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
ecosystem
A
- all the living organisms that interact with one another in a defined area
4
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 - put in an oven at 80 degrees until all water evaporated
- water mass is not living so we don’t want to take it into account
- measures carbon mass and chemical energy of the organism
- organism must be dead
5
Q
why is not all energy transferred at consumer levels?
A
- used in biological processes, so transferred to environment as heat eg. respiration
- not all of an organism is consumed when killed eg. bone
- parts of organism may be indigestible and are lost as faeces eg. cellulose
- energy lost in urine
6
Q
why is not all energy transferred at producer level?
A
- only convert 1-3% sunlight they receive into chemical energy because:
- not all solar energy is available for photosynthesis, 90% reflected
- may be other limiting factors for photosynthesis
- energy used up in photosynthetic reactions
7
Q
how do human activities impact biomass transfer?
A
- agriculture makes food chains simple - producer, primary consumer, secondary consumer
- this means minimum energy is lost as there are fewer trophic levels
8
Q
equation for percentage efficiency of energy transfer
A
efficiency = useful energy output/energy input x 100
9
Q
equation for efficiency of energy transfer between trophic levels
A
efficiency = net productivity of primary consumer/ net productivity of producer x 100
10
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
11
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
12
Q
techniques to manipulate biomass transfer in agriculture
A
- artificial light in greenhouses
- optimising distances between plants
- irrigation
- fertilisers
- selective breeding
- fungicides/pesticides
13
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
14
Q
decomposer
A
- feeds on and breaks down dead plant or animal matter, turning organic compounds into inorganic ones available to photosynthetic producers
- saprotrophs - obtain energy from dead organic material by externally secreting enzymes which break down material into simple soluble molecules to be absorbed by the decomposer
15
Q
why is nutrient cycling of nitrogen important?
A
- allows for a constant supply of nutrients for the next trophic level
- fundamental to create proteins and nucleic acids
16
Q
detritivores
A
- organisms involved in decomposition
- speed up decay process by feeding on dead material
- they break it into smaller pieces of organic material, increasing SA for decomposers to work on
- eg. woodlice break down wood
17
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
18
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
19
Q
azotobacter
A
- free-living soil bacterium involved in nitrogen fixation
20
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
21
Q
ammonification
A
- decomposers break down dead organisms, faeces and urine into ammonia and then ammonium ions
22
Q
nitrification
A
- converting ammonia to nitrites then nitrates
- only occurs in well-aerated soil
- nitrifying bacteria:
nitrosomonas - oxidises ammonium into nitrites
nitrobacter - oxidises nitrites into nitrates - nitrite ions are soluble so can enter plants this way
23
Q
denitrification
A
- anaerobic conditions cause denitrifying bacteria to convert nitrates in the soil back into nitrogen gas in the atmosphere
- bacteria use nitrates as source of energy for respiration and nitrogen gas is released
24
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
25
nitrogen cycle steps
1. nitrogen fixation
2. nitrification
3. denitrification
4. ammonification
26
carbon cycle
- 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
27
why are CO2 levels higher at night?
- photosysnthesis only takes place in the light, CO2 only removed from atmosphere in the day
- respiration happens throughout the day and the night, releasing CO2 into atmosphere
28
how does human activity affect CO2 levels and what are the effects?
- combustion of fossil fuels - releases CO2 that has been trapped for years underground
- deforestation - less CO2 removed from atmosphere
- increased CO2 levels trap more thermal energy (greenhouse gas) in the atmosphere
- higher temperature of sea - less gas is dissolved, increasing temp of atmosphere further
29
succession
all biotic and abiotic changes in an ecosystem over time
30
primary succession stages
occurs where soil has not formed yet
- 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
31
pioneer species adaptations to colonise the environement
- produce large quantities of seeds or spores
- seeds germinate rapidly
- photosynthesise to produce own energy
- tolerance to extreme environments
- ability to nitrogen fix from atmosphere, adding to mineral content of soil
32
secondary succession
- 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
33
how can human activity disturb succession?
human activity can cause deflected succession
- 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
34
plagioclimax
- name of final stage of succession if it's stopped artificially eg. by agriculture
35
how do you measure distribution of organisms?
- line transect - laying a line along the ground and taking samples at regular intervals
- belt transect - 2 parallel lines marked, samples taken of area between them
36
how do you measure abundance of organisms?
- use random sampling and as large a sample size as possible to decrease the influence of chance
1. capture individuals in sample area
2. mark each individual
3. release and allow time to redistribute
4. recapture in original sample area
5. record no. of marked and unmarked present
6. estimated population size = first sample x second sample / no. recaptures marked individuals
