Embryology & Cnidarians Assessment

What traits do all cnidarians share?

single opening that is used as a mouth and anus, radial symmetry, and stinging cells (cnidocytes) that contain venomous nematocysts

polyp

sessile, cylindrical form with mouth and tentacles facing upwards, like sea anemones

medusa

free swimming bell shaped form with the mouth and tentacles hanging downwards such as a jellyfish

Describe how the tissue layers of the embryo give rise to the tissue layers in the organism

The ectoderm forms the outer epidermis, while the endoderm forms the inner gastrodermis that lines the digestive cavity. A non-living, jelly-like layer called the mesoglea is found between these two living layers.

Describe the process of the stinging cells firing to capture prey

fire a coiled harpoon-like thread called a nematocyst when a triggering hair, or cnidocil, is touched. injects venom to kill its prey

Describe how digestion and absorption takes place in cnidarians

extracellular digestion takes place as enzymes secreted into the gastrovascular cavity break down food;

second, intracellular digestion completes the process when gastrodermal cells engulf the partially digested fragments and absorb the nutrients

Identify the different stages of a jellyfish (moon jelly)  life cycle

free swimming planula large that becomes a polyp, which then asexually buds off ephyrae. ( disc shaped jellyfish) that mature into the adult free swimming Medusa stage which reproduces asexually 

Identify 3 emergent traits found in Phylum Cnidaria

radial symmetry, stinging cells (cnidocytes) and a nerve net for sensory and motor functions

Depict and describe how coral polyps excrete CaCO3 to form the foundation of reefs

Coral polyps excrete calcium carbonate CaCO3 by taking carbon from seawater and the algae living inside them. They combine this carbon with calcium ions in the water, creating a hard, external skeleton that forms the base of the reef

Understand two examples of mutualistic relationships in Cnidarians with other organisms (anemones w/ fish & coral with zooxanthellae)

the anemone provides the clownfish with protection from predators, while the clownfish defends the anemone from certain fish and can provide nutrients. In the second, the algae provide the coral with essential nutrients and oxygen through photosynthesis, and the coral provides the algae with a protected environment and CO2

Differentiate between one asexual form of reproduction in Cnidarian (budding or strobila) & at least one form of sexual form of reproduction (internal with moon jellies or external with coral)

asexual- budding (ex: hydroids use budding to produce new genetically identical polyps) schphozoans (true jellyfish) use strobilation rapidly buds off a series of immature medusae called ephrae which turn into adult jellyfish

sexual- external fertelization (ex: coral) release egg+sperm into water forming a zygote that develps into a free swimming planula larva

internal fetilization (ex: moon jellys) males release sperm into water

Phylum Cnidaria

jellyfish,coral,sea anemones

Diploblast

Two germ layers

Ectoderm

outer of the two main cell layers which develops into the outer protective layer

epidermis

outermost tissue layer of the body wall, helps form the simple body structure

endoderm

inner germ layer of tissue that lines the gastrovascular cavity and is responsible for digestion 

gastrodermis

is the inner tissue layer that lines the gastrovascular cavity (the digestive sac) and is responsible for digestion and nutrient absorption

gastrovascular cavity

a central digestive and circulatory structure in cnidarians, use this cavity to digest food, distribute nutrients, and facilitate gas exchange throughout their simple bodies.

mesoglea

provides structural support

nerve net

a simple, diffuse nervous system found in organisms

Nematocysts

stinging cells

aboral

end furthest from the mouth

margain

outer rim

lappet

edge of margain

rhopalia

sensory organs

radial canal

a part of the circulatory system which radiates from a central cavity to distribute nutrients and gases

gonads

produces gametes

sessile

fixed in one place

motile

moveable

mutualism for Zooxanthellae

coral provides a home for photosynthesis and a symbiotic relationship where both partners benefit from the zooxanthellae giving 90% of their energy too the coral through photosynthesis, provides sugar and nutrients

mutualism for clown fish

clownfish is protected from predators by the anemones stinging tentacles the clownfish cleans the anemones defends it from certain predators and provides it with food

Calcium Carbonate Exoskeleton (Coralite)

a complex structure built from calcium carbonate, primarily in a crystalline form called aragonite, secreted by the polyps to form this protective external skeleton.

Calcium Carbonate Exoskeleton (Calicoblastic Cells)

Calicoblastic cells are specialized cells in the calicodermis of corals that are responsible for building the calcium carbonate. These cells influencing the nucleation and growth of aragonite crystals, the main component of the coral skeleton

planula

free-swimming, ciliated larval stage of a cnidarian

strobila

the segmented body of a tapeworm or the chained, segmented stage of a jellyfish larva

euphyra

the juvenile, free-swimming larval stage of a jellyfish, resembling a tiny, star-shaped snowflake