6.3 Ecosystems Flashcards
habitat definition
where an organism lives
biotic factors examples
interspecific and intraspecific competion for food/nutrient
predation
disease
abiotic factors examples
wind speed temperature light intensity CO2 conc. soil/water pH humidity weather
biotic factors definition
how living organisms affect the distribution of other organisms
abiotic factors definition
non-living factors in an ecosystem that can affect the distribution of organisms
niche definition
the role of an organism in an ecosystem
community definition
all of the populations of different species who live in the same place at the same time and can interact with each other
population definition
all of the organisms of one species who live in the same place at the same time and breed together
ecosystem definition
any group of living organisms and non-living things occuring together and the interrelationships between them
producer definition
organism that produces organic molecules using sunlight energy
consumer definition
organism that eats other organisms
decomposer definition
organism that breaks down dead or undigested organic material
trophic level definition
stage in food chain occupied by a particular group of organisms
e.g. producers are first trophic level
energy transfer through ecosystems
photosynthesis is the main route energy takes to enter an ecosystem
sunlight energy converted to chemical potential energy and stored as biomass
biomass/energy is transferred when organisms eat other organisms e.g. producer -> primary consumer -> secondary consumer etc.
energy locked up in things that cant be eaten e.g. bones, faeces broken down and recycled back into ecosystem by decomposers
biomass definition
dry mass of organic material on an organism
function of food chains and food webs
food chains show simple lines of energy transfer
food webs show lots of food chains in an ecosystem and how they overlap (shows interdependence between organisms)
why biomass is lost from food chains at each trophic levels
some food cant be eaten (e.g. bones)
energy released from organic molecules e.g. CO2 and heat from respiration lost
waste products and dead organisms contains biomass only available to decomposers
least efficient transfer and why
producers and primary consumers as they lack cellulase to digest cellulose cell walls
some parts of producers may not be eaten e.g. roots
pyramid of numbers
shows numbers of species in a food chain
area of bar proportional to numbers of individual
why its rare for chains to go past 4/5 trophic levels
energy is lost from food chain at each trophic level
limited energy transferred from one level to next
limits length of food chains
top consumers unable to eat enough animals at level below to provide sufficient energy to live
pyramids of biomass
shows biomass at each trophic level
takes into account size of organisms and mass of material at each level
problems of constructing pyramids of biomass
organisms heated in oven to evaporate all water
weighed periodically until all water evaporated and mass doesn’t reduce more
destructive as organism dies
instead wet mass measured and dry mass is estimated using old published data
productivity definition
rate of production of new biomass
rate of energy flow through each trophic level
productivity units
kg/MJ m^-2 yr^-1
net primary productivity formula
gross primary productivity - respiration
primary productivity definition
total amount of energy fixed by photosynthesis
gross primary productivity definition
rate at which plants convert light energy to chemical energy through photosynthesis
net primary productivity definition
NPP
rate of production of new biomass available for heterotrophic consumption and therefore the amount of energy available to them
why 90% of sunlight not converted into biomass
reflected off plant/only certain wavelengths of light can be absorbed
absorbed by non-photosynthetic parts (e.g. bark)
misses chlorophyll/chloroplast
some energy lost as heat in respiration
how to improve NPP
make energy conversion more efficient
reduce energy levels
why improve NPP
increases crop yield
how farmers could improve NPP
ensure max rate of photosynthesis by controlling:
light levels (grow in light banks for longer growing seasons)
temp (greenhouses)
CO2 conc (greenhouses)
water (irrigation techniques, drought resistant plants)
nutrients (fertilisers, crop rotation with legumes -> nitrogen fixing)
reduced yield from pests (use pesticides, pest-resistant plants)
competition from weeds (use herbicides)
why improve secondary productivity
(improve rate of generation of biomass in heterotrophs)
necessary as energy transfer from producer to consumer is very inefficient and lots of energy lost as not all of producer is consumed/digestible, heat loss during respiration, egestion losses
how to improve secondary productivity
growth steroid treatment (illegal)
selective breeding
antibiotics (less energy lost fighting pathogens)
battery farming (reduce movement and warm stable environment so less energy used in respiration and maintaining body temp.)
succession definition
natural directional change in species composition in an area over a period of time
primary succession definition
when succession begins an area where previous life has not previously existed
secondary succession definition
when succession begins in an area where previous life had existed but was destroyed
not on bare ground
pioneer species definition
organisms with suitably adapted characteristics that enable them to colonise an area with no organisms
pioneer species stabilise environment by
developing soil (make it deeper from rotting organisms)
increase in availability of water
cause more minerals to be available (some carry out nitrogen fixation)
create habitats, provide shelter
change soil pH
climatic climax community definition
stable, self-sustained community in equilibrium with its environment, dependent on climate of area
final stage in succession
seres definition
seral stages
various stages through which succession takes place
plagioclimax definition
succession held at an earlier stage usually by human interference (e.g. grazing, trampling, cutting)
what happens as succession continues
development of deeper soil
soil accumulates more minerals and more fertile
dominant species change
plant species get larger
deflected succession definition
when something prevents succession and establishment of the next community
sub-climax community = plagioclimax
why succession occurs
each community changes conditions e.g. depth of soil
allows for a new community to establish
how succession leads to development of an ecosystem
every time the plant community changes in succession, the habitat changes, changing the ecosystem
generally the later the stage of succession, the large the plant species therefore more habitats are created, developing the ecosystem further.
decomposition definition
breakdown of dead matter/waste
or
conversiom of organic matter to inorganic matter
why study ecosystems/habitats
measure the biodiversity of a habitat (to monitor population sizes/ habitat destruction)
find out if abundance of one species depends on biotic/abiotic factors
why sample?
impossible to count all of every organism in a habitat
study a small area closely instead and then extrapolate the data to e.g. estimate numbers in the habitat
how carbon can be stored in land
dead organic matter can become:
fossil fuels when no decomposers present
limestone and chalk on sea floor
released back into atmosphere by:
being drawn into Earth (by movement of tectonic plates) and become CO2
become land then weathered chemically (acid rain) and physically (e.g. animals, plant roots)
chemical weathering causes mineral ions and HCO3- ions to be released and enter groundwater then rivers and oceans
can then combine to form carbon-containing compounds e.g. CaCO3
how carbon can be stored in the oceans
CO2 also dissolves directly into oceans then released back into atmosphere
stored in deep ocean currents for hundreds of years
nitrogen cycle stages
nitrogen fixation (ammonification + nitrification) denitrification
ammonification facts
nitrogen gas converted into ammonium ions by bacteria to be used by plants
forms mutualistic relationship where bacteria provides nitrogen compounds and plant provides carbohydrates
nitrification facts
ammonium ions in soil changed into nitrogen compounds used by plants (nitrates) Nitrosomonas change ammonium ions into nitrites Nitrobacters change nitrites into nitrates bacteria are chemoautotropic requires oxygen (only in well-aerated soil)
bacteria in ammonification
Rhizobium found inside root nodules of legumes (mutualistic)
Azotobacter found in soil (non-mutualistic)
denitrification facts
nitrates in soil converted into nitrogen gas by denitrifying bacteria (use nitrates in soil for anaerobic respiration as source of oxygen to produce nitrogen gas)
only occurs under anaerobic conditions
alternate ways nitrogen introduced into ecosystem
lightning (fixes atmospheric nitrogen)
artificial fertilisers
why Rhizobium and legumes have mutualistic relationship
Rhizobium fixes nitrogen for plant’s amino acid production
plant produced glucose for Rhizobium
why Rhizobium needs to be under anaerobic conditions for ammonification
O2 acts as inhibitor of nitrogenase enzyme in Rhizobium
chemoautotropic definition
release energy by oxidising
when eutrophication occurs
when nitrates from fertilisers leech into rivers
eutrophication impact method
causes algal bloom (nitrates allow rapid protein production and growth of algae)
blocks light for photosynthetic plants below algae
plants die and are decomposed
decomposers use up O2 in water
aquatic life die as no O2 for respiration as no photosynthesis from aquatic plants (anoxic)
crop rotation method
different crops grown in field at each year
some years nothing planted
why crop rotation
different crops have different nitrate requirements
each year nitrates not being removed at same rate
in year of no crops, no nutrients removed so build back up
use legumes in rotation to put ammonium ions
