D4.2 Transfers of Energy and Matter

ecosystem

all the organisms (biotic) and abiotic factors in an area

open system

energy and matter (chemical resources) are exchanged

ex: ecosystem

• exchange energy and matter with adjacent ecosystems/environments
  ex: animal migration, crop harvesting, gas/water flow

closed system

only energy is exchanged

• matter (chemical resources) cannot be removed or replaced

ex: mesocosm, winogradsky column

isolated system

energy and matter are trapped inside (NO EXCHANGE)
ex: universe

impact of sunlight in ecosystems

initial/primary energy source for most ecosystems

• producers convert solar energy (heat and light) into chemical energy (through photosynthesis)

EXCEPTION:

• ocean levels below light penetration
  -cave ecosystem

why does light intensity and content/proportion absorbed vary?

light intensity and content/proportion absorbed varies:

• different global position (proximity to equator)
• different depths/conditions in aquatic environment
  (sunlight penetration, murky/cloudy water)

exception of sunlight as a primary source of energy in an ecosystem

1. ocean levels below sunlight penetration
2. cave ecosystems
   == rely of other energy sources

• open caves:
  every source: dead organisms that flow into the cave
  -> digested by saprotrophs
  ex: faeces, detritus, decaying organisms

• closed caves:
  chemosynthetic bacteria (chemoautotrophs)
  -> energy from chemical reactions (oxidation reactions)

chemical energy flow through food chains

producers (autotrophs) -> primary consumers -> secondary consumers -> tertiary consumers

Chemical energy (energy molecules such as carbohydrates) gets passed on to a consumer as it feeds on an organism that is the previous stage (trophic level) in a food chain.

• This energy transfer allows for the movement of energy from producers to consumers in an ecosystem.

food web

decomposers

Organisms that break down the organic matter (dead remains)

• get energy through CARBON COMPOUNDS in organic matter
  ex: saprotrophic bacteria, fungi

categories:

• saprotrophs
  -detritivours

how is dead organic matter generated

• death of whole organisms
• defecation (removal of faeces from the gut)
• shedding of leaves, skin cells, hairs, arthropod exoskeletons (moulting) and other unwanted body parts.

how does dead organic matter contain chemical energy

carbon compounds

how are ions like ammonium released into the abiotic environment

through decomposers

saprotrophs

a type of decomposer that digests things externally

• through saprotrophic digestion

detritivores

decomposer that digest internally

autotrophs

organisms that can synthesise all the necessary carbon compounds itself using inorganic substances in the environment

• through carbon fixation and anabolic reactions (require energy source ex: inorganic chemical reactions, light)

such as: carbohydrates, amino acids, fatty acids, steroids, nucleotides etc

ex: plants, algae, cyanobacteria

• self feeding
• make and oxidise their own carbon compounds

photoautotrophs

use sunlight to make carbon compounds by photosynthesis
ex: plants

how do autotrophs get energy

anabolic reactions (condensation reactions) - building larger molecules (example - to synthesis carbon compounds) - REQUIRES ENERGY:

carbon fixation (calvin cycle) - photosynthesis

sunlight - used by photoautotrophs

chemical reactions (oxidisation) - used by chemoautotrophs

chemoautotrophs

use energy from oxidisation (electron - energy- removed) reactions to synthesise carbon compounds
ex:

• bacteria
• archaea

example: acidithiobacillus ferrooxidans (iron oxidising bacteria)

• absorbs Fe2+ ions from environment and removes an electron

Fe 2+ -> Fe 3+ + electron (excited)

iron oxidising bacteria and energy

absorbs Fe2+ ions from environment and removes an electron

Fe 2+ -> Fe 3+ + electron (excited)

oxidisation: energy loss

iron is oxidised when exposed to air
oxidation releases energy
iron-oxidising bacteria harnesses this energy

bacteria captures the electrons (gets reduced) to use in ways similar to ATP production in respiration and ATP usage in calvin cycle

heterotrophs

organisms that receives carbon compounds (and energy) by feeding on other organisms

• oxidise carbon compounds they consume

digestion

chemical breakdown of molecules (so that they can be absorbed to synthesise new compounds)

2 categories:

• digest internally: consumers (ingest food, digest and absorb)
• digest externally:
  saprotrophs
  (secrete enzymes that digest, then absorb)

why do all organisms need ATP energy

• anabolic (condensation) reactions to synthesise larger molecules
  ex: proteins, polysaccharides, triglycerides, nucleic acids

• active transport

• movement of vesicles and other structures, locomotion, muscle contraction

• maintain constant body temperature

how to autotrophs and heterotrophs produce ATP

during cell respiration

carbon compounds (ex: carbs, lipids) are oxidised to release energy (e-) and this energy (e-) is used to phosphorylate ADP to ATP

contruction of energy pyramids

show the amount of energy gained per year per unit of area at each trophic level
unit: (MJ m-2 y-1)

• 10% transferred only in each tropic

• label with trophic level, energy value, units

energy loss in trophic levels

only 10% of energy is transferred to the next trophic level

• 90% of energy is lost between trophic levels

reasons for energy loss:

• incomplete consumption:
  not all food is consumed

• incomplete digestible:
  not every part eaten is digested or digestible

• cell respiration:
  carbon compounds that have been oxidised in respiration cannot pass to the next trophic level + heat

heat loss due to conversion of chemical energy during respiration

• useful to some organisms (warm blooded organisms)

• heat cannot be converted back into chemical energy and therefore cannot be passed onto the next trophic level

• constant energy flow is necessary for ecosystem sustainability

how does energy loss limit trophic levels

90% energy is lost between each tropic level

this limits:

• the amount of biomass at each level
  (biomass of consumers reduces at each trophic level)
  ex: there are more secondary consumers than tertiary, more primary than secondary, more producers than primary)

• number of trophic levels

how do autotrophs and heterotrophs increase biomass

growth and reproduction

• lead to an increase in biomass (carbon compounds)

gross primary production GPP

total biomass of carbon compounds made during photosynthesis

unit: g C m-2 yr-1

GPP = NPP + respiration

net primary production NPP

the amount of biomass available to consumers due to the loss of biomass during respiration in plant cells

unit: g C m-2 yr-1

NPP = GPP - respiration

how do biomes have different biomass production capacities

biomes vary in capacity to accumulate biomass, depending mainly on rate of photosynthesis

how do heterotrophs grow and reproduce to raise biomass

using carbon compounds (ex: sugars, amino acids) obtained by organisms from lower trophic levels

secondary production

increase in carbon compounds in biomass by heterotrophs

how does secondary production affect ecosystems

• secondary production is lower than primary production

• secondary production declines with each next trophic level (less oxidisable carbon compounds) - less biomass per unit of area produced as you add trophic levels

pool

reserve or storage place for certain elements

BOXES USED

flux

transfer of an element from one pool to another

ARROWS USED

• width indicates relative size of fluxes

carbon cycle

carbon fluxes:

1. photosynthesis:
   absorption of CO2 from air/water and conversion to carbon compounds

2. feeding:
   gaining carbon compounds from other organisms

3. respiration:
   release to the atmosphere of CO2 by respiring cells

carbon sink

net uptake of carbon
store more than released

stored fossil fuels, boreal forests

carbon source

net release of carbon
release more than stored

combustion of fossil fuels (carbon sink)

what influences carbon sinks and stores

• decomposition rates

• bio sequestration

• fires

• combustion
  etc

• amount of photosynthesis

• amount of respiration

fossilisation as a carbon sink

fossilisation creates a carbon sink in the form of peat, coal, oil, natural gas

• combustion released carbon = becoming a carbon source from a sink

in order for the atmospheric CO2 levels to remain constant, uptake in sinks needs to be equal to release from sources

anthropogenic causes of climate change:

• causes release to outpace uptake of carbon

keeling curve

overall trend:
UP - due to human activity

annual trend:
UP AND DOWN - due to photosynthesis rates

y axis: CO2 conc
x axis: year

what type of relationship do autotrophs and heterotrophs have

DEPENDENT:
autotrophs and heterotrophs are dependent on each other for metabolic substrates

photosynthesis:
6CO2 + 6H2O => C6H12O6 + 6O2

aerobic respiration:
C6H12O6 + 6O2 => 6CO2 + 6H2O

huge amounts measured/estimated in gigatonnes (10^15 grams)

recycling of chemical elements in ecosystems

all organisms have:
C H O N P + small amounts of other elements

• obtained through absorption or consumption

• no amount of element has ever run out because it is used and recycled by decomposers who return elements to the soil/environment for reuptake

nutrients cycle while its energy flows