BIOL 1202 : Test 4 Notes 1
Chapter 33: Invertebrates
• no back bone
• diploblastic=2 tissue layers (EX: cnidarian and ctenophore)
• triploblastic=3 tissue layers
• ectoderm=germ layer covering the outermost surface of the embryo and gives rise to the
outer covering of the animal
• endoderm=the innermost germ layer which lines the pouch that forms during gastrulation
and gives rise to the lining of the digestive tract
• mesoderm=third tissue layer which fills much of the space between the ectoderm and the
endoderm
Sponges
• basal animals that lack true tissues
• live in fresh and marine water habitats
• organized at the cellular level
• asymmetrical body: no fixed shape
• sponges are suspension feeders
• filter water passing through their bodies
• chanoocytes: line the spongocoel; movement of flagella sets up water flow
• chanocytes trap food and ingest it by phagocytosis; pass it along to amebocytes
• amebocytes: transport nutrients to other cells; secretes spicules
• pores: doughnut shaped cells that span the body wall
•
Water movement through a sponge would follow what path?
• pore--> spongocoel --> osculum
Concept 33.2: Cnidarians are an ancient phylum of eumtazoans
• Cnidarians
• a wide range of sessile and floating forms including jellyfish, corals, and hydras
• simple diploblastic, radial body plan
• body plan is a sac with a central gastrovascular cavity
• single opening serves as both mouth and anus
• mesoglea layer is between epidermis and endodermis (gastrodermis)
• asymmetrical symmetry-
• radial symmetry-a slice through the central axis divides the animal into mirror images, no
distinct left/right front/back sides
• bilateral symmetry-only one imaginary cut divides the animal into mirror images, distinct left
and right sides
• animals with bilateral symmetry are also said to be triploblastic
•
• Cnidarian Body Plan
• polyp form is generally sessile
• medusa form moves freely in water by passive drifting and contractions of the bell
•
• some cnidarians will switch between the two forms and some will stay one form forever
• Defining feature of cnidarians
• cnidocytes
• unique cells that function in defense and the capture of prey
• stimulus causes the cell to evert releasing thread
• some cnidocytes sting, others just entangle prey
• Cnidarian Diversity
• hydrozoa
• alternate between polyp and medusa, when in the polyp stage they are colonial and
group together
• scyphozoans
• basic jellyfish, some alternate but other are only in the medusa form
• cubozoans
• rectangular, have specialized cells on the exterior that are called eye cells, extremely
toxic
• anthozoans
• mostly sessile, no medusa stage at all, many are colonial, they can be very small or very
large, one mouth, two tissue layers
•
Which of the following animals is responsible for more lethal attacks on humans each
year?
• cubozoans
How many planes through the central axis will divide and organism with radial symmetry
into roughly equal halves?
• many
Concept 33.3: lophotrochozoans, a clade identified by molecular data, have the widest
range of animal body forms
• bilateria show cephaliztion and 3 tissue layer
•
• coelomate-an animal with a true coelom
• a true coelom form from tissue derived from the mesoderm
• a mesoderm that surrounds the endoderm and one that is against the other tissue layer as
well, they have an open body cavity
• have a body cavity completely lined by tissue derived from the mesoderm
• pseudocoelomate- animals that have a body cavity that is formed from mesoderm and
endoderm
• open body cavity, mesoderm only touches the other tissue layer
• have a body cavity lined in part by tissue derive from the mesoderm, but also by tissue
derived from the endoderm
• acoelomate-do not have an open body cavity but they still have the 3 tissue layers, this is
the most basic
Document Summary
Water movement through a sponge would follow what path: pore--> spongocoel --> osculum. Which of the following animals is responsible for more lethal attacks on humans each year: cubozoans, many. Sponge bob is a member of which phylum: porifera. Cnidarians use _____ to immobilize or trap prey: cnidocytes, arthropoda. Which of the following does not have a coelom: annelids, arthropods, molluscs, platyhelminths-flatworm, have 3 tissue layers but do not have a true body cavity ever. The animal phylum that contains the greatest number of named species is _____: arthropoda. Chapter 34: vertebrates: vertebrates have a back bone, humans are chordates. Chordate phylogeny: outgroup is echinoderms, they are grouped with chordates because they are deuterostomes. Which of the following statements is not true: all chordates have notochords, all chordates have pharyngeal pouches, all chordates have a post anal tail, all chordates have vertebrates.
