Porifera and Cnidaria

1
Porifera and Cnidaria

• Why are sponges and Cnidarias animals and not
  plants?
• 2-28-07

2
Porifera

• Multicellular, heterotrophic, no cell wall, and
  contain a few specialized cells
• pore-bearers
• Independent evolution from other animals?

3
Body Plan

• Asymmetrical with a central cavity
• Choanocytes specialized cells that use flagella
  to create a current of water
• Water current enters through side pores and
  leaves through a large hole at the top called
  osculum
• Simple skeleton made of either spicule or spongin
• Spicule spike shaped structure made of calcium
  carbonate or silica produced by archaeocytes
• Spongin flexible protein fibers

4
Feeding

• Filter feeders
• Digestion is intracellular
• Food is trapped by choanocytes and digested
• Digested food passed to archaeocytes to transport
  food throughout sponge

5
Respiration, Circulation, Excretion

• Relies solely on the movement of water
• Oxygen diffuses into cells
• Carbon dioxide and wasted diffuse out of cell

6
Response

• Do not have a nervous system to respond to
  environment
• Many sponges protect themselves by producing
  toxins
• Sponges can respond to extreme cold and drought
  by producing gemmules, which are a group of
  archaeocytes surrounded by a tough layer of
  spicules

7
Movement

• Sessile during adult life
• During development, larvae are motile and usually
  carried by currents before settling to the ocean
  floor

8
Reproduction

• Can sexually and asexually reproduce
• Internal fertilization fertilizing eggs inside
  of the animals body
• After fertilization, zygote develops into a larva
• Larva immature stage of an organism that looks
  different from the adult form

9
Cnidarians

• Soft-bodied carnivorous animals that have
  stinging tentacles encircling their mouths
• Simplest animal to have body symmetry and
  specialized tissues
• Cnidocytes stinging cells
• Nematocyst poison filled stinging structure that
  contains a coiled dart

10
Body Plan

• Radial symmetry
• Life cycle consists of 2 stages with distinctive
  looking structure
• Polyp cylindrical body with armlike tentacles
  and mouth that is at the top
• Medusa bell shaped body with mouth at the bottom

11
(No Transcript)
12
Feeding

• After paralyzing prey, pulls food into
  gastrovascular cavity, which is a digestive
  chamber with one opening
• Digestion is extracellular within cavity
• Partially digested food absorbed by gastroderm
  and completed intracellularly

13
Respiration, Circulation, Excretion

• Nutrients transported throughout body by
  diffusion
• Respire and eliminate waste by diffusion through
  body wall

14
Response

• Gather environmental information by specialized
  sensory cells
• Nerve net loosely organized network of nerve
  cells that detect stimuli such as touch
• Statocysts detect direction of gravity
• Ocelli eyespots that detect light

15
Movement

• Hydrostatic skeleton layer of circular muscles
  and a layer of longitudinal muscle that work with
  the water in the gastrovascular cavity
• Water pressure makes polyps taller
• Contractions allow medusas jet propulsion

16
Reproduction

• Reproduce both sexually and asexually
• External fertilization fertilization that takes
  place outside of the females body

17
Groups

• Class Scyphozoa cup animals, jellyfish
• Class Hydrozoa hydra (polyp only)
• Class Anthozoa flower animal, sea anemone
  (polyp only) and coral

18
Ecology of Coral

• Essentials temperature, water depth, and light
  intensity
• Symbiotic algae
• Coral bleaching