3. nutrient cycles

to make proteins and nucleic acids (DNA / RNA)

NITROGEN GAS -> NITROGEN CONTAINING COMPOUNDS • nitrogen gas in atmosphere turned into nitrogen containing compounds • bacteria Rhizobium (found in root nodules) - turn nitrogen into ammonia which can be used by plants • mutualistic relationship - provide plant with nitrogen compounds, plant provides them with carbs

NITROGEN COMPOUNDS -> AMMONIA -> AMMONIUM IONS 1. nitrogen compounds from dead organisms / animal waste turned into ammonia by saprobionts. forms ammonium ions in soil

AMMONIUM IONS -> NITRITES -> NITRATES • nitrifying bacteria (nitrosomonas) change ammonium ions into nitrites • nitrifying bacteria (nitrobacter) change nitrites into nitrates • nitrates can then be used by plants

NITRATES -> NITROGEN GAS • denitrifying bacteria use nitrates in soil to carry out respiration and produce nitrogen gas • anaerobic conditions e.g. waterlogged soil

microorganisms such as bacteria or fungi that are decomposers

break down organic molecules into inorganic ions

• fungi symbiotic relationship with roots of plants • made up of long thin strands called hyphae which connect to plant roots increasing surface area • help plants absorb ions from soil which are scarce and increase uptake of water (in turn obtain organic compounds)

phospholipids, DNA, ATP

• phosphate ions (PO4 3-) in rocks released into soil by weathering • taken into plant through roots (with help of mycorrhizae) • transferred through food chain (plants eaten, consumers eaten) • lost from animal in waste products • when plants and animals die saprobionts break down organic compound releasing phosphate ions in soil for assimilation by plants. saprobionts also release from urine and faeces • weathering of rocks releases phosphate ions into sea, lakes, rivers. taken up by aquatic produces which is passed along food chain to birds • waste of sea birds (guano) high proportion of phosphate ions. returns phosphate ions to soils/ often used as natural fertiliser