Phylum Coelenterata Characteristics

Questions and Answers

What is the main characteristic of hydrozoans?

They are all solitary and never colonial.

They have a simple body structure with no distinct organs.

They are exclusively marine.

They have a complex life cycle involving both asexual and sexual phases. (correct)

What is the function of the perisarc in colonial hydrozoans?

To provide protection to the coenosarc (correct)

To facilitate the exchange of oxygen and carbon dioxide

To regulate the water flow around the colony

To provide nutrition to the zooids

What is the name of the larval stage resulting from the union of sperm and egg in scyphozoans?

Polyp

Scyphistoma

Planula (correct)

Ephyra

What is the function of statocysts in scyphozoans?

To maintain balance and orientation Signup and view all the answers

What is the term for the process by which scyphistomae produce additional scyphistomae in scyphozoans?

Budding Signup and view all the answers

What is the name of the stage that results from the strobilation process in scyphozoans?

Ephyra Signup and view all the answers

What is the name of the structure that contains the statocysts and ocelli in scyphozoans?

Rhopalia Signup and view all the answers

Which of the following is a characteristic of anthozoans?

They are exclusively marine. Signup and view all the answers

What is the shape of the body of cnidarians?

Cylindrical Signup and view all the answers

What is the function of nematocysts in cnidarians?

To capture prey Signup and view all the answers

What is the function of the oral disc in cnidarians?

To capture prey Signup and view all the answers

What is the mode of reproduction in cnidarians?

Both asexual and sexual Signup and view all the answers

What is the feature of the gastrovascular cavity in cnidarians?

It is divided into compartments by septa Signup and view all the answers

What is the term for the life cycle of cnidarians?

Alternation of generations Signup and view all the answers

What is the function of the mouth in cnidarians?

To take in food and expel waste Signup and view all the answers

What is the type of digestion that occurs in cnidarians?

Extracellular digestion Signup and view all the answers

What is the characteristic of Coelenterates' body organization?

Tissue level of organization Signup and view all the answers

What is the function of nematocysts in Coelenterates?

For food collection, defence, and locomotion Signup and view all the answers

What type of symmetry do Coelenterates exhibit?

Radial symmetry Signup and view all the answers

What is the characteristic of the body wall of Coelenterates?

Consists of epidermis, gastrodermis, and mesoglea Signup and view all the answers

What is the type of skeleton found in Coelenterates?

Endo or exoskeleton Signup and view all the answers

What is the mode of digestion in Coelenterates?

Both extracellular and intracellular digestion Signup and view all the answers

What is the characteristic of the nervous system in Coelenterates?

Consists of one or more networks of nerve cells Signup and view all the answers

What is the characteristic of the reproduction in Coelenterates?

Both asexual and sexual reproduction Signup and view all the answers

What type of cells are responsible for phagocytizing the products of digestion in the coelenteron?

Gastrodermal cells Signup and view all the answers

What is the primary function of mucous cells in the coelenteron?

Lubricating food materials Signup and view all the answers

How do coelenterates obtain oxygen for respiration?

By diffusion from water Signup and view all the answers

What is the outcome of fertilization in coelenterates?

A planula larva is produced Signup and view all the answers

What is the characteristic feature of cubozoans?

Each polyp transforms entirely into a medusa Signup and view all the answers

What is the process by which scyphistomae produce immature medusae?

Strobilation Signup and view all the answers

Which phase of coelenterates has a more developed nerve net?

Medusa phase Signup and view all the answers

What is a characteristic feature of cnidarians?

They have a capacity for regeneration Signup and view all the answers

Study Notes

Phylum Coelenterata (Cnidaria)

Coelenterates include over 9,000 species, mostly marine, and are important in coral reef ecosystems.
Characteristics of Coelenterates:
- Acoelomate, diploblastic metazoans
- Multicellular, at the tissue level of organization
- Aquatic, mostly marine, with few freshwater species
- Sedentary or free-swimming, solitary or colonial
- Radially symmetrical, with a central gastrovascular cavity leading to the exterior by the mouth
- Body wall consists of an outer epidermis (ectoderm) and inner gastrodermis (endoderm) with a gelatinous mesoglea in between

Body Structure

Mouth is surrounded by tentacles with nematocysts, which function in food collection, defense, and locomotion
Individuals are armed with stinging cells called nematocysts
Body wall consists of an outer ectoderm and inner endoderm
Gastrodermal tissues lack nematocysts
Species may be solitary or colonial, freshwater or marine, with sessile and free-swimming forms

Zooids

Coelenterates exhibit polymorphism, with each individual known as a zooid
Main types of zooids in polymorphic forms are polyps and medusa
Polyp is the sessile and asexual zooid, while medusa is the free-swimming and sexual zooid

Nutrition and Digestion

Coelenterates are carnivorous, with extracellular and intracellular digestion
Anus is absent, and digestion occurs in the gastrovascular cavity
Food is taken in and wastes are discharged through the mouth
Coelenteron is a simple digestive sac with a single opening, lined by mucous cells, gland cells, and gastrodermal cells

Respiration and Excretion

Respiration and excretion occur at the individual cell level, with oxygen obtained directly from water and metabolic wastes returned to it by diffusion

Reproduction

All coelenterate species are capable of sexual reproduction, which occurs in the medusa phase
Asexual reproduction may occur in both phases (polyp and medusa phase)
Asexual reproduction is by budding, while sexual reproduction involves the production of male and female gametes
Fertilization produces a solid-bodied planula larva, which undergoes metamorphosis into a tiny polyp or scyphistoma depending on the group

Nervous System

Medusae have a more developed nerve net than polyps, associated with a more active way of life
Nerve net consists of one or more networks of nerve cells

Examples of Coelenterates

Hydra, Tubularia, Bougainvillea, Obelia, Physalia, Aurelia, Rhizostoma, Pelagia, Telesto, Xenia, Heliopora, Renilla, Actinia, Zoanthus, Metridium

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Description

Learn about the characteristics of phylum Coelenterata, including their body structure, habitat, and importance in coral reef ecosystems.