6.5 Ecosystems Flashcards
define climax community
the final stable community that exists after the process of succession has occured
define deflected succession
happens when succession is stopped or interferred with (eg grazing/ lawn is mowed)
define pioneer species
species that begin the process of succession, colonising an area as the first living things there
define succession
progressive change in a community of organisms over time
define primary succession
when plants plants grow where no plants have grown before
define secondary succession
when plants grow where there has been a previous population (these will have been destroyed previously eg. fire)
describe the process of succession
1- algae and lichens begin to live on bare rock
2-erosion of rock and build up of dead/rotten organic material produce soil for larger plants (moss/ferns)
3- larger plants succeed smaller plants until final stable community is reached
describe the process of succession on sand dunes
1-pioneer species (sea rocket) colonise sand just above the high water ark as they can tolerate salty water and unstable sand
2-wind blown sands build up around there, forming mini sand dunes
3- when dunes get bigger, plants (sea sandwort) colonise it as previous plants die and decay which accumulates nutrients in the dune
4-w/ more stability and nutrients, plants like marram grass start to grow
5- as the sand dune and nutrients build up, other plants colonise the land
define leguminous
plants which convert nitrogen into nitrate which allows more species to colonise the dunes and stabilise it further
give an example of deflected succession
grassman cutting grass in a gold course is keeping area at one stage in a succession
if area was left for years, succession would continue and reach climax commuinity
define plagioclimax
the sub climax community that occurs due to deflected succession
identify ways succession can be deflected
grazing
burning
application of fertiliser/herbicide
exposure to excessive amounts of wind
identify the similarities of succesion on bare rock and a sand dune
The stages of succession are the same in both habitats followed by a build-up of organic material or nutrients to allow colonisation by larger species and eventually a climax community results
climax communities in both habitats will usually be woodland.
identify the differences between succession on bare rock and sand dunes
On bare rock algae and lichens are the pioneer species, as they do not need to be anchored in the soil.
in a sand dune community, the species have sand in which to anchor, but that sand is devoid of nutrients so at this stage it cannot easily sustain species. The likely pioneer species are able to withstand these conditions
why are all stages of succession visible in a sand dune
The sea deposits sand on the beach: the sand nearest to the sea is deposited more recently than the sand further away. This means that the sand closest to the beach is at the start of succession, whereas the sand further away might already have reached its climax community.
why can it be useful to conserve some habitats which have not reached their climax community
Sub-climax communities have a higher diversity than climax communities as they still contain some sub-climax species as well as the climax species. Maintaining a range of communities that have not reached their climax means that we are conserving a much wider diversity of plants and animals that do not live in the climax community
what is each stage of succession called
a SERE
why do ecologists study ecosystems
to find out whether the abundance and distribution of a species is related to that of other species or environmental factors
what are the types of data you can collect using a quadrat
-presence or absense of each species
-number of individuals of each species (percentage cover)
how can you estimate percentage cover?
lower a point frame into a quadrat and record any plants touching the needles
where can you place quadrats to avoid bias?
-lay 2 tape measures to create axis and generate random coordinates to place quadrat
-take samples at regular distances across the habitat
how many samples should you take when using a quadrat?
creats a cumulative frequency table and plot the cumulative frequency against the quadrat number. Where the curve levels off, tells you how many quadrats to use
how can you work out the population size of a species in a whole habitat
mean number of individuals of a species in each quadrat/ fraction of the total habitat area covered by a single quadrat
how can you look at changes in vegetation across a habitat
by using a transect
what is a transect
line taken across a habitat
what are the two approached of using a transect
-line transect
-belt transect
what is a line transect
at regular intervals take note of which species is touching the tape
what is a interrupted belt transect
at regular intervals, place quadrat next to line
what is a continuous belt transect
place quadrat next to line moving it along and looking at each quadrat
define ecosystem
a community of animals, plants and bacteria interrelated with the physical and chemical environment
define habitat
place where an organism lives
define population
all of the organisms of one species who live in the same place and time and can breed together
define community
all the populations of different species who live in the same place and time and can interact with each other
define niche
the role of each species in an ecosystem
define abiotic factors
non living components of an ecosystem that affect other living organisms
examples of abiotic factors
PH of soil, wind speed, light levels, amount of rainfall
define biotic factors
environmental factors associated with living organisms in an ecosystem that affect each other
examples of biotic factors
competition, disease, predation, parasitism, producers + consumers
why are ecosystems termed as dynamic
as they are always changing
what are the 3 types of ecosystem changes
cyclic, directional, unpredictable
define cyclic changes
these are changes which repeat themselves in a rhythm (eg movement of tides)
define directional changes
go in one direction and tend to last longer than the lifetime of organisms (eg coastal erosion/deposition)
define unpredictable changes
no rhythm and no constant direction (lightning/ hurricanes)
describe trophic levels
they are feeding levels
10% of energy is transferred from one trophic levels to the next
This is why there are limits to our food chains
sun —–>kelp——->sea urchin——->crab——->octopus
100%. 10%. 1%. 0%
what are the reasons for energy loss
Movement
Reproduction
Sensitivity
Growth
Respiration
Excretion
Nutrition
what happens at each trophic level
living organisms need to carry out life processes, respiration releases energy from organic molecules eg. glucose some is converted to heat and material are lost in CO2 and water
what do pyramids of numbers present
the idea of trophic levels
can be drawn for individual food chains or for an ecosystem as a whole
the area of each bar is proportional to the number of individuals or the dry mass of all the organisms at that trophic level
how can you work out the biomass
kill organisms, put in oven to dry out water
and measure periodically to see when all water has evaporated
how do you calculate the efficiency of biomass transfer between trophic levels
biomass at the higher trophic level/biomass at the lower trophic level X 100
what do the arrows show in a food web
the flow of energy/biomass
define productivity
the rate of production of new biomass by producers
define gross productivity
the rate at which plants convert light energy into chemical energy through photosynthesis
define net productivity
the proportion of energy from the sun available to enter the food chain
define primary productivity
the rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances
define secondary productivity
the rate at which these consumers convert the chemical energy of their food into their own biomass
describe methods of improving primary productivity
-light levels limit the rate of photosynthesis (crops planted early to provide longer growing season and more light)
-drought resistant strains are bred
-greenhouses provide warmer temp, increase rate of photosynthesis and production of biomass
-use of fertiliser when there is a lack of nutrients
-pesticides to remove insects that eat plants
-fungicide to prevent fungal disease reducing biomass
describe methods of improving secondary productivity
-harvesting animals before adulthood minimises loss of energy
-selective breeding to improve animal breeds
-animals treated w/ antibiotics to avoid loss of energy from pathogens
-no grazing, no movement, constant temp and supply food to prevent energy loss
define decomposers
organisms that feed on dead and waste organic material releasing the nutrients and energy
define saprotrophs
secretive digestive enzymes externally and then absorb the small molecules
define detritivores
ingest larger amounts of dead matter and break this into smaller molecules
describe the nitrogen cycle
nitrogen in air goes to leguminous plant (peas, beans), other plants and animals through nitrogen fixation (rhizobium). Plants die and animals excrete creating nitrogen in soil –>urea then this turns to ammonium through ammonification. this turns to nitrite (nitrosommnas) then into nitrate (nitrobacter) this is nitrification. Lightining and fertilisers can also create nitrate. This returns to nitrogen in air through denitrification
identify bacteria in nitrogen fixation
rhizobium (leguminous plants)
aztobacter (for other plants)
identify bacteria in nitrification
nitrosommnas (ammonia to nitrite)
nitrobacter (nitrite to nitrate)
