Lecture 10 - Cnidaria Flashcards
1
Q
Explain the Phylum : Cnidaria
A
- Radially symmetrical ( tubular / bell-shaped )
- Known for presence of stinging cell
- called cnidocyte in epidermis - Nematocyst = capsule
- inside = cnidocyte and thread that stings - Body consists of two layers
- Gastrodermis = lining of gastrovascular cavity
- In between two layers = mesoglea
- Posses muscle fibres and nerve fibers in mesglea
2
Q
Explain the phylum cnidaria body layers
A
- Outer epidermis = ectodermal
- Inner gastrodermis = endodermal
3
Q
Explain the life cycle of cnidaria
A
- Egg and sperm = fertilisation
- Zygote
- Planula
- Polyp
- Polyp undergoes budding forming hydrozoans
4
Q
What are the classes of Cnidaria
A
- Class : Hydrozoa
- Class : Anthozoa
- Class : Scyphozoa
5
Q
Explain Class : Hydrozoa
A
- Polyp is dominant with medusoid forms in some species
eg ) 1. Physalia ( Portugese man-of-war) and Obelia (marine colonial forms )
- Hydra (freshwater dominant polyp)
6
Q
Explain Class : Anthozoa
A
- Dominat polyp
- Single or colonial ( corals and sea anemones )
eg) 1. Bunodosoma
2. Pseudactinia
7
Q
Explain Class : Scyphozoa
A
- Dominant medusa (jellyfish)
- Zooplankton
eg) 1. Chrysaora hysoscella
2. Eupilema inexpectata
8
Q
Explain the lifecycle of Obelia
A
- Sperm and egg fertilise
- Zygote
- Blastula
- Swimming planula
- Planula
-Starts new colony by asexual budding - Medusa
9
Q
Explain protostome animal division
A
- Divided on the basis of whether they molt and the type of larva they produce
- Ecdysozoa
- Lophotrochozoans produce one of the following two types of larvae :
- Lophophore larva:
ciliated ring of tentacles surround the mouth - Trochophore larva: free swimming larva,
Cilia around the middle
10
Q
Explain Phylum: Platyhelminthes
A
- Flatworms
- Bilateral symmetry
- 3 germ layers
- Body cavity is absent ( acoelomate )
- Sac-like body plan ( one opening into gut )
- FFree living or parasitic
11
Q
What are the classes of Phylum: Platyhelminthes
A
- Class: Turbellaria – free-living flatworms
- Class: Trematoda – parasitic flukes
- Class: Cestoda – parasitic tapeworms
12
Q
Explain the Class: Turbellaria
A
- Free living
- Mostly in fresh water
- Display definite cephalisation
- Incomplete digestive system ( sac body plan )
- Excretory systems present consisting of flame cells
- Muscular systems present
- May reproduce asexually by fragmentation
- Cross-fertilization is rule in this hermaphroditic (produces both sperm and egg cell) taxon
Example - Dugesia sp.
13
Q
Explain Class: Trematoda
A
- Includes parasitic flukes
- Parasites of liver or blood or lungs of the primary host
- Make uses of an intermediary/secondary host
- Transmits the parasite to the PRIMARY HOST
- The external tegument protects the parasite from being digested by digestive enzymes of the primary host
- The head ill-defined and consists of hooks and/or suckers
- Hooks and suckers allows for attachment to host tissue.
- Nervous system and digestive system rudimentary- poorly developed
- Reproductive system is well developed
- Some species sexes separate (male and female forms); others are hermaphroditic
Examples: Schistosoma mansoni, Fasciola hepatica
14
Q
Explain the Class: Cestoda
A
- They include tapeworms; They are Internal parasites
- Digestive system and nervous systems are either absent or reduced
- Head consists of a series of hooks called the scolex
- Youngest proglottids in neck region, closest to the scolex
- Reproductive system extensive
- Hermaphroditic: produce both sperm and eggs
- Gravid proglottids filled with ripe eggs; They break off and are excreted by the host along with faeces.
Examples: Taenia solium, Dipylidium caninum
15
Q
Explain primary and secondary hosts of Cestoda
A
- In the secondary host: cyst with bladder worm in muscle tissue.
- In the primary host the parasite attaches to the intestines and absorb hosts digested food.
16
Q
Explain the scolex
A
- Behind the scolex are the proglottids (segments) presents
17
Q
Explain Phylum: Annelida
A
- External annules (rings) – pronounced segmentation
- Coelom divided by septa – hydrostatic skeleton
- Tube-within-a-tube body plan
- Nervous system, digestive system well-developed
- Closed blood vascular system – haemoglobin
- Excretory system - nephridium
18
Q
What are the advantages of coelomates
A
- Having a coelom/body cavity has the following advantages for an animal
- Unrestricted body movement is possible– outer layers are not constricted by internal organs
- A Complex Digestive system can develop.
- Coelom fluid – acts as a hydroskeleton
- Reservoir for gametes, metabolic waste
- Protect internal organs (damage and temperature fluctuations)
- Coelom fluid aids in physiology
- Assist in respiration, circulation (O2 and nutrient availability)
19
Q
Explain protostome coelomates fully
A
- Bilateral symmetry
- Three germ layers
- Organ level of organization
- Tube-within-tube body plan
( Acoelomate; pseudocoelomate and coelomate )
20
Q
What are the classes of Phylum: Annelida
A
- Class: Polychaeta
- Class: Oligochaeta
- Class: Hirudinea
21
Q
Explain the Class: Polychaeta
A
- They are marine worms
- They have pronounced segmentation
- They possess chaetae (= bristles)
- Assist in locomotion and attachment
- Chaetae arranged in bundles (= parapodia)
- Motile or sessile/tube dwelling
Example: Gunnarea capensis
22
Q
Explain the Class: Oligochaeta
A
- Pronounced segmentation
- Head not well developed
- Parapodia not well developed
- Chaetae direct from body
- Digestive system well developed
- Digestive system have expended region, the typhlosole, to aid in absorption of nutrients.
- They live on detritus, thus scavengers. They live in soil, have a moist body wall.
- They are hermaphrodites
eg) Lumbricus terrestris (earthworm)
23
Q
Explain the Class: Hirudinea
A
- Known as leeches
- Mostly freshwater, some marine or terrestrial
- Chaetae are absent
- Each body ring with transverse grooves
- Two mouth suckers present
- This animal secretes Hirudin to prevent coagulation(clotting) of host blood
eg) Hirudo medicinale (medicinal leech)
