populations in ecosystems

• community

  Multiple populations (of different species) living and interacting in the same area
• ecosystem


  The interaction between a community (the living, biotic part) and the non-living (abiotic) parts of the environment
• Ecosystem


  A relatively self-contained community of interacting organisms and the environment they live in, and interact with
• Flow of energy within an ecosystem

  Nutrients within it are recycled (e.g. the carbon, nitrogen and phosphorus cycles)
• Components of an ecosystem

  • Living (biotic)
  • Non-living (abiotic)
• Ecosystems


  • Small pond in a back garden
  • Open ocean
• Ecosystems

  • Vary in complexity
  • A desert is a relatively simple ecosystem
  • A tropical rainforest is a very complex ecosystem
• No ecosystem is completely self-contained as organisms from one ecosystem are often linked to organisms from another
• habitat


  place where species live within an ecosystem
• role that a species plays within its habitat is known as its niche, including:

  • The biotic interactions of the species (e.g. the organisms it feeds on and the organisms that feed on it)
  • The abiotic interactions (e.g. how much oxygen and carbon dioxide the species exchanges with the atmosphere)
• A niche can only be occupied by one species, meaning that every individual species has its own unique niche
• • If two species try to occupy the same niche, they will compete with each other for the same resources
  • One of the species will be more successful and out-compete the other species until only one species is left and the other is either forced to occupy a new, slightly different niche or to go extinct from the habitat or ecosystem altogether
• Adaptations to abiotic and biotic conditions

  • Adaptations are features of organisms that increase their changes of surviving and reproducing. These adaptations can be:
  • Anatomical (e.g. structural features such as horns, claws or feathers)
  • Behavioural (e.g. courtship of defensive behaviours)
  • Physiological (e.g. processes inside the body such as venom production or the ability to digest cellulose)
  • A species must be adapted to both the biotic and abiotic factors within its habitat in order to use this habitat in a way no other species can (i.e. in order to occupy its unique niche)
• changes that species produce in their abiotic environment can actually result in a less hostile environment

  • As a result, this can change or sometimes increase the biodiversity within that environment
• carrying capacity


  maximum stable population size of species that an ecosystem can support
• • Every individual within a species population has the potential to reproduce and have offspring which contribute to population growth
  • In reality, however, there are many abiotic and biotic factors that prevent every individual in a population from making it to adulthood and reproducing
• Abiotic factors involve the non-living parts of an ecosystem
• examples of abiotic factors that can limit population size include:

  • light availability
  • water supply
  • temperature
  • amount of space available
  • soil pH
• Biotic factors involve the living parts of an ecosystem

  • Biotic factors are the interactions between organisms includes competition for resources and predation
• Biotic factors can be split into three main types:

  • Interspecific competition
  • Intraspecific competition
  • Predation
• Interspecific competition


  Competition for the same resources between individuals from different species
• Competition between species


  Sizes of both populations are limited
• Competition between species

  Can lead to a decrease in the population size of one species and an increase in the population size of the other
• Intraspecific competition

  • This is competition for the same resources between individuals from the same species
  • For example:
  • When resources are plentiful, the population increases
  • As the population increases, however, there are more individuals competing for these resources (e.g. food and shelter)
  • At some point, the resources become limiting and the population can no longer grow in size - the carrying capacity has been reached
• Predation

  • Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers who are themselves eaten by tertiary consumers
  • Consumers that kill and eat other animals are known as predators, and those eaten are known as prey
  • In a stable community, the numbers of predators and prey rise and fall in cycles, limiting the population sizes of both predators and prey
• Sampling methods

  • There are three main sampling methods used when trying the estimate the size of a population:
  • Quadrats (for non-motile or slow-moving species)
  • Transects (for non-motile or slow-moving species)
  • Mark-release-recapture (for motile species)
• distribution of a species describes how it is spread throughout the ecosystem
• abundance of a species is the number of individuals of that species
• • The distribution and abundance of non-motile or slow-moving species in an area can be assessed using two different practical methods:
  • Frame Quadrats
  • Belt Transects
• Ecosystems are dynamic, meaning that they are constantly changing
• • Sometimes, ecosystems change from being very simple to being relatively complex
  • This process is known as succession
  • During succession, the biotic conditions (i.e. the living factors) and the abiotic conditions (i.e. the non-living factors) change over time
• • Primary succession is the process that occurs when newly formed or newly exposed land (with no species present) is gradually colonised (inhabited) by an increasing number of species
• Preventing Succession

  1. Introducing grazing animals temporarily

  2. Using managed burning to control fires and burn away shrubs and trees
• Grazing animals

  • Eat the growing shoots of shrubs and trees, stopping them from establishing and preventing succession
• Managed burning


  • Controlled fires are deliberately lit and allowed to burn away the shrubs and trees
  • Species such as heather (a key moorland plant) grow back quickly in their place
  • Resets the process of succession, meaning the larger, woody plants will take a long time to grow back, at which point the burning can be repeated
• National parks


  • Areas within countries where the wildlife and environment are protected
  • Governments control these areas and pass legislation to ensure their protection
  • Humans access is strictly controlled
  • Industrial activities such as agriculture and building are tightly regulated
  • Hunting is limited or completely prohibited
• Marine parks


  • Protected areas of water that have been set up for the conservation of endangered marine ecosystems and species
  • They also have restrictions to prevent overfishing and pollution
• Public engagement with conservation efforts

  Important for long term success
• Benefits of national and marine parks

  • Attract thousands of tourists each year which increases money and awareness for the conservation effort
  • Involving members of the local community in the management of protected areas can provide jobs and increase acceptance of the parks
  • Some of the profits made from parks can be used to improve the health and education standards in the nearby communities to illustrate the benefits of having such areas nearby
• Zoos

  Can contribute towards the conservation of endangered animal species