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38 Cards in this Set

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Cnidaria and Ctenophora
Cnidaria and Ctenophora ‘Jellyfish’, Hydra and anenomes, corals and comb jellies
• Evolutionary Advances beyond Porifera: tissues, symmetry
• Defining Characteristics
-Polyp and medusa anatomies
-Feeding: cnida and nematocysts; digestion, symbiosis in corals
-Reproduction: sexual and asexual
-Circulation and gas exchange
Diploblastic embryos
• Diploblastic embryos- radial symmetry, have nerve and muscle cells
1. Ctenophora are comb jellies
2. embroyonic – radial cleavage, zygote make parallel division
3. gastrulation- bastula gastrulation
2 Primary Tissue Layers
• Ectoderm forms epidermis
• Endoderm forms gastrodermis
• Many have jelly-like, supportive layer in between: mesencyme or mesoglea
Complex Life cycles (Polyp and medusa stages)
• One opening gut
• Blind gut (no anus)
• Cnidocytes (cells with stinging or trapping organelles like nematocysts)
• Medusa sexual stage, larvae on substratepolyps  undergo asexual reproduction - 1) leave bits of themselves around.. so more polyps -- produce medusa through segmentation, grow them and pop them off.. -free swimming medusa (complete)
• Can capture food while they’re still immature ..
Phylum Ctenophora has
• One way gut (anal canal) -
• ‘comb plates’ with cilia for swimming locomotion, cilia in groups in a coordinated fashion
• Colloblast cells that produce glue to catch prey
• No polyp stage, never colonial, no nematocysts
• Has bioluminescence, startle predator (glows, green jelly)
Hydrozoans and anthozoans spend most time in the polyp form
• The polyp- solitary or colonial
• Mostly sessile
• Mouth surrounded by tentacles
• Radially symmetrical, sometimes branching
• Tissues= outer epidermis and inner gastrodermis
• Jelly-like mesoglea between epidermis and gastrodermis
Gastrodermic lines the gut (gastrovascular cavity)
• Functions: digestion and circulation of digested materials
The Medusa
• Solitary, free swimming (macroplankton)
• Mesogleal layer (mesenchme) generally thickened- jelly like
• Radial canals extend the gastrovascular cavity through the body.
• Ring canal around the edge of the ‘umbrella’-
• Jelly like skeleton thickens, help animal keep its shape and contract again
Macro-plankton
big thing that can’t swim well
Usually Carnivores
• Cnidocyte cells expel singers, lassoes or adhesives
• ‘Nematocysts’ are cnida that sting and capture prey (poisonous)
- Explosion is striggered by cnidocil hair, prey chemicals (2 meters/sec)
- prey capture, nematcysis, part of cell organelle, generated by noomatysis hair that sticks up… interacts wit lil lid hair.. will shoot out and go right to prey with a lot of prey. Poisions and paraplyze prey (corals produce muscus , trap small particles of prey… and digest whatever prey stuck on sticky substance, mucus net suspension trap)
Corals (other Cnidara) may feed in two other ways
• Particles trapped in mucus are swept into the polyp mouth by cilia (muscus net suspension feeding)
• Corals can get nutrition from symbiotic algae
• Symmetrical- divide in different planes
• algae get protected by corals
• coral doesn’t usually need algae
• environmental stressors can cause coral to get rid of algae
• coral bleaching= symbiosis between coral and algae breaks down
Why is alternative generations important?
• Dispersal (medusa stage)
• Ability to exploit different ecological niches (polyp thrive in hidden environment)
• Advantages of both asexuality and sexuality
• Asexuality:
-propagation of known successful forms
-no ‘cost of sex’ (all of own genes passed down, less loss of gametes)
• Sexuality
-variability of offspring, new genetic combinations
Coloniality occurs when identical or nearly identical organisms grow together
• Common in species during sexual stages, when offspring do not separate completely from parents
• Continuum between separate individuals, interdependent related individuals (like social insects), and colonial species.
• Colonies of polypoid Cnidaria often share gastrovascular cavities
Advantages of Coloniality
• Food sharing
• Mutual defense
• Large size- ability to subdue larger prey and compete against other species, building larger structures (as in coral reefs)
• Specialization- not all individuals have to perform all tasks ex. Man-O-War
Man-O-War Specialized Zooids
• Gastrozooids (gastro = stomach), branched tentacles (up to 13 m!) with cnidae and mouth
• Dactylozooids-defense and prey capture, form long and unbranched tentacles with cnidae, but no mouth
• Gonozooids (gono = seed)- reproductive, produce the medusoid stage: No mouth or tentacles
• Pneumatophore- (pneumato – air phore = to bera) gas-filled zooid that acts as a float
How does a lack of a circulatory system constrain Cnidaria?
• All food and gas exchange is local and must move from cell to cell
• Cells reach farther from the surface= less nutrition, less ability to exchange gases and expel wastes
• Cube-shaped animal with length of any side x
- surface area – 6x (squared) (surface area increases as the square of the linear dimension
-volume = x (cubed) (volume increases as the cute of a linear dimension
• Volume increases faster than surface area
Passive diffusion of gases works best at thickness of only 1 mm
• Thin tissues (many cnidarians; those with thick mesoglea have few cells in the mesoglea)
• Small
• Long and thin (thread like)
• Increase surface area by folding or canals
• Flat shape
• Adhesives (locomotion…)-
Hydrotheca
Hydrotheca- epidermis
Pigment
Pigment- light sensory cells
Genetic diversity importance?
Genetic diversity important because environment might change so asexual and sexual (the one that floats around will be more likely change.
1. What is a cnida, and what is its function?
• Intracellular stinging organelle of cnidarians
• Cnidae are produced by specialized cells, cnidocytes and has capsule containing a long coiled thread-like tube
-tread bears barbs or spines
• After being triggered by a mechanoreceptor, (bristle hair), cnidar discharges explosively as a result of hydrostatic ressure
• Cnidae can entangle prey and inject them with toxins.
• Double-walled capsule contain toxins called “nematocysts”
2. Distinguish between polyp and medusa forms of a cnidarian
• Polyp- tube shaped and (usually) sessile form
-anchored to a substrate
-ex sea anemones (solitary) and corals (colonial)
• Medusa- bell or umbrella shaped organism
-free living
-Oral end on the concave side of the animal
-ex, jellyfish, many cnidarians alternate between a polyp and medusa during life cycle
3. Describe the life cycle of a scyphozoan cnidarian
• Most scyphozoans have an “alternation of generations” between asexually reproducing polyp stage and a more sexually reproducing medusa stage
• Scyphistoma- asexual polyp is a tiny organism
-reproduces asexually
• STrobilation- medusa forms are produced (asexually(, scyphistomas now known as strobila undergoes repeated transverse fissioning events
• Ephrae- immature medusae (singular: ephyra)
-they break loose and deelop into adult medusae (which we call jellyfish)
-mature medusa reproduces seuxlaly
• Fertilization- open ocean or in the female’s gastrovascular cavity, if followed by a planula larval stage ..
4. Why might coloniality be advantageous over living as solitary individuals in the Cnidaria?
• -Coloniality produces functional units that are larger in size
-improves feeding efficiency
-allow larger prey to be captured
-reduce the risk of predation by other animals
-ability to monopolize space may also be enhanced
-allows specialization among unit within the colony, ex some polyps can specialize on feeding, defense, reproduction, and increase the overall efficiency of each task.
5. Explain the concept of mutualism and give one or more examples from the Cnidaria
• Mutualistic- relationship between two (or more) kinds of organisms
-both partners gain fitness benefit from the association
-ex anemone fish and sea anemone: fish gains protection and food leftovers,
-sea anemone enjoy improved ventilation and increased numbers of prey (lured by ten anemone fish)
-corals and their symbiotic algae (zooxanthellae.)
How does a lack of a circulatory system constrain Cnidaria?
• All food and gas exchange is local and must move from cell to cell
• Cells reach farther from the surface= less nutrition, less ability to exchange gases and expel wastes
• Cube-shaped animal with length of any side x
- surface area – 6x (squared) (surface area increases as the square of the linear dimension
-volume = x (cubed) (volume increases as the cute of a linear dimension
• Volume increases faster than surface area
Passive diffusion of gases works best at thickness of only 1 mm
• Thin tissues (many cnidarians; those with thick mesoglea have few cells in the mesoglea)
• Small
• Long and thin (thread like)
• Increase surface area by folding or canals
• Flat shape
• Adhesives (locomotion…)-
Tentacles in back
Tentacles in the back use to capture prey
Tissues- epidermis---- mouth interior gastodermine (underlining) food digestion take places… through chemical breakdown in interior of gut, cell pick up smaller particles (inner digestion) gastrovascular cavity run thoroughly,
Hydrotheca
Hydrotheca- epidermis
Pigment
Pigment- light sensory cells
Larvae swim.. metamorposis with planlula
Laravae swim around attach to metamorphosis .. planlula find a good site to attach with food, it attaches to substrate through phrasal disk, attack tentacles, forms a mouth. Cytosoain, fully develop, tentacles, mouth in middle, one way digestive part… move around.. leave lil bits of food on substrate (protosis), has all the tissues in it, differentiate … become fully grown polyp stage. .. will mature. Medusee will be around
Genetic diversity importance?
Genetic diversity important because environment might change so asexual and sexual (the one that floats around will be more likely change.
1. What is a cnida, and what is its function?
• Intracellular stinging organelle of cnidarians
• Cnidae are produced by specialized cells, cnidocytes and has capsule containing a long coiled thread-like tube
-tread bears barbs or spines
• After being triggered by a mechanoreceptor, (bristle hair), cnidar discharges explosively as a result of hydrostatic ressure
• Cnidae can entangle prey and inject them with toxins.
• Double-walled capsule contain toxins called “nematocysts”
2. Distinguish between polyp and medusa forms of a cnidarian
• Polyp- tube shaped and (usually) sessile form
-anchored to a substrate
-ex sea anemones (solitary) and corals (colonial)
• Medusa- bell or umbrella shaped organism
-free living
-Oral end on the concave side of the animal
-ex, jellyfish, many cnidarians alternate between a polyp and medusa during life cycle
3. Describe the life cycle of a scyphozoan cnidarian
• Most scyphozoans have an “alternation of generations” between asexually reproducing polyp stage and a more sexually reproducing medusa stage
• Scyphistoma- asexual polyp is a tiny organism
-reproduces asexually
• STrobilation- medusa forms are produced (asexually(, scyphistomas now known as strobila undergoes repeated transverse fissioning events
• Ephrae- immature medusae (singular: ephyra)
-they break loose and deelop into adult medusae (which we call jellyfish)
-mature medusa reproduces seuxlaly
• Fertilization- open ocean or in the female’s gastrovascular cavity, if followed by a planula larval stage ..
Larval stage
-larval state is ciliated and swims about.. eventually attaches to the substrate and metamorphoses into a scyphistoma
4. Why might coloniality be advantageous over living as solitary individuals in the Cnidaria?
• -Coloniality produces functional units that are larger in size
-improves feeding efficiency
-allow larger prey to be captured
-reduce the risk of predation by other animals
-ability to monopolize space may also be enhanced
-allows specialization among unit within the colony, ex some polyps can specialize on feeding, defense, reproduction, and increase the overall efficiency of each task.
5. Explain the concept of mutualism and give one or more examples from the Cnidaria
• Mutualistic- relationship between two (or more) kinds of organisms
-both partners gain fitness benefit from the association
-ex anemone fish and sea anemone: fish gains protection and food leftovers,
-sea anemone enjoy improved ventilation and increased numbers of prey (lured by ten anemone fish)
-corals and their symbiotic algae (zooxanthellae.)