Ecosystems chp 23 only done Flashcards
what is decomposition
chemical process where compounds are broken down into smaller molecules or its constituent elements
- define decomposer
- give features of them
- an organism that feeds on and breaks down dead animal/plant matter, turning organic material to inorganic
- they are saprotrophs
- primarily fungi and bacteria
what is a saprotroph
- obtain their energy from dead/waste organic material (saprobiotic nutrition)
how do decomposers digest food
digest food externally by secreting enzymes onto organic matter, this breaks the substances down and then the decomposer absorb these smaller molecules
what are detritivores
- help to speed up decaying process by feeding on detritus (dead/decaying matter)
- examples include woodlice and earthworms
what are some examples of nitrogen fixing bacteria
- azotobacter (found in soil)
- rhizobium (found In root nodules of leguminous plants)
what actualy is the process of nitrogen fixation
- bacteria containing nitrogenase combine atmospheric nitrogen with hydrogen to produce ammonia
what are the benefits of rhizobium (nitrogen fixing bacteria) living within a plants roots
- plant gains amino acids from rhizobium, produced by fixing nitrogen gas into ammonia
- bacteria gain carbohydrates produced by plant, which they use an energy source
what produces ammonia/ammonium ions in the nitrogen cycle
produced by nitrogen-fixing bacteria and decomposers
what producers nitries [NO2-] in the nitrogen cycle
- formed by nitrifying bacteria from ammonia
- plants cannot absord these
what produces nitrates [NO3-] in the nitrogen cycle
produced by nitrifying bacteria from nitrites [NO2-]
what is nitrification
- process where ammonium compounds in soil are converted into nitrogen-containing molecules that can be used by plants
what type of reaction is nitrification and how does this effect it
- oxidation reaction
- only occurs I well aerated soil
what are the steps of nitrification
- nitrifying bacteria oxidise ammonium compounds into [NO2-]
- nitrobacter oxidises nitrites into nitrates [NO3-]
what are some examples of nitrifying bacteria
- nitrosomonas
- nitrobacter
what is denitrification
- process where nitrates in soil converted back to nitrogen gas
- bacteria use nitrates as source of energy for respiration and nitrogen gas is realeased
what conditions must exist for denitrification to occur
- only happens under anaerobic conditions
what is ammonification
process by which decompress convert nitrogen containing molecules in dead/waste organic material into ammonium compounds
what are some abiotic factors that have that can fix nitrogen
- lighting strikes and the haber process
what are some abiotic factors that have that can fix nitrogen
carbon dioxide in the atmosphere & dissolved in the seas
what can turn inorganic carbon to organic carbon-containing molecules
- photosynthesis in plants
- carbon is used to produce carbohydrates, proteins & lipids
how can carbon be trapped under ground
- if dead organic matter is in a location where decomposers are not present the carbon it contains will not be released
- forms fossil fuels
what are the main reasons for the atmospheric rise in carbon dioxide levels
- combustion of fossil fuels (releases carbon dioxide)
- deforestation - removed massive parts of earths photosynthesising biomass, means less CO2 removed from atmosphere
define an ecosystem
- made up of all living organisms that interact with one another in a defined area
- also contains physical factors in regions
what 2 groups can factors that effect ecosystems be split into
- biotic and abiotic factors
what are biotic factors
- living factors
- can refer to interactions between living organisms
what are abiotic factors
- non-living/physical factors
what are some examples of abiotic factors
- light (effect photosynthesis)
- temperature (effects enzymes controlling metabolism)
- water availability
- oxygen availability
- edaphic (soil) factors
what are some different types of soil and what are there characteristics
- clay: has fine particles, easily waterlogged
- loam: has different-sized particles, retains water but doesn’t become water logged
- sandy: well separated particles, doesn’t not retain water well, is eroded easily
what are trophic levels
- stages in food chain/web
what is the 1st trophic level
- producer
what is the 2nd trophic level
- primary consumer
what is a meant by a producer
- organism that converts light energy into chemical energy via photosynthesis
what are primary, secondary, tertiary and quaternary consumers
- primary = animal that eats producer
- secondary = animal that eats primary consumer
- tertiary = animal that eats secondary consumer
- quaternary = animal that eats tertiary consumer
what is biomass
- the mass of living material present in a particular place/organism
how do you calculate biomass
- biomass present in each organism x number of organisms in that trophic level
what must be excluded from biomass mass
the mass of water in the organism
how can the problem of water influencing biomass be overcome
- by finding dry mass (mass of organism without water)
what is a problem with finding dry mass of an organism
- organisms have to be killed in order to be dryed
- only small amount of organism is taken (may not represent whole organism)
what is biomass measured in
- measured in kg or grams per square metre (kg or g m^-2) for areas of land
- in kg or g per cubed metre for areas of water (kg or g m^-3
- what is the trend of biomass as you go up trophic levels
- why is this
- biomass is always less that trophic level below
- small proportion of food ingested is converted into new tissue
- some is excreted, some is used in respiration, some is made into inedible tissues
- what is ecological efficiency
- what is the equation to find it
- efficiency with which biomass/energy is transferred from one trophic level to the next
- (energy/biomass available after transfer) / (energy/biomass available before transfer) x 100
what percentage of sunlight is actually converted into chemical energy by producers
- 1 - 3 %
why are producers so inefficient at converting sunlight to chemical energy
- roughly 90% is reflected
- some is transmitted through leaf
- some is unusable wavelength
- other factors may limit photosynthesis
- proportion or energy is lost as it used for photosynthesis and respiration reactions
what is meant by gross product in reference to biomass
- rate at which energy is incorporated into organic molecules by an ecosystem
what is the calculation to find net primary product for plants
- gross primary product - respiration losses
what is net primary productvity
- rate at which energy is transferred into the organic molecules that make up the new plant biomass
what is the difference between inter and intra
- inter = between species
- intra = between organisms in species
define succession when talking about ecosystems
process where ecosystems change overtime from nothing to climax communities
define primary succession
- occurs on area of land that has been newly formed/exposed
- no organic material has been there before
define secondary succession
- occurs on areas of land where soil is present
- organic material has been there before but there is none currently
such as forest after fire
give some examples of where primary succession may still occur
- volcanoes erupting, depositing lava and creating rock
- sand blows creating new sand dunes
- glaciers retreat exposing rock
- define seral stages
- what can be seen at any given stage
plural: sere
- steps of succession
- at each stage key species are seen that changed the abiotic factors to make it more suitable for other species
what are the main serial stages
- pioneer community (e.g. mosses, lichen)
- intermediate community (grasses, shrubs)
- climax community (large trees)
how do pioneer communities get to uninhabitable environments
- seeds are carried by animals or wind and deposited to environments
what adaptations do pioneer species have that allow them to live in extreme environments
- produce large quantities of seeds/spores
- seeds germinate rapidly
- can photosynthesis
- tolerant to extreme environments
- can fix nitrogen from air
- define humus
- how is it produced
- organic component of soil
- as pioneer species die and decompose they deposit organic products into soil
How does the climax community change after being established
- the community is in stable state
- will show very little change over time
What is the trend in biodiveristy throughout all the seral stages
- biodiversity reaches a peak in mid-succession
^after this tends to decrease as dominant species out compete others
what are the differences between animal and plant succession
- animal succession tends to be slower as must move in from neighbouring areas
^even harder if land is isolated - secondary consumers must wait till sufficent habitats and food supplies have been attained to move in
define plagioclimax
- the final stage reached after succession has been halted artificially by humans
what are some examples of where humans can stop succession
- grazing and trampling of vegetation by animals
- removing existing vegetation to plant crops
- burning to clear forest
what is the equation for estimated number of individuals in population for plants and slow moving animals
- number of individuals in sample / area of sample
How can estimated population size be calculated from capture-mark-release-recpature
- number of individuals in first sample x number of individuals in second sample / number of recaptured marked individuals
outline the process of mark-capture-release-recapture
- capture as many animals as possible, mark them and release
^mark cannot effect success of animals - leave population to redistribute themselves through habitat
- recapture as many individuals as possible
important process in carbon cycle
respiration
photosyntehsis
combustion
effect of plants on carbon cycle
take CO2 from air via photosynthesis
producer CO2 via respiration
death transfer carbon into soil
how do animals affecct carbon cycle
respire to let CO2 into air
feed on organic matter to take into carbon
death transfer carbon into soil
how do decomposers affect carbon cycle
respire to give out CO2
How do fossil feuls affect carbon cycle
combusted to give out lots of CO2 into atmosphere
