2.5 investing ecosystems Flashcards
How do we know what is going on inside an ecosystem?
In order to understand an ecosystem properly we need to measure various biotic and abiotic factors.
How do we decide where to measure?
Quadrats
Transects
why are quadrats and transect good?
they give a representative
Sample of a large area and
save time
How do we know where to place the quadrat?
“Throw it over your shoulder”
Draw a grid over your sample area.
Use a random number generator.
This is the square that you sample.
what do you do with the quadratic when your habitat has two types of vegetation?
If your habitat has two (or more) different vegetation types then samples should be taken in each area.
what does the transect do?
Look at changes over an environmental gradient e.g. zonation
how many measurements do you need from a transect?
Need more than 1 for a valuable results. (At least 3)
how can you sample your transect?
Random number generator for 2 numbers
Use transect to “connect” these
Random direction = random sampling
Unless you want to particularly follow a gradient = systematic sampling. This means samples are chosen in a regular way.
what are some abiotic factors you can measure in a water habitat?
turbidity.
flow velocity
ph
temp
salinity
disolved oxegen
what is turbidity?
the cloudiness of the water
how do you measure turbidity?
Use Secchi disk
Lower into water until no longer visible
what is the advnatges of measuring turbidity?
cheap and simple
what are the disadvantages of measuring turbidity?
Need a boat for deep water measurements
Different people see the disk at different depths
what is flow velocity?
speed at which river flows
how do you measure flow velocity?
Use a flow meter
Put in water, speed of rotation tells you speed of river flow
what is the advantage with measuring flow velocity?
it is often accurate
what are the disadvantages of measuring flow velocity ?
Expensive
Water and electricity can cause problems
how do you measure PH, temp and salinity?
using probes.
what are the advantages of using probes?
These are easy and quick to use
Attaching to a data logger means readings can be taken continuously over a period of time
what are the disadvantages of using probes?
Expensive
Can be faulty without you knowing
how do you messure dissolved oxegen?
Probe and data logger
Or Winkler titration
what are some abiotic factors you would measure in a terrestrial ecosystem?
air temperature,
light intensity
wind speed
rainfall
soil texture
slope angle
how do you measure air temperature and what is the benefit of them?
Simple thermometers
Probes
Probes can be used for continuous data logging
how do you measure light intercity?
Electronic meters
how do you measure wind speed?
Anemometer
Or observing effect of wind on objects and relating to Beaufort scale
how do you measure rainfall?
Rain gauge
Check same time every day and measure rain in measuring cylinder
how do you measure soil texture?
Different particles are measured differently
Measured individuals, sieved, sedimentation, light scattering etc
how do you measure slope angle? and what are the benefits and negatives to this method?
Using clinometer
Simple, cheap, fast
However
Inaccurate
what does measuring biotic factors involve?
it involves estimating the biomass and energy of trophic levels.
what can we measure to measure biotic factors in an ecosystem?
Plant biomass
Primary productivity (NPP and GPP)
Secondary productivity (NSP and GSP)
Frequency of motile/non-motile organisms
what are the steps to measure plant biomass?
Place quadrat
Harvest all above ground vegetation
Wash and remove insects
Dry until constant mass is achieved
Should be repeat 3-5 times
Can be extrapolated.
what are the pros and cons of messuring plant biomass?
Pro’s
-can extrapolate using a small area for data collection
Cons’
-destructive
-inaccurate for large organisms
how do we measure primary productivity in Terrestrial Ecosystems?
-calculate dry mass of quadrat A
-calculate dry mass of B and C after a month
-the increase from A to C is the NPP
-B has not been able to photosynthesise so any loss is through respiration ( R )
-can calculate GPP using these known numbers by rearranging equation NPP = GPP - R
what are the pros and cons for the measuring of primary productivity (gross and net)?
Similar pro’s/con’s to measuring plant biomass
Also difficult to make all 3 areas of vegetation identical
how do we Measure Primary Productivity in Aquatic Ecosystems?
The Bottle Method
2 bottles with water from ecosystem, one covered
Measure O2 conc
Place equal amount of plants in both bottles
Leave to stand for several hours
Measure O2 conc and compare with original levels
In light bottle, photosynthesis and respiration occurs
In dark bottle, respiration only
NPP = GPP - R
how do we calculate secondary productivity?
Weigh organism at beginning and end
(NSP = end - start)
Weigh food given/faeces produced
(GSP = food eaten - faecal loss)
what are the pros and cons of measuring secondary productivity?
Pro’s
-can extrapolate from small sample
Con’s
-not accurate
-only for small, non-aggressive animals
how do we measure the Abundance of Non-Motile Organisms?
Quadrats are used for non-motile organisms
what are the pros of a quadrat when it comes to measuring non-motile organism?
Quick and easy
Accurate for large species
Allows comparisons over time or space
what are the cons of a quadrat when looking at motile organism?
Difficult with small species
Can miss species in layered vegetation
Relies on correct identification of species
what are the Direct and Indirect Methods for Estimating Abundance of Motile Organisms?
Direct method:
Sampling
Indirect methods:
Capture-mark-recapture and application of the Lincoln Index
how do we sample motile organism in a terrestrial environment?
Pitfall Traps
Sweep nets
Tree Beating
Pooters
how do we sample motile organism in a aquatic ecosystem?
Kick sampling
can you give some features of a pit fall trap?
it caches Insects and other small invertebrates
Number of each species recorded
No fluid in the bottom and provide food/bedding
can you give some features of a sweeping net? and then their pros and cons?
Capture flying insects/stream invertebrates
Sweep through vegetation for set time
Identify and count insects
-easy to miss insects so inaccurate
-dangerous if insects sting
what is tree beating?
finding insects in the tree branches changing tray put beneath and tree is gently tapped.
what are some features of kick sampling (aquatic).
Catch stream invertebrates
Net against bottom of stream
Other person kicks sediment at bottom of stream approx a metre away from the net
Disturbed organisms caught in net downstream
Problematic if kick sites are near by as organisms may “drift” into other samples
in general what are the pros and cons of motile organism catching?
Pros:
Non lethal
Simple
Cons:
Careless handling can cause harm/death
Causes stress
Only for small, nonaggressive animals
what is a way we can identify organisms?
Dichotomous Keys
what does dichotomous mean?
Dichotomous = divided into two parts
can you give the general description of a dichotomous key?
Numbered series of pairs of descriptors
One matches the species, the other is wrong
Each pair leads to another pair of descriptors OR an identification
what do you need to make sure of when picking your features for the dichotomous key?
Features chosen for descriptors should be easily visible and observable
what are some Alternative Ways
to Identify Species
Without Using a
Key?
Photos and illustrations
DNA technology
Field guide
what is the Lincoln index? and can you give an example of how we collect data for it?
The Lincoln Index lets us estimate a population size.
We can carry out capture-mark-recapture then apply the Lincoln Index to get an estimation of the population size
what are some of the assumption that come up when you use the capture-mark-realse method?
The population of organisms must be closed – no immigration or emigration
The time between samples must be small compared to the life span of the organism
The marker organisms must mix completely with the rest of the population during the time between sampling
what are the negatives of the capture-mark-release method?
Capture of animals can injure them
Capture can alter animals behaviour
Mark could rub off between release and recapture
Marks may increase/decrease predation
Mark could be unknowingly toxic
Animals can become “trap happy” or “trap shy” causing over/under estimations
what is species diversity?
The number of different species and the relative number of individuals in the species.
what do you use to measure specs diversity?
= species richness and
Species evenness
what index do you use to quantify species diversity?
Can be quantified using Simpsons Diversity Index
on the formula for the Simpson diversity index (which you are given in the exam) there are the letters D,N,n. what do they mean?
D = Simpson diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species
what can we use the Simmons diversity index for?
We can use the index to compare diversity of 2 different ecosystems
what are the only two surcumstances when you can use Simpsons index?
Simpson’s Index of Diversity is only useful when comparing 2 similar habitats or the same habitat over time.
why do we use sampling strategies?
To measure changes in biotic and abiotic factors:
Along environmental gradients
Over time
Before/after human impacts like oil silly, deforestation, overexploitation.
on the Simmons diversity index, what does the big N mean?
the sum of all the individuals
on the Simmons diversity index, what does the small n mean?
the number of individuals in a species.
Watch a vedio of how to use Simmons diversity index!
Watch a vedio of how to use Simmons diversity index!
