Ecosystems Flashcards
1
Q
food chain
A
- shows flow of energy in the direction of the consumer
- linear
eg. plant–> herbivore—>omnivore —>tertiary consumer
2
Q
food web
A
- shows flow of energy between many different organisms
- shows all organisms that eat another and all that eat that one and so on
3
Q
what is biomass and how is it measured?
A
- mass of living material in an organism or tissue
- measured by dehydrating an organism to measure the dry mass
- water mass is not living so we don’t want to take it into account
- measures carbon mass ad chemical energy of the organism
4
Q
what happens to the energy transferred between trophic levels?
A
- used in biological processes eg. respiration
- not all of an organism is consumed when killed eg. bone
- parts of organism may be undigestable and is lost as faeces eg. cellulose
- not all wavelengths of light can be absorbed in photosynthesis eg. green light is reflected
- not all sunlight reaches leaves eg. shady areas
5
Q
equation for percentage efficiency of energy transfer
A
efficiency = useful energy output/energy input x 100
6
Q
equation for efficiency of energy transfer between trophic levels
A
efficiency = net productivity of primary consumer/ net productivity of producer x 100
7
Q
productivity - gross and net
A
- the rate at which plants convert light energy into chemical potential energy
- gross primary productivity - total quantity of energy transferred by plants from sunlight
- net primary productivity - energy left as chemical energy after respiration
8
Q
how do you measure energy transfer between trophic levels?
A
- measure dry mass and burn it in a calorimeter
- energy in a 1g sample x dry mass of 1 organism x number of organisms = energy content
9
Q
techniques to manipulate biomass transfer in agriculture
A
- artificial light in greenhouses
- optimising distances between plants
- irrigation
- fertilisers
- selective breeding
- fungicides/pesticides
10
Q
techniques to manipulate biomass transfer in livestock
A
- antibiotics and vaccines
- control predation by fences
- reduce competition for grazing
-indoor barns to reduce movement and so heat loss
11
Q
why is nutrient cycling important?
A
- allows for a constant supply of nutrients for the next trophic level
- fundamental to create proteins and nucleic acids
11
Q
why is nutrient cycling important?
A
- ensures nutrients are available for the next trophic level
12
Q
A
12
Q
nitrogen fixation
A
- nitrogen needs to be converted into a more useful form such as ammonia or nitrate
- Azotobacter - lives freely in the soil
- rhizobium - lives inside root nodules - mutualistic relationship
- these bacteria contain the enzyme nitrogenase which combines atmospheric nitrogen (N2) with hydrogen (H2) to produce ammonia (NH3) which can be absorbed and used by plants
13
Q
rhizobium
A
- nitrogen fixing bacteria living inside root nodules - growths on leguminous plants
- mutualistic relationship - plant gains amino acids from ammonia, bacteria gains carbohydrates from photosynthesis from plant, used as energy source
14
Q
how does lightening link to nitrogen fixation?
A
- high temps of lightening bolts break bonds in atmospheric nitrogen
- this causes free nitrogen atoms in the air to bond with oxygen - nitrogen oxides
- these dissolve in moisture to form nitrates which are carried in the soil by the rainfall to producers
15
Q
ammonification
A
- organic material broken down by saprophytic bacteria to release ammonium ions into soil
- decomposers break down dead organisms, faeces and urine
16
Q
nitrification
A
- converting ammonia to nitrites then nitrates
- nitrifying bacteria:
nitrosomonas - oxidises ammonium into nitrites
nitrobacter - oxidises nitrites into nitrates - nitrite ions are soluble so can enter plants this way
17
Q
denitrification
A
- anaerobic conditions cause denitrifying bacteria in the soil back into nitrogen gas in the atmosphere
-bacteria use nitrates as source of energy for respiration and nitrogen gas is released
18
Q
assimilation of nitrogen from animals
A
- animals digest plants and convert their proteins into amino acids
- once absorbed they are built up again into proteins
- excess amino acids are deaminated in the liver to form urea
19
Q
carbon cycle
A
- animal respiration releases CO2
- plants use CO2 in photosynthesis
- dead organisms and waste products release carbon compounds through decomposition
- carbon released back into atmosphere when decomposers respire
- dead organic matter accumulates where decomposers aren’t present - form fossil fuels
- fossil fuels are burnt and CO2 is released back into the atmosphere - combustion
20
Q
succession
A
all biotic and abiotic changes in an ecosystem over time
21
Q
primary succession stages
A
- seeds and spores carried by wind land on newly formed or exposed rock and begin to grow
- these are called pioneer species eg. moss, lichen
- they decompose and the dead organic matter forms a layer of soil called humus
- seeds of small plants carried by wind or bird faeces land on humus and adapt to growing in nutrient-poor soil
- these plants die and decompose, the soil becomes deeper and more nutrient-rich
- larger plants and shrubs begin to grow in the deeper soil (more water and nutrients) - intermediate species
- once soil deep enough, large trees can grow and become the dominant species
- this is now a climax community
22
Q
secondary succession
A
- after a disturbance to a climax community or intermediate community eg. wildfire
- process of succession restarts but not from beginning as some nutrients still exist in the soil
23
Q
how can human activity disturb succession?
A
- mowing lawn
- livestock grazing eg. lake district lets sheep graze to prevent larger communities growing
- managed burning eg. Heather Moorland - burn old Heather allowing grouse to live there attracting tourists wishing to shoot them
