Chapter 13: Radiate Animals

Question 0

Extant Species?

Answer 0

most common in shallow marine environment
some fresh
none are terrestrial

Question 1

Specimens date back ?

Answer 1

over 700 million years ago…

Question 2

What phylums eat hydroids to gain their stinging nematocysts for defence purposes. (3)

Answer 2

ctenophores, molluscs and flatworms

Question 3

What are the four classes of Cnidaria? Ex of each

Answer 3

1. Hydrozoa: hydra
2. Scyphozoa : jelly fish
3. Cubozoa: box jelly
4. Anthozoa: coral, sea anemone

Question 4

Characteristics of Phylum Cnidaria?
-habitat
-symmetry (2)
-body types (2)
-Germ layers? whats up with those?
I> Mesoglea?
-Gut is_______ aka a _________ cavity. Extracellular digestion in_______ and Intracellular digestion in __________ cells.
-_______ usually circle mouth/oral region.
-Muscular contractions via _________ cells, outer layer of _____ fibres and an inner layer of ______ fibres.
- Sense organs for balance : ______ and photosensitivity______.

Answer 4

-aquatic and mostly marine
-radial or biradial
- free-swimming medusae and sessile polyps
-Diploblastic
I> epidermis and gastrodermis
I> extracellular matrix that lies between ectodermis and gastrodermis.
-incomplete, gastrovascular, gastrovascular cavity gastrodermal cells
- tentacles
-epitheliomuscular, longitudinal, circular
-statocyst, ocelli

Question 5

Nerve net has _________ and _______ synapses.

two more points to be noted…conduction and rings

Answer 5

symmetrical, asymmetrical
diffuse conduction
two nerve rings in hydrozoan medusae

Question 6

Asexual Reproduction?

Answer 6

budding in polyps

some colonies exhibit polymorphism

Question 7

Sexual Reproduction?

Answer 7

gametes in all medusae and some polyps
monoecious or dioecious
holoblastic indeterminate cleavage

Question 8

Why is their not excretory or respiratory system?

Answer 8

diffusion occurs…no need for either..

Question 9

Polyp Body Plan

• life style?
• body shape?
• pedal disc?
• reproduction?
• colonial forms?

Answer 9

• hydroid form
• sedentary life
• tubular body with mouth directed upward and surrounded by tentacles
• aboral end attached to substratum by pedal disc
• reproduces asexually by budding, fission or pedal laceration.
• polyps may be specialized for feeding, reproduction or defense.

Question 10

Polymorphism?

Answer 10

a single genotype can express more than one body form (phenotype) via asexual reproduction

Question 11

How do you distinguish feeding polyps known as ________ from reproductive polyps known as _________. ? (class hydrozoa)

Answer 11

• hydranths
• gonangia

*** Gonangia do not have tentacles!!! and often produce medusae

Question 12

Medusa??(other body form)

• shape
• mouth direction
• tentacles extend from?
• sensory ??
• integration of sensory info to motor response ?

Answer 12

• bell or umbrella-shaped
• free swimming norm
• mouth directed downward
• tentacles may extend down from rim of umbrella
• equipped with statocysts and ocelli
• nerve ring around base of the bell = integration of sensory information into motor response.

Question 13

What is the difference between Hydromedusae and Scyhomedusae?
pro of having this difference?

Answer 13

the presence of velum…a shelflike fold of tissue from the bottom of the bell that extend into the bell…increases exit velocity of water making each pulsation more efficient. (hydromedusae)

Question 14

Budding (polyps)
Strobilation (polyps)
Both produce medusa.

Answer 14

Strobilation- repeated, linear budding of individuals..

Question 15

Reproduction for Medusae? (gen over view of characteristics etc)

• sep sexes or both in one?
• Sycphozoa is a ?…sizes of medusa and polyps
• Colonial hydroids have what two stages?
• Some Hydrozoans (Physalia) form this?
• Hydras?

Answer 15

-dioecious
-reproduce sexually
- True Jellyfish (class sycphozoa)
I> medusa is large and conspicuous ..polyps typically very small
-Most Colonial Hydroids - feature a polyp stage and a pelagic medusa stage….
-floating colonies….
-In Hydra only stage is a small freshwater polyp.

Question 16

Pelagic?

Answer 16

open water environment

Question 17

Benthic?

Answer 17

bottom environments…

Question 18

The body wall of Cnidarians:

• inner layer, outer layer
• mesoglea?
• think/thin in ?
• continuous in?
• function?

Answer 18

-Outer epidermis which is derived from the ectoderm
-inner gastrodermis derived from the endoderm
-mesoglea separates them
I> gelatinous (95% water)
I> continuous in polyps, extending through body and tentacles
I> supports body
I> thick in anthozoans and scyphozoan medusae
L> Thinner in hydromedusae…

Question 19

In Hydra? (body wall) cont

Answer 19

epidermis contains epitheliomuscular, interstitial, gland, sensory and nerve cells.

Question 20

Cnidarian bodies can ______,________ and _______
no muscle cells derived from _________?
they have __________ cells which form most of the epidermis covering the organism and function in muscle contraction.

Answer 20

extend, bend and pulse.

• mesoderm
• epitheliomuscular

Question 21

Cnidocytes?
location?
produces ?
one of which is?

Answer 21

• located in invaginations of ectodermal cells and some gastrodermal..
• produces one of over 20 of cnidae
• one type is Nematocyst.

Question 22

Nematocysts?

• shape, material coating?
• filament may have?
• Cnidocil?
• stimulation needed to discharge is?
• what occurs after discharge

Answer 22

• tiny capsules made of chitin-like material and containing a coiled filament.
• end of capsule is covered
• filament may have tiny barbs or spines
• other than anthozoa, Cnidocytes are quipped with a trigger like cnidocil (modified cilium)
• tactile stimulation causes the nematocyst to discharge…after the cnidae discharge, cnidocyte is absorbed and another develops.

Question 23

Walk through the mechanism of Nematocyst discharge

3

Answer 23

• water rush into capsule
• operculum (lid that covers the end of the capsule) opens and rapidly launches the filament
• barbs inject poison

Question 24

Feeding and Digestion - Polyps

• catch method
• digestion
• intra digestion

Answer 24

• carnivorous
• catch prey with tentacles and pass them to the gastrovascular cavity
• gland cells discharge enzymes to begin extracellular digestion
• intracellular digestion occurs in gastrodermis…

Question 25

Feeding and Digestion- Polyps in Colonial Hydrozoans

- hydromedusae version?

Answer 25

• pass food into a common gastrovascular cavity

- feeding in hydromedusae similar to polyps

Question 26

Feeding and Digestion- Anthozoan polyps 
type?
-method
-smaller ones?
-coral?

Answer 26

carnivorous
expand and stretch tentacles in search of prey
-smaller ones: feed on minute forms captured by ciliary currents
- corals supplement their nutrition via carbohydrates from algal symbionts

Question 27

Nerve net yo? Whats up with that thingy that can fire in multiple ways-neat.

• nervous system is?
• location of the two nerve nets
• how does it transmits two ways?
• What makes up the neuromuscular system?
• nerve cell synapses have what? (2)

Answer 27

• diffuse nervous system
• one at base of epidermis and one at the base of gastrodermis interconnected
• neurotransmitters on both sides of the synapses aka transmission either way…no myelin sheath
• contractile fibres of epitheliomuscular cells+ sensory nerve cell net
• nerve cells have synapses with slender sensory cells for external stimuli and they have synapses with epitheliomuscular cells and nematocysts.

Question 28

Class Hydrozoa?

Answer 28

• most marine and colonial with both polyp and medusa forms BUT hydra is not typical
• base which colonial hydroids attach