19: Populations in ecosystems Flashcards
Population
group of organisms of the same species living in the same habitat
habitat
part of ecosystem in which organisms live
community
all the populations of different species in the same area at same time
ecosystem
a community and the non living components of an environment (biotic and abiotic) range in size
Niche
an organisms role within the ecosystem, including their position in the food web and habitat. each species occupies their ow niche governed by adaptation to both biotic and abiotic conditions
carrying capacity
the maximum population size an ecosystem can support
abiotic factors
- non living
- affect the size of different populations in an ecosystem
- plants and animals are adapted to them
- these adaptions are through natural selection over generations
- less harsh abiotic factors = larger range of species and larger population sizes
biotic factors
- living components of an ecosystem that interact together such as intraspecific and interspecific competition and predation also affect population size
twp types of competiton
- interspecific and intraspecific
- interspecific: members of different species are in competition for resource in limited supply. individual better adapted for the environment is more likely to succeed
- intraspecific; members of same species are in competition for resources and a mate. links to courtship rituals. fitter individuals more energy to perform more impressive courtship ritual or have feathers in better condition to attract mate
why do we sample?
- more time efficient and if implemented correctly it can be more accurate
- must accurately represent the population
- random sampling eliminates bias
- at least 30 samples
sampling summary
- if its slow or not moving = quadrat.
if uniform distribution use random sampling (random generator coordinates, repeat at least 30x for mean)
if uneven distribution use line transect (like river or shore, belt transect and interrupted belt transect) - if motile organism use mark-release-recapture method
mark release recapture
- inital sample captured and marked. number recorded
- released and left for period of time to allow them to randomly disperse through habitat
- second sample captured, amount recored and total number of marked ones recaptured recorded
- size of population then estimated based on principle that proportion of marked second sample is the proportion of marked in whole population
- number of organisms caught first x number of organisms in second divided by number of recaptured
ethics and assumptions of mark-release-recapture
- how you capture and mark them must cause no permanent harm
marking must be; - non toxic
- must not increase chances of predation
- must not reduce chances of reproduction
assumptions;
- estimate may not be accurate as ur assuming
- population size is constant
- the animals always redistribute evenly
Succession
the change in an ecological community over time
primary succession
- starts with pioneer species (lichen) colonising bare rock and sand.
- adapted to survive harsh abiotic factors. death and decompostion causes them to change the abiotic factors to be less harsh
- form a thin layer of soil called humus
- smaller plants can now survive and further increase depth and nutrient content in soil
- abiotic factors less harsh so large plants can survive and further changes the environment
- each new species may change environment so its less suitable for previous species. outcompeted by new species colonising
- less hostile environment, increased biodiveristy
- climax community - dominated by trees
