2.5 Investigating ecosystems

Question 1

Identifying organisms

Answer 1

dichotomous key
often use technical terms only understood by experts
→ may not be a key for the type of organism available
→ some features of organisms are difficult to identify in wild

Question 2

Marine measure of abiotic components

Answer 2

salinity, pH, dissolved oxygen, wave action, temperature

Question 3

Freshwater measure of abiotic components

Answer 3

turbidity, dissolved oxygen, pH, flow velocity, temperature

Question 4

Terrestrial measure of abiotic components

Answer 4

light intensity, slope, wind speed, temperature, mineral content, drainage, soil moisture

Question 5

Light measure

Answer 5

ight meter, meter must be held at a fixed height and at the same angle.

Question 6

Temperature measure

Answer 6

electronic thermometer with probes, soil / air / water. Data loggers allow long term fluctuations to be taken into account.

Question 7

PH measure

Answer 7

pH meter or data logger

Question 8

Turbidity measure

Answer 8

measured using secchi disc lowered into water - cloudy water = high turbidity, clear water = low turbidity. Indirectly corresponds to rate of photosynthesis.

Question 9

Estimating abundance of species

Answer 9

motile → pitfall traps, nets, light interception traps, small mammal traps
non-motile → quadrats, point frames

Question 10

Abundance

Answer 10

the relative representation of a species in an ecosystem. Can be done by directly counting organisms (non-motile) or indirectly estimating using Lincoln index (motile).

Question 11

Lincoln index

Answer 11

estimates total population size of a motile animal - ‘capture-mark-release-recapture’ technique.
[indirect]

Question 12

Species richness and diversity

Answer 12

Richness → number of species in a community
Diversity → a species’ relative abundance in a given area.

Question 13

Changes along environemtnal gradient

Answer 13

grid quadrat, point quadrats
→ line transect, belt transect (continuous or interrupted)
→ transects should be controlled for atmospheric conditions and repeated to ensure reliability.

Question 14

Changes due to humans

Answer 14

landfills, eutrophication, oil spills, change in land use, overexploitation
→ can use: diversity index, measure of abiotic variables, soil erosion (pH etc), lincoln index on various disturbed and undisturbed sites