2.5b Investigation Ecosystems (Biotic Factors) Flashcards
What are “probes” and what can they measure?
Probes are recent technological devices that have interchangeable probes allowing you to measure various abiotic factors.
- Salinity
- pH
- Temperature
- Dissolved oxygen
- Light intensity
- Soil moisture
- Mineral content
What are some advantages and disadvantages of probes?
Advantages:
- Quick
- Accurate
- Easy to use.
- When attached to a datalogger they can take continuous readings over a period of time.
Disadvantages:
- May be expensive.
- Can break down and give false readings without you knowing.
- May not be available in all countries.
How do you measure “Turbidity”?
Turbidity refers to the cloudiness of the water body (transparency). It is measured using a Secchi disk.
–> The clearer the water the lower the turbidity and the higher the Secchi depth will be
Method:
- Slowly lower the Secchi disk into the water until it is no longer visible.
- Record the depth at which it disappears – this is called the Secchi depth.
- Repeat at least 5 times for accuracy and take the mean of the 5 readings.
- The same person must take all the readings and they must be in the same position every time
What are some advantages and disadvantages of Secchi Disks?
Secchi Disks are used to measure Turbidity:
Advantages:
- Simple instrument - no mechanics to go wrong.
- Easy to make one for yourself.
- Cheap
Disadvantages:
- Need a boat or a dock to get into deep enough water to lower the disk.
- Different people may have different abilities to see the disk.
How do you measure “Flow Velocity”?
- Flow Meter
- Float/ Pooh Stick
What are Flow Meters?
The speed at which a river flows can be measured with a flow meter.
–> you put an impellor in the water and the speed at which it rotates tells you the speed at which the river is flowing in m/sec
What are some advantages and disadvantages of Flow Meters?
Advantages:
- Accurate
- Readings can be taken at varying depths.
Disadvantages:
- Can be expensive.
- Mixing water and electricity can cause some problems.
What are Float/Pooh Sticks?
- Select a straight section of the river
- Have a person on either end (measured distance)
- Drop a float into the river and start the timer
- Stop the timer when float arrives at other person
- -> Time taken for float / distance
What are some advantages and disadvantages of Float/Pooh Sticks?
Advantages:
- Needs limited equipment.
- Cheap
Disadvantages:
- Not very accurate.
- Readings can only be taken at the surface and flow velocity varies with depth.
How do you measure “Wind Speed”?
Use an Anemometer:
Very easy to use, hold them in the path of the wind and let the wind blow through it
–> will give you a reading
What are some advantages and disadvantages of Anemometers?
Anemometers are used to measure wind speed
Advantages:
- Gives an immediate reading with no calculations needed.
- Quick results.
- Simple to use
Disadvantages:
- May be expensive.
- May not be available in some countries.
How do you measure “Slope Angle”?
Slope angle is measured using a clinometer - these can be bought or made using a protractor, a string and a weight
Method:
- Take two 1M poles and place them apart on a slope
- Place the clinometer close to the top of the pole and look up at the top of the other pole
- -> Weighted string will drop straight down and show the number of degrees
How do you measure “Soil”? (composure)
- Take soil and place it in a bottle
- Add water and shake (+leave to rest)
- Measure the depth of the layers that form
- -> Calculate the percentage of each particle size
What are some advantages and disadvantages the soil in jar method?
Advantages:
- Simple and cheap.
- The hand identification is quick.
- The hand identification can be done in the field.
Disadvantages:
- Neither method is that accurate.
- The hand identification is subjective and opinions may vary between people.
- The settling method is slow.
