nutrient cycles Flashcards
what do fungi and bacteria have an important role in
nutrient recycling
what is a natural ecosystem
A natural ecosystem is one that hasn’t been changed by human activity. In natural ecosystems nutrients
are recycle d though the food we bs, but human activity often disrupts the cyclin g of nutrients.
what are saprobionts
a type of decomposer
microorganisms such as bacteria and fungi are an important part of food webs, why?
Many are saprobionts (a type
of decomposer) — they feed on the remains of dead plants and animals and on their waste products (faeces,
urine), breaking them d own. This allows important chemical elements in the remains to be recycled.
how do saprobionts work
Saprobionts secrete enzymes and digest their food externally, then absorb the nutrients they need. This is
known as extracellular digestion. During this process, organic molecules are broken d own into inorganic ions.
Obtaining nutrients from dead organic matter using extra cellular digestion is known as saprobiotic nutrition
what do some fungi have symbiotic relationships with
the roots of plants
these relationships are known as mycorrhizae
what are the fungi made up of in mycorrhizae
The fungi are made up of long, thin strands called hyphae, which connect to the plant’s roots
what do the hyphae greatly increase the surface area of in mycorrhizae
The hyphae greatly increase the surface are a of the plant’s root system, helping the plant to absorb ions from
the soil that are usually scarce (e.g. phosphorus). Hyphae also increase the uptake of water by the plant.
what does the fungi obtain from the plant in the mycorrhizae
the fungi obtain organic compounds, such as glucose, from the plant.
what does the nitrogen cycle show
how nitrogen is recycled in ecostsystems
what do plants and animals need nitrogen to do
Plants and animals need nitrogen to make proteins and nucleic acids (D N A and RN A). The atmosphere’s made
up of about 78% nitrogen gas, but plants and animals can’t use it in that form — they need bacteria to convert it
into nitrogen-containing compounds first.
what does the nitrogen cycle show
The nitrogen cycle shows how nitrogen is converted into a usable form
and then passed on between different living organisms and the non-living environment.
what does the nitrogen cycle include
The nitrogen c y c le includes food chains (nitrogen is passed on when organisms are eaten), and four different
processes that involve bacteria — nitrogen fixation, am monification, nitrification and denitrification:
what is nitrogen fixation
Nitrogen fixation is when nitrogen gas in the
atmosphere is turned into nitrogen-containing
compounds.
Biological nitrogen fixation is carried out
by bacteria such as Rhizobium. They turn nitrogen
into ammonia, which goes on to form ammonium
ions in solution that can then be used by plants.
Rhizobium are found inside root nodules (growths on the
roots) of leguminous plants (e.g. peas, beans and clover).
They form a mutualistic relationship with the plants
— they provide the plant with nitrogen compounds
and the plant provides them with carbohydrates.
what is ammonification
Ammonification is when nitrogen
compounds from dead organisms are
turned into ammonia by saprobionts,
which goes on to form ammonium ions.
Animal waste (urine and faeces) also
contains nitrogen compounds. These are
also turned into ammonia by saprobionts
and go on to form ammonium ions.
