The two types of reproduction, sexual and asexual, result in different patterns of population growth. Simple organisms like bacteria multiply and reproduce through asexual reproduction causing the population to double each time the bacteria reproduce (see figure 1), whereas mammals such as humans reproduce through sexual reproduction and consequently follow a different pattern of population growth. Offspring produced via sexual reproduction are genetically different from their parents adding diversity and variation to the population.
Populations are also affected by limiting factors such as the availability of food and space, as well as competition between species, known as density dependent limitation.
Furthermore, the population growth of predators and prey are also dependent upon one another, with the number of predators in relation to prey influencing the growth of each population. This can be seen in the Lotka-Volterra model (see figure 2).
The growth of a population is also limited by the carrying capacity of its surrounding environment. Due to the environment only being able to provide a certain amount of food and space, it can only support a limited number of individuals. Exceeding this carrying capacity often leads to crashes in populations as resources become exploited to exhaustion.
Figure 1- A bacteria dividing through asexual reproduction
‘vandermeer_figure1_ksm’, 2010, graphic, John Vandermeer. Source: https://www.nature.com/scitable/knowledge/library/how-populations-grow-the-exponential-and-logistic-13240157
Figure 2 – the Lotka-Volterra model of predator-prey relationships. The red line represents prey and the blue line represents predator. The X axis is time and the Y axis is the number of individuals in the population.
‘Lotka-Volterra predator-prey time series’, 2006, graphic, Roberto Zanasi. Source: https://commons.wikimedia.org/wiki/File:Lotka-Volterra.png
Asexual reproduction – Where offspring are produced from a single organism, inheriting the genetic information of only that parent.
Bacteria – A type of single-celled organisms.
Carrying capacity – The maximum number of organisms that an environment can support.
Density dependent limitation – Factors that prevent a population from growing as fast as it could due to the size of a population and the area it inhabits.
Organism – An individual animal, plant, or single-celled life form.
Population – A group of individuals of the same species living in an area.
Sexual reproduction – Where offspring are produced from two organisms mating causing it to inherit genetic information from both parents.