populations in ecosystems Flashcards
what is a population
a group of organisms of the same species living in the same place at the same time
what is a community
all the populations of different species living in the same place at the same time
what is an ecosystem
a community plus all the non living (abiotic) conditions of their environment
ecosystems are dynamic and can range in size
what is a niche
the role of a species within its habitat eg. what it eats where and when it feeds
each species has us own unique niche
if two species try to occupy the same niche one will out compete the other
what is a abiotic condition
non living features of an ecosystem
eg. temperature and pH
what is a biotic condition
the living features of an ecosystem
eg. predation disease food
what is the carrying capacity
maximum stable population size an ecosystem can support
what is the effect of abiotic factors on population size
ideal conditions mean organism grow fast and reproduce successfully
what is the effect of interspecific competition on population size
competition between species
reduces resources available to both -> limits both populations
if one species is better adapted it will outcompete others
what is the effect of intraspecific competition on population size
competition within a species
smaller population = less competition-> better growth and reproduction -> larger population = more competition-> less growth and reproduction-> smaller population…
what is the effect of predation on population size
increased predator population-> more prey eaten -> prey population falls -> less food for predators-> predators population falls -> prey population rises -> predator population rises …
how to estimate population size using randomly placed quadrats
use a grid
obtain random coordinates using random number generator
count frequency of species in quadrat
calculate mean per quadrat
calculate population size = mean x no. quadrats
how to estimate population size using quadrats along a belt transect
looks at changes in distribution
lay tape measure from one place to another
place quadrat at regular intervals
count frequently/ percentage cover
how to estimate population size with mark release recapture
motile organisms
capture species, mark harmlessly and release
leave enough time to randomly distribute before collecting second sample
population size = (number in sample 1 x number in sample 2 ) / number marked in sample 2
what are the assumptions of mark release recapture
sufficient time for marked individuals to mix with population
marking not removed and doesn’t affect chance of survival
no immigration / emigration
no births / deaths / breeding
