Energy + Ecosystems Flashcards
What does an ecosystem in a particular area include?
- biotic (living) factors: e.g. organisms + their interactions
- abiotic (non-living) factors: e.g. T°C + rainfall
What do all ecosystems depend on?
- primary producers
What are (primary) producers?
- organisms able to make their own usable carbon compounds (e.g. glucose) using CO2 in atmo
How does energy enter an ecosystem?
- through producers: e.g. plants convert sunlight to CPE stored in organic molecules from CO2 in atmo (terrestrial ecosystems) or CO2 dissolved in water (aquatic ecosystems) by photosynthesis
What are e.g.s of products formed from photosynthesis?
- respiratory substrates (e.g. glucose)
- starch: ST energy storage molecule
- cellulose: structural component of plant cell walls
- lipids: LT energy storage molecule
- proteins: sugars combine w nitrates to make AAs = used to produce proteins
What is biomass?
- total mass of living material in a specific area over a set period of time
How can biomass be measured?
- dry mass/mass of C of organism/tissue in a given area
What is dry mass?
- mass or organism/tissue once water has been removed
What can be used to estimate the chemical energy stored in dry biomass?
- calorimetry
Describe the method of how calorimetry can be used to estimate the chemical energy stored in dry biomass.
Find dry mass of plant sample:
- weight crucible w/o sample then place sample in crucible + place in oven
- remove + weigh crucible at regular intervals during drying
- once mass of crucible stops dec. + becomes constant, sample is fully dehydrated
- subtract original mass of crucible to find dry mass of sample
Find energy released by sample of plant biomass:
- use a calorimeter to burn dried sample which uses energy released to heat a known volume of water
- measure T°C change of water (used to estimate chemical energy stored in sample)
- energy measured in J or kJ
What are the limitations of using calorimetry to estimate the chemical energy stored in dry biomass?
- can take a long time to fully dehydrate plant sample to find dry mass
- precise equipment (e.g. precise digital balance + thermometer) required
- more simple + basic calorimeter = less accurate estimate will be bc heat energy lost to surroundings
What is Gross Primary Productivity (GPP)?
- chemical energy store in plant biomass, in a given area/volume, in a given time resulting from photosynthesis
What is Net Primary Productivity (NPP)?
- chemical energy store, available to next trophic lvl in a food web (can be used to create new biomass), in plant biomass after energy lost from respiration (R)
What is the equation for Net Primary Productivity (NPP)?
NPP = GPP - R
What are the units for Gross Primary Productivity (GPP) + Net Primary Productivity (NPP)?
- kJ m^-2 yr^-1
- per unit area to standardise results: allows comparison of envi.s
- recorded per yr to account impact seasons have on rain, light + heat: provides annual avg to allow fair comparisons between envi.s
What is a tropic level?
- position of an organism in a food chain, web or pyramid
What is a food chain?
- linear sequence of organisms that show how energy + nutrients pass through an ecosystem
What is a food web?
- network of food chains in an ecosystem that shows how energy + nutrients move between organisms
What are consumers?
- organisms that obtain energy by eating other organisms bc it can’t make its own food
What are decomposers?
- organisms that break down dead organic matter into small soluble food molecules that they absorb by secreting digestive enzymes
- also release nutrients back into ecosystem: essential for growth of plants + other producers
How is energy transferred between organisms in an ecosystem?
- primary producers convert light energy into chemical energy, stored as biomass in biological molecules, by photosynthesis
- consumers (organisms in higher trophic lvls) ingest producers, transferring chemical energy in biomass of producers to biomass of consumers
How is energy lost along a food chain (why isn’t all energy transferred to consumer)?
- not all biomass of food is eaten (e.g. roots of plants/bones of animals) so chemical energy in this biomass is lost to envi.
- consumers can’t digest 100% of food they ingest so chemical energy in biomass of faeces egested is lost to envi.
- chemical (heat) energy lost to envi. when consumers respire + during excretion of waste products
How do you calculate the net production of consumers (N)?
N = I - (F+R)
- I: energy from ingested food
- F: energy lost to envi through faeces + urine
- R: energy lost from respiration
How do you calculate the % (efficiency) of energy transfer from 1 trophic lvl to the next?
- % efficiency = (chemical energy in consumer / chemical energy in ingested food) x 100
What strategies do farmers use to inc the yield of their crops or livestock?
- dec energy lost from crops to other organisms by removing pests
- dec energy lost from livestock through respiration by restricting their movement (pens) + keeping them warm (indoor + heated pens)
How do you calculate % yield?
% yield = (actual yield / theoretical yield) x 100
How can farmers remove pest species?
- using chemical pesticides: insecticides (chemicals that kill insect pests that eat + damage crops) + herbicides (chemicals that kill weeds that compete w crops for sunlight + water)
- using biological control: e.g. introducing a consumer of pest
