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
