6.3.1- Ecosystems Flashcards
what is an ecosystem?
self-contained community of interacting organisms, and abiotic factors, as well as the environment that they live in and interact in.
what is a niche?
the role an organism plays within an ecosystem
name some examples of biotic (alive) factors?
- predators
-competition (intraspecific/interspecific)
-disease
- pathogens
name some examples of abiotic (not alive) factors?
- light intensity
- temperature
- pH levels
-water availability
-oxygen availability
-edaphic factors
what are some examples of ecosystems, of different sizes?
- rock pool
- playing field
- large tree
what is biomass?
The total mass of organic material, measured in a specific area over a set time period.
This can be calculated in terms of dry mass.
what is succession?
this describes the changes in a community of organisms, occupying a certain area over time.
what are the 2 types of succession and what are they described as?
- PRIMARY= establishment of a community where no community previously existed
- SECONDARY= establishment of a new community where a previous one has been disrupted
what are some examples of primary and secondary succession?
- P= sand dunes, bare rock
- S= neglected farm land
what are two terms associated with biomass?
- mass of living material
- stored chemical energy
how can biomass be measured? (3)
- dry mass in a given area
- mass of carbon a tissue contains
- chemical energy content when burned in pure oxygen
what is the mass of carbon that a sample contains said to be?
50% of the dry mass of the sample
what is dry mass?
the mass of a tissue after all the water has been removed
what can the dry mass be used for?
to calculate the biomass of a whole population
what two units is biomass given in?
- kg
- time (as it can change over time/through seasons)
what is calorimetry used for?
to estimate the chemical energy stored in dry biomass
what happens to biomass throughout a food chain?
biomass is lost at each stage, due to organisms using it for energy
-therefore, food chains only tend to be 3 to 4 links long
how do you work out efficiency of transfer?
efficiency of transfer= (biomass transferred/biomass intake) x 100
what is the order from biosphere to physiological ecology? (7)
1- biosphere 2- biome 3- landscape 4- ecosystem 5- community 6- population 7- physiological ecology
what are the 3 main types of edaphic factors (soil) and explain them?
1= clay, fine particles that are easily waterlogged
2= loam, different sized particles that are not easily waterlogged but does retain water
3= sandy, coarse separated particles that are not easily water logged and does retain water
what do food chains show?
show how the energy is transferred from one living organism to another.
what is the trophic level?
the level at which an organism feeds in a food chain
what are producers?
autotrophic organisms that convert light energy to chemical energy
what are consumers? and what are the 3 types?
organisms that feed on other living organisms
-primary= eat plants
-secondary= eat animals
-tertiary= eat secondary consumers
what are decomposers?
organisms that feed on waste materials or dead organisms
what are food webs and what do they show?
a series of interconnecting food chains, showing how energy flows through the whole ecosystem
they show that organisms are usually members of more than one food chain, and often feed at different trophic levels in different chains
what are pyramids?
show the energy transfer between trophic levels in which the area of each bar is proportional to the property being measured.
what are the 4 types of pyramids?
-pyramid of numbers
-pyramid of biomass
-pyramid of energy
-pyramid of productivity
what are the pros and cons of pyramid of numbers?
pros= quite easy to count, non-destructive
cons= doesn’t take into account size
what are the pros and cons of pyramid of biomass?
pros= quite easy to measure either wet mass or dry mass, takes into account size
cons= wet mass can be inaccurate as water content varies, dry mass is destructive (organisms put at 80 degrees until water evaporates), different species contain different amounts of energy per unit mass
what are the pros and cons of pyramid of energy?
pros= takes into account energy per unit mass, use of calorimeter, calculated from temp rise
cons= destructive, time-consuming, only provides a snapshot of an ecosystem at one moment in time
what are the pros and cons of pyramid of productivity?
pros= always gives a true pyramid, true representation of rate of energy flow, takes into account energy, area and time
cons= destructive, time-consuming
what units are used in the pyramid of productivity?
MJm^2yr^-1
what is net primary productivity?
the energy available to consumers after plants have used some biomass fixed in photosynthesis for their own respiration
what is gross primary productivity?
the rate at which plants convert light energy into chemical energy during photosynthesis
what is the equation for net production?
net production= gross production - respiratory losses
what is the equation for ecological efficiency?
(energy or biomass available after the transfer / energy or biomass available before the transfer) x 100
what happens to the energy converted to chemical energy by producers?
it ends up as heat in respiration
what are decomposers?
microorganism that break down dead and waste material
-they are saprotrophs and feed saprotrophically by extracellular digestion
what are detritivores?
they help speed up the decay process by feeding on detritus breaking it down into smaller pieces, increasing the surface area for the decomposers.
what is the symbol for nitrogen gas?
N2
what is the symbol for ammonium gas?
NH4+
what is the symbol for the nitrite ions?
NO2-
what is the symbol for nitrate ions?
NO3-
what is the symbol for organic nitrogen compounds?
-N-
what is the nitrogen cycle?
shows how N atoms are recycled
what are the 5 stages of the nitrogen cycle?
-nitrogen fixation
-nitrification
-assimulation
-decomposition
-dentrification
what happens during nitrogen fixation?
-nitrogen gas is converted to ammonia
-bacteria living freely in soil= azotobacter (in soil)
-mutualistic bacteria= rhizobium (in root nodules)
-nitrogenase reductase enzyme in rhizobium, works anaerobically
what are the names of the two bacteria in nitrogen fixation?
-azotobacter
-rhizobium
what occurs in nitrification?
-ammonia converted to nitrites that are converted to nitrates
-nitrosomonas bacteria= converts ammonia to nitrites
-nitrobacter= converts nitrites to nitrates
what occurs in assimilation?
-introduces nitrogen to the food chain
-nitrates converted into nitrogen compounds
-plants absorb nitrate ions through root hairs by diffusion/active transport
-nitrate ions are transported through plant dissolved in water
-they are used to make organic nitrogen compounds such as nucleotides and amino acids
-animals obtain nitrogen by eating plants
what happens in decomposition?
-saphrotrophic microorganism break down organic nitrogen compounds found in urine and faeces and shed/dead body parts
-release nitrogen back into the cycle in the form of ammonium ions
what occurs in denitrification?
-converts nitrates back to nitrogen gas
-denitrifying bacteria reduce nitrate ions in soil to nitrogen gas
what bacteria is used in denitrification?
Pseudomonas
=uses nitrates for the final acceptor in their respiration
state whether each stage of the nitrogen cycle is oxidation or reduction?
-nitrogen fixation= reduction
-nitrification= oxidative
-decomposition= oxidative
-denitrification= reduction
what bacteria is used in nitrification?
-nitrosomonas
-nitrobacter
what is the carbon cycle?
the way carbon is recycled through the environment via processes
what are the 6 processes of the carbon cycle?
-decomposition
-death
-photosynthesis
-respiration
-feeding
-combustion
why do carbon dioxide levels in the atmosphere fluctuate during the day and in season?
day= lower levels during the day due to photosynthesis taking place.
seasons= lower in summer due to more photosynthesis
what are the two reasons why carbon dioxide levels have increased significantly?
-combustion of fossil fuel
-deforestation
why is carbon dioxide called a greenhouse gas?
it traps more thermal heat energy in the atmosphere, resulting in climate change
how is the level of carbon dioxide tested?
-samples taken from glaciers
-test air bubbles in ice
-bubbles reflect the composition at that time, so reveals the composition of atmosphere at this point in time
what is succession?
a directional change in a community of organisms over time
what is primary succession?
the development of a community from bare ground
why does succession occur?
because organisms gradually alter their habitat, leading to changes in the community which lives there.
what are the series of distinct stages that occur in succession called?
seres
what is a pioneer community?
the first species to colonise on bare rock
what are intermediate species?
the stages in between
what is a climax community?
the final, stable community for a given climate
what is the order of primary succession?
-bare rock
-algae and lichens
-mosses and horsetails
-grasses and ferns
-large shrubs
-small trees
-mature woodland
what is the 5 adaptations of a pioneer species?
-ability to produce large quantities of seeds/spores
-seeds that germinate quickly
-ability to photosynthesise to produce own energy
-tolerance to extreme environments
-ability to fix nitrogen from the atmosphere, which adds to the mineral content of the soil
what is deflected succession?
human activity that can halt the natural flow of succession and prevents the ecosystem from reaching a climax community
what is the final stage of deflected succession known as?
Plagioclimax community.
what are the 3 main reasons why agriculture is one of the reasons why deflected succession occurs?
-removing existing vegetation to plant crops
-grazing and trampling of vegetation by domesticated animals which results in large areas remaining as grassland
-burning for forest clearance
what is a good example of where primary succession takes place?
sand dunes, as it displays all the stages of succession in the same place at the same time
what is sampling?
when a small area is sampled, studied and assumed that they represent the habitat as a whole
what is random sampling?
involves sampling a habitat at random points
what does systematic sampling involve?
involves sampling at random intervals
what are quadrats used for?
used to estimate the percentage cover of plants
what are point quadrats used for? and how do they work?
point frame improves the estimate percentage cover
=the point frame has needles which touch each species, the number of needles that touch each species is proportional to the percentage cover for that species
what is a line transect?
-taking samples at regular intervals (systemic sampling)
what is a belt transect?
-samples taken of the area between 2 points (systemic sampling)
what is distribution?
the presence or absence of each species
what is abundance?
the number of individuals of each species
what is used to measure distribution and abundance?
quadrats
what is percentage cover?
the estimate of area covered by a species
how is the population size measured using a quadrat?
the mean number of individuals of each species in each quadrat/fraction of the total habitat covered by a quadrat
what is zonation and what is used to study it?
=related to the changes in biotic and abiotic factors within the marine littoral
-studied using a belt transect
what type of transect quadrat measures abundance?
belt transect
what type of transect quadrat measures distribution?
line transect
how do you work out the estimated number in the population?
number of individuals in sample/area of sample
what are the units used for the estimated number in population?
m^-2
what technique is used for animal abundance?
mark-release-recapture
what is the equation for mark-release-recapture?
no. of individuals in first sample x no. of individuals in second sample/ no. of recaptured individuals
what is conservation?
the management of ecosystems so that natural resources in them can be used without running out. Maintenance of biodiversity through human action or management.
what is preservation?
the protection of of an area by restricting/banning human interference so that the ecosystem is kept its original state.
what is one example of ecosystem management?
Masai Mara National Reserve in Southern Kenya
