Ecology

The age pyramids of peripheral countries or underdeveloped countries have characteristics related to the poverty of such populations, with wider base and narrow apex. The base age range if much wider than the other levels showing high birth rate. The levels just above the base may present impressive reduction in poorer populations due to infant mortality. Ranges that represent the youth are also wide showing future pressure on job and habitation needs. The widths of the rectangles diminish as age increases to the apex that represents the elderly, demonstrating difficult life conditions, precarious health services, and low life expectancy.

In a stabilized human population, the age pyramid has narrower base since the reproduction rate is not so high. The adult age ranges are generally wider than the infantile ranges showing that in practice there is no population growth. There is a proportionally high number of old individuals meaning that the life quality is elevated and the population has access to health services and good nutrition. These are features of the age pyramids of developed countries.

Population Ecology - Image Diversity: france age pyramid

The difference between the real population growth curve (number of individuals x time) and the population growth according to the biotic potential curve of a given population is a result of the environmental resistance.

Age pyramids are graphical representations in form of superposed rectangles each representing the number of individuals included in age ranges into which a population is divided. Generally, the lower age ranges are represented more to the bottom of the pyramid, always below higher ranges, and the variable dimension that represents the number of individuals is the width (there are age pyramids however, in which the variable dimension is the height).

Population Ecology - Image Diversity: age pyramids

The growth curve according to the biotic potential of virus and bacteria both present positive exponential pattern. The difference between them is that in each time period bacteria double their population while the viral population multiplies dozen or hundred times. The viral population growth curve thus has more intense growth. This happens because bacteria reproduce by binary division, each cell generating two daughter cells, while each virus replicate generating dozens or even hundreds of new virus.

The environmental problem concerning waste worsens with the industrial development and the global growth of consumption societies in the XX and XXI centuries, factors that cause the immense volume of residuals produced by humankind in the last decades. The increased waste generation raises the issue about what to do with waste since nature is not able to degrade and resorb with adequate speed and efficiency most part of the residuals. Therefore, the several kinds of waste accumulate, polluting the environment and creating danger to humans and nature.

In most cases, pollution is caused by the human activity. Other species and some abiotic factors however can also pollute an ecosystem. For example, the red tide is created by proliferation of some algae and the volcano dust is a consequence of the internal activity of the planet.

Pollution is the contamination of an ecosystem by factors that are harmful for the equilibrium of its biotic or abiotic constituents.

Environmental Issues: pollution

To treat sewage is much cheaper for society. The non-treated sewage pollutes rivers, lakes and the sea, being a cause of diseases transmitted through water. For the society, the costs of these diseases are much higher than the cost of the sewage treatment.

One of the most economical systems to treat sewage is the aerobic treatment system, reservatories kept much oxygenated for aerobic bacteria to decompose organic material.

Environmental Issues: sewage treatment

Recyclable waste is the waste that can be reprocessed and used again. Waste recycling depends on the separation of the recyclable residuals from non-recyclable ones and on the classification of the recyclable into plastics, metals, papers, etc. The function of the selective waste collection is to ease that separation for the waste to be sorted in the point of origin. Selective collection also helps the creation of environmental conscience in the people that produce the waste.

Environmental Issues: selective waste collection

Biodigester is equipment that produces carbon dioxide, hydrogen sulfide, and fuel gases (biogases) like methane from organic material under decomposition (dung, food waste, sugar cane waste, etc.). The biogas is used in heating, as energy for motors and machines and it has even industrial uses. Biodigesters are widely used in public waste depositories and in rural areas. Besides producing biogas the organic waste can be turned into good quality fertilizer.

Environmental Issues: biodigester

Mercury is a metal that when present in the water of rivers, lakes, and seas contaminates fishes, crustaceans, molluscs and other living beings. The mercury accumulates along the food chain and in each following trophic level; the amount of the metal within the individuals is higher. When humans eat contaminated animals they also became contaminated and severe nervous system injuries may come out. The main sources of mercury pollution are gold mining and the use of derived substances in industry and agriculture.

Environmental Issues: mercury pollution

Ozone, O3, is a gas of the atmosphere that filters ultraviolet radiation from the sun disallowing most of that radiation of reaching the surface of the planet. Ultraviolet radiation is harmful for living beings because it is a mutagen and can cause cancer (mainly skin cancer), other DNA mutations, and even burns.

Environmental Issues: ozone layer

The mains chemical compounds that destroy the ozone layer are the CFCs, chlorofluorocarbons, or freons, substances used in the past in refrigerators, airconditioners and spray cans.

Chlorofluorocarbons react with ozone in the high atmosphere releasing molecular oxygen and therefore the amount of ozone in the atmosphere is reduced.

Other substance that destroys the ozone layer is methyl bromide, used in agricultural insecticides.