energy and ecosystems Flashcards
what are the principles of an ecosystem
producers (autotrophs)
- photosutotrophs use light energy , chemoautothropes use inorganic molecules
- through photosynthesis plant’s synthesis organic compounds from atmospheric or aquatic carbon dioxide
- most sugars synthesised are used as respiratory substrates
- rest used to make other biological molecules : biomass
heterotrophs cannot synthesise own energy but obtain from autotrophs or other heterotrophs as they act as consumers
biomass and it’s stored energy are transferred through trophic levels in a food web
how can you measure biomass
mass of carbon or dry mass of tissue per given area
- sample if organism dried in oven at low temp to avoid combustion
- sample reweighed at regular intervals
- all water removed when mass remains constant
- mass of carbon taken to be 50% of dry mass
dry mass more representative because water content of samples varies
the chemical energy stored in dry biomass can be estimated using calorimetry
- sample of dry biomass burnt
- energy released is used to heat known volume of water
- change in temp of water used to calculate chemical energy
what is gross primary production
chemical energy store in plant biomass in a given area in a given time
eg. total energy resulting from photosynthesis
what is net primary production and how to work it out
chemical energy store in plant biomass after respiratory losses
GPP-R
NPP is available for plant growth and reproduction and also to other trophic levels in the ecosystem
how to work out the net production of consumers
N= I-(F+R)
I - the chemical energy stored in ingested food
F- chemical energy lost through farces and urine
R - respiratory losses
what are the rates of productivity units
kJ ha^-1 year^-1
year takes into account seasonal variation
per unit area takes into account environments vary in size
why is energy transfer between the sun and producer inefficient
wrong wavelength of light
light strikes no photosynthetic region eg. barn
light is reflected
lost as heat
why is the energy transfer between producers and primary consumers inefficient
respiration loss
lost as heat
not all plant/ animal eaten eg. bones
some food not digested
what farming practices in crops can be used to increase energy transfer efficiency
herbicides kill weeds-> less competition -> more energy to create biomass
fungicides reduce fungal infections-> more energy to create biomass
pesticides - reduce loss of biomass from crops
fertilisers prevent poor growth from lack of nutrients
what farming practices in livestock can be used to increase energy transfer efficiency
reducing respiratory losses
- restrict movement
- keep warm
slaughter animal while still growing when most of their energy is used for growth
selective breeding to produce breeds with higher growth rates
tested with antibiotics to prevent loss of energy to die to pathogens