Cnidarians

Question 1

What other Phlyum was paired with Cnidarians?

Answer 1

Ctenaphoras

(In phylum Coelenterata with Cnidarians but no longer classified as that

Question 2

Give examples of Cnidarians.

(3 given examples in the slides)

Answer 2

Jellyfish, sea anemones, corals

Question 3

Two forms of locomotion exhibited by Cnidarians.

(still and moveing)

Answer 3

Sessile and Free-swimming

Question 4

What type of nutrition do they require?

(prey or predators)

Answer 4

Predators.

Question 5

What type of organization do they have?

(Higher than porifera).

Answer 5

Tissue level organization

Question 6

Skeleton may be made of what?

(3 things)

Answer 6

Hydrostatic, Calcium carbonate, chitin

Question 7

What is the phlyum named after?

Answer 7

Its iconic cells cnidocytes or cnidae present in cnidocytes.

Question 8

Habitat of cnidarians?

Answer 8

Marine & freshwater

Question 9

Type of organization

Answer 9

Tissue level organisation

Question 10

Type of symmetry for ctenophores?

Answer 10

Like ctenophores: Radial or biradial

Question 11

Type of gut for ctenophores and cnidarians?

(complete or incomplete?)

Answer 11

Incomplete gut

Question 12

Where does extracellular digestion occur?

Answer 12

Gastrocavity or gastrodermal cells

Question 13

Two sense organs present in cnidaria

Answer 13

Statocyst and ocelli

Question 14

What type of coelom?

Answer 14

Acoelomate (do not have one)

Question 15

What are to two life forms of cnidarians?

Answer 15

Polyp and medusa

Question 16

Describe the polyp form.

Answer 16

Tubular, sessile, mouth leads to gastrovascular cavity, aboral end attach to substrate. Asexual reproduction, polymorphism , modular colonies.

Question 17

How do polyps reproduce asexually?

Answer 17

Budding, fission and pedal laceration (fragmentation)

Question 18

Describe the medusa form.

Answer 18

• Tetramerous
• Bell shape
• Mouth on concave side of the bell.
• Tentacles on the rim of the medusa.
• Free-swimming

Question 19

What sensory structures are present in the medusae form?

Answer 19

• Statocyst
• Ocelli

Question 20

How many germ layers do the mesdusa have?

Answer 20

2. They are diploblastic.

(epidermis & gastrodermis) middle is mesoglea.

Question 21

What are the 5 cells of Cnidarians ?

Answer 21

1. Epitheliomuscular
2. Interstitial
3. Mucus gland cells
4. Cnidocytes
5. Sensory cells.

Question 22

What is the purpose of the epitheliomuscular cell?

Answer 22

Affect muscular contraction of the outter epidermis.

Question 23

What causes contractions in the cnidaria outer epidermal cells?

Answer 23

Myofibrils

Question 24

What is the purpose of mesoglea ?

Answer 24

Jelly like, thickness vary with different cnidaria,** supports and acts as an elastic skeletal.**

Question 25

Nerve Net | (location, what causes nerve action potential, what is it?).

Answer 25

* Is a diffused nervous system. * located at the base of the epidermis and gastrodermis. * Nerve action potentials transmited by neurotransmitters.

Question 26

Explain the life cycle of a typical Cnidarian

Answer 26

Zygote developed into a planulae -> settles on a substrate -> planulae forms into polyp-> asexually form more polyps + medusae -> reproduce sexually.

Question 27

Name the 4 classes of the Cnidaria

Answer 27

Hydrozoa Scyphozoa Cubozoa Anthozoa

Question 28

Example of the hydrozoa

Answer 28

Fire corals

Question 29

Key features of the Hydrozoa

Answer 29

* Velum present * 4 radial canals * Acellular mesoglea * Hydromedusae * Polyp conspicous * Manbrium in which the mouth is at the end. * Colonial * Marine * Gametes release outside the body

Question 30

Example of the Scyphozoa

Answer 30

Upsidedown jelly fish

Question 31

Key features of the scyphozoa

Answer 31

* Bell margin scalloped * Have lappets * Lappets have sensory structure called Rhopalium * Free swiming * Medusae dominant * Tentacles on subumbrella side * Mouth leads to stomach * nerve net * No velum * distinct sexes * reproduce sexually *

Question 32

Describe cubozoa

Answer 32

* Strong swimmer * Medusoid stage dominant * Polyp is inconspicuous or absent * tentacles at corner at the Pedalium * 24 well developed eyes * Have rhopalia * Margin not scalloped * Boxed shaped in transverse section.

Question 33

Example of cubozoa

Answer 33

Box jellyfish

Question 34

Key characteristics of anthozoa

Answer 34

* Medusa stage absent * coral polyp * biradial symmetric * polyp more complex and larger than other stages. * have amoeboid mesenchyme cells * Mouth leads to Pharynx * Solitary or colonial * marine * have 3 subclases: main subclasses are Hexacorallia and Octocorallia.

Question 35

Which subclass covers hard corals ?

Answer 35

Hexacorallia

Question 36

Which subclass of anthozoa covers soft corals?

Answer 36

Ocotocorallia

Question 37

Difference between hexacorallia and Octocorallia.

Answer 37

Hexamerous vs octomerous simpler tentacles vs pinnate tentacles

Question 38

About scleractinian

Answer 38

* Have cups formed from Calcium carbonate named Calyx. * Have cups where polyp can retract to. * Skeleton secreted at base of polyp. * Gastrovascular connected by coensarc. * Sclerosepta sticks in true septa. * Skeleton made of aragonite.

Question 39

An example of the Scleractinian

Answer 39

Brain corals.

Question 40

Describe octocorallia

Answer 40

* Solenia (gastrovascular cavity communicates through it) * 8 pinnate tentacles. * 8 unpaired septa. * cellular thick mesoglea * Horny protein or fused spicules endoskeleton * Cnidocytes in both layers. * colonial * Septa goes into the upper body.

Question 41

What is a key feature of cnidocytes?

Answer 41

Cnidae or nematocytes.

Question 42

Prey-capture in Cnidarian

Answer 42

Cnidocil triggered from hydrostactic pressure (high tensional and osmotic pressure or forces) and the hollow barbed or spiculated threads are released and they sting prey, release toxins and immobolize them.