Cnidarians and Ctenophores Review

Why are coral reefs considered the rainforests of the ocean?

"For their astounding richness of life."

cnidocyte/nematocyst

Compare: Both are involved in the capturing of the prey. Contrast: Cnidocyte is a type of cell that helps predation of cnidarians whereas nematocyst is an organelle consisting of a coiled, thread-like stinger.

What causes coral bleaching?

Climate change, too much sunlight, pollution, extremely low tides

What is the difference between colloblasts and apical organs on ctenophores?

Colloblasts: Found on tentacles of Ctenophores; are sticky/adhesive. Prey becomes stuck to them and tentacles are then retracted. Apical organs: located on the aboral end of Ctenophores. Functions in maintaining body orientation by controlling the comb rows.

List 2 symbiotic relationships formed with cnidarians..

Portuguese man-of-war and man-of-war fish Reef-forming corals and zooxanthellae

Why are ctenophores not jellyfish? (5 differences)

1. Ctenophores do not pulsate but moved smoothly by cilia. 2. No cnidocytes 3. Have colloblasts on tentacles (these cells secrete sticky substance to bind to prey.) 4. Ctenophores have an apical organ- a sensory structure to help them find their orientation in the water. 5. Ctenophores have bioluminescence- the production of light by means of chemical reaction.

polyp/medusa

Compare: both have a body wall, both have aquatic organisms, both have a mouth and are surrounded by tentacles Contrast: Polyp are sessile while medusa are mobile, polyp present a tubular shape with the mouth facing upwards, while medusa presents a bell shape with the mouth facing the water downwards.

C. Scyphoza

Ex. Aurelia

C. Anthozoa

Ex. sea anemones and corals

C. Cubozoa

Ex. sea wasp

4 classes of cnidarians

Hydrozoa, Scyphozoa, Cubozoa, Anthozoa

Phylum Ctenophore

Phylum Name Meaning: "Comb holder" Organisms found there: Comb jellyfish Key Characteristics: -They are free-swimming, marine, solitary, pelagic animals. No polymorphism and no attached stages were found. - The body is transparent, gelatinous, pear-shaped, cylindrical, or flat-ribbon shaped. - Lack nematocysts - have a pair of long, solid, retractile, tentacles. Type of symmetry: biradial How they kill their prey: They are gelatinous like sea jellies but lack their stinging cells. Instead, they use sticky cells called colloblasts to capture prey. These colloblasts are typically found at the ends of the comb jelly tentacles. Special features: Contains 8 rows of comb-like rows of cilia that run along the outside of the animal.

Phylum Cnidaria

Phylum Name Meaning: Named after the cnidarians stinging cells found on their tentacles called cnidocytes. Organisms found there: Corals, hydra, jellyfish, sea anemonies Key Characteristics: Tentacles, Cnidocytes (stinging cells), nematocysts (barbs), gastrovascular activity for digestion, most have radial symmetry, nerve net Type of symmetry: Radial How they kill their prey: They are distinguished from all other animals by having cnidocytes that fire harpoon-like structures and are usually used mainly to capture prey. Special features: Contain specialized cells known as cnidocytes ("stinging cells") containing organelles called nematocysts (stingers).

Cnidarians are tissue animals. What does this mean?

They possess only two tissue layers. The outer layer is the epidermis, whereas the inner layer is called the gastrodermis and lines the digestive cavity.

What is the best cure for jellyfish stings?

Vinegar

Nerve net

a network of nerve cells and fibers that extend throughout the entire body.

C. Hydroza

ex. Portugese man of war, freshwater hydra

2 body forms of cnidarians

polyp and medusa