Energy transfers and nutrient cycles

ecosystem

• all organisms living in a particular area amongst all abiotic conditions

producers

• make their own food

• e.g glucose in photosynthesis

biomass

• mass of living material

• dry matter

• chemical energy stored

• measured using calorimeter

• dry out sample- heating until mass stays constant

• burn and that energy heats a set volume of water above

• temp change of water calculate chemical energy of dry biomass

GPP- gross primary production

• total amount of chemical energy converted from light energy by plants in a given area

• 50% is lost to the environment when plants respire

NPP- net primary production

• energy available for growth and reproduction- stored in biomass

• energy available for next stage of food chain

formula for NPP

• NPP= GPP- R

why is energy lost between trophic levels

• not all food eaten

• respiration

• excretion

forumla for net production

• N= I - (F + R)

• I= chemical ebergy ingested

• F= energy lost in faeces

• R= respiratory loss

farming practices to increase production

• reducing respiratory loss

  • keeping animals in pens to restrict movement

  • unethical

• simplifying food webs

  • pesticides- more crops

saprobionts

• micororganisms that are decomposers

symbiotic relationships

• mutually beneficial

• mycorrhizae- fungi made up of long thin strands that connect to plant roots

• increase surface area so plants can absorb water and ions in areas that may be scarce

• in return fungi get the orgnaic compounds - glucose made from the plants

nitrogen cycle

• nitrogen in atmosphere—→ ammonia= nitrogen fixation by nitrogen fixing bacteria found in root nodules of legumenous plants

• nitrogen in atmosphere—→ nitrates by lightning

• ammonia—> nitrite—> nitrate= nitrification by nitrifying bacteria

• nitrate—→ nitrogen in air= denitrifying by denitrifying bacteria- dont want his- anaerobic conditions

• nitrate—→ plants by active transport

• animals eat plants then animals die/ plants die—→ ammonia= decomposing by saprobionts

phosphorus cycle

• phosphorus in rock

• rock gets weathered and releases phosphates into soil

• plants take up phosphates by active transport

• animals eat plants

• animals excrete

• phosphates back in soil

• phsophates into seas/rivers/lakes

• taken up by algae

• algae eaten by animals e.g fish

• fish eaten by birds

• birds excrete

• back in soil

• sedimentation back to rock

how are nutrients lost

• harvesting crops- minerals in pkants removed from their nutrient cycles

• animals get slaughtered- no waste- no nutrients back in cycle

artificial/ natural fertilisers

• fertilisers replace lost nutrients

• artificial= inorganic- contain pure chemicals

• natural= organic matter e.g manure

environmental issues of fertilisers

• leaching- fertiliseres get into water ways especially after heavy rainfall- leading to eutrophication

• less likely in natural fertilisers becuase organic compunds are decomposed before being absorbed by plants

• can cause crops to die if they get too much of one nutrient and less of another- phosphates less soluble than nitrates

eutrophication

• minerals get inot water ways-lakes/rivers

• rapid growth of algae on surface

• blocks light reaching plants below surface

• those plants die becuase they can’t photosynthesise

• bacteria feed on dead plant matter

• more bacteria carrying out aerobic respiration

• lowes oxygen conc in water

• fish die- not enough oxygen