Required practical 12 - Effect of different variables on species distribution

Outline the method:

• Layout two tape measures at a right angle to each other. Then get a random number generator to get random two numbers (to avoid bias) that act as coordinate points about 25 sets

• Go to these coordinates, place the quadrat (bottom left corner on the coordinates) and count the number of dandelions

• Calculate the percentage cover.

• Repeat the experiment with the other coordinates

• Repeat the experiment with the non-herbicide lawn

The idea behind this practical - for example, the effect of herbicide on the distribution of dandelions on a lawn:

• Using a quadrat

• Herbicides (abiotic factor - non-living factor) - effecting the growth of a plant

• So, compare the distribution of dandelions to a lawn treated with herbicides to a lawn not treated with herbicides

Practical implications:

Difficult to count accurately, leading to inaccurate readings - where plants could be overlapping each other.

What are some abiotic and biotic factors?

Abiotic factors:

• light intensity

• Temperature

• water concentration

• Nutrient supply

• Humidity

• Wind speed

Biotic factors:

• Predetors

• Disease

• Competition for resources

How to test if there is a relationship between the chosen factor and percentage cover?

• Use a statistical test to test if there is a corrlation to be significant

State the assimptions for the mark-release-recapture method:

• No births, deaths or immigration

• Random mixing of marked individuals with population

• Marking does not make the species vulnerable to predators