6.3 Ecosystems Flashcards
Define habit
The place where an organism lives
Define population
A group of organisms of the same species living in the same area at a particular time
Define communitry
All the populations of different species living in a habitat
Define ecosystem
A physical area that includes all living and non-living components and their interactions
Define niche
The unique role of an organism in its environment
Define species
A group of similar organisms that can interbreed to produce fertile offspring
Define ecology
The study of interactions between living organisms and their environment
What are biotic and abiotic factors?
Biotic: Living factors of an ecosystem
Abiotic: Non-living factors
What changes can occur to an ecosystem? (6)
- human activity
- migration/species introduction
- natural selection
- climate change
- natural disasters
- succession
What is a dynamic ecosystem?
An ecosystem where changes are occuring all the time
Give examples of abiotic factors (8)
- light intensity
- wind velocity
- rainfall
- temperature
- water availability
- pH
- oxygen availability
- inorganic ion availability
Give examples of biotic factors (7)
- competition (food, mates)
- predators
- grazers
- disease
- parasites
- humans cutting down vegetation
- reduced pollinators
Why is only some 1-3% of the sun’s light energy used by producers to make biomass (3)
- 90% reflected by leaf (only some wavelengths (red/blue) used by chlorophyll
- some light transmitted through the leaf without hitting a chloroplast
- other limiting factors e.g. CO2 concentration, temperature
What are trophic levels?
Each stage of a food chain/web
What is a producer?
Autotrophic organisms that create organic molecles from inorganic molecules - the start of food chains
How to calculate ecological efficiency?
(Energy after transfer/energy after transfer) x 100
(Biomass after transfer/biomass before transfer) x 100
What is a consumer?
Organisms that derive energy from feeding on other organisms
What is a primary consumer?
Occupies the 2nd trophic level + gains energy from feeding on producers
What is a tertiary consumer?
Occupies the 4rd trophic level + gains energy from feeding on secondary consumers
What is a quaternary consumer?
Occupies the 4rd trophic level + gains energy from feeding on tertiary consumers
What is a secondary consumer?
Occupies the 3rd trophic level + gains energy from feeding on primary consumers
Why are quaternary consumers usually the last trophic level?
There is not sufficient biomass/energy left to support more organisms as energy is lost between each trophic level
Give key aspects of pyramids of numbers (6)
- size of the bars is proportional to the number of organisms at each trophic level in the food chain
- easiest to produce as just requires counting of organisms
- producers alwasys at bottom
- doesn’t account for size of organisams
- not always pyramid shape
- watch out for trees + parasites
Give key aspects of pyramids of biomass (4)
- size of bars is proportional to biomass of each organism at each trophic level of food chain
- biomass measured by dry mass for land gm-2 or seas gm-3
- quick snapshot at particular time - not representative of seasonal changes
- difficult to get data for as organisms must be killed but are quite accurate
Explain the proces of obtaining biomass weight for use in a pyramid of biomass (3)
- Organism collected from environment
- Dried in oven at 105 to evaporate water
- Weigh until mass remains the same
Give key aspects of pyramids of energy (3)
- size of bars is proportional to the energy at each trophic level in the food chain
- most accurate and measure energy (kJ m-2) as different biomass material may have different energy content
- results more reliable than biomass
sExplain the proces of obtaining energy from an organism for use in a pyramid of energy
- Collect organism from environment
- Dry in oven at 105 to evaporate water
- Weigh unil mass remains the same
- Burn in O2 and record temp rise of fixed volume of water using calorimeter
Why does so little energy get passed between different trophic levels? (4)
- lost to environment as heat due to respiration + movement
- not all an organism is eaten e.g. bone, fur, feathers
- some parts indigestible so are egested as feaces
- lost in excretory materials e.g. urine
Why do secondary/tertiary consumers often access a higher % of energy avaialbe from the previous trophic levels compared to producers? (3)
- they are consuming meat which is more digestible and contains mainy proteins and fats.
- meat doesn’t contain cellulose, which can’t be digested by many secondary/tertiary consumers
- althoug some animals have indigestible parts e.g. fur, feathers, scales, bones
Define gross primary production
The total solar energy converted into organic matter in producers - mainly dependant on how much photosynthesis is occuring
Define net primary production
What’s left of the gross production after respiration has occured - biomass available for primary consumers
How to calculate net primary production?
Gross primary production - respiratory loss
Define net secondary production
What’s left of the biomass/energy in primary consumers after respiartion has occured - energy available for secondary consumers
Define net tertiary production
What’s left of the biomass/energy in secondary consumers after respiartion has occured - energy available for tertiary consumers
Give key aspects of agricultural ecosystems (3)
- ecosystem of domesticated animals or plants for food consumption
- humans try and get maximum energy transfer possible into food product
- fewer trophic levels is key
Compare natural and agricultural ecosystems (7)
Natural Ecosystem
- solar energy only
- low productivity
- more species diversity
- more genetic biodiversity
- nutrients recycled, little added
- population controlled naturally
- natural climax community
Agricultural Ecosystem
- solar + food + fossil fuel energy
- high productivity
- less species diversity
- less genetic diversity
- less recycled, more added e.g. fertilisers
- populations controlled with pesticides
- artificial community (no succession)
How can a plant’s net production be lowered? (9)
- eaten by pests
- leaves fall off
- low temperature
- not enough minerals
- not enough watrer
- not enough light
- too many minerals
- high temperature
- not enough CO2
How can photosynthesis be controlled? (8)
- temperature controlled by heaters + ventilation
- optimum temp for enzyme activity in photosynthesis
- light wave length controlled if dark
- higher light intensity more light dependent reaction
- cO2 controled by burning fuel
- more CO2 fixed in calvin cycle
- water supply controlled
- use of fertilisers + pesticides
How can productivity producing livestock be reduced (7)
- predation
- random reproduction
- heat loss to environment
- low food intake
- not enough water
- too much muscle movement
- killed by disease
How can livestock productivity be incresed? (7)
- fencing in
- selective breeding
- temperature control
- high protein meals
- provide water
- reduce movement
- vaccination
Define decomposition
Chemical process where larger organic molecules are broken down into smaller inorganic molecules
Give key aspects of decomposers (5)
- organisms that feed on and break down plant or animal matter
- turn organic molecules into inorganic molecules for uptake by plants
- include fungi + bactreria
- saprotrophs obtain energy from dead or waste organic material
- extracellular digestion means enzymes are secreted outside cells
Give key aspects of detritivores (5)
- organisms that feed on dead and decaying material
- break down into smaller pieces of organic material
- increase surface area for decomposers
- speed up decomposition
- perform internal digestion
Why are there short term fluctuations in atmoshperic CO2? (3)
Photosyntheis removes CO2 from the atmosphere and respiartion adds CO2 to the atmosphere
- reduced CO2 concentration during the day as photosynthesis rate is higher than repsiration rate
- increased CO2 concentration during the night as photosynthesis rate is lower than repsiration rate
What biological molecules contain nitrogen? (6)
- amino acids
- proteins
- nucleotides
- DNA
- RNA
- ATP
Why does nitrogen fixation have to occur? (3)
- N2 in the air can’t be accessed by plants
- it has to be fixed into the soil by nitrogen fixing bacteria
- so it becomes NH4+ which plants can use
Give key aspects of azotobacter (3)
- free living nitrogen fixing bacteria
- in the soil
- convert N2 to NH4+ using nitrogenase enzyme
Give key aspects of rhizobium (3)
- nitrogen fixing bacteria
- in root nodules of leguminous plants
- mutualistic symbiotic relationship
- rhizobium gain carbs from plant for respiration
- convert N2 to NH4+ using nitrogenase enzyme
Give key aspects of nitrifying bacteria (3)
Nitrosomonas - oxidise ammonium compounds into nitrites
Nitrobacter - oxidise nitrites into nitrates
- nitrates are highly soluble and are the form of which more nitrogen enters a plant
How else can nitrogen be fixed?
Non-living nitrogen fixation - Elecetrical energy in lightning combines oxygen and nitrogen in air to form nitrites + nitrates
Give key aspects of denitrification
Denitrifying bacteria converts nitrates back into nitrogen gas
- happens in anaerobic conditions - waterlogged soil
- bacteria use nitrates as an energy source creating nitrogen gas
Give an overview of ammonification (2)
- caused by decomposers/saprotrohps e.g. bacteria + fungi
- N2 in organic molecules into NH4+ & NH3
Give an overview of nitrogen fixation (2)
- caused by nitrogen fixing bacteria (rhizobium + azotobacter)
- N2 to NH4
Give an overview of nitrification (2)
- caused by nitrifying bacteria (nitrosomonas + Nitrobacter)
- NH4+ (ammonium ions) to NO2- (nitrites) to NO3- (nitrates)
Give key aspects of primary succession (3)
- starts with bare rock or sand
- no soil or organic material present to begin with
- could occur after volcanic eruption, earthquake, retreating glacier etc
How does ploughing fields increase plant growth? (6)
- Oxygen enters the soil
- Nitrifying bacteria respire
- Ammonium to nitrite
- Nitrite to nitrate
- To make protein
- Leading to growth
Give an overview of denitrifcation (3)
- caused by denitrfying bacteria
- NO3- (nitrates) to N2 (gas)
- only in anaerobicconditions (water logged)
How can adding manure increase crop yield? (5)
- Ammonium ions made from decomposition of manure containing proteins
- Ammonium ions converted into nitrate ions
- By nitrifying bacteria
- Nitrate ions taken up by plants
- Nitrogen needed for plant grwoth
Define succession (5)
- changes in abiotic factors
- caused by decomposition of current species
- to make the environment suitable for new species
- while other species interspecifically out compete earlier species
- repeated until a climax community is formed
Give key aspects of secondary succession (2)
- starts with a thin layer of soil
- contains no plant or animal species
What are sereal stages?
The steps of sucession
- pioneer community
- intermediate community
- climax community
Explain the stages of succession
- Barren land/bare rock
- Pioneer community coloniers
- Secondary colonisers
- Tertiary colonisers
- Tertiart colonisers
- Scrubland
- Climax community
Give key aspects of barren land/bare rock (2)
- no soil or organisms
e.g. retreating glacier, volcano lava cooling, sand dunes formation, mud forming in estuary
Give key aspects of pioneer species (8)
- suited to harsh environments
e.g. lichens, xerophytes, algae, mosses - arrive as spores/ seeds carried by wind or animal passing through
- die + decompose adding humus which contains nirates and can retain water
- produce wind-despersing seeds that reach new locations
- seeds germinate quickly
- can photosynthesise to produce food
- can fix nitrogen from the air
- can cope with extreme abiotic conditions e.g. drough, heat, cold
Give key aspects of tertiary colonisers (4)
- as environmental conditions imrpove, new species of plants arrive
e.g. ferns + grasses - rock continues to be eroded + mass of organic matter increases as organisms die
- organisms decompose to contribute to nutrient rich soil
Give key aspects of secondary colonisers (3)
- arrive as spores + seeds
e.g. mosses - die and decompose to form humus + soil
Give key aspects of scrubland (2)
- small trees + shrubs with many deep roots
- change abiotic factors + may out compete many earlier species
Give key aspects of climax communities (6)
- stable community
- little changes over time + no further succession
- few dominant species
- creation of many habitats, niches, food webs
- abiotic conditions very stable
- not always most biodiverse
Which part of succession is most diverse?
Between intermediate and climax community
What is deflected succession?
When succession is prevented by humans to stop climax communities being reached
What is animal succession?
As plant species change more habitats and food for consumers are created
What are plagioclimax communities?
Where a plant community is stopped or reaches its full climatic climax artifically by humans
How can humans control succession? (5)
- cutting down existing vegitation
- burning for forest clearance
- planting trees/crops
- grazing/trampling by domesticated animals
- harvesting planted crops
