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Dissection and the Lab Practical

From a student's point-of-view...

Our class was fortunate to dissect a crayfish, earthworm, grasshopper, starfish, and squid. During the crayfish dissection, we first observed many of the external parts of the anatomy. We removed and mounted parts such as the eyes, antennae, walking legs, swimmerets, uropod, and telson. We then observed the internal anatomy by cutting down the top of the crayfish. We removed and observed the gills, which were feathery and attached to the legs.

Our next dissection was one of the earthworm. We looked at the mouth, anus, and clitelium of the earthworm. Inside the earthworm we observed the intestine that ran throughout the body. The grasshopper dissection was only an external investigation. We looked at its hindwings and forewings, tympanic membrane, and ovipositor, which presence determines the grasshopper's sex as female.

The fourth dissection our class participated in was one of a starfish. We first identified the mouth and ambulacral grooves that extended from each ray. We also closely observed the numerous tube feet that are necessary for locomotion and the absorption of oxygen. We then looked at the internal anatomy of the starfish.

The fifth and final dissection of the invertebrate unit was of a squid. We first observed the soft shell, or mantle, that enclosed most of the body. We also looked at the ten tentacles at the mollusk foot. We then opened the mantle and observed the gills. We identified the siphon, which serves as an opening for water to be expelled from the body and act a jet propulsion. We opened the head and beak to observe the toungelike radula that held many sharp points for chewing. We also observed the large eyes.

After completing the dissections was had a test, or lab practical. In this, Mrs. Mazen set up booths, each containing an invertebrate we had dissected. These invertebrates were already cut open and colored pins were stuck in different places. It was our job to identify the body parts the pins were in.

Below are images from the lab practical. It was an interesting way to be tested!

The lab practical is harder than we thought!
One student has to identify all of the parts of a squid for the lab practical.

It's exposed!
In this open crayfish, the blue pin is placed in the heart. The red pin is in the abdominal muscle, and the yellow pin is in the uropod.

Another view of the squid.
An extrenal identification of a squid. The yellow pin is placed on the beak and the brown is on a tentacle.

There's no way to look over another student's shoulder.
Behind the divider, Mrs. Mazen explains a question about the pin locations to a student.

The starfish is next.
An open starfish exposes its digestive glands and gonads. The digestive glands are olive green.

Now, the earthworm.
The internal anatomy of an earthworm is more complicated than you might think. The red pin points to its anus. Also exposed are the aortic arches, mouth, crop, gizzard, and intestine.

Yes, you can use a microscope.
A student observes a body part under a dissecting microscope for a better look.

Don't forget the other side!
The underside of a starfish reveals the tube feet and the stomach.

No peeking!
The booths provide privacy for two students. One observes a squid, the other a crayfish.

When all else fails, check the Web!
Access to the Web from the lab offers the chance to publish pages like this one!

For more description of the dissections and the lab practical, check the BioPoint Scrapbook.

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