sampling Flashcards
what is sampling?
taking measurements of a limited number of organisms in an area to estimate the total number of organisms in an area
what does sampling measure?
particular characteristics or numbers
what is the ‘abundance’ of an organism?
the number of individuals of a species present in an area
what is random sampling?
selecting individuals by chance
how could random sampling be carried out?
using a random number generator to select coordinates
what is non random sampling?
the sample is not chosen at random
what is opportunistic sampling?
using the species which are readily available (may not be representative of the population)
what is stratified sampling?
population divided into subgroups based on characteristics and a random sample is taken which is proportionate to the population
what is systematic sampling?
different areas in an overall habitat are identified and then sampled
what is a line transect?
tape measure placed along a single line through an ecosystem and the plants touching the line at each interval are recorded
what is a belt transect?
place quadrats along a line and measure what is in each
what is sampling bias?
selection process may be accidentally or deliberately biased. reduced by using a random sample
what is chance?
the selected organisms may be unrepresentative of the population by chance. effects minimised by using a large sample size
what type of sampling would be used to study how organisms differ through the length of a stream? (2 marks)
systematic sampling as abiotic conditions vary downstream which affects the type / abundance of organisms present
what type of sampling would be used to study the distribution of organisms on a school field? (2 marks)
random sampling as it is easy to study and reduces sample bias
