energy transfers and the nutrient cycle

an ecosystem is a form of biological community containing all living and non-living factors

all living organisms require energy to live for various processes e.g. some organisms obtain energy from the sun (plants) and some from consuming other organisms

energy is used (and CO2) to synthesise organic compounds e.g. in plants most sugars synthesised by plants are used as respiratory substances, the rest are used to form other biological molecules e.g. lipids These molecules form the biomass

it is measured in terms of carbon or dry mass of tissue per given area Or chemical energy store in dry biomass which is measured using calorimetry.

chemical energy store in dry biomass which is measured using calorimetry. The amount of heat given off tells you how much energy is in it. Energy is measured in joules (J) or kilojoules (kJ). A sample of dry biomass is burnt and the energy is used to heat to heat a known volume of water. The change in temperature is used to calculate the chemical energy of the dry biomass

food chains consists of many trophic levels

energy is transferred throughout these trophic levels Energy is lost throughout the food chain through process like respiration, excretion of faeces and urine

net production of trophic level / net production of previous trophic level x 100

net primary production (NPP) net production

NPP = GPP-R is is mainly used for plant forwth an reproduction because it does not take into accoint energy losses due to excretion and urine. However it is available for herbivores and decomposes as they mainly obtain their energy via producers

we can use via gross production (GPP) which is the chemical energy store in PLANTS’ biomass, in a given area or volume

After knowing the GPP we can measure the NPP (net primary production) which is the chemcial energy store in plant biomass AFTER RESPIRATORY LOSSES to the environment

net production is used for consumers higher up the tropic level we use this equation: N = I -(F+R) I= Chemical energy store in injested food F= Chemical energy lost to the environment in faeces and urine R= respiriroy losses to the environment

the rate of primary/ secondary production is called primary/ secondary PRODUCTIVITY This measured as biomass in a given area per time it is a good way to measure primary and secondary production as it often changes with seasons

nutrients are recycled within natural ecosystems in order to build important organic materials e.g. DNA

the main microorganisms are saprobiants saprobiants are organisms that digest their food EXTERNALLY and then ABSORB THE PRODUCTS e,g, fungi

they are fungal “associations” or a connection between plant roots and fungi Mycorrhizae provide a large surface area for the uptake of water and inorganic ions They act like a sponge so they can absorb and absorb and hold water and minerals

the relationship between plants and fungi are mutualistic/ symbiotic as the plant provides the fungi with carbohydrates while the fungi provides the plant inorganic ions/ water

• nitrogen - fixation • ammonification • nitrification • denitrification

• nitrogen fixing bacteria converts atmospheric nitrogen to ammonium ions the nitrogen fixing bacteria are either free - living in the soil or have a mutualistic relationship with legumious plants e.g. clovers and beans as they can live in their ROOT NODULES

• ammonium ions in ammonification are produced from organic nitrogen e.g. decomposition of proteins, DNA, urea e.t.c are converted to ammonium ions which are released into the soil • this is carried out by saprrobiants: bacteria and fungi that can digest waste externally

• ammonium ions in the soil (produced via ammonification and nitrogen fixation) are oxidised to nitrites then nitrates by nitrifying bacteria this is a two stage oxidation reaction

• it converts nitrogen in compounds back to nitrogen gas • denitrification is not a useful process as nitrogen gas cannot be absorbed by plants It is carried out by Anaerobic denitrifying bacteria which iswh farmers aerate their soil so denitrification is limited

• environmental conditions e.g. erosion and weathering causes the release of phosphate ions by rocks into soil and bodies of water • plants assimilate (take in) these phosphate ions the phosphate ions are used by plants to sythesise DNA e.t.c • animals eat the plants and use the ions to sythesise organic materials • animals die and decompose returining the phosphate to the soil • bacteria (sapriobiants) in the soul break down phosphate into inorganic form (mineralisation) • inorganic forms of phosphorus can end up in water via rainfall again and be assimilated by plants