Ecosystems (Cambridge (CIE) AS Environmental Management)

Introduction to Ecosystems

• The biosphere is the life-sustaining zone where the air (atmosphere), water (hydrosphere) and land (lithosphere) meet

• Many different biomes and ecosystems exist within the biosphere

  • The type of biomes and ecosystems present depends on which area of the planet they are located in

  • These biomes and ecosystems are mainly determined by the levels of water availability and the amount of insolation (the amount of sunlight they receive)

Biomes

• Biomes are large-scale ecological communities or ecosystem types that are characterised by their dominant vegetation, climate, and other abiotic factors that shape their biotic communities

• Biomes cover large geographic areas (different ecosystems can be found within a single biome)

• Biomes are classified into five major classes:

  • Aquatic

  • Forest

  • Grassland

  • Desert

  • Tundra

Ecosystems

• Ecosystems cover smaller geographic areas compared to biomes

• An ecosystem includes living, biotic components (such as plants, animals and other species present) and the physical environment (the non-living, abiotic components) they interact with

  • These physical, abiotic components include factors such as temperature, light availability, humidity, water availability, oxygen levels, salinity, and pH

Population

• A population is defined as a group of organisms of the same species living in the same area at the same time

Community

• A community includes all of the populations living in the same area at the same time

  • Within a community, each species depends on other species for food, shelter, pollination, seed dispersal etc

  • If one species is removed it can affect the whole community

  • This is called interdependence

Habitat

• A habitat is the local environment in which a species normally lives

  • E.g. badgers, deer, oak trees and ants are all species that would live in a woodland habitat

• Organisms adapt to their habitat through natural selection, in order to survive and reproduce successfully

Niche

• A niche describes the particular set of abiotic and biotic conditions and resources to which an organism or population responds

• 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

• For example, the three North American warbler species shown below all occupy the same habitat (spruces and other conifer trees) but occupy slightly different niches as each species feeds at a different height within the trees

  • This avoids competition between the three species, allowing them to co-exist closely with each other in the same habitat