Biology-Mr. Willets
Lab- Simple Animals
I.Phylum Porifera contains the sponges, the simplest of all animal types. The name "porifera" means "full of holes". They are all aquatic, sessile (they live their lives attached to something) and have a hollow body where water circulates (food, however, is not digested here and so this hollow space is not called a gut). The skeletal structures of sponges vary. Some sponges are asymmetrical (irregular shape) others have radial symmetry: they have a definite top and bottom but no front or rear.
A) Rhabdodermella - This is a simple fresh water sponge. Get a specimen from the front desk and examine it using the stereoscopes. Then use scanning power on the compound scope.
There is a large opening at the top through which water leaves. You might have to look from the side to see this. This opening is called the excurrent pore ( pore=opening, current=water moves, ex= out).
Spicules are tiny pieces of mineral that serve as the skeleton for some sponges They are thin, clear and have three points. There are lots of spicules throughout the body of the sponge. They might be seen with scanning power.
The body of the sponge has many small openings through which water enters. These cannot be seen. These openings are called incurrent pores. Food particles come in with the water. This is called filter feeding (sponges filter the water for food) At the other end of the sponge is the long thin base which attaches to rocks etc. Since there is a top (where the excurrent pore is) and a bottom where the sponge attaches to rocks, this sponge has radial symmetry.
Make a diagram of the shape of this sponge. Label-excurrent pore, base attachment. See page 394.
B) A microscope will be set up on the side bench showing some sponge spicules more clearly. The cells of the sponge have been removed. Make a simple diagram showing the spicule shape.
C) Along the side bench are some sponge skeletons (these are just the skeletons- no cells). These sponges have a skeleton made of a network of elastic fibers made of spongin. Sponge skeletons like these can be sold and used as bath sponges. Notice that the shape is irregular- these sponges have asymmetry.
II.Phylum Cnidaria contains organisms that have tentacles with stinging cells, and a hollow cavity where food is digested (called the gut or gastrovascular cavity). Cnidarians come in two basic body forms: the polyp which is tube-like and the medusa which is somewhat umbrella-shaped. Some cnidarians alternate between these two forms (alternation of generations). Most polyp type cnidarians are sessile (attached). Most medusa type cnidarians are planktonic (floaters) with some ability to swim. All members of this phylum have radial symmetry. This phylum includes sea jellies (jellyfish), corals, Hydra among others. Sea jellies keep their shape because of the large amount of mesoglea (jelly) between their outer and inner cell layers. When they die, this is what remains and is often found on the beach.
A. Hydra- a fresh water cnidarian (note hydra can be a common name or a genus name) Hydra is a good example of the polyp body form.
1) Get a slide of hydra. Examine it using the stereoscope or scanning power (whichever is best). There are several structures easily seen:
a) tentacles surrounding the mouth which might be seen as a slit (you should position the slide so that the tentacles are on the top)
b) groups of stinging cells on the tentacles appear as bumps (these are seen better with low power)
c) basal disc at the end opposite the tentacles- this secretes a substance that attaches hydra to rocks etc.
Make a simple diagram of hydra- label: tentacles, mouth, stinging cells, basal disc. See page 396
2) Get a slide of hydra budding- examine it using the stereoscope. This slide shows a hydra with a bud growing from its side. Budding is a form of asexual reproduction. Make a simple diagram of this. Label the bud.
B. Obelia- a Colonial Cnidarian
1) Get a slide of the Obelia colony and examine using the stereoscope. Notice there are several polyps that are all connected. This makes it a colony of polyps. Some of these polyps have tentacles. These are feeding polyps. Other polyps do not have tentacles. These are reproductive polyps. Inside of the reproductive polyps are tiny buds that will eventually break off and leave. This is a form of asexual reproduction. When these buds leave the parent, they will grow into a different body shape called a medusa. When these medusa reproduce (sexually), their offspring will form a new colony of polyps. This is alternation of generations. Use the compound scopes to examine these polyps more closely. Look for the buds inside the reproductive polyps.
Make a diagram of the Obelia colony. Include at least 3 polyps. Label: feeding polyp, reproductive polyp, medusa buds (inside the reproductive polyps). The large chart at the back of the room can help with this.
2) Get a slide of Obelia medusa. Examine using the stereoscope and then the compound scope. These look like little sea jelly. These form from the buds growing inside the reproductive polyps you just examined. They leave the Obelia colony and reproduce sexually. Their offspring grow into new colonies of polyps like in the last slide you looked at. Make a simple diagram of the Obelia medusa.
C. Aurelia-
Aurelia is the common sea jelly seen in the North Atlantic. Get a specimen from the front of the room. Examine it with the naked eye and the stereoscope. This is obviously the medusa form. You will notice that it has very small tentacles around the edges which tells us that it does not capture large food. It tends to filter the water for bits and pieces. This means it is not harmful to us. The most obvious structures seen are the 4 semi-circular gonads (testes or ovaries)near the middle of the organism. These can be used to identify this organism as being Aurelia.
D. Corals-
Coral is a cnidarian in the polyp form. The most obvious difference between corals and other cnidarians is that the coral polyp forms a hard lime (calcium carbonate) skeleton around itself. (this skeleton is also called coral) In some forms, these can build up to form large reefs.
Examine some coral skeletons that are on the side bench. Look for the places where the polyps lived. Astrangia is the only kind of stony coral found in the North Atlantic. It does not form reefs.
Questions-
1) Sponges can have __________________ symmetry or they can be _______________________
2) An organism with radial symmetry has a ________________ and a ________________ but does not have a ________________ or ________________
3) Sponges are in which phylum? _____________________
What does this name mean? _________________________
4) Sponges have a hollow body but the space inside is not a gut- why not? _____________________
______________________________________
5) Water enters the space inside sponges through openings called ____________________________ and leaves through the large opening called the ___________________________________.
6) What comes in with the water? ___________________ This method is called _______________feeding.
7) The tiny pieces of mineral that make the skeleton of some sponges are called __________________
8) Some sponges have a skeleton made of a network of ____________ fibers. These fibers are made of
____________________. Of what value to us is this type of sponge skeleton? _________________
__________________________________________________________________________
9) Members of Phylum Cnidaria all have ____________________ with _____________ cells.
These organisms have a hollow body where food is digested. The two names for this space are _________
and ____________________________ cavity.
10) Cnidarians can have two body forms: a) the _______________ which is tube-like. This form tends to live attached to things. What word describes this life style? ____________________
b) the __________________ which is umbrella like. This form tends to ______________ in the water. What word describes this._______________________ All members of this phylum have what kind of symmetry? ______________________
11)What body form does Hydra have? ___________
12) Obelia is a __________________ of polyps all attached to each other. What feature do the feeding polyps have? _____________________________ The reproductive polyps have ___________
growing inside. When these buds leave, what body type will they have? ________________ When these then reproduce, their offspring will grow into a new colony of ________________ This life cycle can be called __________________________ of __________________________
13) What body form do sea jellies have? ___________
14) What is the name for the common sea jelly seen in the North Atlantic? __________________
You can easily identify this organism by the shape of its ______________ (which are either _____________ or ______________)
15) Corals have which body form? (polyp or medusa) __________________ Corals are different from other cnidarians because they form a _________________ made of _____________________