Unit 5, Part 1: Phylums: Porifera, Cnidaria, Ctenophora

^^Phylum Porifera:^^

• They are primarily marine animals
• Made of loosely organized cells
• There are about 9,000 species

Main Characteristics:

• They are asymmetrical
• ^^Spongocoel^^: central cavity (branching chamber) through which water circulates
• They have no tissues or organs
• They have an ^^Osculum: openings where water leaves out from^^

Cell types of Porifera:

• ^^Pinacocytes^^: cells that line the outer surface

• ^^Porocytes^^: openings where water entered and these cells regulate water circulation

• ^^Mesohyl^^: jellylike layer of cells that lies under pinacocytes

• ^^Mesenchyme^^ ^^cells^^: amoeboid cells that function for reproduction, transporting and storing food (they do not filter out food)

• ^^Choanocytes^^: (collar cells) that line the inner chamber and has flagellum that creates water currents and filters out food particles

  

Sponge Skeleton Makeup:

• ^^Spicules^^: needle like spikes
• ^^Spongin^^: fibrous material made of collagen

Body Forms:

• Three Types of Body Forms

  • ^^Ascon^^: vase like body form
  • ^^Sycon^^: body form where walls appear folded
  • ^^Leucon^^: body form with extensively branched canal system
  • 

  Water Currents:

  1. Water enters through the porocytes
  2. The water then enters into the spongocoel where the choanocytes that line the walls whip their fagellum around to seperate the water from the food
  3. The water exits out through the osculum

  Maintenance Functions:

• ^^Sponges are filter feeders through choanocytes^^

• Mesenchyme cells distribute food to the other cells of the sponge

• Waste is eliminated through simple diffusion

• Sponges have no nerve cells

Reproduction:

• ^^Monoecious:^^ both sexes occur in the same individual
• These sponges ^^DO NOT self-fertilize^^
  • Sperm exits through the osculum and then enters another sponge through incurrent water
• The fertilization then results in flagellated larvae
• Asexual Reproduction: ^^Gemmules^^
  • ^^Gemmules are resistant capsules containing mesenchyme cells (amoebic cells)^^
  • These gemmules occur when conditions are unfavorable
  • These gemmules can then reorganize into a sponge

Classes of Porifera:

• ^^Class Calcarea^^:

  • Spicules of calcium carbonate
  • These sponges are responsible for the limestone in the ocean
  • Capable of all body forms
  • All marine
  • 

• ==Class Hexactinella:== “glass sponges”

  • Spicules of silica (glass)
  • Can have sycon or leucon body form
  • All marine
  • 

• @@Class Demospongiae:@@

  • Brightly colored
  • Spicules or sponging (or both)
  • Only leucon body forms
  • Freshwater or marine
  • These are bath sponges
  • 

• %%Class Homoscleromorpha%%

  • Simplest ones
  • Small or absent spicules
  • All marine

  

==Phylum Cnidaria:==

Main Characteristics:

• ==Mostly marine==
• Over 9,000 species
• ==Radial== symmetry
• ==Diploblastic==; has only two germ layers

Body Wall:

• ==Epidermis==: outer layer of the body wall
• ==Gastrodermis==: inner layer of the body wall
• ==Mesoglea==: the jelly-like material between the epidermis and gastrodermis'

Cnidocytes:

• ==These are stinging cells== that are made of either gastrodermal or epidermal cells
• ==Cnidocytes produce cnida==
  • ==Cnida==: fluid filled capsule containing coiled hollow tube
  • ==Nematocysts==: type of cnida used in food gathering and defense (they deliver paralyzing toxin)

Reproduction: (Dioecious)

• ==Alternation of generations==: the life cycle of cnidarians includes both body forms

  • ==Polyp stage:==
  • Usually asexual and sessile during this stage
  • Mouth is surrounded by tentacles and the aboral end is attached to substrate
  • ==Medusa stage:==
  • Free swimming
  • Shaped like an inverted bowl
  • Mouth centrally located and facing down

  Maintenance Functions:

  • ==Gastrovascular Cavity==; digestions, exchange of gases and waste, discharge of gametes
  • Most eat small crustaceans or fish
  • Enzymes help digest in food vacuoles

“Skeleton”:

• ==Hydrostatic Skeleton==: water filled gastrovascular cavity contracts and causes movements as it propels itself
• Polyps:
  • move through somersaulting and gliding along the substrate
• Medusae:
  • move through swimming and floating

Nerve Cells:

• ==Most primitive nerve cells in animal kingdom==
• ==Have no brain==
• ==Located below epidermis and form a nerve net==
• Conducts impulses around body in response to stimulus

Waste:

• Large surface area to volume ratio
• Waste is eliminated through diffusion
  • ==They only have one opening so waster is disposed through the mouth==

Reproduction:

• Cnidarians (jellyfish) are dioecious

  • Meaning that each individual has one sex (male or female)

• ==Life Cycle:==

  • After fertilization of and egg than a blastula is formed
  • This blastula matures into free swimming planula larva
  • The planula larvaa then settles on a substrate as a polyp
  • Medusa body stage forms from budding polyp

  

Classes of Cnidarians:

• ==Class Hydrozoa:==

  • Small, mostly marine
  • But, they do have some freshwater species
  • Some do not have a medusa stage
  • Can exist as colonial polyps through budding (diagram)
  • ==Gastrozooid==: feeding polyp
  • ==Gonoozoid==: reproductive polyp

• ==Class Staurozoa:==

  • All marine
  • Lack a medusa stage
  • Crawling planula larvae

• ==Class Scyphozoa:==

  • All marine
  • True “jellyfish”
  • Dominant medusa stage

• ==Class Cubozoa:==

  • Cube shaped medusa
  • Polyps are small
  • Active swimmers
  • Some are very dangerous

• ==Class Anthozoa (Anemones):==

  • Lack medusa
  • Solitary or colonial
  • Anemones, soft or stony corals
  • All marine

%%Phylum Ctenophora:%%

• %%Comb jellies%%

• Same basic characteristics as cnidarians

• Bioluminescent

  • %%Comb Rows:%%
  • %%Rows of thousands of cillia that are used for motion%%
  • %%Colloblasts:%%
  • %%Cells used to capture prey%%