Tuesday, April 25, 2006

Killer Jellies


Explain how the killer box jellies can cause death in unsuspecting swimmers.

Monday, April 24, 2006

Cnidarians

BODY PLAN OF CNIDARIANS
- Animals in the phylum Cnidaria are radially symmetrical aquatic invertebrates that are more complex than the sponges. They have tissues and simple organs.
- The cnidarian body is either a sessile polyp or a swimming medusae. Some cnidarians alternate between both types during their life cycles.

The body of a cnidarian consists of two cell layers:
1) an outer epidermis
2) an inner gastrodermis
- The layers are separated by the mesoglea.
- The gastrovascular cavity has a single opening (the mouth) surrounded by tentacles.

FEEDING AND DEFENSE IN CNIDARIANS
- Cnidarians have cells called cnidocytes.
- Each cnidocyte contains a nematocyst.
- When a cnidocyte is stimulated. its nematocyst (stinger) ejects a filament that can paralyze or ensnate prey.

NERVOUS SYSTEM IN CNIDARIANS
- The cnidarian nervous system is a diffuse web of interconnected nerve cells called a nerve net.

CLASSIFICATION OF CNIDARIANS
- The three classes of cnidarians are:
1) Class Hydrozoa
a) This class includes Obelia, man-o-war, and the hydra.
b) Hydrozoans may live as polyps, medusae, or mixed colonies.

2) Class Scyphozoa
a) This class includes jellyfish.
b) Scyphozoans spend most of their lives as medusae.

3) Class Anthzoa
a) This class includes anemones and corals.
b) Anthzoa only live as polyps.

Today's objectives were: Complete 26.2 discussion, 26.2 Cnidarian Section Review, and TEST THURSDAY on 26.1 AND 26.2

The next blogger is Ashley

Thursday, April 20, 2006

Sponges

What are Sponges?

-Sponges are in the phylum Porifera which means pore-bearer.
-Sponges are asymmetrical aquatic animals that have a variety of shapes, sizes, and colors.
-Most sponges live in a marine environment
100 of 5000 live in fresh water
BODY PLAN
-Sponges are sessile invertebrates that have no true tissue or organs. A simple sponge is hollow cylinders.
-The body wall is made of two layers of cells seperated by jellylike substance called meshyl.
Choanocyes-is the inner layer that draws water.
Ostia(pores)-the penetrate the body wall. Water leaves through the osculum.
-The body is supported by a skeleton made of spongion spicules or both.
*Pore cell(ostio)-Bring water carrying food and oxygen into the sponge.
*Epithelial Cells-thin,flat cells control opening in pore cells.
*Colar cells(choanocytes)-Flagellated cells that line the inner surface of a sponge.
*Amoebocytes-locted between the two cell layers, carry nutrients and aid in reproduction.
*Spicules-form the hand support system of sponges.
FEEDING AND DIGESTION OF SPONGES
Sponges can reproduce asexually through:
producing buds or gemmules
regenrration of missing parts
Budding new sponges that break off and form new sponges
They reproduce sexualy through the joining off egg and sperm.
Most sponges are hermaphrodites, which can produce both egg and sperm.
The next blogger is Nicole.