Energy and ecosystems Flashcards
What is meant by an ecosystem
a form of a biological community containing all living an non living factors
2 ways organisms obtain energy
Plants can obtain energy from the sun
some organisms consume other organisms to obtain energy
2 ways biomass can be measured
the mass of carbon or dry mass of tissue per given area
chemical energy store in dry biomass can be measured using calorimetry
Structure of a food chain
producer –> primary consumer –> secondary consumer –> tertiary consumer
How do plants use energy
To synthesise sugars which are used either as respiratory substrates or to form other biological molecules which form the biomass of the plant
2 ways energy is lost through trophic levels
respiration
excretion
what is gross primary production
the chemical energy store in plant biomass in a given area or volume
What is net primary production
the chemical energy store in plant biomass after respiratory losses have been accounted for
What is net primary production used for
plant growth and reproduction but is available for other trophic levels such as herbivores or decomposers
Net production formula
N = I - (F + R)
I = chemical energy store in food
F = chemical energy lost by excretion
R = respiratory losses
How is rate of primary/secondary production measured
as biomass in a given area in a given time
What are Saprobionts and an example
organisms that digest their food externally then absorb the products
fungi are saprobiotic
What is mycorrhizae and what does it do
Fungal associations between plant roots and fungi
provides a large surface area for uptake of water and inorganic ions
acts like a sponge so can absorb and hold water and minerals easily
What type of relationship do plants and fungi have
mutualistic, as the plant provides the fungi with carbohydrates and the fungi provides the plants with water and inorganic ions
The 4 steps of the nitrogen cycle and why is it important
Nitrogen fixation
ammonification
nitrification
denitrification
needed to create DNA, RNA, ATP etc
Describe nitrogen fixation and where are nitrogen fixing bacteria found
nitrogen fixing bacteria convert atmospheric nitrogen to ammonium ions
these bacteria are either free living in the soil or have a mutualistic relationships with leguminous plants and live in their root nodules
Describe ammonification and what organisms carry this out
Organic nitrogen from decomposition of proteins, DNA , urea etc are converted to ammonium ions which are released into the soil
carried out by Saprobionts, bacteria or fungi that can digest waste extracellularly
Describe nitrification
ammonium ions in the soil are oxidised to nitrites then nitrates by nitrifying bacteria
2 STEP OXIDATION
Describe denitrification and what organisms carry this out
Converts nitrogen compounds back into nitrogen gas
not as useful as nitrogen gas cant be absorbed by plants
carried out by anaerobic denitrifying bacteria
The role of fertilisers and the two types
replace the nitrates and phosphates lost by harvesting plants and removing livestock
natural or artificial fertilisers
examples of natural fertilisers and the advantages/disadvantages
manure, peat, seaweed, guano
cheaper, or free if from own livestock
exact minerals and proportions cant be controlled
the advantages/disadvantages of artificial fertilisers
they contain exact amounts of minerals, they are more water soluble so higher absorption of inorganic ions
can lead to leaching and eutrophication
what is leaching
the washing of water soluble compounds into bodies of water
the leaching of nitrogen fertilisers can lead to eutrophication
stages of eutrophication
leaching of nitrates can cause algae growth on the surface
excessive algae growth restricts light intensity underwater, so aquatic plants cant photosynthesis and can die
aerobic bacteria feed on the dead plant matter and respire, using up the oxygen in the water
fish and other aerobic organisms die due to lack of oxygen
