populations in ecosystems

enviroment

all organisms surroundings

habitat

the place where an organism lives

carrying capacity

the maximum population size an ecosystem can support

humus

head organic matter- adds to the ions and nutrient composition of soil

population

all the organisms of the same species living in the same environment at the same time that can interbreed to produce fertile off spring

community

all the organisms of different species in the same area at the same time.

pioneer species

a plant or fungal (mosses/lichens) species which can colonise a hostile environment and change it so its more suitable for different species or larger plants.

niche

organisms role within an ecosystem. each organism has its own based of adaptions to abiotic and biotic factors

examples of Abiotic factors- non living

• temperature

• oxygen concentration

• carbon concentration

• light intensity

• soil condition

biotic- living factors

the living components of an ecosystem interacting together

how the biotic factor effects population size

predation- the presence of a predator (herbivore) reduces the number of prey (plants) in the population

pathogens and parasites - if disease is widespread, then population growth is slowed

intraspecific- competition between members of the same species reduces population growth

interspecific- when two species compete for the same resources,

intraspecific competition

members of the same species are in competition for resources and a mate.

mates link to courtship rituals. those that are fitter have more energy and therefore perform better.better looking fur and feathers attract also

interspecific competition

members of different species compete for the same resources (food/habitat/water) that is in limited supply.

species better adapted to environment are more likely to succeed.

when do you do a random sample

• slow moving/non-motile

• uniform distribution (environment is the same/similar all the way

• using a quadrat

random sampling method

1. divide the area into a grid, using two tape measures at right angles.

2. use a random number generator to generate many pairs of coordinates.

3. go to each coordinate and count the number of organisms in the quadrat repeat for at least 30.

4. calculate the mean. add all the 30 repeats, and divide by 30.

things to consider with random sampling

• random coordinates remove bias.

• large sample = more representative

• standardised counting (everyone counts differently) - count any plants that are fully in and partially in the north + west region.

• ethical issues - trampling and using qudrats is damaging to ecosystem.

when do you use a systematic sample

help find out how plants are distributed across a change over a distance.

continuous belt transect

tape measure is placed along a linear path quadrats are placed next to each other to work out species frequency and percentage cover along the transect.

interupted belt transect

take measurements at regular (systematic) intervals.

line transect

1. place the tape measure at a right angle to the shore line

2. place the quadrat every 5 meters/every position

3. collect the data (density/percentage cover/local frequency)

4. repeat by placing another 30 transects along the beach at right angles to the shoreline.