Biology- Mr. Willets
Porifera / Cnidaria
The two simplest types of animals are the members of Phylum Porifera and Phylum Cnidaria. The word porifera means "full of holes." This group is the sponges. Cnidarians include sea jelly, coral and other related organisms.
Sponges are barely multicellular. They all live in water (aquatic), mostly the ocean (marine). They live their lives attached to objects (rocks etc.) This type of lifestyle is called sessile. They generally have an irregular shape (they are asymmetrical). They have cells that create water currents to bring water with food into a hollow space within the body. From there the food is taken into cells and digested. This is called filter feeding. Since the food is digested inside the cells (intra-cellular digestion) and not in the hollow space, that space is not considered to be a gut (a gut is a space in an animal where food is digested).
The body of a sponge has many small openings that water goes through bringing in food and oxygen. These are called incurrent pores (the meaning of incurrent should be obvious). There are also larger openings through which the water leaves. These are called excurrent pores.
Sponges have some kind of skeleton to help support the body. In some sponges, the skeleton is made of many interconnected small pieces of glass. Other sponges have skeletons made of small pieces of calcium carbonate. In either case, these small hard pieces are called spicules. A third kind of skeleton is made of a network of elastic fibers. These fibers are called spongin. Spongin skeletons are used as bath sponges and we have copied their design to make our artificial plastic versions.
Sponges reproduce sexually (sperm and egg) or asexually (budding). Fresh water sponges produce a bud with a protective coat to survive freezing and/or drying out. These special buds are called gemmules.
If a large sponge is cut into several pieces, each piece will grow to full size. This is called regeneration. Sponge divers would purposely do this to some of the sponges they removed and throw the pieces back into the ocean to make sure there would always be sponges to harvest and sell.
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The cnidarians have two interesting features- tentacles that have stinging cells. Cnidarians are aquatic (mostly marine) and have radial symmetry. This means their bodies have a top and a bottom but no front or rear. The tentacles are used to capture and sting their food although some use their tentacles to filter feed.
Cnidarians have two type of bodies. The polyp form is long and thin with the tentacles on the top. The bottom attaches to rocks etc. This form is sessile. The medusa form is umbrella shaped. It floats in the water with the tentacles hanging down. Its lifestyle is planktonic. Sea Jellies (jellyfish) have this type of body.
Some members of this phylum alternate between the two forms (alternation of generations). Both forms have a space inside the body where food is digested (a gut)but there is only one opening (mouth) to it. Food enters and wastes leave through the mouth. This gut also servesto circulate the digested food so it is officially a gastrovascular cavity.
Members of this phylum include the common North Atlantic sea jelly named Aurelia. This is the sea jelly you are most likely to see around here. The Portuguese Man of War is more common south of here but occasionally drifts this far north. It is not officially a sea jelly but rather a floating colony of polyps and medusas. These have very long tentacles (15 feet or more) and very large nasty stinging cells.
Corals have the polyp form but have a hard outer skeleton around it. Some corals attach their skeletons to others and build large masses of coral. This is called a coral reef. Corals that do this live in warm shallow water because they contain symbiotic algae (which need the light).
Coral reefs can protect harbors from waves and can also damage boats that run into them. A coral reef may be pushed above the surface of the water to become a coral island. Bermuda is such an island.
A ring of coral islands is called an atoll. Atolls are often found in the middle of the Pacific Ocean. The water is shallow in some places because of undersea volcanos. The coral grows along the rim of the volcano. Atolls were used in the 50's and 60's as places to test nuclear weapons. Bikini Atoll was such a place.
A fresh water cnidarian is Hydra. It has the polyp form and will be seen in lab.
Questions-
1) What organisms are in Phylum Porifera? _____________________
2) The two types of openings in sponges are the _______________________________ and the _____________________________
3) The method of getting food that sponges use is called ____________________________
4) Tiny skeletal pieces in sponges are called ___________________ What two materials might these be made of? _________________ or ____________________________ The type of sponge skeleton that we use a bath sponges is made of elastic _________________ called ___________________.
5) What do sponge divers do to make sure the area does not run out of sponges? _____________________
_____________________________________________________________________________
This ability that sponges have is called _____________________________
6) Sponges are sessile. What does that mean? ____________________________________________
7) Most sponges are asymmetrical. What does that mean?____________________________________
8) Why is the hollow space in a sponge body not a gut? ______________________________________
____________________________________________________________________________
9) Where in a sponge is the food digested? _____________________________ This is called
______________________________ digestion.
10) Why do fresh water sponges form gemmules but not marine sponges? _________________________
___________________________________________________________________________
11) All members of Phylum Cnidaria have _____________________ with _________________cells.
12) Cnidarians have ________________ symmetry. Cnidarians can have two body forms:
a) the ______________ form and b) the ________________ form. Which is sessile? ____________ The other is ______________________ A sea jelly has which form? _____________________
13) Some cnidarians use both forms. This life cycle is called ________________________ of
____________________________.
14) The gut of cnidarians serves two purposes. It is the place where food is _____________________ and it ___________________________ the digested food. This type of gut that does these two jobs is called a ______________________________________(abbreviated GVC)
15) The gut of cnidarians has only one _______________ called the _______________. What two things happen here? _____________________________________________________
16) The Portuguese Man of War is not a sea jelly but rather a floating ____________________ of
_________________ and ___________________
17) The most common sea jelly around here is __________________
18) Coral is a cnidarian with the polyp form that builds a ______________________ around itself.
19) If many coral build their skeletons together, this can form a _______________________
These type of coral live in ______________________ water and contain a symbiotic _____________
20) What vacation island is a coral island? ____________________
21) A ring of coral islands is called an ____________________ The coral grows on the rim of an undersea _______________________.