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Water Flea

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What are some effects of the drugs found in household products? Instead of using people, you'll use a water flea to study the effects of some common drugs. Your challenge is to add different drugs and dosages to water fleas to find the effects the drugs have on the heart rate of a water flea. You'll study body mass, gender, and drug effects. Sorry, but I've got to go. All this talk of fleas is making me itch...I wonder what kind of drugs are in the itch cream?

Planning and Carrying Out Investigations

Water Flea Brochure

Water Flea Brochure

What are drugs?

Any substance that causes a physical or mental change in humans or other organisms can be classified as a drug. People around the world have used drugs since the beginning of recorded history. The Incas of South America chewed on coca leaves to produce feelings of well-being. The ancient Chinese used drugs to soothe pain, produce sleep, change emotions, and cure diseases.

What are stimulants and depressants?

Stimulants and depressants are two common classes of drugs found in many household products. Stimulants excite the central nervous system, causing an increase in body activity. Stimulants work by speeding up the body's metabolism, increasing blood pressure, heart rate, and respiratory rates. They cause pupils to dilate, reduce appetite, and produce a feeling of alertness and confidence. Examples of stimulants include caffeine, diet pills, nicotine, cocaine, and amphetamines. Depressants slow down the central nervous system and decreases body activity. They have the opposite effect on the human body as stimulants. They decrease awareness and relieve tension and inhibitions. Depressants include alcohol, sleeping pills, tranquilizers, barbiturates, and PCP (phencyclidine hydrochloride).

What is a dosage effect?

Drugs do not necessarily have an all-or-none effect. Degrees of effectiveness are recognized, and some substances are more effective (and dangerous) than others. The dosage is the amount of a drug that may be taken safely and still have the desired effects of the drug. Dosage depends on a number of factors, including the type of drug, the health, age, gender and mass of the individual taking the drug, the way the drug is administered, and any other drugs the individual is also taking. Children usually require a smaller dosage of a given drug than adults due to their smaller masses.

What is a lethal dosage?

Anyone who uses drugs must be aware of the possibility of overdosing on the drug. That's why you should always carefully read and follow all of the directions for using both prescribed and over-the-counter drugs. Scientists have created a value that describes the toxicity of a drug called the lethal dose 50 (LD50). The LD50 value states the amount of a solid or liquid material that it takes to kill 50% of test animals in one dose. Most people don't think of something like table salt as being toxic, yet the LD50 of table salt is about 200 grams for a normal-sized adult. Nicotine's LD50 is only 60 milligrams per kilogram of body mass if administered orally, so that's why people who smoke should not carelessly leave cigarettes around the house. Toddlers like to put just about anything in their mouths, including cigarettes. Ingesting just two cigarettes could make most toddlers very ill and lead to death.

What are some drug interaction effects?

In practice, 50 percent of adult overdoses and 90 percent of narcotic overdoses involve mixtures of drugs, and often the substances ingested are not known. The LD50 test does not account for drug interactions and is therefore of little use in such cases. Taking two or more drugs together can have dramatic effects on a person. In fact, even foods and herbs can alter the intended effects of drugs. Three major interaction effects can occur when two or more drugs are taken at the same time: additive, antagonistic, and synergistic effects. Additive effects happen when the impact of one drug is added to the impact of another drug. For instance, if alcohol is taken with marijuana, the individual effect of the marijuana is doubled. You can think of an additive effect as adding one drug and another drug and getting an effect twice as large as either drug taken by itself. Antagonistic effects occur when one drug cancels the effects of another drug. Most antibiotics lose their effectiveness if consumed with alcohol. The alcohol cancels the effect of the antibiotic. You can think of an antagonistic effect as adding one drug and another drug and getting little or no effect from the desired drug taken by itself. Synergistic effects take place when one drug multiplies the impact of another drug. In this case the effects of the two drugs are not just doubled; they might be tripled or even increased seven times as much. For example, many overdoses and deaths befall people when they take sleeping pills with alcohol. The alcohol magnifies the sleeping pill's effects many times, often leading to emergency room visits and even death.

What is the difference between toxic and poisonous substances?

A poison is any substance that causes damage to a living organism. The poison may enter the organism a number of ways: by ingesting, inhaling, or by injecting or absorbing through the skin. Some living organisms produce poisons called toxins. The toxins usually consist of an amino acid chain. A variety of organisms, including bacteria, fungi, algae and plants, make toxins. Many toxins are very poisonous; in fact, living organisms make the most dangerous substances known to humans. Bacteria found in improperly canned foods can cause severe food poisoning, a condition that is extremely fatal. A single teaspoon filled with the Botulinum Toxin A would be a lethal dose for over 2,400,000,000 people!

What are some ways that changes may be measured in an organism?

Physiology is the study of how organisms carry on their life processes. This branch of science focuses on how the different parts of an organism perform their specific function. A few of an organism's life processes include motion, heart rate, and respiration. Can you think of some different ways to measure the heart rate of an organism? How about by listening to the sound of the heart? By viewing the heart directly? By feeling the blood flow through the organism at another part of the circulatory system? All of these methods work in different situations. For instance, aren't you glad that the doctor doesn't determine your heart rate by opening your chest and watching your heart? Instead, most doctors listen for the sounds your heart makes. They also might feel your pulse to determine how well your heart is working.

What are water fleas?

Water fleas are small (0.2-6 mm) aquatic Crustaceans that inhabit quiet fresh waters. They make up most of the freshwater zooplankton. Most water fleas are filter feeders that eat phytoplankton. They have enlarged second antennae that provide their means of locomotion by acting like an oar. The body is divided into a head, thorax, and an abdomen. The thorax and abdomen are enclosed in a rigid outer covering that is usually transparent, so the inside anatomy of the water flea can be easily viewed without having to dissect the creature. The oval heart can be seen on the dorsal side of the thorax. If your specimen is alive, you can easily see it beating. You can count the number of beats and perform simple physiological experiments. Contractions of the heart force blood towards the head and other parts of the body. The water flea's intestines look like the letter "C." The intestines run almost the entire length of the water flea, from its mouth all the way to the very end of the body. Green or brown phytoplankton, the water flea's recent meals, can usually be seen in the intestine.
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