Factors that influence the growth and size of a populationA population is defined as a number of organisms of the same species that live together in such a way that they influence each other, for example example they can reproduce, protect each other from each other, compete with each other for food, shelter, space, light, water, etc. The population size of organisms changes over time, increasing with births and immigrants but decreasing with deaths and emigrants. Below is a diagram showing 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.[IMAGE]The lag phase of the graph is a period of slow growth. There are many different reasons for this delay, one being that the microorganisms may need to synthesize the enzymes needed to utilize a new food source. Species that reproduce sexually can take some time to grow and reach maturity. The growth phase (exponential phase) is a period of rapid and unrestricted growth. Conditions are favourable, food is plentiful and there are no limiting factors. Growth begins to slow due to limiting factors; this is known as environmental resistance. The population begins to stabilize at the stable (carrying capacity) phase on the graph, this is the size of the population that can be supported. The population size remains stable because the death rate equals the birth rate. Once the death rate exceeds the birth rate, the population number decreases, and this is known as the death phase. There are two types of factors that influence population growth and size and these are abiotic and biotic factors. Abiotic factors are non-living factors t...... middle of paper ...... supply is a very important factor in population size. Therefore, the greater the prey population, the greater the predator population. Although predators do not usually control prey populations, they can greatly influence them if this is a major food source. 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 influence the growth and size of a population, these are divided into two groups, abiotic factors and biotic factors. Both sets of factors significantly influence the growth and size of a population.