-
What are the two Phyla included in this group?
Cnidaria and Ctenophora
-
What are the two distinguishing features of this group?
Radial or Biradial symmetry and diploblastic development.
-
Explain radial and biradial symmetry.
Radial - body shape where ANY slice through the centre of the organism would divide the animal into equal halves. Biradial - at least one set of structures is paired, resulting in only two planes of symmetry.
-
Explain diploblastic development.
This is when an organism develops from two embryonic tissue layers, separated by a non-cellular layer. (Ectoderm, mesoglea and endoderm) This is achieved through gastrulation of the blastula into a gastrula.
-
List two evolutionary facts about Cnidaria.
They diverged from sponges c. 700 mya. They are diverse; with over 10000 living species.
-
List four facts about the ecology of Cnidaria.
- 1. Mostly marine: most prefer shallow tropical seas, a few live in fresh water.
- 2. All are carnivorous.
- 3. May be solitary or colonial.
- 4.Can be sessile, floating, or slow moving. Can alternate in different stages of the life cycle.
-
Describe the basic body shape of a Cnidaria.
Main part of the body is a body stalk which is hollow, containing a gastrovascular cavity. This has a single opening which serves as both a mouth and an anus. The mouth/anus is surrounded by a hypostome attached to which is a whorl of tentacles.
-
Name the three body layers of a Cnidaria.
- 1. Epidermis
- 2. Mesoglea
- 3. Gastrodermis
-
Describe the function of the epidermis in Cnidaria.
It is the outer layer contacting the environment, consisting of tightly packed cells resting on a basal membrane. It tightly regulates what passes through the body wall.
-
Name and describe the function of the six cell types found in the epidermis of a Cnidaria.
- 1. Epitheliomuscular cells - serve as a protective layer and muscle contraction (cell base contains contractile myofibrils)
- 2. Nerve cells. - Form a nerve net which conducts in all directions.
- 3. Sensory cells - balance, touch, light, chemosensory ("taste/smell")
- 4. Gland cells - Secrete glue for attachment and sometimes release gas bubbles for floating.
- 5. Cnidocytes - Stinging cells
- 6. Interstitial cells - undifferentiated cells which form any of the above (except 1 that reproduce themselves), and gametes.
-
Describe the structure and function of a Cnidocyte.
- Stinging cells used for feeding and defence located on the tentacles of a Cnidaria.
- Each has a stinging capsule (nematocyst) containing a coiled stinging thread that
- everts when the "trigger" is touched and injects venom into the prey/preadetor.
-
List the four cell types found in the Gastrodermis of a Cnidaria and describe their basic function.
- 1. Nutritive cells - Muscular cells that may have cilia (create water flow)
- 2. Gland cells - Secrete enzymes for digestion and mucous for lubrication
- 3. Nerve cells - Sensory input and motor output (sometimes found)
- 4. Interstitial cells - Can form the above cell types
-
Describe the structure and function of the mesoglea in Cnidaria.
- A non-cellular, gelatinous layer between the epidermis and gastrodermis that provides skeletal support and buoyancy in medusa forms.
- In some Cnidaria, epidermal and endodermal cells migrate into the mesoglea.
-
Name and describe the two body forms possible for a Cnidaria.
- Polyp - Generally the sessile form. Upright, with tentacles and mouth/anus on the superficial surface.
- Medusa - Inverted polyp, mobile form: swims by contracting the "bell". Has a think mesoglea for buoyancy)
-
Name the four classes of Cnidaria.
Hydrozoa (The Hydras), Seyphozoa (The Jellyfish), Cubozoa (The Box Jellyfish and Sea Wasps) and Anthrozoa (The Corals and Anemones)
-
List three characteristics of the class Hydrozoa.
- 1. Mostly marine.
- 2. Mostly colonial
- 3. Life cycle usually alternates between a polyp (The most conspicuous stage, usually reproduces asexually by budding) and a medusa form (reproduces sexually)
-
List three characteristics of the class Seyphozoa.
- 1. All marine with medusa form as the main stage in the life cycle.
- 2. Most coastal species have brief sessile polyp stage.
- 3. Open ocean species generally lack the polyp stage, instead they form part of the plankton.
-
List three characteristics of the Cubozoa class.
- 1. Box-shaped medusa stage
- 2. Complex eyes around medusa fringe
- 3. Very deadly species eg. Sea Wasp and Portuguese Man O' War.
-
List two characteristics of the Anthrozoa class.
- 1. Occur only as polyps (medusa stage absent)
- 2. May be solitary (anemones & some corals) or colonial (some corals)
-
Are the phyla Ctenophora shallow or deep water organisms?
Deep water
-
Are the Ctenophora mostly free swimming or sessile?
Free swimming.
-
List two facts about the evolution of Ctenophora.
- 1. Low diversity (about 100 spp)
- 2. Most basal known lineage of animals. (May be older than Porifera)
-
List three things that Ctenophora have in common with Cnidaria.
- 1. Tissue level of organisation
- 2. Diploblastic
- 3. Biradial symmetry
-
Do Ctenophora have a combined mouth/anus or two separate openings?
Separate mouth and anus.
-
How do the Ctenophora swim?
Using comb rows consisting of comb plates that have beating cilia to cause forward or reverse movement.
-
How do Ctenophora catch prey?
Using colloblasts on their tentacles that secrete sticky adhesive granules that trap prey.
|
|