biodiversity Flashcards
3 levels of biodiversity
- genetic
- allelic variation within a species - habitat
- no. of different habitats in an area - species
- no. of species in an area
population
total number of individuals
species
group of organisms that can interbreed and produce fertile offspring
habitat
an environment in which a particular species lives
biodiversity
the variety of life within an area, including both biotic and abiotic factors
sampling general
- taking measurements of a limited number of individual organisms present in a particular area
- carried out when it’s difficult to count every single individual
- produces a representative estimate of a whole area
random vs non-random sampling
random
- every element has an equal chance of being picked
- sampling frame required
- elements selected randomly
non-random
- elements are picked according to a system
- elements have different chances of being picked
3 types
- opportunistic
- stratified
- systematic
random sampling
- allocate a number to each element
- use a random number generator to generate numbers
/
avoids bias
easy
fast
X
difficult for large populations
less representative
systematic
- population grouped within itself
- different areas identified
- each area sampled separately based on a system i.e. every 3rd element
/
simple
suitable for large samples
X
can introduce bias
stratified
- population divided into groups
- random sample taken from each stratum proportional to the size of the group
/
reflects population structure
proportional representation of groups within the population
X introduces bias more resources required the population must be divided into groups difficult with larger populations
opportunistic
- sample picked based on availability/accessibility as long as they fit specific criteria
/
easy
fast
suitable for large populations
X
bias
not representative
PLANT sampling techniques
- quadrat
grid using a tape measure, place quadrat at coordinations calculate the number of plants or percentage cover (use a key to help identify plants) - transect
belt or line (shows change in areas well)
use a tape measure as a transect, count the number of organisms touching the line - point quadrat
sampling frame
holds vertical pins, record the number of times the pin “hits” the organism being investigated
ANIMAL/INSECT sampling techniques
- sweep net
in tall vegetation
hold sweep net and move side to side in an arc
count no. of organisms collected - pooter
insects
the jar used to collect insects, apply suction on one side and insect drawn in on other - pitfall trap
ground surface organisms
a device, such as buried beaker, traps insects and small animals which are then counted - tullgren funnel
extraction on invertebrates from the soil/ litter
the sample is placed in the funnel above disc, placed under light, heat dries the sample, animals fall into the beaker
why measure biodiversity?
measuring biodiversity gives a baseline to test the effects of human activity, climate change and disease
Simpson’s index
D = 1 - (sum of (n/N)2^)
D = biodiversity n = number of organisms of specific species N = total number of organisms of all species
LOW = dominated by 1/ few species, low species richness and evenness, an unstable ecosystem which is less likely to cope with change
HIGH = many species, not dominated, high species richness and evenness, a more stable ecosystem
