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AFW, freshwater S, saline B, benthic or attached P, planktonic. Source Horne and Goldman (1994). aFW, freshwater S, saline B, benthic or attached P, planktonic. Source Horne and Goldman (1994). TABLE 15.7 Characteristics of Some Common Insect Larvae Damselflies (Odonata) Dragonflies (Odonata) Water bugs (Hemiptera) Caddisfly (Trichoptera) Water beetles (Coleoptera) Order Diptera (and family) Mosquitoes Blackflies True midges (chironomids) Horseflies Slow and stagnant Slow and stagnant All...

Effects on Particular Organs or Organ Systems

The discussion in this section concerns effects in organs or organ systems of vertebrate animals. Within that group the emphasis is, of course, on humans. As mentioned above, particular toxins will tend to target particular organs or organ systems. The liver and the kidney are common targets of toxic activity because of their role in detoxification and their large blood flow. The skin and eyes, lungs, and digestive tract are vulnerable to the more reactive toxicants, as they are the sites of...

Testing for Carcinogenicity and Teratogenicity

Carcinogenic potential can be detected by three types of tests long-term carcinogenicity studies, rapid screening tests, and biomarkers. Long-term tests are the most definitive. These generally use mice or rats and last the lifetime of the animals (18 and 24 months, respectively). Two or three dose levels are usually used, the highest being the maximum tolerated dose'' (MTD). The MTD is estimated from 90-day studies and is chosen so as not to produce severe noncarcinogenic toxicological effects...

Eukaryotic Cell Structure And Function

Membranes, penetrated by numerous protein pores. (In prokaryotes, the DNA is not isolated from the cytoplasm by a membrane, and the structure is called a nuclear region rather than a nucleus.) Each of the DNA molecules in the nucleus is contained in a chromosome. A chromosome is a complex of a DNA molecule and associated proteins. Chromosomal DNA forms a template for protein synthesis. Protein synthesis takes place outside the nucleus in the cytoplasm. The nucleus synthesizes RNA molecules,...

Chordates Including the Vertebrates

Finally, we come to the phylum that includes ourselves. The chordates incorporated evolutionary innovations that made it possible for them to grow to great size, forming the largest animals on land (dinosaurs and elephants) and in the water (whales). The four unique characteristics of the phylum Chordata are 1. They have the presence of a notocord at some point in their development. The notocord is a flexible skeletal rod that runs the length of the organism. It remains in adult lampreys and...

Water And Wastewater Disinfection Treatment

One of the most significant public health advances over the past century was that of developing, and then routinely applying, suitable engineering methods for disinfecting potable waters that could retard, and ideally obviate, the transmission of waterborne disease. Rudimental disinfection measures based on water filtration used by the ancient Egyptians and heat treatment have long been practiced, but the advent of commercially available chlorine during the late nineteenth and early twentieth...

Arthropods

Arthropods jointed legs include the spiders, centipedes, millipedes, insects, and crustaceans. They represent an evolutionary advance that allowed them to form the greatest diversity and number of species of all the phyla, about 1 million species known. The advance was the development of a jointed exoskeleton made of chitin, a nitrogenous poly-saccharide, bound with protein. In crustaceans the exoskeleton also contains calcium salts for added strength. Other innovations with this phylum are...