5 Energy transfers- Nutrient Cycles Flashcards
What are saprobionts and what do they play an important role in?
Microorganisms that feed on dead/decaying organic matter
Play important role in decomposition & recycling nutrients , eg in nitrogen cycle
What is the importance of nutrient recycling?
It allows nutrients to be continuously recycled in an ecosystem
What is extracellular digestion and what does it enable?
Extracellular digestion- saprobionts excreting enzymes onto dead organic matter
The enymes break down large, insoluble molecules into smaller, soluble ones which can be absorbed by saprobionts. They then store the molecules or use it in respiration
What is the role of saprobionts in the nitrogen cycle?
-Important in the ammonification stage of nitrogen cycle
-Through extracellular digestion, saprobionts break down organic matter containing nitrogen (eg urea, proteins)
-Ammonium ions are released, which move to the next stage of the cycle; nitrification
What is the first stage of the nitrogen cycle and what occurs?
Nitrogen fixation
-Atmospheric nitrogen (N²) is converted to ammonia (NH^3) by nitrogen-fixing bacteria in soil
-Bacteria form a symbiotic relationship with leguminous plants by inhabiting their root nodules; bacteria gives source of ammonium ions for plants and plants provide sugars
What is the second stage of the nitrogen cycle and what occurs?
Ammonification
-When an organism dies/produces waste (eg faeces), its decomposed by saprobionts
-This releases the nutrients contained inside
-Saprobionts decompose the organisms’ biomass via extracellular digestion & inorganic ammonium ions are released into soil
-Ammonification is a by-product of saprobiont nutrition
What is the third stage of the nitrogen cycle and what occurs?
Nitrification
-Ammonium ions release from ammonification are converted—> nitrates by bacteria in soil
-Nitrifying bacteria convert NH4+ ions to nitrites
-Another bacteria then convert nitrites to nitrates
What is the last stage of the nitrogen cycle and what occurs?
Denitrification
-Denitrifying bacteria convert nitrates in soil back into atmospheric nitrogen (N²), which takes place in anaerobic conditions (eg waterlogged soils)
What are mycorrhizae?
-Fungi that form symbiotic relationships with roots of plants
-They help plants absorb inorganic ions & water from soil
What is the structure of mycorrhizae?
-The fungi associate with the roots using hyphae (long strands that extend from the cell body)
What is the function of hyphae?
Increase surface area of the plant root system, which helps plants take up ions in short supply (like phosphorus) & water at a faster rate
How are phosphate ions taken up?
Phosphate ions are assimilated by plants because of symbiotic relationship between plant roots + mycorrhizae (help increase uptake)
How are phosphate ions broken down?
As phosphate ions are transferred through food chain, they’re lost as waste products/when organisms die
-Saprobionts decompose the waste/dead organisms through extracellular digestion
-Phosphate ions are released into soil & can be recycled to reuse in cycle
What is the use of fertilisers?
Replace nutrients lost from soil during harvesting & removing livestock to help maximise yields in agriculture
What are the agricultural impacts on soil?
-Leads to depleted levels of nutrients in soil (eg nitrogen, phosphate)
-This is because when crops are removed for harvest, they aren’t decomposed & nutrients aren’t returned to soil for reuse
-Removing livestock for slaughter also decreases nutrient levels as they aren’t replaced by decomposition
