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AAll are bacteria, except Plasmodium, a protozoan. A disease mainly of animals that also can be transmitted to humans (such as anthrax) is called a zoonosis (plural, zoonoses). Some infectious agents are able to survive in the environment, outside any host. This includes some species, referred to as opportunistic pathogens, which normally grow in soil or water or other environments but are capable of infecting a host that is compromised (weakened) by an injury, condition, or disease. The human...

Biological Effects Of Greenhouse Gases And Climate Change

Our industrial economy is almost entirely heterotrophic, relying on energy stored in coal and petroleum deposits. These were formed from atmospheric CO2 removed over the eons by primary production of ages past. The combustion of these resources is returning much of this to the atmosphere. The CO2 and other anthropogenic gas emissions have already resulted in more than 1 increase in the amount of energy from the sun being trapped at Earth's surface (Section 14.2.2). Now the question is What are...

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...

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...

Immunity and Vaccination

Immunity (the ability to resist infection based on mobilization of the immune system) to many diseases can result from a prior infection of the same agent. Getting the measles, for example, protects the host from being infected again later. Thus, a person can contract many diseases only once. Colds and influenza, on the other hand, stem from viruses that continue to produce new strains that avoid the body's predeveloped defenses, so that they may be contracted repeatedly. Prior exposure also...

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,...

Excretory System

Excretion is the elimination of waste products from the body. We excrete substances mostly in the urine or the feces, but also by sweat, milk, other body fluids, and even in our hair. Excretion is important from an environmental viewpoint for two reasons (1) It is a means by which the body eliminates toxic substances and (2) excretory organs may themselves be susceptible to the action of toxic substances, damaging their ability to maintain homeostasis. In this section we focus on urinary...

Nitrogen Cycle Reservoirs

Nitrogen Cycle Wastewater

Eventually, the oxygen concentration dropped from the normal 21 to a dangerous 14 , and the total volume of the atmosphere decreased. (Huge, flexible lungs connected to the system gradually collapsed to maintain atmospheric pressure within.) It was suspected that the oxygen was being lost to respiration, but mysteriously, the increase in CO2 from 330 ppmv to 4000 ppmv could not account for this. The high CO2 levels lowered the pH of the crew's blood, which decreased the ability...

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Figure 13.19 Nitrogen fixation pathway. strategies include producing a physical barrier, forming a protective complex with another protein, and or maintaining high rates of respiration to deplete oxygen near and within the cell. Thus, another advantage of being within a root nodule is the more restricted flux of oxygen. Klebsiella and some other free-living bacteria can also produce a thick slime layer. Being in the rhizosphere, where root exudates produce a higher concentration of respirable...

Hydrophytic Vegetation

Living things can often be used as environmental indicators, due to their function as integrators of environmental conditions. That is, they respond to conditions over a period time rather than just reflecting current conditions. That is why wetland vegetation is an important clue to identifying a wetland. Wetlands are not always wet, and wetland soil is not always readily identifiable as a hydric soil. Hydrophytic vegetation are macrophytic plants that grow in areas where soil saturation or...

Respiratory System

Lower Respiratory System Inferior Lobe

The respiratory system has the primary function of exchanging the gases O2 and CO2 between the blood and the atmosphere. Along with the integument and the digestive tract, it is a major area of contact between the body and the environment. In fact, it is the major area of exposure, in terms of the volume of environmental material contacted. Besides infectious illness, the respiratory system is susceptible to gaseous and particulate pollutants, ranging from irritants to carcinogens. The upper...

Synaptic Transmission

Synaptic Knobs

At the end of the axon, the neuron must transmit the signal to another neuron or to an effector. This is done through the synapse. Most synapses involve the use of a chemical, called a neurotransmitter, to communicate the signal across a gap from one cell to another. One of the most widespread neurotransmitters is acetylcholine ACh . This neurotransmitter is a target of many insecticides, in particular the organophosphorus and carbamate pesticides. The axon ends in a synaptic knob Figure 9.3 ,...

Aerobic Respiration

Bartha Biometer Flasks

A generalized overall reaction for aerobic respiration of organic material can be expressed as organic matter O2 CO2 H2O new biomass energy Analogous reactions can be developed for inorganic substrates such as ammonia and hydrogen sulfide, which are used by lithotrophic organisms. The rate of change of each of the six quantities in this equation in theory could be used to measure the rate of aerobic microbial activity. This is typically done by making repetitive measurements of disappearance or...

Counts Of Microorganism Numbers

Direct Counts Microorganisms

Counts of microorganisms may be made by direct microscopic techniques or through indirect methods such as culturing. Figure 11.9 Petroff-Hauser counting cell. Figure 11.9 Petroff-Hauser counting cell. In some samples, microorganisms can simply be counted under the microscope. Counting chambers specialized microscope slides with wells holding a fixed volume are available for this purpose. Some, such as the Petroff-Hauser cell Figure 11.9 , also have a grid marked on them. An example of a chamber...

Arthropods

Arthropods Crabs Respiratory System

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...

Genetic Engineering and Society

Along with the benefits of genetic engineering described above come numerous actual and potential dangers in its application. Experience with introduction of natural nonnative species into an ecosystem has shown the potential for disaster. Often introduced deliberately, they have often been found to occupy unexpected niches in the ecosystem, displacing other organisms. Many examples exist. The kudzu vine was introduced to the southern United States to control erosion, but proliferated beyond...

Cloning and Recombinant DNA

A clone is a genetically identical copy of a DNA molecule, a cell, or an organism. Clones of DNA are produced in order to obtain sufficient genetic material for applications, such as DNA analysis or for producing recombinant DNA. Recombinant DNA is DNA formed by joining segments of DNA from different organisms. Recall that recombination occurs naturally between chromosomes in the same cell during meiosis and results in segments of DNA from one chromosome being included in another. Recombinant...