Ecology

Pollutant low altitude thermal inversion occurs in the winter. In this period of the year, the sun heats the soil less and the natural upward move of warm air decreases. Therefore, the pollutants form a low altitude layer between the cold air layer near the ground and another layer of warmer air above. The pollutant layer over industrial areas or big urban concentrations reduces the penetration of the sun energy and the air bellow takes an even longer time to warm.

Environmental Issues: thermal inversion

Thermal inversion confines at low altitude, layer of pollutants that would have been dispersed by the natural upward move of warm air. The solid particles present in the atmosphere cause health problems, like the exacerbation of asthma and other pulmonary diseases, cough, respiratory unease and ocular discharges; later the pollution can also trigger the appearing of cardiovascular and neoplastic diseases.

Transgenic beings are animals, microorganisms and plants that contain recombinant DNA, i.e., genes from other plants, microorganisms or animals artificially inserted into their genetic material. Transgenic beings are made for scientific and economic purposes, in this last case with the intention of improving their commercial features. For example, bacteria that produce human insulin are transgenic beings made by biotechnology. The main targets of the transgenic technology are the eatable vegetables, like soy, corn, potato, and tomato.

Environmental Issues: transgenic beings

Examples of other heavy metals that cause toxic pollution are lead, cadmium, and chromium.

The upward move of warm air is a natural method of dispersion of pollutants. The air near the ground is hotter because the sun heats the soil and the soil heats the air nearby. Since it is less dense, the warm air tends to move towards higher and colder strata of the atmosphere. Such movement helps the dispersion of pollutants.

Bioremediation is the use of microorganisms, like bacteria, protists and fungi, to degrade noxious substances turning them into non toxic or less toxic substances. Bioremediation employs microorganisms whose metabolism uses contaminants as reagents.

Bioremediation is used, for example, in the decontamination of environments polluted by oil spill. In this process, bacteria that use hydrocarbons as substrate for their cellular respiration are employed.

Environmental Issues: bioremediation

Population growth rate (PGR) is the percent variation between the numbers of individuals in a population in two different times. Therefore, the population growth rate can be positive or negative.

The main factors that make populations grow are births and immigration. The main factors that make populations decrease are deaths and emigration.

Biotic potential is the capability of growth of a given population under hypothetical optimum conditions, i.e., in an environment without limiting factors to such growth. Under such conditions, the population tends to grow indefinitely.

Population Ecology - Image Diversity: biotic potential curve

Examples of migratory animals are: southern right whales from Antarctica, that procreate in the Brazilian coast; migratory salmons that are born in the river, go to the sea and return to the river to reproduce and die; migratory birds from cold regions that spend the winter in tropical regions; etc.

Population Ecology - Image Diversity: migratory animals

The factors that limit the growth of a population can be divided into biotic factors and abiotic factors. The main abiotic limiting factors are availability of water and light, availability of shelter. The main limiting biotic factors are population density and inharmonious (negative) ecological interactions (competition, predatism, parasitism, ammensalism).

Migration is the moving of individuals of a species from one place to other. Emigration is the migration seen as exit of individuals from one region (to other where they will settle permanently or temporarily). Immigration is the migration seen as the settling in one region (permanently or temporarily) of individuals coming from other region. Therefore, individuals emigrate "from" and immigrate "to".

Environmental resistance is the action of limiting abiotic and biotic factors that disallow the growth of a population, as it would grow according to its biotic potential. Actually, each ecosystem is able to sustain a limited number of individuals of a given species.

The environmental resistance is an important concept of population ecology.

A typical population growth curve (number of individuals x time, linear scale) has sigmoidal shape. There is a short and slow initial growth followed by a fast and longer growth and again a decrease in growth preceding the stabilization or equilibrium stage.

The population growth according to the biotic potential curve however is not sigmoidal, it is only crescent and points up to the infinite of the scale (there is not a decreasing stage in any equilibrium).

Population Ecology - Image Diversity: population growth curve