Interdependence and competition
All organisms in an The living organisms in a particular area, together with the non-living components of the environment.depend upon each other. If the All of the members of a single species that live within a geographical area. of one organism rises or falls, then this can affect the rest of the ecosystem.
Within a All the organisms that live in a habitat (plants and animals)., each A type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully. depends on other species, for instance for:
- food
- shelter
- successful pollination
- successful seed dispersal
The most common Refers to the fact that all organisms that live in an ecosystem depend upon each other, for food, protection, shelter, etc, in order to survive. is for food. For example, in the simple A sequence (usually shown as a diagram) of feeding relationships between organisms, showing which organisms eat what and the movement of energy through trophic levels.:
grass → rabbit → fox
If the foxes in this food chain were killed, the population of rabbits would increase because they are no longer prey to the foxes. As a result, the amount of grass would decrease because the increased population of rabbits would be eating it.
Very small changes to ecosystems have large consequences, which can be difficult to predict. This means that all the organisms in an ecosystem are dependent upon each other. We call this interdependence.
A stable community is one in which the size of the populations of all species remain relatively constant over time. In the example above, the amount of grass, and the numbers of rabbits and foxes would all remain relatively constant. The different populations are living in a healthy balance within their environment.
Competition
Often, the organisms within an ecosystem compete for resources.
Competition can be The competition which occurs between organisms of different species for a common resource. or The competition between organisms within the same species. depending on whether organisms from different species or the same species are competing for these resources.
Competition in plants
Plants compete for:
- light, which is necessary for A chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic.
- space, avoiding shading so the plant can get maximum light for photosynthesis
- water from the soil, which is necessary as a The liquid in which the solute dissolves to form a solution. for chemical reactions and for photosynthesis
- minerals from the soil, so that the plant can form other products from the glucose produced by photosynthesis
Competition in animals
Animals might compete for:
- food
- a mate, so they can pass on theirThe basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production. to offspring
- territory - an animal may defend the territory where it lives
Competition creates a 'struggle for existence'. Individuals within a species that cannot compete effectively are unlikely to reproduce, and may die. This can be referred to as 'survival of the fittest' and is a driver for The process of change in the inherited traits of a population of organisms from one generation to the next.. Species that are unable to effectively compete may become A species that has completely died out..
Learn more about biotic and abiotic factors with Dr Alex Lathbridge.
Listen to the full series on BBC Sounds.
In this podcast, learn the key facts about biotic and abiotic factors. Listen to the full series on BBC Sounds.
