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7.4 populations in ecosystems - Coggle Diagram
7.4 populations in ecosystems
lesson 1: carrying capacity and niches
defintions
species
a group of organisms that can breed together to produce fertile offspring
population
a group of organisms of the same species living in the same area at the same time
community
the populations of all different species living in the same area at the same time
habitat
the part of an ecosystem where an organism lives
ecosystem
the community and non-living components of the environment in an area and the interactions between them
biotic factors
the interactions between organisms (living factors e.g plants and animals) within in ecosystem (that can affect other organisms)
abiotic factors
the non-living factors within an ecosystem that can affect organisms e.g oxygen, carbon dioxide, temp
intraspecific competition
competition within a species
interspecific competiton
competition between species
niches
a niche is the role the organism plays within its habitat - where it feeds and what it feeds on
this is determined by its adaptations to biotic and abiotic factors
every species occupies a different niche
by having different niches (i.e feeding on different organisms or living/feeding in different parts of a habitat) different species reduce interspecific competition for food and other resources
carrying capacity
the size of a population of a particular species an ecosystem supports. may vary through year to year (dependent on biotic and abiotic factors)
predator-prey cycles
predators eat the prey which reduces the prey population size
fewer prey are then available, the predators are in greater competition for food - greater infraspecific competition
predator population size Is reduced
fewer predators which results in less prey being eaten and so more survive and reproduce
prey population increases
more prey now available, predator competition reduces, predator population increases
lesson 2: sampling of non-motile organisms
sampling
sampling is taking a group/sample from a population to make inferences about the whole population
a representative sample is a sample that accurately reflects the characteristics of the wider population
random sampling is the most representative form of sampling - we used a representative sample to remove bias and to make the experiment valid
frame quadrats
provides a sampling area of a known size
the size of the quadrant should be relative to the size of the organisms and area being sampled
3 different ways of estimating population/abundance of non-motile organisms using a frame quadrat
1) count the number of individuals of a species in each quadrat
2) estimate the percentage of area covered by a species
3) count the number of quadrants with species in
point quadrats
estimating abundance of non-motile organisms using a point quadrat
used for layered vegetation
each species that touches the pin is recorded
used to calculate % cover/abunance
% cover = number of hits / total number of pins x 100
random sampling method
divide the area into a grid using measuring tapes
generate coordinates using a random number generator
place a quadrat at each coordinate and count/record percentage cover/measure
repeat until you have a large sample size
calculate a mean
if calculating population multiply mean by 1m^2 by size of area in metres squared
lesson 3: sampling
systematic sampling
investigating distribution of non-motile organisms using a belt transect
