Key Area 2 - Distribution Of Organisms Flashcards
Give examples of biotic sources
Competition (for resources), grazing, predation, disease, food availability
Give examples of abiotic sources
light intensity, temperature, rainfall, (soil or water) pH, (soil) moisture
How can temperature, light intensity, pH, soil moisture be measured
Temperature - thermometer - Insert probe into soil or water and wait until the reading has stabilised
pH - pH meter or chemical test/indicator - insert pH probe of meter into soil and read from scale
Light intensity- light meter - hold light sensitive panel towards light to be measured and read result from scale, ensure you’re not casting a shadow
Soil moisture - moisture meter - Insert probe into soil and read level from scale, ensure to wipe the probe so moisture from prophecies readings doesn’t affect the results
Give the possible sources of error, how to minimise these errors, and the limitations of using a pitfall trap
Sources of error - organisms may not be able to climb into the container, trapped organisms may be eaten by birds, trapped organisms may eat each other
How to minimise - make sure that the container is level with the soil surface, cover trap with a raised stone or leaf to create a roof, use a preservative like 50% ethanol or check traps regularly
Limitations - the size of the trap can limit what can be successfully caught, if the number of traps set it low then results may not be representative of the whole area
Give the possible sources of error, how to minimise these errors, and the limitations of using a quadrat
Sources of error - not placed randomly so the abundance of particular organisms can not be accurately estimated, some plants that are partly in the quadrat are recorded and others are not
How to minimise - ensure that quadrats are placed at random, establish a rule for plants that are partially included and apply consistently to all quadrats in the study
Limitations - if the number of quadrats placed is low then the results may not be representative of the whole area
Remember the 4 Rs
Repeat, Random and Representative Results
What is a paired statement key?
A key used to help identify the species that sampled organisms belong to.
What are the effects of predation on biodiversity and distribution of organisms?
Lack of predation can lead to over-grazing, reducing plant species diversity
What are the effects of grazing on biodiversity and distribution of organisms?
At low levels of grazing the plant species diversity tends to be low as a few dominant species will prevent other species of plants from growing there
As grazing intensity increases plant species diversity also increases as the dominant species is primarily eaten by herbivores giving an opportunity for other species to grow
If grazing intensity is too high, plant species diversity will decrease
What are the effects of temperature on biodiversity and distribution of organisms?
Temperature affects which organisms can survive in a region
What are the effects of pH on biodiversity and distribution of organisms?
Acid rain for example can alter the pH of a body of water and only some aquatic species will be able to survive
What is an indicator species?
A species that by its presence or absence shows the environmental quality/ levels of pollution
