Interdependence of Ecosystems
- An ecosystem is the living (biotic) and non-living (abiotic) components of an ecosystem
- Ecosystems vary in size and scale
- A small ecosystem could be a garden pond
- A large scale ecosystem could be all tropical rainforests - this is known as a biome
- Biodiversity is the variety of plant and animal species within an ecosystem
- The level of biodiversity depends on the climate, available habitats and food sources
- Within an ecosystem the different biotic components depend on each other and the abiotic components for survival (food, water and shelter)
- This is known as interdependence
- It means that changes in one component can have significant impacts on other parts of the ecosystem
- One of the main interactions between biotic components is feeding
- These links can be shown as food chains and food webs
- Within all food chains and food webs there are examples of:
- Producers: Food chains always start with a producer
- Primary consumers: Producers are eaten by primary consumers (herbivores/omnivores)
- Secondary consumer: Primary consumers are eaten by secondary consumers (carnivores/omnivores)
- Tertiary consumer: Secondary consumers are eaten by tertiary consumers (carnivores/omnivores)
- There are also decomposers, these are fungi and bacteria. They:
- Help to return energy/nutrients back to the soil
- Break down dead organic matter plant/animal waste
- Release energy from organic matter so it can be recycled
Food chains
- A food chain shows the feeding interactions and transfer of energy from one organism to the next
- The source of energy in a food chain is light energy from the sun
Simple Food Chain Diagram
An example of a food chain
Food webs
- The links between the biotic components can also be shown as a food web
- Food webs show the complex interaction of plants and animals that feed on each other
Food Web Diagram
A food web shows the interdependence of organisms
Interdependence
- The biotic and abiotic parts of the woodland are linked through nutrient cycle and food webs
- Trees such as the rowan, rely on birds eating the berries to disperse their seeds
- Some berries are dropped during flight to a new location
- The seeds have an indigestible coating which means that seeds which are eaten are deposited in droppings
- Oak trees rely on squirrels burying the acorns to store for winter. Acorns which are forgotten then germinate
- The trees in the woodland are mostly deciduous which means that they lose their leaves covering the ground with a thick layer which then decomposes adding nutrients to the soil
- A shrub layer of brambles, grass, bracken and other plants are the main producers
- In spring, before the trees come into leaf, more light reaches the woodland floor, allowing bluebells and daffodils to bloom
Impact of a change
- Deciduous woodlands in the UK have been affected by ash dieback
- Over 1000 species are dependent on ash including, wood mice, wrens, bats, lichen and beetles
- It is a significant tree for about 89 invertebrate species including, the endangered Violet Click beetle and the Hawk Moth caterpillar
- The removal and death of ash trees impact all of these species, which then has a knock-on effect on the species which feed on them
- Woodpeckers, other birds and small mammals which feed on the insects living on and in ash trees may experience a population decrease
- This impacts owls and other birds of prey, that feed on the smaller birds and mammals
- In the food web example above, if the population of caterpillars decreased:
- The population of grass plants would increase, as there are now fewer species feeding off them
- The populations of sparrows would decrease significantly, as earthworms are their only food source
- The population of hawks would decrease slightly, as they eat sparrows but also have another food source to rely on (mice and frogs)
Worked example
Select the correct definition of an ecosystem
(1 mark)
A. A type of tourism that protects the environment
B. The interconnectedness of environments
C. The interdependence of plants and animals with the environment they live in
D. The place where plants and animals live
Answer:
C. The interdependence of plants and animals with the environment they live in (1)
- The alternative answers are incorrect because:
- A: This is ecotourism
- B: It is not interconnectedness between environments
- D: This is a habitat
Ecosystem balance
- A stable ecosystem is one where all the biotic and abiotic components are in balance, so that the populations remain constant
- This may take hundreds of years to develop, but the balance can be disturbed very suddenly
- Disruptions to the ecosystem can be the result of either natural events or the result of human activity
- Natural events may include:
- Wildfires caused by lightning
- Climate change (though it can be argued this is human-induced)
- Spread of invasive species
- Disease
- Extreme weather events, e.g. flood or drought
- Human activities may include:
- Deforestation
- Hunting of animals/birds
- Introduction of invasive species such as grey squirrels which outcompete red squirrels for food and space. They also carry a disease called squirrel pox which kills red squirrels but not grey squirrels
- Hedgerow removal
- Changes to water supply/drainage patterns or temperature
- Addition of chemicals, e.g. fertilisers/herbicides/pesticides
- Fires used to clear land
- Natural events may include:
