Introduction to Biomes and Ecosystems

What is an ecosystem?

A community of organisms and the physical environment it occupies together forms an ecosystem.

 

(Source; Quest Garden- I spy an Ecosystem, Getting Kids activity in Science)

The Physical and biological components of ecosystems are linked by the process that it cycles nutrients and transfers energy through the systems

 

usage of.....FOOD WEBS AND TROPHIC PYRAMIDS (as depictions of carbon cycling and energy flow ecosystems)

 

 

Marine ecosystems:

          Open ocean (pelagic)

          Deep ocean (energy is transferred by chemical reactions)

          Upwellings (fertile due to nutrients from deep ocean)

          Continental Shelf (inshore/shallow seas)

          Estuaries and other land/sea ecotones (coves, bays, rias, lochs, saltmarsh, littoral zone, Mangrove swamps, coral reefs etc.).

 

Freshwater ecosystems/habitats:

          Lentic (standing water = lakes and ponds)

          Lotic (running water - rivers and streams)

          Wetlands (marsh and swamp forest)

 

Aquatic Habitats =

 

         Marine - sea water ≈ 1000 mOsm

Brackish -

         Intertidal -

Freshwater ≈ 2.7 mOsm

Marsh/swamp/bog -  Saltmarsh

 

Terrestrial Biomes: (biome = major regional ecological community)

         

Tundra (arctic and alpine)

Boreal Coniferous forest

Temperate Deciduous forest

Temperate Grassland (prairies and steppes)

Tropical Grassland  and Savannah (grassland with some trees)

Chaparral/Mediterranean   (Winter rain, summer drought)

Desert
 

Semi-evergreen tropical forest (pronounced wet and dry seasons)

Evergreen tropical rain forest

 

Domesticated Ecosystems:

 

Agroecosystems

Rural techno-ecosystems (small towns, motorways, railways etc.)

Urban-industrial techno-ecosystems (Metropolitan districts)

 

Terrestrial Habitats =

 

Arboreal - herb layer – shrub layer - tree layer – canopy

Desert

Soil Dwelling

Others (e.g. cave-dwelling/house dwelling)

 

What are the constituents of an ecosystem?

 

Two basic components:

 

Autotrophs: (self-nourishing) = primary producers

         

Photoautotrophs = photosynthetic bacteria, algae and plants.

 

Chemoautotrophs - e.g. nitrifying bacteria,

                             purple sulphur bacteria,

                             methanogens (use ammonium, nitrate,sulphur or hydrogen as substrate).

 

Heterotrophs: (Other-nourishing) = consumers

 

These can be further sub-divided into:

        Herbivores

        Carnivores (primary and secondary)

        Omnivores

        Detritivores = Saprovores.

 

Each of these groups of producers and consumers are said operate at different trophic levels.

Thus

1.  primary producers operate at the 1st trophic level

 

2.  primary consumers operate at 2nd trophic level

 

3.  secondary consumers operate at the 3rd trophic level

4.  tertiary consumers at fourth, etc. etc.

 

 

Taken in a simple form, links between trophic levels are termed food chains - eg., grass, antelope, lion.

 

Materials form CYCLES which may be relatively closed or open, depending on the system - e.g. Nitrogen cycle in rainforests is relatively closed compared to nitrogen use in agriculture.

Main elements are carbon, sulphur, nitrogen, phosphorus (no gaseous phase), oxygen and chlorine.

Most important substance = water