Monday, December 19, 2011


A true fruit is derived solely from the carpel or carpels of a flower after pollination. Some fruits are juicy, but many others are dry when they are ripe and they split open to release their seeds. Pea and bean pods are examples although we eat some of them before they are ripe. Botanists split juicy fruits into several groups. Berries generally have many seed embedded in the soft flesh. Grapes, gooseberries and citrus fruits are familiar examples.
The fruit and vegetables that we eat contain starch, sugar and other foodstuffs that the plants have stored up for their own use. Botanically speaking, fruits are formed from the pollinated flowers of plants. They always contain seeds. The term vegetable is generally used in amore loose way, often simply referring to plants eaten with the main course of the meal. This can cause some confusion. Cucumbers, marrows, peppers and tomatoes are commonly considered vegetables, although to the botanist they are in fact fruits.
Almost juicy fruits are rich in sugar and therefore quite sweet when they are ripe. Some also store starch and oils. These food reserves are not consumed by the plants themselves, but serve to attract animals that eat the flesh and scatter the seed. Most commercial fruits are obtained from trees and shrubs, although some important one, such as strawberries and pineapples, come from herbaceous plants. A few fruits are still gathered mainly from the wild, but the majority is now cultivated in plantations or orchards and, as with the vegetables, many are now larger and tastier than their ancestral forms.

Wednesday, December 7, 2011


Botanically speaking, a nut is a dry fruit containing a single seed and having a hard, woody outer coat. Hazelnuts and sweet chestnuts are true nuts, and so are cashews and macadamia nuts, but in fact most of the other “nuts” that we buy in the shops are not nuts at all. They are mostly the inner parts of other kinds of fruits.

Walnuts, pecans and almonds, for example, are the equivalents of peach or plum stones, and until they fall from the trees they are enclosed in tough, leathery cases that correspond to the flesh of the peach or plum. Even the hard shelled coconuts are also the inner parts of the fruit, although here the outer part is thick and fibrous – it is used for coconut matting. Brazil nuts are actually hard shelled seeds that are obtained from ball shaped woody fruits.

Ground nuts or peanuts are the seeds of a leguminous plant, carried in pods. In all these examples, the parts that we actually eat are the seeds or kernels- the embryonic next generation of plants and their food reserves.

Tuesday, December 6, 2011

Unusual Adaptation

Flowering plants have evolved in many directions, becoming adapted to a wide range of habitats and acquiring many life styles. Plants growing on high mountains or on the northern tundra usually form mats or cushions close to the ground to escape the violent winds. The dwarf willow Salix herbacea, for example is a true willow, but it has underground stems and its aerial branches are rarely more than 3cm above the ground. The leaves and flowers of many mountain plants are darker than those of their low land relatives; dark colours absorb heat more efficiently in the cold climate.

Many plants manage to live in deserts despite the scarcity of water. Some of them are quick growing annuals that complete their life cycles in a short time and are not affected by the drought, but the typical desert plants store water through the dry season. Waxy or hairy coatings, and breathing pores sunk in deep grooves ensure that evaporation is cut to minimum. Many of the plants have very small leaves or none at all, although some species sprout leaves when the rains come and then drop them for the dry season.

Cacti nearly all grow in the American deserts and can survive prolonged drought. They have no proper leaves and their ribbed grooves store all their food. Wide spreading roots catch nearly all the rain that falls in the wet season and the stems swell up as they take up water. The stems shrink as they use up water in the dry season, and the grooves become deeper. The breathing pores in the grooves thus become better protected from the dry air. Spines protect the cacti from grazing animals seeking moisture.

Friday, October 21, 2011

Mosses, Ferns and Conifers

Mosses and the closely related liverworts carry spores in stalked capsules. The capsules form only after the union of male and female sex cells. As in ferns the cells need moist condition so mosses flourish mainly in damp environment.

Ferns generally carry their spores in little capsules under the leaves. The related horsetails carry their in fleshy cones at the tips of the stems. Although the reproductive process needs water, mature ferns can survive in dry places.


Conifers bear sees on the scales of their cones. The cones are small and soft at first, but swell and become woody after pollination. When the seeds are ripe the cones either open slightly or fall to pieces to release them. Conifers are the best known of the cone bearing plants, known as gymnosperms.

Thursday, October 13, 2011

The Plants

With something in the region of 300000 different kinds or species, plants make up one of the two great kingdoms of the living world. The chlorophyll they contain is responsible for the essentially green nature of the planet. Unlike animals, plants can manufacture their own food from simple inorganic materials mainly water and the carbon dioxide gas in the air, they are thus the primary producers of food and all terrestrial animal life depends on them, either directly or indirectly, for food.
Most animals stop growing when they reach maturity and each species has a fixed shape. But plants go on growing throughout their lives and although the leaves and flowers of a particular species generally have a fixed shape, the overall shape and size of the plant can vary a good deal according to its situation.

Leaving aside the flowers or other reproductive organs, a typical plant has three main regions – root, stem and leaf. The root anchors the plant and absorbs water and dissolved minerals from the soil by means of osmosis. Growth takes place by elongation of the cells just behind the tip and this forces the root down. Delicate root hairs just behind the growing regions absorb the water and pass it to tubes in the centre of the root.
The stem which may be soft or woody carries water and dissolved minerals from the roots to the leaves through a ring of tubes. Another set of tubes carries manufactured food down from the leaves and distribute it around the plant. The stem also arranges the leaves in the most efficient way for catching sunlight and in flowering plants, displays the flowers in the best position for achieving pollination. The leaves are the plant’s food factories. They are usually flat and have a number of veins. Continues with the tubes in the stems, the veins carry water to the leaf tissues for photosynthesis and also carry away the manufactured food. The undersides of the leaves have thousands of microscopic breathing pores that allow carbon dioxide in and oxygen out. They also release a lot of water vapor by evapo-transpiration.

Wednesday, September 7, 2011

Truffles, Gills and Pores, Lichens


Truffles are subterranean fungi with solid, globular fruiting bodies. They grow mainly in broad leaved woods. The perigord truffle of southern France is a much prized and very expensive delicacy. The traditional way of finding truffles is to train pigs or dogs to sniff them out. Most attempts at cultivating truffles commercially have failed.

Gills and Pores

The typical mushroom gets its food from decaying matter in the ground. Its fruiting body is spherical when it first bursts through the soil, but it quickly expands to form a cap and stalk. The latter, often called the stipe, may have a ring showing where the rim of the cap was originally attached and there may be a cup or volva, at the base. Under the cap, most species bear numerous fragile gills arranged like spokes in a wheel. The gill surfaces release millions of spores, the equivalent of seeds in flowering plants. Other mushrooms looks more like sponges, scattering their seeds from thousands of minute pores.


Lichens are among the hardiest of all organisms, growing in some of the hottest and coldest places. They clothe much of the arctic tundra. Each of the many species is actually a combination of a fungus and an alga. The alga can exist along, but the fungus cannot, so lichens are regarded as special kinds of fungi that rely on algae to provide much of their food.

Sunday, August 21, 2011

The Fungi

The fungi were once regarded as simple plants, but their chemical makeup is very different from that of plants and they are now placed in a separate kingdom. A fungus consists essentially of a mass of slender threads, called hyphae, which absorb food from other living or dead organisms. The familiar mushrooms and toadstools are the reproductive stages of the fungi and are often called fruiting bodies. They are composed of tightly compacted hyphae and their role is to produce and scatter the dust like spores. If a spore reaches a place with enough food and moisture for survival, it will grow sending out a hypha. The name mushroom was originally used for just one or two species of fungi with edible fruiting bodies, all the other fungi with umbrella shaped fruiting bodies being called toadstools. However, the modern tendency is for all umbrellas shaped fruiting bodies, whether edible or not, to be called mushrooms. Although many species are edible and very tasty, they contain little food value.
Relatively few of the 100,000 or more known fungi are really poisonous but a handful is truly deadly. The death cam probably kills more people than any other fungus. Growing in broad leaved woodlands, this fungus has a greenish cap with white gills. One specimen is more than enough to kill a person, with a slow and painful death. Several related fungi can produce sever illness if eaten although they are not necessarily deadly. These include the fly agaric, common under birch and pine trees, the blusher common I both deciduous and coniferous woodland, and the verdigris fungus common in grass and woodlands.

Saturday, August 20, 2011

Convergent Evolution

Convergent evolution is a common phenomenon, in which unrelated plants or animals come to resemble each other because they have adapted to similar ways of life. The similarity of some species of American cacti and certain desert living spurges in Africa is a good example. Seals and Penguins are apparently very different animals, but both are superbly adapted for swimming. Their limbs and general body shapes appear similar when observed in the water.
Few animals have a clear fossil record as the horse. The oldest known fossils of this family, from rocks some 55 million years old, are of a fox sized creature called Hyracotherium. Its teeth indicate that it ate leaves, and it probably lived in the forests. Fossils from successively younger rock layers show that the descendants of Hyracotheium gradually became larger and were represented by several distinct genera before producing the modern horse about two million years ago. Their toes were reduced to one on each foot and their teeth became larger and stronger to deal with tough grasses.

Sunday, July 3, 2011

Taxonomy and Evolution

The sequence of bases along the DNA molecule may be compared between species. If the base sequences are similar then the species are closely related. For example, there is a 1.2 percent difference between the DNA of humans and that of chimpanzees, and a 1.4 percent differences between humans and gorillas, making the chimpanzee a closer relative to humans than the gorilla. Humans and orangutans share 97.6 percent of their DNA, but this does not match the 98.8 percent shared by chimpanzee and human.

Evolution is the process of gradual change by which the characteristics of living organization are altered from generation to generation the changes in given organism eventually become so great that it can no longer be regarded as the same species. Fossil records show that such replacement of one species by a more advanced one has been taking place for many millions of years, and that most species have survived for only about ten million years. The idea that living things have all evolved from simple ancestors was first put forward by the ancient Greeks, but until Charles Darwin and Alfred Russel Wallace published their work on natural selection no one could give satisfactory explanation.

Darwin and Wallace noticed that plants and animals produce large numbers of offspring and that there is a struggle for existence among the progeny- competition to find food and avoid predators as well as a struggle against adverse environmental factors. They also realized that the progeny vary, and reasoned that only those most suited to their surroundings would survive. The progressive improvement shown throughout evolution is thus brought about by natural selection of the best in each generation.

Sunday, June 19, 2011

Human Chromosomes and DNA Fingerprinting

Every human body cell, except for sperm and egg cells, contain 46 chromosomes.  These contain around 100000 genes that between them determine all of an individual’s characteristics, from hair colour to potential height. Sperm and egg cells each contain 23 chromosomes. When they fuse during fertilization, the chromosome number is restored to 46, or 23 pairs of chromosomes. Thus everybody cell nucleus contains 23 paternal chromosomes paired up with 23 maternal chromosomes. 

 DNA fingerprinting, also known as genetic finger printing this process is used to reveal the genetic identity of an individual. The arrangement of bases within his or her DNA is unique to that individual, just as his or her fingerprints are; the only exceptions are identical twins, who share the same DNA. A tissue sample, usually of blood, is taken from the person and DNA molecules are then cut into small pieces and separated. By adding a radioactive probe, and using an X-ray film, a banded strip is produced, unique to its owner. The more closely two people are related, the greater the similarity between the pattern of bands. Genetic fingerprinting was used to confirm the human remains found in Russia were those of the Romanovs, the Russian royal family, by comparing DNA fingerprints from the remains with those of the Romanovs’  living relatives. Genetic fingerprinting is similarly used to prove paternity. In criminal cases such as rape, DNA extracted from the perpetrator’s semen or other body fluids can be used to confirm his identity.

Tuesday, May 31, 2011


Deoxyribonucleic acid or DNA is the nucleic acid, containing the sugar deoxyribose, which forms the materials of which the chromosomes and genes of organisms are composed. It carries the blueprint for construction of all the cells of an organism and all instructions that control their activities, and which enables these instructions to be passed on from one generation to the next. DNA is found in all living organisms except certain viruses which contain RNA (ribonucleic acid), a closely related nucleic acid.
In eukaryotic ells- which make up the majority of organisms- DNA is found in the membrane bound sphere called the nucleus. Here, it forms chromosomes, normally long threads (but in cells that are about to divide chromosomes form separate X shapes as they duplicate themselves). Within the chromosomes DNA is tightly packed in coils and super coils. Once unraveled, DNA can be seen to consist of two long strands wound around each other in spiral structure or double helix, like a twisted ladder. The rungs of this ladder are made up of different bases. A rung is formed when adenine from one DNA strand binds with thymine on the other. The arrangement of bases along the double helix constitutes the genetic code, which controls production of the protein molecules that facilitate all cell activities, including metabolism and construction.

Tuesday, May 3, 2011

Classification of Plants and Animals

Every different kind of organism called a species, and closely related species are grouped together into genera (the singular of with is genus). Each species has a two part scientific name, composed of its generic name and its species name. For example, the house fly, which belongs to the genus Musca, is scientifically known as Musca domestica. Where a number of members of the genus Musca are mentioned, later examples may be abbreviated to, for instance, M. domestica. By convention the genus name begins with a capital letter.
Related genera are grouped into families, related families are grouped into Orders, Orders are grouped into classes, and classes are grouped into phyla. The latter are the largest divisions of each kingdom. Family names in the animal kingdom always end in  …idea, while  plant families always end in  ..aceae.

Monday, May 2, 2011


Viruses are on the borderline of living and non living things and do not fit into the five kingdoms of the living world. They are much smaller than bacteria and each consists simply of a lump of DNA inside a protein envelope.
There are many different kinds of viruses and they all produce disease in plants and animals by invading living cells and interfering with their normal functions. The viruses can be converted to a crystalline form, in which they can survive for a very long time, but they cannot grow or reproduce on their own. They need the help of the host cells for this. The virus DNA takes control of the cell nucleus and instructs it to make more virus mater. The new virus particles then escape from the host cell and rapidly infect other cells. Human diseases caused by viruses include the common cold, measles, polio and aids

Animal and Plant Cells

All living things are made of cells and part from those of the bacteria the cells all have much the same internal structure, although their external appearance varies enormously according to the jobs they have to do. A variety of animal cells are shown on the right below. There are several hundred different kinds of cells in the human body, and the total number of cells may exceed ten trillion. Most of them are obviously extremely small, and it is only recently that powerful microscopes have revealed their detailed structure. The nucleus the most conspicuous of the internal structures or organelles is the cell’s control center. It is bounded by the nuclear membrane and it contains the chromosomes that carry all the hereditary material. The nucleus produces the ribosomes, which themselves are responsible for the formation of the cell’s proteins. This takes place on the surface of the endoplasmic reticulum, which is a network of flattened and connected to the nuclear membrane and spreading throughout the cell.

Sunday, April 24, 2011

The Kingdom Protoctista

This kingdom contains all single celled organisms in which there is a distinct nucleus enclosed in a membrane, and in which there are also other discrete organelles, such as mitochondria and endoplasmic reticula. It includes all those microscopic organisms, such as amoeba and paramecium that were once regarded as single celled animals and placed in the phylum Protozoa. It also includes the slime moulds. The large sea weeds that is also included in the Protoctista because, although they are multi cellular organisms, their cells are all alike and not easily differentiable from single celled algae.

The sea weeds include species with fronds many meters long and made up of millions of cells, but they are included with the single celled organisms in the Protoctita because their cells are all more or less alike. Some biologists regard the seaweeds as assemblages of cells rather than true multi cellular organisms. There are three major groups or phyla- the green sea weeds (Chlorophyta), the brown sea weeds (phaeophyta) and the red sea weeds (Rhodophyta). All contains chlorophyll and make their food by photosynthesis, but the brown and red seaweeds contain other pigments that mask the chlorophyll. They have a variety of reproductive strategies.

Thursday, April 21, 2011

The Five Kingdom of Life and The Characteristics Of Living Things

Until fair recently, all living things were classified as either plants or animals this simple division is perfectly adequate for non scientific purposes, but most biologists now recognize five separate kingdoms of life, based largely on microscopic structure and bio chemical activity, these are the bacterial kingdom, or Prokaryote; the Protoctista; the Fungal kingdom; the Plant kingdom and the Animal kingdom.
Although we cannot give a simple definition of life, there are seven distinctive features that are shared by all living things and distinguish them from inanimate objects.

These characteristics are:
The initial letters of these features form the word MERRING, a convenient mnemonic for keeping them in mind.
The Kingdom of Prokaryote:
This kingdom contains the bacteria. These are all microscopic, single celled organisms, but their structure is very different from that of other single celled organisms, with no obvious nuclei or other well defined structures – organelles- within the cell division, sometimes as often as once every 15 minutes. Some bacteria can carry out photosynthesis, using the energy of sunlight just as plants do, but most of them rely on other chemical reactions to provide their energy. Bacteria play a major role in the natural world, where they are heavily involved in the breakdown of dead plants and animals and return back to the soil.

Tuesday, April 19, 2011

Origin of Life

The earliest traces of the life on earth have been found in the rocks about 3.5 billion years old. They are layered structures similar to those formed by some of today’s marine bacteria, and it is generally accepted that the first forms of life were some kind of bacteria. We do not know exactly how these first living things or organisms were produced, and probably never will, but laboratory experiments suggest that energy from lightning or from ultra violet radiation could have caused gases, like methane and ammonia to combine with simple minerals to produce proteins and other building blocks of life such reactions would probably have taken place in shallow water.
As more and more life’s building blocks were formed, they inevitably mingled and reacted with each other to form new compounds. Eventually, a chance combination gave rise to a molecule of DNA, a self replicating material that is the basis of all living matter. Here, perhaps, was the “spark of life” and the scene was then set for the appearance of the first cells and the subsequent evolution of all life on Earth. Since the beginning of life, millions of different kinds of organisms have come and gone. It is estimated that there are about 300,000 different kinds of plants in the world at the present time, and there may be over five million kinds of animals- or some estimates, nearer ten million – although only a little over a million of these have so far been described.

Thursday, April 14, 2011

Map Projections

Representing a globe on a flat plane requires the use of projections. Cylindrical projections are created by wrapping a piece of paper around the equator to form a cylinder. This was the principle used by the Flemish geographer Geradus Mercator to draw up one of the first reasonably accurate maps of the world in 1569. A Mercator projection shows equatorial regions very accurately and has the advantage that the shape of the landmasses o the map are the same as on the ground, which is useful for navigators. However, away from the equator, the actual areas of the landmasses become more and more distorted so that Greenland seems bigger than Africa. Mercator’s projection is most distorted at the poles because the point of each pole is stretched out into a line as long as the equator.

Arno Peter, a German historian, devised an alternative in 1973. Peter’s projection is also cylindrical but it differs in that the north south scale is adjusted so that the actual areas of the landmasses are accurately represented at all latitudes, although Peters’ projections shows the correct areas of all landmasses, it distorts their shapes. For example Africa appears to have been stretched while Greenland seems squashed.

Another form projection is the Zenithal or Azimuthal projection. The paper remains flat and touches the globe at the north or South Pole. Lines of longitude show their correct angles. For this reason they are often used to represent polar region.

A conical projection , in which the paper is rolled into come and placed over the globe to touch it along the line of latitude, shows countries with the minimum of distortion.

Google’s projection is not strictly a projection but a series of manipulations of the curved surface of the sphere. Such maps look rather like the skin of an orange after it has been removed in one piece and rolled out flat. The continents are shown accurately but the oceans are opened up to stretch the segments on to the paper.

Thursday, March 3, 2011

Mapping Symbols

          A large scale map can show a relatively high level of detail, whereas a small scale map contains more information in relation to its size. The scale of a map is expressed as the ratio between the size of the map and the size of the corresponding area on the ground. This can be expressed as a simple ratio, for example 1:100, where one unit on a map is equal to 100 of the same units on the ground.  Alternatively, the ratio may be expressed using different units, for example 1cm: 1km, in which one centimeter on the map represents one kilometer on the ground. Many maps also show scale in the form of a scale bar which can be used to calculate any distance on the map. The scale dictates the level of detail shown by the map. Because maps are smaller than the areas they represent, symbols are used to indicate the features on the ground. Many symbols do not resemble the things the things they represent and so they are often explained in a key.

Tuesday, March 1, 2011

Map Coordinates Latitude Longitude

Lines of latitude and longitude form a grid from which the position of any point on the Earth’s surface can be measured.  An obvious reference point is the equator and latitude is the angle of a place north or south of it as measured from the center of the Earth. Lines of latitude form horizontal rings around the Earth parallel with the equator. They become shorter as they get closer to the poles. Lines of latitude divide up the Earth through its poles, like the segments of an orange. Each line is a great circle going right round the Earth. Lines of longitude have no obvious reference point such as the equator, so English navigators used the longitude or their home port, Greenwich, on the Thames near London. Longitude is still measured east or west of the Greenwich meridian. Early navigators used the stars to find out their position. Latitude was calculated from the heights of the stars in the sky or the position of the Sun as it rose, set or reached its zenith. Longitude is also measured against the stars but it is necessary to know the exact time because the stars move east to west across the sky. It was only after the perfection of the marine chronometer by John Harrison in the mid 18th century that accurate longitude measurements, and hence accurate map making, become possible.

Friday, February 25, 2011

Map Making

A map is a schematic representation of an area. Maps are primarily used to help locate places or plan a journey, and can range from a plan of a farm to a map of the world. Maps may also be used to illustrate information about a particular area; for example, distribution of population, resources or climate. These specialized maps are known as thematic maps.

                In any map the way reality is represented depends on the amount of information it contains, the used of diagrams and other graphic devices, and the scale- the size of the map in relation to the area it shows. The oldest surviving maps were made by the Babylonians more than 4000 years ago. Many ancient mapmakers assumed that the Earth was flat, but the circumnavigation of the globe in the 15th century led to great improvements in the accuracy of map making.  

                Maps show a range of information by the use of symbols and approximations. The first stage of map making is to construct a network of fixed points, from which everything else can be located. That way subsequent error will not accumulate and cause major distortions.  Before map makers had aerial photographs and satellite images to help them, the fixed points were plotted by a process called triangulation. Triangulation points are set up on landmarks such as hilltops. From the angles between these points, distance can be calculated without the need to take measurements on the ground. Adding vertical angle measurements give the heights. The height information on maps is normally shown as contours- lines linking points of the same elevation. It was by setting up a triangulation system across India from the coast to the Himalayas that cartographers first established the Mount Everest was the highest mountain in the world.  Today, satellite images provide the framework and maps are stored on computer so that they can be updated quickly without the need for redrawing.   

Wednesday, February 23, 2011

Stop Climate Change


            The Earth’s atmosphere is now changing more quickly than at any time in the past. In the last 150 years there had been a 25 percent increase in carbon dioxide and a 100 percent increase in methane in the atmosphere, largely as a result of the burning of fossil fuels, the expansion of agriculture and rapid deforestation.

Over the same period, the world‘s climate changed by an average of 0.05 degree Centigrade, as green house gases trap the Sun’s heat within the atmosphere. Computer models predict a continued warming of 0.5 degree a decade unless steps are taken to limit emissions. The climate change would be greater were it not for pollutants such as sulphur dioxide which scatter sunlight back into space. Other gases- notably CFCs from fridges, aerosols and fire extinguishers- are damaging the tenuous layer of ozone in the stratosphere which screens out ultra violet radiation from the Sun. 

Steps have been taken to phase out CFCs. They are also powerful greenhouse gases, but legislation to reduce other green house gases will be harder to implement since the practices that produce them are central to modern life. Many nations have pledged to reduce emissions to their 1990 levels, but stronger measures will be needed for stop climate change.

Monday, February 21, 2011

Causes of Climate change

Humans have farmed for thousands of years but in just the last few decades burgeoning populations have called for more agricultural ingenuity than ever before and subsequently agriculture becomes one of the causes of climate change. The breeding of new crop varieties, the use of fertilizers and pesticides and the bringing of more and more land under cultivation have kept production ahead of population growth throughout most of history which are the main causes of Climate change.. Since 1985, however, the limit seems to have been reached and per capita grain production has started to fall.
                In 1987 world grain reserves were sufficient for 100 days; by 1989 there were only enough for 54 days, yet there are 100 million more people to feed every year. There have been hidden costs to the increases in productivity. It is thought that about 40000 people in the developing world die of pesticide poisoning every year and the pesticides also one of the environment hazards.  Twenty four billion tones of top soil are lost from crop lands each year, eroded by wind and water.
                Irrigation is lowering the water table beneath eight states in the Great Plains of the USA by a meter a year, and the diversion of rivers for irrigation in the former Soviet has reduced the Aral Sea to about a third of the size it was 25 years ago. One tenth of the Earth’s land surface is currently given over to agriculture but there will have to be yet further changes before food production is sustainable.

Tuesday, February 15, 2011

Human Impact on Earth: urbanization

           As the world’s population expands past the six billion mark, it becomes more and more unevenly distributed. The great concentrations do not always occur on the most productive land; and people tend to gravitate towards what are often already large cities. In 1950 the largest metropolitan areas were all in the developed metropolitan areas were all in the developed world – New York, London, Tokyo and Paris. Now those have been over taken dramatically by Mexico City and Sao Paulo, with Shanghai, Calcutta, Bombay and Jakarta rising rapidly on the list.

                The developing world’s urban population is now larger than the total population of Europe, North America and Japan combined. Many of the cities have grown beyond the control of planners and include illegal slums that pack millions of people together and concentrate populations and disease. An estimated 600 million people in the cities of the developing world lack clean water, sanitation and secure homes. Even if living standards improve, cities seem set to expand, putting more land under concrete and producing more fumes from industry and vehicles in congested streets.

Monday, February 14, 2011

Human Impact: Riches from the Earth

              The Earth is minded for building materials, metals, chemicals and fuels. Powerful machinery, industrial processing and international trade mean that individual deposits are exploited on a scale far beyond local needs. An estimated 23 billion tones of non fuel minerals are extracted each year, about twice the amount of sediment carried each year by the world’s river systems. As a result, an estimated half a million hectares of land are scarred each year. As the most concentrated ore deposits become exhausted, lower grade ores are used, such that to produce an estimated nice million tons of copper in 1990, 990 million tons of ore had to be mined. The open cast Bingham Canyon copper mine in Utah, USA, 775m deep, is the largest human excavation in the world.

      The legacy of mining is not only the hole in the ground and the pile of spoil left behind; it can affect air and water over great distances. The Ilo smelter in Peru emits 600000 tons of Sulphur compounds each year, and cyanide in the waste affects marine life in a 20,000 hectares area. Small scale gold mining by hundreds of thousands of miners in the Amazon basin releases a estimated 100 tones of mercury into the river system each year.

Saturday, February 12, 2011

Human Impact – Interactive processes

             Mining and industry can release toxic metals and other wastes into ground water, and they release metals into the atmosphere as fine particles. They produce acidic gases, such as sulphur dioxide and nitrogen oxides and green house gases, notably carbon dioxide. Human activities, using fossil fuels, notably power generation and transport, are the biggest net emitters of green house gases since they extract the carbon from no renewable sources.
                 Farming practices result in the release of nitrates and phosphates from fertilizers and animal waste into ground water and rivers, adding to sewage already released into rivers and seas and causing blooms of algae which subsequently deplete the oxygen in water.  Although crops absorb carbon dioxide as they grow, they do not store it to the extent that a forest does, and rice cultivation and cattle rising produce another green house gas, methane. Clearance of natural vegetation releases carbon dioxide into the air and soil minerals into water and increases the likelihood of soil erosion.
                Natural systems absorb some, but not all, of the excesses of human activity. Alkaline soils can neutralize acidic gases washed out of the air; forests, grasslands and plankton can absorb carbon dioxide; some waste decomposes and some nutrients are recycled. But few human activities are sustainable in the long term.