SAMPLING BIODIVERSITY Flashcards
Define succession
Occurs as a result of changes to the environment (the abiotic factors), causing the plant and animal species present to change
Primary succession
Occurs on an area of land has been newly formed or exposed such as bare rock
There is no soil or organic material present to begin with
Secondary succession
Occurs on areas of land where soil is present, but it contains no plant or animal species
An example would be the bare earth that remains after the forest fire
What does succession occur as
A sere
Pioneer community
First serial stage
Occurs on land that has been newly formed or exposed
Begins with colonisation hospitable enviro, organisms= pioneer
Species arrive as spores or seeds
E.g. algae
Very well adapted for survival
Intermediate community
Happens on land with soil
When pioneer species die and decompose, organic components absorbed into soil
Means intermediate community provided with more nutrients
Climax community
The community in a stable state- little change over time
Which species make up climax community depends on the climate
E.g. mild temp with plenty of water will have large trees
What happens to biodiversity during succession and why
Increases as succession takes place, however climax community is always most diverse
Reaches peak in mid succession, then decreases as dominant species out compete pioneer + others= elimination
Describe the process of succession on sand dunes
Youngest dunes found closest to shore and will mainly be bare ground
Pioneer- most likely marram grass
Intermediate- consist of shrubs
Climax- further from shore, e.g. oak trees
Deflected succession
Human activities can prevent succession reaching the climax community
Final stage referred to as the plagioclimax
E.g. grass lawn, animals graze
Define abundance
How many of the organisms are present
Define distribution
Where in the ecosystem the organism lives
What do random samples avoid
Bias
Describe how you would decide where to place your quadratic in a given area
Random number generator on calculator Apply to axis Place quadratic in designated area Count number of different species Repeat
Limitations of random sampling with quadrats
- placement of axis can be bias- use larger area
- several sampling areas
- placing quadrat may be inaccurate
- seasonal variation
How can you reduce effect of chance meaning that your sample is not representative of the area
Take more recordings
Define non random sampling
May be useful to ensure all areas of a habitat where there is a lot of variation are studied and to look at the distribution of organisms
Non random sampling:
Opportunistic
Using organisms that are continently available
Weakest form as organisms may not be representative
Non random sampling:
Stratified
Dividing populations or habitats into sub-groups (strata) based on particular characteristics
Random sample then taken from each strata proportional to its size
Non random sampling:
Systematic
Sample taken at fixed intervals
Useful when studying a gradient in amitotic factors affect the species present
Line transect- stretch string across habitat + record plants touching at regular intervals
Belt transect- 2 parallel lines marked + samples are taken of the area between lines
Describe how to use a frame quadratic
Count n umber of species in each square
Estimate % cover
Use an abundance scale
Point quadratic + percentage cover
Drop pin through holes and record everything that touches it
Number of hits of species/total number of pins x100
Advantages and disadvantages of two types of quadrats
More objective than frame
Representative
Small area compared to frame
