ECOSYSTEMS

Learning objectives

Terms and definitions Define the term ecosystem and be aware of variations in ecosystem scale ranging from micro-scales to macro-scales (biomes). Be able to define ecosystems in terms of inputs, flows, stores and outputs.  

Biotic and abiotic components Demonstrate an awareness of how the biotic (plants, animals, soil, bacteria, fungi) and abiotic (water, air, minerals, nutrients, light) components interrelate to form a natural functioning system, taking into account other contributory factors of acidity, temperature, humidity and wind.

Links between the various components Understand the relevant concepts of dynamic equilibrium, food webs and food chains. Demonstrate an awareness of the complexity of links between biotic and abiotic components and how changes to one or more of the components can disturb the equilibrium of the system, especially as a result of human activity. Understand how positive and negative feedback contribute to the stability of the system.

Fragility, vulnerability and resilience of the system Understand that changes to ecosystems may be temporary (where recovery may occur leading to the re-establishment of the system) or permanent, leading to modification of the system.  

biosphere The part of the Earth including air (atmosphere), water (hydrosphere) and minerals (lithosphere) where life can exist is called the biosphere.

One particular type of organism. Homo sapiens species One particular type of organism. Homo sapiens

population All the members of a species living in a particular area at the same time.

community All of the different populations of organisms which live together for example the grasses, trees, insects, deer and birds which live in a part of a wood.

biota or the biotic factors The living organisms in an ecosystem – the plants, animals, and micro-organisms.

The non-living chemical and physical parts of the environment. abiotic factors The non-living chemical and physical parts of the environment.

sun’s energy + = carbohydrates producers sun’s energy + = carbohydrates

consumers

detritivores and decomposers Detritivores digest the organic matter internally after ingesting it. They speed up decay by shredding the dead matter, thereby increasing the surface area for attack by the decomposers - bacteria and fungi (e.g., mushrooms). Both bacteria and fungi have the capacity to release enzymes that break apart the organic molecules, thereby releasing the inorganic elements into the environment (e.g., soil or water). This process is called decomposition.

Some of these elements are then taken inside the bacteria or fungus to provide them with nutrients, as well as energy; those that are not taken in may be absorbed by plants and are eventually passed to herbivores and carnivores in the food chain. Nutrient cycling within an ecosystem is not a perfect process because some nutrients may be lost from the ecosystem as a result of soil erosion.

Detritus - Dead organic matter Detritus - Dead organic matter. It includes the dead bodies of all organisms, as well as fecal matter and shed body parts (e.g., snake skin, outer shell of crayfish after it is molted). Detritivore - Organism that eats detritus. These are important in decomposition, but they are not decomposers. The term scavenger specifically refers to animals that feed on dead animals or their remains. Decomposer - Organism (bacteria or fungi) that is able to release enzymes outside of its body in order to digest organic matter into inorganic elements (saprophytes). Decomposition - gradual disintegration of dead organic matter resulting in the release of energy and inorganic elements from their organic state.

food web

feeding or trophic level

pyramid of energy

Energy (90%) is lost at each stage Not all of the plant is eaten Unable to digest or break down all of the material consumed Running Respiration Growing

Pyramid of numbers/ biomass It takes a large number of primary producers to support a smaller number of primary consumers, which in turn provide food for an even smaller number of carnivores. Pyramid of numbers/ biomass

symbiosis Where two organisms live together in an intimate situation that is of benefit to them both.

The place where a particular organism or population lives. habitat The place where a particular organism or population lives.

niche This refers to an animal’s role in a habitat – what it feeds on and when, where it finds shelter, etc.

Competition between two members of the same species. intraspecific Competition between two members of the same species.

Competition between members of two different species. interspecific Competition between members of two different species.

Gradual progression from one community to another. natural succession Gradual progression from one community to another.

primary succession The introduction of species into an area that has never previously been colonised.

primary colonisers form a pioneer community The first species to enter an area.

secondary succession The re-establishment of species into an area that once contained populations of plants and animals, but which have been disturbed.

(climatic) climax community Eventually a stable ecosystem develops which is in equilibrium with its environment and which normally undergoes little further change.

different soil types different climax community edaphic climax different soil types different climax community

plagioclimax A climax community produced by the action of humans. Succession is then said to be deflected.

Environmental factors which produce zonation on rocky shores: Ability to withstand drying (desiccation) Ability to withstand wave pounding

Species diversity (D) can be calculated from the formula: The most common formula for working out Species Diversity is the Simpson’s diversity index Simpson's diversity index, which uses the following formula: Where: D = diversity index N = Total number of organisms of all species found n = number of individuals of a particular species Usually used in studies of vegetation but can also be applied to animals.