New Zeland

 New Zealand (Aotearoa^P in Maori^P)^N is a temperate country located in the southwest Pacific.  It is composed of two main islands and a number of smaller islands, some of which are quite distant.  The South Island is the largest landmass and is divided along its length by the Southern Alps, the highest peak of which is Mount Cook, at 3 754m.  There are eighteen peaks of more than three kilometres in the South Island.  The North Island is less mountainous than the South but is marked by volcanism.  The tallest North Island mountain, Ruapehu^P (2 797m) is an active cone volcano.  The total land area of New Zealand, 270 500km² is somewhat smaller than that of Japan or the British Isles, and slightly larger than that of Colorado in the U.S.A.  The country extends more than 1 600km along its main, north-northeast axis.  The climate throughout the country is mild, rarely falling below 0°C or rising above 30°C.  The daily average temperature in Wellington, the centrally located capital, is 5.9°C in midwinter and 20.3°C in midsummer.

Because of its relative isolation, New Zealand developed a unique ecosystem, the most distinctive feature of which was the absence, until Polynesian colonisation, of any land mammals except three species of New Zealand bat.  Many of the niches that would normally have been occupied by mammals were occupied by birds, including the flightless kiwi and the moa.^P  Moas, now extinct, could grow to a height of up to 3m.  The kiwi and the fern fronds characteristic of New Zealand's native forests serve as national symbols.  New Zealand is also home to the tuatara,^P an ancient form of reptile, and the weta, ^P an insect that can grow to 8cm or more in length.

New Zealand is an independent parliamentary democracy governed by a Parliament of one hundred and twenty members, from which an executive Cabinet of twenty members is selected.  This Cabinet is led by the Prime Minister, currently (May 2001) Helen Clark of the centre-left Labour Party.  Five other parties are also represented, at the time of writing, in the New Zealand Parliament.  New Zealand's head of state is Queen Elizabeth II, who is represented by the Governor-General, The Honourable Dame Silvia Cartwright.

New Zealand is one of the most recently settled major landmasses.  Polynesian settlers arrived, probably sometime between 500 and 1300 A.D., and established the indigenous Maori culture.  The first European explorers to reach New Zealand were Abel Tasman, who arrived from the Netherlands in 1642, and James Cook, an English explorer, whose extensive surveys, which started in 1769, led to significant European colonisation from the 1790s on.  As of the 1996 census, New Zealand's total population was approximately 3.7 million people.  Although the majority of the New Zealand population is now of European origin, Maori and Pacific Islanders are the second and third largest ethnic groups, and Maori culture is a significant feature of New Zealand's public life.  It is perhaps due to the mild climate and low population that outdoor recreation is very popular with New Zealanders.  Rugby, cricket, netball, sailing, tramping and horse racing have enthusiastic followings.

New Zealand is a modern, industrialised country. Its primary export industries are agriculture, horticulture, fishing and forestry.  New Zealand also maintains substantial manufacturing, tourism and service industries.  The country's currency is the New Zealand Dollar.

Source: Nupedia by Michael Witbrock

Bacteria

Bacteria are microscopic unicellular organisms characterized by the lack of a membrane-bound nucleus and membrane-bound organelles.  They were once considered part of the plant kingdom, but eventually, they were placed in a separate kingdom, Monera, also referred to as Eubacteria in recent taxonomic schemes. Monera includes bacteria and cyanobacteria (blue-green algae).  The term "bacterium" (plural bacteria) was introduced by German scientist C.G. Ehrenberg in 1828 as a representative name for some bacterial types.  The name bacteria comes from the Greek word, βακτηριον meaning "small stick."  In 1878, French surgeon Charles Emmanuel Sedillot coined the term "microbe," which is also used to describe a bacterial cell.  Since bacteria are unicellular microscopic organisms, they are not visible with the naked eye and require the use of a microscope to be seen.  In 1683, Antony van Leeuwenhoek was the first to report viewing bacteria with the aid of a single-lens microscope of his design, at a magnification of about 200 times actual size.  Louis Pasteur (1822-1895) and Robert Koch (1843-1910) described the role of bacteria in causing disease, and in 1866, E.H. Haeckel, a German zoologist, suggested the name "Protista" to include all unicellular organisms (bacteria, algae, fungi, and protozoa). Microorganisms are widely distributed and are most abundant where they have food, moisture, and the right temperature for their multiplication and growth.  Bacteria can be carried by air currents from one place to another.  The human body is home to billions of microorganisms; they can be found on skin surfaces, in the intestinal tract, in the mouth, nose, and other body openings.  They are in the air one breathes, the water one drinks, and the food one eats.  Not all bacteria are harmful, and in some cases, their presence is a necessity for the human body--for example, their presence in the large intestine can help prevent the growth of potentially harmful microbes. Bacteria are minute, with physical dimensions typically in the range of 0.5 to 5.0 micrometres (one micrometre is about 1/25,400 inch).

Bacteria are grouped in a number of different ways. Bacteria exist in a number of shapes (Fig. 1). Most bacteria are of one of three shapes: The Bacillus is rod-shaped; the Coccus is spherical in shape (e.g. Streptococcus or Staphylococcus), and the Spirillum is spiral-shaped. An additional group, the Vibrio, is comma-shaped. The structure of bacteria is very simple--that of a prokaryotic cell, which does not have membrane-bound organelles such as mitochondria and chloroplasts, but does have cell walls.  On the basis of the composition of the cell walls, that is, the number and placement of cell membranes, bacteria are divided into two groups, gram-positive and gram-negative. (The name "gram" comes from the Danish biologist who developed the technique of gram staining.) Some bacterial cells have capsules outside their cell walls, which are made up of polysaccharides, and form a covering or envelope around the cell.  These capsules help the bacteria to remain dormant during dry seasons and to store food and dispose of waste substances.  Bacteria move from one place to another with the help of thin, hair-like structures called flagella.  Bacteria that possess flagella are categorized as motile; those without flagella are categorized as immotile. Bacterial flagella are arranged in many different ways. Bacteria can have a single polar flagellum at one end of a cell, or they can have clusters of many flagella at one end.  Some bacteria have peritrichous flagella scattered all over the cell.  A unique group of bacteria, the spirochaetes, have structures similar to flagella, called axial filaments, between two membranes in the periplasmic space. The growth of bacterial populations has four different phases: lag phase, exponential or log phase, stationary phase, and death phase (Fig. 2). During the lag phase, bacteria adapt themselves to growth conditions.  At the exponential phase, bacteria are reproducing at their maximum rate; therefore, their number increases during this phase.  During the stationary phase, the growth rate slows due to depletion of nutrients.  At the 
death phase, bacteria run out of nutrients and die.

Figure 1: The different shapes of bacteria
(Image created by the author and donated to Nupedia.)
(A)Rod-shaped bacteria. (B) Round-shaped or spherical bacteria. (C) Round-shaped bacteria in clusters. (D) Round-shaped bacteria in twos. (E) Spiral-shaped bacteria. (F) Comma-shaped bacteria.

Figure 2: Hypothetical bacterial growth curve
(Image created by the author and donated to Nupedia.)
Growth is shown as L(log numbers) = colony forming units per ml, over T(time.) A) Lag phase. B) Log phase. C) Stationary phase. D) Death phase.

Bacteria reproduce both asexually and by genetic recombination. The primary means of reproduction in bacteria is binary fission, an asexual process.  In binary fission, one bacterial cell divides into two daughter cells with the development of a transverse cell wall. However, genetic variations can occur within individual cells through recombinant events such as mutation (random genetic change within a cell's own genetic code), transformation (the transfer of naked DNA from one bacterial cell to another in solution), transduction (the transfer of viral, bacterial, or both bacterial and viral DNA from one cell to another via bacteriophage) and conjugation (the transfer of DNA from one bacterial cell to another via a special protein structure called a conjugation pilus).  Bacteria, having acquired DNA from any of these events, can then undergo fission and pass the recombined genome to new progeny cells. Many bacteria harbour plasmids that contain extrachromosomal DNA. In terms of evolution, bacteria are thought to be very old organisms, appearing about 3.7 billion years ago.

The nutritional requirements of bacteria are quite diverse. Some bacteria require only carbon dioxide for their carbon source and are called autotrophs; those that obtain their energy in the form of light are called photoautotrophs, and those that obtain energy by oxidizing chemical compounds are called chemoautotrophs. Another group of bacteria is dependent on an organic form of carbon and they are called heterotrophs.  Other nutritional requirements include nitrogen, sulfur, phosphorous, vitamins and metallic elements such as sodium, potassium, calcium, magnesium, manganese, iron, zinc, and cobalt for normal growth. Based on their response to oxygen, most bacteria can be placed into one of three groups: Some bacteria can grow only in the presence of oxygen and are called aerobes; others can grow only in the absence of oxygen and are called anaerobes, and some can grow in the presence or absence of oxygen and are called facultative anaerobes. Bacteria also thrive in environments that are considered extreme for mankind. These organisms are called extremophiles. Some bacteria inhabit hot springs and are called thermophiles; others inhabit highly saltine lakes and are called halophiles; yet others inhabit acidic or alkaline environments and are called acidophiles and alkaliphiles, respectively; and still others inhabit alpine glaciers and are called psychrophiles.

Bacteria are both harmful and useful to the environment, humans, and animals.  Some bacteria act as pathogens and cause tetanus, typhoid fever, pneumonia, syphilis, cholera, influenza, and tuberculosis.  In plants, bacteria cause leaf spot, fire blight, and wilts.  The mode of infection includes contact, air, food, water, and insect-borne microorganisms.  In soil, microorganisms help in the transformation of nitrogen to ammonia with enzymes secreted by these microbes, which reside in the rhizosphere (a zone that includes the root surface and the soil that adheres to the root after gentle shaking).  Some bacteria are able to use molecular nitrogen as their source of nitrogen, converting it to nitrogenous compounds, a process known as nitrogen fixation.  The ability of bacteria to degrade a variety of organic compounds is remarkable. Highly specialized groups of microorganisms play important roles in the mineralization of specific classes of organic compounds.  For example, the decomposition of cellulose, which is one of the most abundant constituents of plant tissues, is mainly brought about by aerobic bacteria that belong to the group Cytophaga.  Bacteria, often in combination with yeasts and moulds, are used in the preparation of fermented foods such as cheese, pickles, soy sauce, sauerkraut, vinegar, wine, and yoghurt. Using biotechnology techniques, bacteria can be bioengineered for the production of medical compounds, like insulin, or for the bioremediation of toxic wastes.

Source: Nupedia by Nagina Parmar