AQA A Level Biology - Populations in Ecosystems (2021-22)
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Course
Populations in Ecosystems
Institution
AQA
An in-depth informative booklet on Populations in Ecosystems including important definitions, how to investigate populations and much more. Also includes useful summary questions, required practicals relating to this topic and the specification.
, Definitions:
Ecosystem: All the organisms living in a community plus all the non-living (abiotic) conditions in the area in
which they live.
Community: A group of interacting populations of different species living in the same place at the same time.
Population: A group of organisms belonging to the same species found in the same area at the same time and
potentially able to interbreed.
Habitat: The environment in which an organism or population of organisms usually lives.
Biotic: The living features of an ecosystem, for example, the presence of predators or food.
Abiotic: The non-living features of an ecosystem, such as the temperature and the soil.
Niche: Is the role of a species within its habitat, for example, what it eats, when and where it feeds.
Ecosystems
All living things are found in the places where they are adapted to the local conditions, such as the local
temperature and the type of food available. An ecosystem is all the organisms living in a community plus all the
non-living conditions (abiotic conditions) in the area in which they live. Ecosystems include both abiotic and
biotic conditions and can vary in size, they could be as small as a single pond or as large as the ocean. The
place where an organism lives within an ecosystem is known as its habitat.
Ecological Niche
Within an ecosystem each organism has a niche. A niche can only be occupied by one species, however, it
could look like two species are filling the same niche. For example, two species could be eaten by the same
predator but eat a different variety of organisms. The niche a species occupies includes:
• Biotic Interactions: living interactions, what the organism eats and what it is eaten by
• Abiotic Interactions: non-living interactions, the temperature range an organism can live in or the time
of day when an organism is active
Important: If 2 species try to occupy the same niche, they will be in competition with one another. One species
will eventually be more successful than the other, until only one species is left, this is known as Competitive
Exclusion.
Example
A Common Pipistrelle Bat: lives throughout Britain on
farmland, open woodland, hedgerows and urban areas. It
feeds by flying and catching insects using echolocation (high-
pitched sounds) at a frequency of around 45 kHz.
A Soprano Pipistrelle Bat: lives throughout Britain in
woodland areas, near lakes and rivers. It feeds by flying and
catching insects using echolocation at a frequency of around
55 kHz.
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