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Introduction

'Factors affecting the growth and size of a population.' A population is defined as a number of organisms of the same species living together such that they influence each other's lives, e.g. they can reproduce, protect each other, compete with each other for food, shelter, space, light, water, etc. The population size of organisms changes over time, it increases with births and immigrants but decreases with deaths and emigrants. Below is a diagram that shows a population growth curve. A population growth curve is a graph that shows the growth of a population of organisms over a period of time. The lag phase of the graph is a time of slow growth. There are many different reasons for this lag, one is that microorganisms may have to synthesis the enzymes needed to utilise a new food source. Species that reproduce sexually may take a while to grow and reach maturity. The growth phase (exponential phase) is a period of rapid and unrestricted growth. ...read more.

Middle

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. ...read more.

Conclusion

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 Page 1 ...read more.

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