ECOSYSTEMS Flashcards
Define population
All the organisms belonging to one species that live in the same area at the same time and can interbreed
Define a community
Multiple organisms belonging to lots of species living in the same place, cannot interbreed
Define a habitat
Place where organisms live
Define niche
Role of an organism in the ecosystem including how it feeds, reproduces and finds shelter
Define producer
e.g. plant
An organism that transfers energy from light to an inorganic compound to organic compounds
Define a consumer
An organism that obtains energy from organic compounds which they digest and absorb
i.e. feed on other organisms
Define a decomposer
Feed on dead organic matter releasing mineral ions and other matter into soil and air
Define trophic level
Stage at which organism feeds in the food chain
Define an ecosystem
Relatively self contained unit of living organisms interacting with each other and their abiotic environment
Community + habitat
What are ecosystems
Dynamic- constantly changing
What are biotic factors
Living factors- interact between living organisms (e.g. predator/prey)
Feeding- herbivores- plants
Competition- two organisms require something in short supply
What are abiotic factors
Nonliving/physical factors (e.g. rainforest canopy effects temp and humidity)
Water availability
Oxygen conc
What is the result of extreme abiotic factors
Often slow growth, may kill organisms
e.g. temp
Ecological efficiency formula
Biomass/biomass x100
What percentage of sunlight is converted into photosynthesis
Less than 3
What are reasons for energy loss
light not hitting plant
Light being reflected from the leaf surface
Energy may be used to heat the plant or evaporate water
Define gross primary productivity
The light energy converted into chemical energy by photosynthesis
Some GPP used for respiration and energy lost to the environment as heat and materials lost as CO2 and water
GPP= NPP+R
Define NET primary productivity
Biomass and energy remaining in the plant after respiration
NPP is available for primary consumers, less than 10% is passed on
Why?
Not all parts of the plant are eaten (e.g. roots, branches)
Primary consumers can not be digest all the plant (cellulose, passed out in faeces and available for decomposers)
Energy lost as heat in consumers digestive system
Why is the efficiency of biomass transfer affected from consumer to consumer
Some animals are not eaten
Some parts of animals aren’t eaten (e.g. bones)
Energy is lost from the food chain as heat due to respiration
Why is energy loss greater from mammals and birds compared to other organisms
They are endothermic (warm blooded) so will lose more energy as heat
What does the primary productivity of an ecosystem vary due to
Climate- increased light intensity, rainfall, temp
Seasonal variation- organisms photosynthesise at diff times of year
Soil condition- mineral ion availability
State and explain some methods of intensive agriculture to increase production
High crop density- close planting, light hitting photosynthesising plants not the ground
Fertilisers- increase mineral ions in soil, more nitrates= more amino acids
Herbicides- less crop loss, higher yield. Doesn’t c change NPP or GPP, decreases competition
GM- increase efficiency and growth of plants
What is secondary productivity
Using primary consumer
Restrict movement- increase efficiency, decrease animal welfare
High energy foods
Use of antibiotics and steroids, increase resistance
Roles and examples of decomposers
Bacteria and fungi
Recycle nutrients from dead organisms and waste materials back into the ecosystem
How do decomposers feed
Saprotrophically
- secrete enzymes onto dead or waste materials
- digested/hydrolysed into smaller inorganic molecules
- small molecules absorbed into organism
- stored and respired
Examples and roles of detritivores
Earthworms, maggots, woodlice
Speed up decay by feeding on dead material and breaking them into smaller pieces
Increases SA for decomposers to work on
Why do living organisms need nitrogen
To make amino acids and nucleic acids
How do plants get nitrogen
From fixed nitrogen (already reacted)
Ammonium + nitrate ions
Where do animals get their nitrogen from
Food (amino acids)
Nitrogen fixation
Nitrogen gas + other elements –> reactive nitrogen compound
How does nitrogen fixation happen
Lightning strikes- 10%
Haber process
Nitrogen fixing bacteria (in the soil)- 90%
Free living nitrogen fixing bacteria
In soil
Fix nitrogen gas from air spaces in the soil
Manufacturers amino acids for growth
Die, decompose + nitrates to soil
Free living bacteria name
Azotobacter (italics, underline if writing)
Nitrogen fixing bacteria in root nodules
Living in root nodules of leguminous plants such as peas, beans, alfalfa
Rhizobium (underline)
Bacteria have mutualistic relationship with plant- provide plant with fixed nitrogen in return for glucose
Leghaemoglobin in the nodules absorb oxygen oxygen and keeps condition anaerobic- nitrogen reductase to recur nitrogen gas and ammonium ins
Ammonification
Decomposition of amino acids
Bacteria and fungi break down amino acids from dead organisms and nitrogenous waste for energy
-nitorgen compounds–> ammonia and ammonium ions
Nitrification
Ammonium compounds are oxidised by bacteria in the soil into compounds that plants can use
Nitrifying bacteria are chemoautrophic (gain energy from reaction)
Stages of nitrification
Ammonium ions oxidised to form nitrates (Nitrosomonas)
Nitrates are oxidised to nitrates (Nitrobacter)
Need oxygen from air bubbles
Dentrificiation
Some bacteria convert nitrates back into nitrogen gas
These bacteria are present in water logged soils: grow in anaerobic conditions
In this situation they will use nitrates as a source of oxygen for respiration and produce nitrogen gas and nitrous oxide
