Populations In Ecosystems Flashcards
population definition
A population as a group of organisms of the same species
occupying a particular space at a particular time that can potentially
interbreed
what is mark - release recapture
mark - release recapture is a method of measuring abundance of motile organisms
what are motile organisms
capable of movement
what is the process of mark - release recapture
1) capture a sample of a species using an apropriate method eg using pitfall traps
2) count the number of individuals captured
3) mark each of the organisms in a non harmful way eg snail nailvarnish paint
3) release the organisms back into the habitat
4) some time later , capture a second sample from the same population using the same method
5) count the number of marked individuals in thr second sample and the total number of individuals in the second sample
6) estimate the population size using the equation
what is the equation for mark-release recapture
total number of individuals in first sample x total number of individuals in second sample /
number of marked individuals recaptured
what are the assumptions about mark - release recapture
- the proportion of marked to unmarked individuals in the second sample is the same as the proportion of marked to unmarked individuals in the whole population
-marked individuals released actually have enough time to distrubute themselves evenly amongst the population and have time to do that
-theres no immigration or emmigration out of the population
- few or no deaths or births
-mark isnt lost or rubbed off during the investigation
(would decrease the reliability)
what must we take into account we do the mark-release recapture
- marking isnt harmful / toxic and does not make the individuals more visible to predators
- so do not do investigation during breeding season
what are abiotic factors
non living factors in an enviroment eg temperature
what is the process of succession
The land is first colonised with a pioneer species e.g. lichen. They play a crucial role in breaking down the rocks into smaller particles through their root systems and biochemical processes. Pioneer species are adapted to survive in harsh abiotic factors:
Ability to photosynthesise (so not dependant on animals)
Rapid germination of seeds (no dormancy period)
Ability to produce large quantities of wind-dispersed seeds/spores
Asexual reproduction (so a single organism can build up a community)
- as these species change the abiotic factors in the environment. This is because as the pioneer species continue to grow and die, they contribute organic matter that mixes with the broken rock fragments. Over time, this accumulation of organic matter, along with the action of weathering, erosion, and decay, helps to create humus.
-simple plants can now grow
-As there is now a thin layer of soil, mosses and smaller plants can now survive by lodging into the soil which can now retain some water and minerals. As they grow they increase the depth and nutrient content of the soil, changing the abiotic factors. These species outcompete the pioneer species as changing the environment makes it less suitable for the species before and other adaptations are required. This process repeats as the new plants die and decay and new species colonise.
Biodiversity increases during early succession, reaches its peak in mid succession, then decreases slightly as a climax community is being reached due to dominant species out-competing pioneer species.
After many rounds of intermediate succession, the changes to abiotic factors mean that the environment is less hostile. The ecosystem becomes stable as it is in equilibrium with the climate. Biodiversity increases and attracts more animal and plant species, trees dominate a climax community.
what is succession
succession is the change in an ecological community overtime ,from low to high biodiversity
