36 Deuterostome Lab
Lab Objectives
- State the phyla of the organisms discussed in the lab activities
- Use the characteristics of symmetry, coelom, embryo tissue layers, and patterns of development to differentiate between the different organisms
- Describe the general characteristics of echinoderms
- Identify and locate external and internal structures of a starfish
- State the common characteristics of all chordates
- Identify the chordate characteristics on a model or picture
- Identify and locate external and internal structures of a frog
Download a PDF of the lab to print.
Echinoderms
Procedure
Access the page “Reading: Echinoderms.”
Questions
- Skip viewing the slide of the different developmental phases of the sea stars
- Dissect the starfish following the directions on the website. Remember the oral end (with mouth) is actually on the underside of the starfish.
- On the oral side make sure you find the mouth.
- Also on the oral side in the center region of each leg look for the tube feet. Tube feet are used for locomotion powered by the water vascular system. How many rows of tube feet does your starfish have?
- Try to differentiate between the spines and the skin gills. The spines are longer and are used for protection. The skin gills are smaller and used for gas exchange.
- Find the sieve plate/madreporite on the aboral side. This is the water entrance point for the water vascular system used for movement.
- The starfish has plates located underneath the skin for protection and support. What material comprises these plates?
- The starfish has a two-part stomach, the upper pyloric stomach and the lower cardiac stomach. Can you differentiate between the two stomachs on your specimen?
- In the starfish arms you should find both digestive glands and gonads. The digestive glands are brown and typically on top of the off-white gonads. Make sure you can identify both structures.
- The preserved echinoderm specimens will be on display but may differ from the ones directly mentioned in the lab handout. Please make observations on the available specimens and fill in the chart below.
Name of Specimen Physical Description
Chordates
Procedure
Access the page “Reading: Chordates.”
Questions
- There are two groups of invertebrate chordates, the cephalochordates and the urochordates. We don’t have any urochordate examples in the lab.
- View the lancelet slide. The lancelet is an example of a cephalochordate. It contains all four chordate characteristics. List the four chordate characteristics below.
- View the lancelet model. Make sure you can identify all four chordate characteristics on the model.
Dissection
Our vertebrate chordate example of today’s lab is the frog. Dissect a frog following the procedure below.
- External anatomy
- Place the frog in the dissection pan legs down.
- Identify the eyes, covered by a nictitating membrane, the external nares (nostrils), and the tympanum located behind each eye.
- What is the function of the tympanum?
- Examine the front and back limbs. How many phalanges are on the hindfeet? The forefeet? Which pair of limbs is the longest? How does this assist the frog in its movement?
- Mouth
- Turn the frog over and open the mouth as wide as you can. You can cut the hinges of the jaw if necessary. Identify the following structures:
- Two vomerine teeth located in the middle of the roof of the mouth
- Maxillary teeth (smaller) located on the sides of the upper jaw
- Tongue
- Pharynx (located behind the tongue)
- Esophagus, the opening leading to the stomach
- Glottis, slit where air passes through to enter the trachea, which leads to the lungs
- Eustachian tubes (2) openings that lead to the ears. They are located in the angle of the jaw.
- Turn the frog over and open the mouth as wide as you can. You can cut the hinges of the jaw if necessary. Identify the following structures:
- Body Dissection
- Place the frog belly-side up in the dissecting tray. You can pin down the limbs if necessary.
- Lift up the skin with forceps midway between the hind legs of the frog. Use scissors to cut the skin along the midline of the frog starting between the hind legs and ending at the neck. Be careful not to cut too deeply.
- Cut the skin horizontally above the hind legs and below the front legs creating skin flaps.
- Pick up a skin flap with forceps and use a scalpel to separate the skin from the muscle below.
- Pin the skin flaps to the dissection tray.
- Repeat the same procedure to cut through the muscles. Create one long incision along the midline of the frog from between the hind legs to the neck. Be careful not to cut too deeply and damage the internal organs. When you reach the area just below the front legs of the frog, turn your scissors sideways to cut through the chest bones and avoid damaging the heart and lungs. Then make horizontal incisions above the rear legs and between the front legs. Use forceps and a scalpel to separate the muscle from the tissue below. Then pin the muscle to the dissection tray.
- Internal Organs
- The most prominent organ is the liver, dark brown in color, and taking up most of the abdominal cavity
- Identify the lungs, two small pouches on opposite sides of the frog midline. They may be partially hidden by the liver.
- Lift up the liver and underneath locate the gallbladder.
- Identify the heart covered by the protective pericardium. Frogs have a three-chambered heart with two atria and one ventricle. Try to locate these different areas of the frog’s heart.
- How is it a disadvantage to have a 3 chambered heart?
- The stomach is a J-shaped organ located underneath the left lobe of the liver. It connects to the esophagus bringing food from the mouth and the small intestine used for nutrient absorption.
- The small intestine connects to the large intestine, which carries any undigested material to the cloaca. Frogs have one opening to the outside environment and the cloaca receives materials from the intestine, the urinary system, and the reproductive system.
- Find the pancreas, a yellow ribbon located between the stomach and the small intestine.
- Locate the spleen, shaped similarly to a pea and located near the stomach.
- You will be able to see the yellow, finger-like, fat bodies, which the frog uses to store fat.
- The kidneys of the frog are long and narrow and located along the back body wall.
- Try to find the mesonephric ducts, thin white tubes that carry urine from the kidney to the cloaca.
- If your frog is female, the abdominal cavity will be filled with black and white eggs. The eggs are stored in the ovaries.
- If you have a male frog, locate the testes. The testes are shaped like a bean and located at the top of the kidneys. They are yellow/tan in color.
- Do you have a male or female frog?
Review Questions
Answer the review questions below. The phyla we viewed today were the echinodermata and the chordata.
- Which phyla observed today were deuterostomes?
- Which phyla exhibited cephalization?
- Which phyla were coelomates?
- What does the name “echinodermata” mean?
- What type of symmetry does the echinoderm larva display?
- Give an example of an echinoderm example other than a starfish.
- What unique system does the starfish use for movement?
- Give an example of a chordate that is not a vertebrate.
- State the four common characteristics shared by all chordates.
- Name the two types of teeth found in frogs.
- Frogs have small lungs that are inefficient. What other structure do frogs use for gas exchange?
- Frogs have one opening to the outside environment, the cloaca. What three areas transfer material outside through the cloaca?
Licensing & Attributions
CC licensed content, Original
Biology 102 Labs. Authored by: Lynette Hauser. Provided by: Tidewater Community College. Located at: https://www.tcc.edu/. License: CC BY: Attribution