Site hosted by Angelfire.com: Build your free website today!
Angelfire Free Home Pages Free E-mail Browse WhoWhere? People Finder

1. Outline the classification and include living examples at all levels of classification.

Bacteria is the most common name given to most organisms in the kingdom monera. All monerans are prokaryotic - they are characterized by the absence of a nucleus and membrane-bound organelles. They are also microscopic. For example, the smallest cell known to exist are monerans called mycoplasmas, which measure 0.20 to 0.25 m in diameter. The average moneran is about 1 m long; some however may be as long as 500m.

The kingdom monera is subdivided into four phyla; Archaebacteria, Schizophyta, Cyanophyta, and Prochlorophyta. These organisms differ in both morphology an physiology.

Monerans are usually spherical, rod shaped, or spiral. Spherical monerans are called cocci; rod-shaped monerans, bacilli; and spiral monerans, spirilli.

Some monerans cluster together; others form chains or filaments. The prefix Staphylo- is used to describe cells that form clusters. Therefore a cluster of spherical moneran cells is called a staphylococcus. The prefix strepto- is used to describe cells that form filaments. Therefore a filament of rod-shaped moneran cells is called a streptobacillus.

Members of the Phylum Archaebacteria are adapted to the harsh environments in which they live. Although Archaebacteria are similar in many ways to other monerans, they also have unique characteristics that have led scientists to place them in their own phylum. For example, the transfer RNA's and cell walls of Archaebacteria differ from those of other bacteria. Archaebacteria include methanogens, extreme halophiles, and thermoacidophiles.

The methanogens live only in the absence of free oxygen. These anaerobic monerans are called methanogens because they use carbon dioxide and hydrogen to form methane and water. Methanogens live in the digestive track of sheep and cattle and at bottoms of bogs, lakes and sewage treatment ponds.

The extreme halophiles live only in areas of high salt concentration, such as the Great Salt Lake and the Dead Sea. The thermoacidophiles live only in places that are very acidic and where temperatures are very hot, often reaching 90 degrees Celsius. For example, members of the genus Sulfolobus live in acidic hot springs where the temperature averages 80 degrees Celsius and the pH level is less then 2. Nevertheless, these monerans maintain an internal pH that is nearly neutral. Members of the genus Thermoplasma are found in smoldering coal tailings where the temperatures are often higher then 90 degrees Celsius.

Some other kinds of Archaebacteria live around volcanic vents that are found miles below the oceans surface. These monerans use the sulfur gases that bubble from the vents as their energy source. Scientists think that the environments in which present day Archaebacteria live may be similar to those that existed during the formative stages of life on earth.

The largest moneran phylum is Schizophyta, all the members which are commonly referred to as bacteria. Schyzophyta is divided into four classes:

Class Eubacteria contains the largest number of and many of the most familiar bacteria

Class Actinomycota contains rod-shaped organisms that form branched filaments

Class Rickettsiae contains mostly nonmotile intracellular parasites

Class Spirochaeta contains large spiral shaped organisms

Most members of the class Eubacteria are free-living soil and water bacteria. Eubacteria tend to live in less harsh environments then Archaebacteria. Eubacteria are further classified by their reaction to a Gram stain. A gram stain is a test that uses a series of dyes to stain bacterial walls. Gram-negative bacteria have an outer covering of lipopolysaccharides and stain pink. Gram-positive bacteria lack this covering and stain purple. Gram-positive Eubacteria are susceptible to antibiotics. Gram-negative Eubacteria are difficult to treat with antibiotics. Mycoplasmas, the smallest monerans are Eubacteria.

Members of the class Actinomycota, called actinomycotes, are Gram-positive bacteria that form colonies of branching, multicellular filaments. Some actinomycotes decompose dead plants and animals; some cause diseases; such as diphtheria and tuberculosis. Others, especially members of the species Streptomyces, are the source of many antibiotics.

Members of the class Rickettsiae, called Rickettsiae, are parasitic Gram-negative bacteria that can reproduce only in certain cells of a specific host. Insects often carry these bacteria and transmit them to mammals. Typhus , for example, is a Rickettsial disease transmitted by lice.

Members of the Class Spirochaeta , called Spirochetes, are spiral-shaped or curved bacteria. Most Spirochetes use flagella to move. One specie of spirochete causes the sexually transmitted disease syphilis. Another cause Lyme disease, an ailment with symptoms similar to those of arthritis that is transmitted by ticks.

Members of the phylum Cyanophyta are called blue-green bacteria. These bacteria have some traits that are similar to those of plants and plantlike protists. Blue-green bacteria are photosynthetic. They also capture solar energy with chlorophyll A, one of the pigments found in plants, use water during photosynthesis, and produce oxygen.

Most scientists now classify cyanophytes as monerans because, like other prokaryotes, they lack membrane-bound nuclei. In addition, their cell walls are chemically similar to those of other prokaryotes. Unlike other prokaryotes, however, blue-green bacteria are usually encased in jelly like substance and often clump together in colonies. For example, Anabaena is a single filament, while Nostoc is a cluster of cells.

Some blue-green bacteria are also distinguished from other prokaryotes by having specialized cells and therefore a division of labor within the colony. The members of some genera produce cells called heterocysts when their nitrogen supplies are depleted. Heterocysts are specialized cells that convert nitrogen from the atmosphere into a form that the organism can use in cellular metabolism.

A rapid increase in the population of blue-green bacteria which may discolor a lake, river or ocean is called a bloom. Since blue-green bacteria thrive on the phosphates and nitrates found in savage these population explosions often occur in polluted water.

Members of the phylum Prochlorophyta are photosynthetic bacteria that live symbiotically with marine vertebrates known as tunicates. Members of the genus Prochloron contain photosynthetic pigments unlike those in blue-green bacteria but similar to the chloroplasts of eukaryotes.

2. Discuss the phylogeny and evolutionary status.

Fossil monerans have been found in Australian deposits more than 3.5 billions years old. Monerans have evolved into many forms and now live in nearly every environment, many of which cannot support other living things.

The classification of monerans into an evolutionary hierarchy is not easy. Many of them look alike; it can be difficult to separate them into species based solely on structure. However, by relying on physiology in addition to morphology, scientists have determined a probable phylogenetic classification of monerans.

Not much is known about the evolution of monera, the oldest fossils found are of Archaebacteria.

3. Describe the main characteristics displayed by the phyla. Show examples of how these characteristics are found among all the members of the phyla.

The structures and physiology of monerans are diverse. These variations reflect the numerous habitats to which monerans are adapted.

Monerans are prokaryotic; their DNA is located in the cytoplasm. The DNA is arranged in a single, circular chromosome. In addition, monerans do not have membrane-bound organelles. Some monerans have plasmids, smaller circular strands of DNA that are capable of replicating independently. All monerans except the mycoplasmas have walls that differ structurally and chemically from those of eukaryotes. Some monerans have rigid cell walls; others have flexible ones.

Many monerans can produce capsules, protective layers of polysaccharides around their cell walls. Under natural conditions many prokaryotes also produce a net of polysaccharides called the glycocalyx that helps them stick to the surface of rocks, teeth and host cells. Some monerans attach themselves to objects with protein strands called pili. Under adverse conditions, many monerans encase their DNA and some of their cytoplasm in a tough envelope. This structure, called an endospore, can lie dormant for years. When favorable conditions return, the endospore coating breaks and the cell becomes active. Anthrax, an often fetal disease of sheep and cattle, can survive in endospore form for 60 years.

Monerans have different ways of moving. Many move by rotating stiff flagella that are bent into S-curves. When the flagella are rotated in one direction, the monerans move in a straight line; when rotated in the opposite direction they tumble. Spirochetes use filaments that wrap around the cell to move.

Monerans may be heterothrophic or autotrophic. Most monerans are heterotrophs - that is, they use food produced by other organisms. A Heterotroph that feeds on dead or decayed organic matter is called a saprophyte. By decomposing matter, saprophytic bacteria release carbon and other elements for use by other organisms. Saprophytes are therefore essential to the recycling of nutrients in every ecosystem.

Monerans that produce their own food from inorganic material are autotrophs. Those that use sunlight as a source of energy are called photoautotrophs. Photoautotrophs have different chlorophyll's that enable them to absorb light of various wavelengths. Some have the same pigments found in plants, others have unique pigments that absorb longer wavelengths.

Some autotrophic monerans, called chemoautotrophs, use the energy of chemical reactions instead of sunlight to synthesize food. Some chemoautotrophs can also fix nitrogen. Nitrogen fixation is the process by which gaseous nitrogen (N2) is converted into ammonia compounds. Plants need nitrogen to synthesize proteins, but they cannot use gaseous nitrogen. They can, however, use the nitrogen in NH4OH. Because most of the nitrogen on earth is gaseous and because only monerans can convert gaseous nitrogen into forms that plants can use, plants - and therefore most life forms - depend on these nitrogen fixing monerans.

Many monerans are obligate anaerobes, that is, they cannot survive in the presence of oxygen. Among these are the methanogens. Facultative anaerobes can live with or without oxygen. Escherichia coli, which is common in the human digestive tract, is a facultative anaerobe. Monerans that cannot survive without oxygen are called obligate aerobes. The obligate aerobe that cause tuberculosis, Mycobacterium tuberculosis, lives in the lungs.

Any organism that causes a disease is called a pathogen. Disease that are caused by pathogenic bacteria are bubonic plague, leprosy, tuberculosis and typhus. Most pathogenic bacteria enter the human body throughout the respiratory or gastrointestinal tract.

In most cases bacterial diseases are caused by the toxins that are produced by bacteria. A toxin is a poisonous substance that disrupts the metabolism of the infected organism. Bacteria produce two types of toxins, endotoxins and exotoxins. Endotoxins are found in the cell walls of most Gram-negative bacteria. Endotoxins all cause the same symptoms: fewer, weakness, and damage to the circulatory system. Typhoid fewer is one example of a disease that is caused by endotoxins. Exotoxins which are products of the metabolism of some bacteria, are secreted into the area surrounding the bacteria. Exotoxins are the most potent poisons known. One nanogram of the tetanus exotoxin, for example is sufficient to kill a guinea pig. Exotoxins cause diseases such as diphtheria and botulism.

4. Explain in detail the reproductive patterns found in the phyla. How do these patterns increase the ability of organism to survive natural selection.

Some monerans reproduce rapidly. Under optimal conditions, E. Coli cells for example can divide every 15 minutes. In one week a moneran can produce millions of cells. Heat, cold, predation, and lack of food inhibit the rate of reproduction.

Monerans usually reproduce by splitting in two, an asexual process called binary fission. First the DNA in the cell replicates. Then the plasma membrane and the cell wall grow inward, forming two daughter cells with identical genetic material.

Occasionally the genetic materials of two monerans of the same species are recombined in a process called conjugation. A portion of the DNA of one moneran passes across a bridge, formed by the pili, into another moneran. This piece of DNA then lines up with the homologous piece of DNA in the recipient cell. The homologous portion is destroyed and the new DNA is substituted. This exchange of genetic information increases genetic variability.

5. Describe the relationship of these phyla with humans both positive and negative. Do they effect your survival.

Positive

Decay - causes recycling of garbage, wood and dead bodies

Decay is a factor which contributes to the nitrogen cycle which gives necessary nutrients to certain plants

Soil bacteria contribute to the nitrogen cycle

Blue-green bacteria - when it photosynthesizes it creates oxygen and nutrients

symbiosis of bacteria in cattle in the digestive track to help digest nutrients

In termites live protozoa's which have bacteria that help digest wood, that is why termites can digest food

Bacteria are used in dairy industry

Bacteria change alcohol to vinegar

Bacteria make beer and wine

Bacteria are used in mining to separate minerals

Bacteria are used in savage treatment plans

Bacteria can clean chemical wastes in water and certain types are designed to clean oil from water

Bacteria are used for research and genetic engineering

Bacteria live in our intestines and help us digest food

Negative

Bacteria cause bad breath and body odor

certain types of bacteria are anti-fungal, kill fungi

Bacteria are genetically engineered for biological warfare

Bacteria cause numerous diseases in all organisms

Without bacteria the world we know today would not exist, life would probably exist but at much simpler level. Bacteria are crucial for our survival.

6. Explain something you found interesting about these organisms.

The interesting thing about bacteria is their production of toxins

In most cases bacterial diseases are caused by the toxins that are produced by bacteria. A toxin is a poisonous substance that disrupts the metabolism of the infected organism. Bacteria produce two types of toxins, endotoxins and exotoxins. Endotoxins are found in the cell walls of most Gram-negative bacteria. Endotoxins all cause the same symptoms: fewer, weakness, and damage to the circulatory system. Typhoid fewer is one example of a disease that is caused by endotoxins. Exotoxins which are products of the metabolism of some bacteria, are secreted into the area surrounding the bacteria. Exotoxins are the most potent poisons known. One nanogram of the tetanus exotoxin, for example is sufficient to kill a guinea pig. Exotoxins cause diseases such as diphtheria and botulism.

7. Make a list for each phyla you observe in class.

Clostridium tetani

Disease caused by - tetanus

transmission - endospores enter wound

symptoms - neurotoxins are produced that cause muscle spasms; death results from spasms of respiratory muscles

Clostridium perfringens

disease caused by - gas, gangrene

transmission - endospores enter wound

symptoms - gases are produced that cause soft issues to swell and die

Rickettsia rickettsii

disease caused by - rocky mountain spotted fewer

transmission - carried by ticks

symptoms - chills, fewer, pain in legs and joints

Rickettsia typhi

disease caused by - endemic murine typhus

transmission - carried by rodents and fleas

symptoms - rashes, prolonged high fewer

Salmonella sp.

disease caused by - food poisoning

transmission - contaminated or inadequately cooked food

symptoms - nausea, abdominal cramps, diarrhea

Yersinia pestis

disease - bubonic plague

transmission caused by - carried by fleas on rodents

symptoms - enlarged lymph nodes, hemorrhaging, fewer, possibly death

Streptococcus sp.

disease caused by - strep throat

transmission - airborne

symptoms - fever, exhaustion, sore throat, enlarged lymph nodes

Mycobacterium tuberculosis

disease caused by - tuberculosis

transmission - airborne

symptoms - in active disease, coughing, weight loss, possibly death

Corynebacterium diphtheriae

disease caused by - diphtheria

transmission - airborne

symptoms - fever, sore throat, swelling of neck, possibly death