and also reproduce sexually; are hermaphrodites