Types Of Sampling Flashcards
Sampling
Taking measurements of a limited number of individual organisms present in a particular area
What can sampling be used for ?
- estimate the number of organisms in a area
- the abundance of the organism
- measure a particular characteristic of an organism
Random sampling
The positions of the sampling points are completely random or due to chance
ADVANTAGE : there will be no bias by the person carrying out the sampling that may affect the results
Non - random sampling
Positions of the sampling points are chosen by the person carrying out the sampling
DISADVANTAGE: person choosing could show bias towards or against certain areas
Eg. Individuals may deliberately place the quadrat in areas with the least species as these will be easier and quicker to count
UNREPRESENTATIVE of the whole area
Abundance of species
Number of individuals of that species
Distribution of a species
How it is spread throughout the ecosystem
Non random sampling 3 main techniques
- opportunistic
- stratified
- systematic
Opportunistic sampling
- picking and choosing sampling locations based in various non- random factors
- weakest form as its not representative of the population
Stratified sampling
Involves matching the number of sampling locations in a particular habitat with the relative proportion of area that habitat covers in the whole area being studied
Systematic sampling
Used when there is a clear change in the physical conditions across the area being studied
For eg. Change in altitude, soil pH, light intensity
Methods using transects can help show how species distribution changes with the different physical conditions in that area
Transects
Line represented by a measuring tape along which sample are taken
Line transect
( often used for systematic sampling )
Making a line along the ground between two poles and taking samples at specified points
Belt transect
( systematic sampling )
- Provides more information
- 2 parallel lines are marked and samples are taken of the area between the two lines
Sweeping nets
Large strong nets with a fine material with small holes that are used to catch flying insects and insects that live in oomf grass by sweeping the net back and fourth through the grass
Pitfall traps
Cans or jars that are buried in the ground that are used to catch ground- dwelling insects and other invertebrates as they fall into the trap
Pooters
- Small plastic or glass containers with two tubes sticking out that are used to suck up small insects and other small invertebrates
- 1st tube is placed over the insect and the second tube is used by the scientist to create suction
Tullgren funnel
Funnels with a light bulb above and a container below that are used to collect invertebrates that live in leaf litter r soil
Lead little or soil is placed in the funnel and the light and head forces the invertebrates to move down until they drop into the container
Kick sampling
- catch freshwater invertebrates living in streams or rivers
- a net is placed on the streamed so that the water is flowing into it and the stream bed just above the net if churned by the scientist for a set period of time
- the invertebrates are carried by the stream into the net
Point quadrant
- Consists of a frame containing a horizontal bar
- at set intervals along the bar long pins can be pushed through the bar to reach the ground
- each species or a plant the pin touches is recorded
Frame quadrat
- consists of a square frame divided into a grid of equal sections
- the type and number of species within each section of the quadrat is recorded
Advantage of using a range of sensors to measure abiotic factors
- rapid changes can be detected
- human error in taking a reading is reduced
- a high degree of precision can be often be achieved
- data can be stored and tracked On a computer
Features of habitat in low biodiversity area
- few successful species
- stressful nature of the environment
- few species live in the habitat often with very specific adaptations for the environment
- relatively simple food webs
- major effects on the ecosystem when there is a change
Features of habitat features in a high biodiversity area
- large number of successful species
- not stressful nature of the environment
- many species live in the habitat often with few specific adaptations to the environment
- complex food webs
- if there is a change there is a relatively small effect on the environment of the ecosystem
