Cnidaria

What are the key characteristics of Class Anthozoa

- More than 6000 species - Polyp only - Solitary or colonial - Exclusively marine - Acellular mesoglea - Gastrodermal cnidocytes and gametes - Presence of a pharynx and mesenteries that divides the gastrovascular cavity. - There are 3 subclasses (Know 2)

What are the key characteristics of Phylum Cnidaria

- Radially symmetrical - Sac-like body plan (diploblastic) - Gastrovascular cavity lined with gastrodermis, and with a single opening serving as both the mouth and anus Possess cnidocytes which contain stinging organelles called nematocysts Two polymorphic body forms (polyp and medusa)

What are the key characteristics of Class Hydrozoa

- The life history may include both a polyp and a medusa phase or only one of the above. - Many are colonial - Gastrovascular cavity is without partitions (mesenteries) - Oral end of polyp is elongated into a hypostome - Medusae generally possess a velum (Obelia is an exception) - Gonads are ectodermal

What are the key characteristics of Class Scyphozoa

- The polyp phase is reduced or absent - Exclusively marine - Gonads of medusae are gastrodermal - Medusae do not possess a velum

What are the key characteristics of subclass Hexacorallia

- Usually possess 6, or a multiple of 6, tentacles and mesenteries - Tentacles are simple, not pinnate - Secretes a hard external calcareous skeleton (hard corals) - Soliary (sea anemones) - Colonial (hard corals)

What are the key characteristics of subclass Octocorallia

----Solitary - Polyps have 8 pinnate tentacles and 8 complete mesenteries - One siphonoglyph present ----Colonial - Skeleton of separate calcareous spicules - Colony having a fleshy, flattened body (sea pens)

Match the structure on the left with the correct description from the drop down box. Terms - Medusae - Polyps - Nematocyst - Buds - Statocysts - Occelli Definitions- Usually live attached to substrate - Gravitational detectors - Clusters of photoreceptor cells - Function in prey capture - Free-swimming form - Arises as outpocketing of body wall

-Medusae - Free-swimming form, -Polyps - Usually live attached to substrate, -Nematocyst - Function in prey capture, -Buds - Arises as outpocketing of body wall, -Statocysts - Gravitational detectors, -Occelli - Clusters of photoreceptor cells

How many germ layers do cnidarians have

2 Germ layers (diploblastic) - Epidermis derived from the ectoderm and a gastrodermis derived from the endoderm. - The layers are separated by the mesoglea

Hydromedusae Select one: a. Form gametes in gonads located within the epidermis b. Are asexual stages c. Lack a manubrium and velum d. Produce a sessile actinula larva that develops into a free-swimming planula larva

A hydromedusa is a member of the Class Hydrozoa in its medusoid life stage. Medusae are produced by budding within the gonangia. Young medusae leave the colony as free swimming individuals that mature and form gametes that either remain in the gastrodermis or migrate to the epidermis and form gonads.

What is a velum

A membrane on the subumbrellar surface of jellyfish of class Hydrozoa. Also a ciliated swimming organ of the veliger larva

What are some of the common names of organisms in phylum cnidaria

Anemones and corals Jelly fish Hydroids

Name three classes of cnidaria

Anthozoa Hydrozoa Scyphozoa

What level of organisation are cnidarians

Cell-tissue

Cnidarians exhibit two different body forms (dimorphism), polyp and medusa. The polyp or hydroid form is adapted to a sedentary or sessile life and the medusa is adapted for a floating or free-swimming existence. A life cycle that has two different body forms is called

Dimorphic

What 'group' do cnidarians belong to?

Eumetazoa

Is cnidarian digestion intracellular or extracellular?

Extracellular digestion- in the gastrovascular cavity where digestive enzymes break down the food and the particles then diffuse through the body. Also a little bit of intracellular digestion in the gastrodermal cells.

What kind of body cavity do cnidarians have

Gastrocoel

What is the difference between Gastrozooids and Ganozooids?

Gastrozooids are for feeding and nutrition, Gonozooids for reproduction.

What are the two subclasses of Class Anthozoa?

Hexacorallia (sea anemones and hard corals) Octocorallia (soft corals and sea pens)

Name the skeletal structures

Hydrostatic skeleton- Water in the gastrovascular cavity which provides a solid structure for muscles to move against.

How do cnidarians reproduce

Sessile polyps reproduce asexually where budding produces clones, some colonies then undergo polymorphism to form different polyps within the colony) Mobile medusas reproduce sexually where there are distinct differences between male and females.

What are the epitheliomuscular cells

The cells that are responsible for muscular contractions They form an outer layer of circular fibers at the base of the gastroderm.

How do cnidarians capture prey

They possess specialised cells called cnidocysts, containing nematocysts. Nematocysts are pressurised chambers ready to fire a harpoon-like poisonous thread.

What are some of the defining characteristics of eumetazoa

True tissues Gastrula stage Germ layers Digestive cavity (gut)

Reefs are found only in clear, shallow water because reef corals contain symbiotic zooxanthellae that require light, True or false

True, The distribution of coral reefs is limited to locations that offer optimal conditions for their zooxanthellae. They require warmth, light and the salinity of undiluted sea water, thus limiting coral reefs to shallow waters between 30° N and 30°S latitutde and excluding them from areas with upwelling cold water or areas near major river outflows with attendant low salinity and high turbidity.

Sea anemones feed upon other invertebrates and small fish which are passed down the pharynx and into the gastrovascular cavity, True or false

True, ea anemones are definitely carnivorous, feeding on fish or almost any live animals of suitable size. Sea anemones are cylindrical with a crown of tentacles arranged in one or more circles around the mouth on the oral disc. At one or both ends of the mouth is a ciliated groove called the siphonoglyph which extends to the pharynx. Siphonoglyphs create water currents directed into the pharynx. Normally prey organisms are drawn into the gastrovascular cavity into which gland cells discharge enzymes.

How does excretion occur in cnidarians

Via diffusion

Do cnidarians have a nervous system

Yes, They have a nerve net Nerve cells located at the base of the epidermis near the mesoglea. It interconnects to form a two-dimensional nerve net. They have touch and chemical preceptors and have primitive eyes.

Members of the Phylum Cnidaria: Select one: a. Are mostly marine animals b. Display radial symmetry c. Usually have external fertilization d. All of the above

d) All of the above Cnidarians are found most abundantly in shallow marine habitats, especially in warm temperate and tropical regions. These animals (particularly during the medusa stage of the life cycle) display radial symmetry (i.e. can be divided into similar halves by more than two planes passing through the longitudinal axis). Most cnidarians are dioecious, and many shed their gametes directly into the water.

What is the symmetry of cnidarians

radially symmetrical