ecological techniques Flashcards
deine the term ecology
the scientific sttudy of the factors which determine the distribution and abundance of organisms
define the term population
all the individuals of one species in a habittat
define the term community
all the organisms/ populations present in a habitat/ ecosystem
define the term ecosystem
the community and the non living/ abiotic factors components of the environment
give examples of abiotic factors
- co2
- o2
- water
- ph
- light intensity
- temperature
- shelter
give examples of biotic factors
- competition
- predation
- symobioisi
- parasites
define the term ecological niche
an organisms role in its ecosystem
give the two ways in which the distribution of organisms can be measured
- randomly placed quadrats, or quadrats along a belt transect, for slow-moving or non-motile organisms
- the mark-release-recapture method for motile organisms.
what can quadrats be used to measure?
- density
- frequency
- percentage cover
when using a quadrat what two factors should be considered?
- the positioning
- the number of quadrats used
why is random sampling used?
- avoid bias
- be representative
- produce statistically significant results
how do we select the areas we sample in when using random sampling?
- random number generator
- random number table
how doe the NE rule or equivalent help when using quadrats?
- avoids dealing with only parts of an organism
- avoids counting the same organism twice
- ensures consistency
why does the sample size need to be large?
- so it is representative of the population
- so a statistical test can be carried out
what is the minimum number of quadrats that should be taken?
20
give a technique used to decide if the sample size is large enough
- running mean
- adding the new data collected from the quadrat to the previous quadrat
- when the mean no longer changes you will have collected a big enough sample
describe measuring the frequency of a species
this is when you just record the presence or absence of a species in each quadrat
describe measuring percentage cover
this is a measure of the proportion of the ground occupied by the species in the quadrat, as a percentage of the total area
describe measuring the species density
counting the number of individuals of a species in a quadrat
give the advantages of measuring the frequency of a species
quick and easy in large ecosystems
give the advantages of measuring percentage cover
- quicker than counting
- useful when difficult to distinguish individual plants, and when one finishes an one starts
give the advantages of measuring species density
-allows you to calculate an estimate of the population size can calculate species diversity
give the disadvantages of measuring species density
- time consuming
- miss counts possible if in large numbers
- difficult to distinguish different plants
give the disadvantages of measuring percentage cover
- it is subjective so estimates by different people will differ
- doesnt give an actual population size
give the disadvantages of measuring the frequency of a species
- no estimate of population size
- can give an inaccurate indication of relative abundance
- results not detailed as one organism of a species counts the same as a 100 in a different sample
what is a transect ?
taking a sample along a line
wat is a transect used for ?
investigating how species distribution changes across and area
which is more detailed a line transect or belt transect ?
belt transect
Describe how you would collect data on the population of daisies in a field using random sampling
tape measures to mark out a grid
random numbers, from tables or a calculator to generate coordinates
place quadrat and count all daisies in area – decide on rules for overlapping edges
repeat until you have a large sample/ do a running mean until it settles out
work out the mean number per quadrat and multiply by the number of quadrats in the area, or calculate the mean per m2 and multiply by the area in m2
.
Describe how you would investigate how the
distribution of plants changes from the middle
to the edge of a woodland.
interrupted belt transect
could do more than one quadrat at each point to increase sample size and gain a more representative sample / reduce impact of anomalies / increase reliability
need regular measurements to be able to establish pattern/detect trends
estimate % cover / species frequency / species density
can convert to kite diagram
what is the advantage of doing more than one quadrat at each point?
increase sample size and gain a more representative sample / reduce impact of anomalies / increase reliability
describe the process of a line transect
A measuring tape is stretched across the habitat and plants are sampled at regular intervals, for example every 10cm. Each plant touching the line is identified and recorded.
describe the process of a belt transect
Quadrats can be placed next to each other along a transect and estimates of the percentage cover or frequency of each species is recorded.
what is a pitfall trap used for ?
crawling animals
what trap catches crawling animals?
pitfall trap
what trap catches water or sediment living organisms?
a kick sample net
what is a kick sample net used for catching?
water or sediment living organisms
what catches flying insects?
butterfly net
what assumptions do we make when using the mark recapture release method?
- no immigration or emigration
- no births or deaths
- marking does not increase the likely hood of been recaptured or preyed upon
- marked individuals have had a chance to mix fully back in with the population
give the equation used when using the mark recapture release method
population number estimate= ( the number captured first x the number captured on second occasion) / the number recatured that were marked
describe the method of mark release recapture
- using random sampling a large sample of organisms are caught
- then the organisms are marked, counted and released back into the ecosystem
- after release animals are given time to move around and thoroughly mix with the rest of the population
- then again capture a large sample using the same technique as before
- count the total number captured and the total number marked and then apply the equation
when marking organisms what should you ensure?
the mark does not harm the animal or in any way affect their chance of survival
