Phylum Cnidaria Systematics

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Questions and Answers

What triggers the release or firing of nematocysts?

Thermal stimulation of the hydrocaulus

Chemical stimulation of the cnidocyte

Tactile stimulation of the cnidocil (correct)

Electrical stimulation of the nerve net

What is the function of the annulus in Hydra?

Produces nematocysts for capturing prey

Provides structural support to the body

Regulates water flow through the hydrocaulus

Gives flexibility and support to the hydrocaulus (correct)

What is the primary function of nematocysts in Cnidarians?

Providing structural support to the body

Regulating water flow through the hydrocaulus

Capturing and digesting prey (correct)

Paralyzing predators

How many monophyletic clades are Cnidarians classified into?

Two Signup and view all the answers

What is the shape of the body of Aurelia aurita?

Bell-shaped Signup and view all the answers

What is the function of the cnidocyte?

Produces nematocysts for capturing prey Signup and view all the answers

What is the symmetry type exhibited by Cnidarians?

Radial symmetry Signup and view all the answers

How many species of Cnidarians are estimated to exist?

Around 10,000 Signup and view all the answers

What is the characteristic of the body wall of Cnidaria?

It consists of two living layers: epidermis and gastrodermis, and a nonliving mesoglea in between. Signup and view all the answers

What is the function of the gastrovascular cavity in Cnidaria?

It serves as a digestive tract where extracellular digestion takes place. Signup and view all the answers

What is the characteristic of cnidocytes in Cnidaria?

They are stinging cells that contain nematocysts. Signup and view all the answers

What is the characteristic of the nematocysts in Cnidaria?

They are stinging organelles that contain barbs or spines at the base of the long, coiled thread. Signup and view all the answers

What is the characteristic of the body plans of Cnidaria?

They have radial symmetry. Signup and view all the answers

What is the characteristic of the life cycle of many Cnidaria?

They are dimorphic, exhibiting both body plans during their life cycle. Signup and view all the answers

What is the habitat of most Cnidaria?

Marine. Signup and view all the answers

What is the example of a polymorphic Cnidaria?

Physalia physalis (Portuguese Man-of-War). Signup and view all the answers

What is the function of cnidocil?

To sense mechanical stimuli and elicit nematocyst discharge Signup and view all the answers

What is the term for the 'stinging cells' that contain a nematocyst?

Cnidocyte Signup and view all the answers

What is the function of zooxanthellae in scleractinian corals?

To produce oxygen and help remove waste Signup and view all the answers

What is the term for the stalk-like structure that contains the mouth and connects to the coelenteron?

Manubrium Signup and view all the answers

What is the term for the free-swimming, flattened, ciliated, and bilaterally symmetrical larval form of cnidarians?

Planula Signup and view all the answers

What is the term for the organelle within a cnidocyte that is used for prey capturing and defense?

Nematocyst Signup and view all the answers

What is the term for a strobilating polyp that produces young adult medusae called ephyra?

Strobili Signup and view all the answers

What is the term for a type of medusa that has a velum?

Craspedote Signup and view all the answers

Study Notes

Phylum Cnidaria

Radial symmetry and diploblastic (develop from two embryonic layers: ectoderm and endoderm)
Two distinct body plans: polyp (sessile) and medusa (motile)
Body wall consists of: epidermis, gastrodermis, and non-living, jelly-like mesoglea
Gastrovascular cavity: open only on one end (mouth), serves as digestive tract for extracellular digestion

Characteristics of Cnidarians

Presence of stinging cells called cnidocytes, often located on tentacles, around mouth, and in gastrodermis
Cnidocytes contain stinging organelles called nematocysts, which may contain barbs or spines
Nematocysts are triggered by tactile stimulation of cnidocil (hair-like projection)
Release of nematocysts can entangle or pierce prey, injecting toxic substances to paralyze

Nerve System and Symmetry

Nerve net system complements radial symmetry
Two monophyletic clades: Medusozoa and Anthozoa

Hydra and Other Cnidarians

Hydra: exhibits dimorphism, has spermaries and ovary, and annulus provides flexibility and support to hydrocaulus
Obelia: colonial hydroid, exhibits dimorphism
Aurelia aurita: bell-shaped, saucer-shaped medusa with eight marginal lobes and stinging tentacles
Hydra budding: a method of reproduction

Corals and Zooxanthellae

Mutualistic relationship: coral provides CO2 and water for photosynthesis, and zooxanthellae produce oxygen and help remove waste
Ecological values of coral reefs:
- Protect coastlines from storms and erosion
- Provide ecosystem for underwater life
- Provide source of livelihood for local communities (fishing, tourism)

Cnidarian Terminology

Nematocyst: organelles within a cnidocyte used for prey capturing and defense
Cnidocil: mechanosensory receptor that elicits nematocyst discharge
Cnidocyte: "stinging cells", an explosive cell containing a nematocyst that delivers a sting
Planula: free-swimming, flattened, ciliated, and bilaterally symmetrical larval form of cnidarians
Strobili: a strobilating polyp that produces young adult medusae called ephyra
Manubrium: a stalk-like structure that contains the mouth and connects to the coelenteron
Hydrotheca: a structure that provides protection to the medusae

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Description

This quiz covers the basics of Phylum Cnidaria, including their characteristics, body plans, and development. Learn about radial symmetry, diploblastic development, and the differences between polyp and medusa body plans.