Ecosystems

Question 1

ecosystem

Answer 1

• 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

Question 2

biomes

Answer 2

• 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

Question 3

community

Answer 3

a group of similar organisms of different species found living together in a particular area

Question 4

habitat

Answer 4

the type of environment in which a species lives

Question 5

biomass

Answer 5

the mass of organisms per unit area measured as J/m2 or kg/ha

Question 6

primary productivity

Answer 6

rate of biomass produced by plants measured as J/m2/day or kg/ha/year

Question 7

gross primary productivity

Answer 7

total fixation of energy

Question 8

net primary productivity

Answer 8

GPP minus losses due to respiration = rate of production of new biomass

Question 9

global patterns in primary productivity

Answer 9

• biological activity depends upon solar radiation
• productivity of vegetation follows a latitudinal pattern
• NPP decreases with latitude

Question 10

factor limiting primary productivity

Answer 10

• 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)

Question 11

what determines biome distribution

Answer 11

• 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

Question 12

global distribution of agriculture

Answer 12

• about 40% of global land use is used for agriculture

- changes in demand for food: population growth, but also changed in consumption

Question 13

patterns of local energy flow

Answer 13

• 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

Question 14

ecosystem structure

Answer 14

each higher trophic level contains less energy due to losses to respiration within each level and inefficient transfer of energy between levels

Question 15

biogeochemical cycles

Answer 15

• describe the flow of matter (nutrients, water etc.) through the various compartments
• lithosphere
• atmosphere
• hydrosphere

Question 16

nutrient cycle

Answer 16

• nutrients can be recycled (compared with energy which cannot)
• decomposition produces free inorganic nutrients that can be taken up by plants
• the system is not closed, nutrients are lost in run-off or as gases

Question 17

nutrient budget

Answer 17

• the system is not closed, nutrients are lost in run-off or as gases
• inputs from: weathering of bedrock and soil, atmosphere, hydrological inputs, human activities
• outputs to: atmosphere, groundwater

Question 18

impact of land management

Answer 18

• efficiency of nutrient usage varies according to: vegetation type
• level of nutrient availability
• human activities can have a major impact on nutrient cycles
  deforestation (impacts nitrate levels in groundwater)
• cropping (nitrate leaching reduced)
• livestock

Question 19

nitrate leaching may be reduced by

Answer 19

• keeping vegetation cover (especially in periods of rainfall)
• encouraging accumulation of organic matter
• careful timing or irrigation

Question 20

improving efficiency

Answer 20

• fertiliser type
• application type
• application rate
• fertiliser placement
• plant selection
• microbial inoculants
• soil testing
• improved soil characteristics
• erosion reduction