1. Invertebrates

2. Vertebrates v. Invertebrates
Invertebrates do not belong to any particular scientific group; i.e. there is no “Invertebrata” grouping
An organism is informally classified as an invertebrate if it has no backbone (this is the only requirement)

3. Phylum: Porifera

4. Porifera “To have pores”
-This phylum is made up of Sponges
Vividly colored, Sessile organisms that live in the oceans and occasionally in freshwater
Sessile = permanently attached to rocks or other submerged objects
They can be very large or so small that they are hardly noticed
3 types of general forms: tree-like, vase-like and encrusting (see Fig 2-1)

5. Skeletons Spongy or Prickly? How about both? Spongin
A flexible, fibrous material that makes the sponges feel soft and springy
This is what most sponges are made of
Spicules (see Fig 2-2)
Hard, sliver-like structures made of silicon
dioxide or calcium carbonate
These structures give the sponge a prickly-
feeling, stiff skeleton
How about both?
Some species of sponge have both!

6. Anatomy of a Sponge Pores Epithelial cells Porocyte cells Osculum
Tiny holes in the walls of the sponge; characteristic feature that gave “Porifera” its name
Epithelial cells
The skinlike, outer layer of the sponge; responsible for protecting and enclosing the sponge
They can contract and shorten, causing the sponge body to move slightly
Porocyte cells
A type of epithelial cell; the pores on the outside are actually the hollow insides of these cells
They connect the outside of the cell to the inside cavity; making the sponge like a sieve
Osculum
A large opening on the top of the sponge; simple sponges have only one, complex sponges have many
They can contract and close, but the process is very slow (taking several minutes)

7. Let’s Label Figure 2-6!  (and tape it in if needed!) Collar Cells
Cells that line the inner surface of the sponge
Made up of fine tubes that surround a flagellum
Flagellum
A long, whip-like thread that moves back and forth
As the flagella (plural form) move, they create a current of water that enters through the many small porocyte cells and exits the osculum
Sponges (even the tiny ones) can circulate a gallon of water a day!!
Amoebocyte
Free-moving cells that resemble amoebas
These cells have special functions:
Producing spongin and/or spicules
Digesting and transferring nutrients
Reproduction of amoebocytes
(Tape Fig 2-7 in your notebook, if you haven’t already done so)

8. Feeding and Digestion Detritus feeder
The water currents produced by the flagella move food particles like suspended bacteria, bits of plant/animal detritus, and plankton into the sponge cavity
Detritus =
Or Filter Feeder?
As food flows in, the fine tubes of the collar cells filter out the food particles and move them into the cells
**Because all the cells in a sponge are in contact with or near to the seawater, they all can exchange oxygen, carbons dioxide, and excretory waste with the seawater. This means sponges have no respiratory, circulation or excretory systems.