Download Investigating Arthropods: The Body System of a Grasshopper

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Investigating Arthropods: The Body System of a Grasshopper
Insects have body systems similar to those of humans. Like people, insects have blood that moves in
a circulatory system. A brain and network of nerves control the insect body. Food is handled in the
digestive system. Oxygen enters the body through the respiratory system. Wastes are removed in the
excretory system.
Insects do not have internal skeletons like people. Their bodies are covered with a hard exoskeleton.
It protects the organs and supports the body.
In this lab, you will dissect a grasshopper and examine some of its body systems. The term dissect
does not mean “to cut.” It means “to expose to view.” As you dissect, do as little cutting as possible.
When using scissors, point the tips upward to avoid cutting the structures beneath. Before cutting, lift
the structure with forceps so you can see what you are doing.
Materials
safety goggles
lab coat or apron
gloves
preserved grasshopper
dissecting tray
scissors
probe
forceps
eyedropper
small beaker of water
Procedure
1. Put on safety goggles, a lab coat or apron, and gloves.
2. Place a preserved grasshopper in the dissecting tray.
3. Compare the external features of the grasshopper to the illustration. Identify the following parts:
head, thorax, abdomen, two pairs of wings, three pairs of legs, and one pair of antennae.
4. Examine the first segment of the abdomen. Look under the wing for the oval tympanium. This is
a membrane that acts like an eardrum. Also locate the spiracles on the sides of the abdomen.
Spiracles are tubes that take in air.
5. Use scissors to remove the wings and legs. Safety Alert: Take care when working with scissors.
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Investigating Arthropods: The Body System of a Grasshopper, continued
6. Use scissors to cut along the middle of each side. Cut from the head-end toward the abdomenend.
7. Carefully remove the top portion of the exoskeleton. Use the probe to separate the exoskeleton
from the muscles and organs beneath.
8. With the eyedropper, put a few drops of water on the muscles and organs. This will keep them
from drying out.
9. Look for a sac-like structure in the thorax. This is actually two organs. The head-end of the sac is
the crop, which stores food. The abdomen-end is the muscular gizzard, which grinds food.
10. In front of the crop is a short esophagus. Find the esophagus and follow it to the mouth. Gently
push the crop aside so you can look under it for the salivary glands.
11. The stomach is shaped like a sac and found behind the gizzard. Where the gizzard joins the
stomach, several finger-like gastric caeca extend in both directions. They help the body absorb
nutrients from food.
12. The intestine is a tube that extends from the stomach. Locate the intestine and follow it to the
rectum and anus.
13. Look at the place where the stomach and intestine meet. Thread-like structures in this area are
Malpighian tubules. They are the excretory organs of insects.
14. Small, white tubes in the abdomen are the trachea. They connect to the external spiracles.
15. A thin, thread-like blood vessel lies on top of the organs. This is the aorta. Follow the aorta to the
abdomen until you find areas where it bulges. These bulges in the aorta are the hearts.
16. Identify the reproductive organs in the grasshopper.
17.Use scissors to carefully remove the digestive tract. Examine the body cavity to find the nerve
cord. It runs along the lower surface of the body.
18. Follow the nerve cord to the brain. Several ganglia are located between the two compound eyes.
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Investigating Arthropods: The Body System of a Grasshopper, continued
Cleanup/Disposal
Follow your teacher’s instructions for cleanup and disposal of materials.
Analysis
1. What are the three main body segments of a grasshopper?
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2. Why is the external surface of a grasshopper hard?
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3. What kinds of sensory organs did you find on the grasshopper’s body?
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Conclusions
1. How are body systems in the grasshopper similar to those in humans?
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2. How are body systems in the grasshopper different from those in humans?
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Explore Further
Use a dissecting microscope to closely examine the structures of the grasshopper.
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