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Day 1 - 2 |
Day 3 - 4 |
Lab 1 |
Lab 2 |
Reading Assignment
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Animal Identification Assignment.
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What is the major limiting factor that would keep snails out of a body of water in Texas? |
Members of these phyla have two things in common. They are the first animals we study that have a true body cavity, making them coelomates. They also have a similar embryonic development. The first stage of their larval development is a pear-shaped larva called a trochophore. 
Oklahoma representatives:
Class Gastropoda - snails 
Aquatic snails are by far the most common type in Texas. All have an open circulatory system, while some have gills and others lungs. Most of our snails have seperate sexes with internal fertilization.
Snails have a radula, 
a flexible tongue-like strip covered with chitinous teeth for scraping up algae and other food. They move by wavelike contractions of the muscular foot. The eyes of the snail are located at the end of movable tentacles on the head.
Freshwater snails can tolerate polluted conditions and water with little or no dissolved oxygen. For this reason, they can be found in almost any body of water in Texas. The only limiting factor is the amount of calcium in the water. Snails need the calcium to build their shell. The absence of snails is a good indication that there is little calcium in the water.
Class Gastropoda - slugs 
Slugs are much like snails without a shell. They are terrestrial in nature, but live in moist, shaded environments to protect their skin.
Slugs are most active at night, using their radula to feed on plant material.
The slimy skins of slugs is a water conserving adaptation. This slime layer not only protects the skin, but helps the slug absorb water from the air. It has been shown that even when protected from sunlight, slugs are not as active when the humidity is low. Compared to snails, slugs can survive a greater loss of body water - up to half of the body weight in some species. Slugs can also cool their body by evaporative cooling from their moist skin.
Snails and slugs have a gliding movement produced by their broad ventral foot. This foot has muscle fibers that run in several directions and exert force against the fluid in the circulatory system.
Class Bivalvia - freshwater mussels 
Internal organs of a bivalve. 
Mussels have rudimentary sense organs along the edge of the mantle that respond to light and touch. They have seperate sexes that reproduce by shedding sperm and egg into the water and fertilization occurs externally. The egg forms the trochophore larva that swims using its cilia and eventually settles to the bottom.
Freshwater mussels cannot survive in water with a low oxygen content. They are susceptible to pollution and cannot live in heavily silted water. The presence of mussels is a fair indication that the body of water is in good condition.
This assignment must be turned in by the end of class tomorrow to receive credit.
- Use this planning guide
Hint: use the research links at bottom of this page.
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Do earthworms have eyes? |
Oklahoma representatives:
Class Oligochaeta - earthworms 
Earthworms are free-living, burrowing animals with a body divided into segments. This segmentation is sometimes called metamerism. Each segment, except the first and last, has two pair of small bristles on the lower edges called setae. The setae provide traction as the muscles contract to push the worm through its burrows.
Earthworms are nonselective deposit feeders. This means they burrow by eating the mixture of organic and inorganic material in the soil. The digestible material is absorbed while the undigestible material passes through the digestive system unchanged. Other annelids are selective deposit feeders, ingesting only organic material.
Annelids are complex animals with a well developed nervous system and a closed circulatory system. Their main weakness is their method of respiration. Gases are exchanged through the moist skin. If the skin of an earthworm gets dry, they will quickly die. Because of this, earthworms must avoid sunlight. The epidermis of an earthworm has both chemoreceptors and photoreceptors to keep it aware of its environment. Chemoreceptors function as organs of smell and taste, allowing the earthworm to locate food and other worms. Photoreceptors function as eyes, making the worm aware of differences in bright light and dim. The photoreceptors of an earthworm are unable to form images.
Earthworms are directly related to the health of soils in Texas. The more earthworms found in a particular location, the richer and better the soil.
Class Hirudinea - leeches 
Leeches are blood sucking, segmented worms with no setae. The complex system of muscles allows for a variety of movements. Their photoreceptors form clusters that function as eyes allowing them to detect movement as well as light. They are found in warm, calm bodies of water. In Texas, leeches are small and do not commonly have an impact on humans.
Although a native of Europe, the information on this webpage about , the medicinal leech, can be generally applied to most leeches.
| In-class Assignment 064:
This assignment must be turned in by the end of class tomorrow to receive credit.
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Lab #1 
Lab #2 |
Research Links:
