'Factors affecting the growth and size of a population.'

There are two types of factors that affect the growth and size of a population and these are, abiotic and biotic factors. Abiotic factors are non-living factors that influence the abundance and distribution of animals and plants in an ecosystem and biotic factors are living factors that affect an ecosystem. Examples of abiotic factors are, light intensity, inorganic ions, temperature, salinity and dissolved oxygen in aquatic environments. Light intensity is a very important factor in most ecosystems, because it influences primary productivity and, therefore, the rest of the ecosystem. Temperature is also very important because it affects the metabolism of many organisms, if the temperature is too high, it can denature the enzymes in the organism. Temperature also affects the solubility of oxygen. Without oxygen, organisms that respire aerobically will die. Salinity is a measure of the salt content of sea water, the greater the salinity, the greater the conductivity. pH is a measure of the acidity or alkalinity of a solution, low pH interferes with ion regulation, it reduces the efficiency with which haemoglobin take up oxygen, and increase mucus deposition on the gills. The pH of soil is also important. All these factors mentioned are important abiotic factors, which will be competed for my organisms.

Biotic factors regulate the size of populations more intensely than abiotic factors. The interactions between species have an enormous influence on the size of each other's populations. When two or more organisms in the same community complete for environmental resources that are in limited supply, such as food, water or nesting space, a competition occurs. This occurs at two levels, interspecific competition and intraspecific competition. Interspecific competition is between different species and intraspecific competition is between the same species. Competition may be the result of two different processes, exploitation and interference. Competition by interference occurs when an individual directly prevents the physical establishment of another individual in a portion of a habitat. Established plants prevent the invasion and colonisation of other individuals by means of dense root mats, peat and litter accumulation, or mechanical abrasion. Competition by exploitation happens between organisms when the indirect effects of two or more species or individuals reduce the supply of the limited resource need to survive. The exclusion of one organism by another organism can only take place when the dominant organism requires less of the resource to survive. The dominant organism must also be able to reduce the quantity of the resource to a critical level with respect to the other organism. Exploitation does not always cause the exclusion of a species from a community. It may just cause a reduction in potential growth of the species.

Predation is an interspecific interaction; a predator obtains its food at the expense of its prey. Predator-prey relationships are important in determining the distribution of organisms in an ecosystem. The size of the predator population depends on the availability of its food source. Food supply is a very important factor of the size of a population. Therefore the larger the prey population, the larger the predator population is going to be. Although predators do not usually control prey populations, they can affect it greatly if that is one of there main sources of food. Factors such as food availability and abiotic factors regulate prey populations. Parasites obtain food at the expense of their hosts; they weaken the host but rarely kill it. Some parasites cause disease and sometimes death, these are known as pathogens, and an example of this is the mosquito.

So in conclusion there are many factors that affect the growth and size of a population, these are split into two groups, the abiotic factors and the biotic factors. Both sets of factors affect the growth and size of a population significantly.

Charlotte Nellist Biology Essay

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