Investigating ecosystems

Question 1

What are transects used for?

Answer 1

• Continuous + systematic sampling

- Look at changes in organisms as a result of changes along an environmental gradient e.g. zonation along a slope

Question 2

What is a continuous transect?

Answer 2

The whole line or belt is sampled

Question 3

What is an interrupted transect?

Answer 3

Quadrats placed at intervals along the belt

Question 4

Marine ecosystems // measuring salinity

Answer 4

Measure

• electrical conductivity of water
• density of water

Question 5

Marine ecosystems // measuring pH

Answer 5

Seawater usually has pH of above 7

Can be measured using pH metre

Question 6

Marine ecosystems // measuring temp.

Answer 6

• Temp. affects metabolic rate of organisms as many are ectothermic
• Lower temps. = lower metabolic rates
• Use thermometer

Question 7

Marine ecosystems // what is the solubility of oxygen in water affected by?

Answer 7

TEMP
- higher temps. = lower concentrations of dissolved oxygen

WATER POLLUTION
- cause low oxygen concentrations

Question 8

Marine ecosystems // measuring dissolved oxygen

Answer 8

oxygen-selective electrode connected to an electronic meter (give quick results, but need to be well maintained to give accurate results)

Question 9

Marine ecosystems // wave action

Answer 9

areas with high wave activity = high concentrations of dissolved oxygen

e.g. coral reefs

Question 10

What is turbidity?

Answer 10

The cloudiness of a body of fresh water

High turbidity = cloudy water
Low turbidity = clear water

Question 11

Freshwater ecosystems // measuring turbidity

Answer 11

Turbidity limits penetration of sunlight + therefore the depth at which photosynthesis can occur

Measured using Secchi disc // a black + white disc attached to a graduating rope, the disc is heavy to ensure rope goes vertically down

Question 12

Freshwater ecosystems // measuring flow velocity

Answer 12

• Measure the time a floating object takes to travel a certain distance e.g. an orange
• Floating object should be partially submerged to reduce effect of wind
• Method gives surface flow velocity only
• Divide by 1.25 to give avg flow velocity

Question 13

Freshwater ecosystems // measuring pH

Answer 13

measured using pH meter

Question 14

Terrestrial ecosystems // measuring air temp.

Answer 14

data-logging temperature probe can be used to measure temp. continuously

Question 15

Terrestrial ecosystems // measuring light intensity

Answer 15

use electronic metres

Question 16

Terrestrial ecosystems // measuring wind speed

Answer 16

• a ventimeter is a calibrated tube over which the wind passes
• this reduces pressure in tube, making a pointer move
• inexpensive + easy to use

Question 17

Terrestrial ecosystems // measuring rainfall

Answer 17

use rain gauge + check every 24 hours

Question 18

Soil // measuring soil moisture

Answer 18

• place soil in crucible
• weigh it
• leave for 24 hours to dry + weigh sample, repeat until its mass becomes constant

Question 19

Measuring plant biomass

Answer 19

• dry plant material at 70 degrees until it reaches constant weight
• repeat 3-5 times
• extrapolate result to total biomass of that species in ecosystem

Question 20

What is the Lincoln Index formulae?

Answer 20

N = (n1 x n2) / m2

N = total pop. 
n1 = no. animals first marked + released
n2 = no. animals captured in 2nd sample
m2 = no. marked animals in 2nd sample

Question 21

What is the Simpson diversity index formulae?

Answer 21

D = {N(N-1)} / {n(n-1)}

D = Simpson diversity index
N = total no. of organisms of all species found
n = no. individuals of a particular species

Question 22

What does a high value for D in Simpson diversity index indicate?

Answer 22

High value = highly diverse ecosystem + often stable, ancient site