3.2 Distribution of Organisms Flashcards
What is a biotic factor
An interaction between living things in an ecosystem
What is an abiotic factor
Non-living factors that affect a species
What are 5 examples of biotic factors
Competition
Grazing
Predation
Disease
Food availability
What are 4 examples of abiotic factors
Light intensity
pH
Temperature
Moisture
How do you measure light intensity?
Light meter
1. Set meter to light position
2. Point sensor at light source
3. Take reading when meter is still
What are sources of error when using a light meter and how do you minimise them?
Observer may cast a shadow over the sensor - ensure the sensor is not under your shadow
Clouds may cause fluctuations in readings - all measurements should be taken as closely together as possible
How do you measure soil moisture?
Moisture meter
1. Set meter to moisture position
2. Push probe into soil
3. Take reading once pointer is still
What are sources of error when using a moisture meter and how do you minimise them?
Moisture may be left on the probe - probe should be wiped before each use
Probe may be inserted at different depths each time - ensure probe is inserted at the same depth each time
How do you measure pH?
pH meter
1. Set meter to pH setting
2. Push probe into soil or water
3. Take reading once pointer is still
What are sources of error when using a pH meter and how do you minimise them?
Soil may be left on the probe - probe should be wiped before each use
Probe may be inserted at different depths each time - ensure probe is inserted at the same depth each time
How do you measure temperature?
Thermometer
1. Push into soil
2. Take reading once the level is stable
What are sources of error when using a thermometer and how do you minimise them?
It may not be left for long enough to adjust to the temperature - ensure reading is only taken once the level is stable
How is a quadrat used?
Thrown randomly and multiple times into a large area to estimate the number of organisms in said area without counting them all individually
Only for unmoving organisms (plants)
How is a pitfall trap used?
A small hole is dug, a container is placed into the hole, and it is covered (not airtight) to prevent rain from flooding it, but allowing invertebrates to fall in
It is checked regularly to prevent one organism eating all the others
The edge of the container is in line with the soil to allow invertebrates to fall in
What is a paired statement (dichotomous) key?
A method that allows biologists to identify a species they don’t recognise
