Lecture 10 - Cnidaria

Question 1

Explain the Phylum : Cnidaria

Answer 1

• 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

Question 2

Explain the phylum cnidaria body layers

Answer 2

• Outer epidermis = ectodermal
• Inner gastrodermis = endodermal

Question 3

Explain the life cycle of cnidaria

Answer 3

• Egg and sperm = fertilisation
• Zygote
• Planula
• Polyp
• Polyp undergoes budding forming hydrozoans

Question 4

What are the classes of Cnidaria

Answer 4

• Class : Hydrozoa
• Class : Anthozoa
• Class : Scyphozoa

Question 5

Explain Class : Hydrozoa

Answer 5

• Polyp is dominant with medusoid forms in some species

eg ) 1. Physalia ( Portugese man-of-war) and Obelia (marine colonial forms )

2. Hydra (freshwater dominant polyp)

Question 6

Explain Class : Anthozoa

Answer 6

• Dominat polyp
• Single or colonial ( corals and sea anemones )

eg) 1. Bunodosoma
2. Pseudactinia

Question 7

Explain Class : Scyphozoa

Answer 7

• Dominant medusa (jellyfish)
• Zooplankton

eg) 1. Chrysaora hysoscella
2. Eupilema inexpectata

Question 8

Explain the lifecycle of Obelia

Answer 8

• Sperm and egg fertilise
• Zygote
• Blastula
• Swimming planula
• Planula
  -Starts new colony by asexual budding
• Medusa

Question 9

Explain protostome animal division

Answer 9

• Divided on the basis of whether they molt and the type of larva they produce

1. Ecdysozoa
2. 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

Question 10

Explain Phylum: Platyhelminthes

Answer 10

• Flatworms
• Bilateral symmetry
• 3 germ layers
• Body cavity is absent ( acoelomate )
• Sac-like body plan ( one opening into gut )
• FFree living or parasitic

Question 11

What are the classes of Phylum: Platyhelminthes

Answer 11

1. Class: Turbellaria – free-living flatworms
2. Class: Trematoda – parasitic flukes
3. Class: Cestoda – parasitic tapeworms

Question 12

Explain the Class: Turbellaria

Answer 12

• 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.

Question 13

Explain Class: Trematoda

Answer 13

• 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

Question 14

Explain the Class: Cestoda

Answer 14

• 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

Question 15

Explain primary and secondary hosts of Cestoda

Answer 15

• 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.

Question 16

Explain the scolex

Answer 16

• Behind the scolex are the proglottids (segments) presents

Question 17

Explain Phylum: Annelida

Answer 17

• 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

Question 18

What are the advantages of coelomates

Answer 18

1. Having a coelom/body cavity has the following advantages for an animal
2. Unrestricted body movement is possible– outer layers are not constricted by internal organs
3. A Complex Digestive system can develop.
4. Coelom fluid – acts as a hydroskeleton
5. Reservoir for gametes, metabolic waste
6. Protect internal organs (damage and temperature fluctuations)
7. Coelom fluid aids in physiology
8. Assist in respiration, circulation (O2 and nutrient availability)

Question 19

Explain protostome coelomates fully

Answer 19

• Bilateral symmetry
• Three germ layers
• Organ level of organization
• Tube-within-tube body plan

( Acoelomate; pseudocoelomate and coelomate )

Question 20

What are the classes of Phylum: Annelida

Answer 20

• Class: Polychaeta
• Class: Oligochaeta
• Class: Hirudinea

Question 21

Explain the Class: Polychaeta

Answer 21

• 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

Question 22

Explain the Class: Oligochaeta

Answer 22

• 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)

Question 23

Explain the Class: Hirudinea

Answer 23

• 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)