Ecosystems Flashcards
ecosystem
- all the organisms in an area and their interactions with the physical environment (characterised by flows of energy, matter etc.)
- a dynamic complex of plant, animal and microorganism communities and the non-living environment interacting as a functional unit
biomes
- geographically and climatically defined, usually described using vegetation characteristics and climate
- global patterns of: radiation, temperature and water availability. influence the distribution of vegetation types on a global scale
- biological subdivision reflecting the ecological and physio-gnomic character
community
a group of similar organisms of different species found living together in a particular area
habitat
the type of environment in which a species lives
biomass
the mass of organisms per unit area measured as J/m2 or kg/ha
primary productivity
rate of biomass produced by plants measured as J/m2/day or kg/ha/year
gross primary productivity
total fixation of energy
net primary productivity
GPP minus losses due to respiration = rate of production of new biomass
global patterns in primary productivity
- biological activity depends upon solar radiation
- productivity of vegetation follows a latitudinal pattern
- NPP decreases with latitude
factor limiting primary productivity
- carbon dioxide is normally 0.03% of the atmosphere and is not linked to variation in primary productivity
- other factors constrain productivity, such as local differences in abiotic conditions
- shortage of: water (restricts photosynthesis), mineral nutrients (slows down rate of growth), temperature (lethal or sub-lethal)
what determines biome distribution
- broadly respond to climate regions, though other environmental controls may be important
- biome classification emphasises the adaptation of organisms to the environment
- recognised by the types of species living within them
- water availability and temperature play a major role in distribution
global distribution of agriculture
- about 40% of global land use is used for agriculture
- changes in demand for food: population growth, but also changed in consumption
patterns of local energy flow
- energy enters the biological system when radiation is harnessed in photosynthesis
- grazers consume plants and release some energy in respiration
- dead plant and animal material are decomposed in the soil and more energy released through respiration of microbial decomposition
- energy cannot be recycled or re-used
ecosystem structure
each higher trophic level contains less energy due to losses to respiration within each level and inefficient transfer of energy between levels
biogeochemical cycles
- describe the flow of matter (nutrients, water etc.) through the various compartments
- lithosphere
- atmosphere
- hydrosphere
