Required Practical: Ecosystems Flashcards

All 6 cards in this deck

What are the steps to estimate the population size of a species using quadrats?

e.g. daisies in a field of area $200\ \text{m}^2$ using $1\ \text{m}^2$ quadrats

1. Place quadrats at random positions (random number coordinates), e.g. 10 quadrats.
2. Count the species in each quadrat and find the mean per quadrat, e.g. mean $= 6$ per $\text{m}^2$.
3. Multiply the mean per $\text{m}^2$ by the total area: $6 \times 200 = 1200$ daisies.

Why must quadrat positions be chosen at random when estimating a population size?

To avoid bias, so the sample is representative of the whole habitat.

What is a transect in ecological sampling?

A line across a habitat along which quadrats are placed at intervals, used to show how distribution changes across the habitat.

What are the steps to use a transect to investigate the effect of a factor on distribution?

e.g. effect of distance from a pond on rushes

1. Lay a tape measure in a line from the pond outwards.
2. Place a quadrat at regular intervals along the line, e.g. every 2 m, and record the number or percentage cover.
3. Measure the factor at each point (e.g. soil moisture) and plot abundance against distance.

True or false? The median of a set of abundance data is the most common value.

False. The most common value is the mode; the median is the middle value when the data are put in order.

When plotting abundance data on a graph, how should you choose the scales for the axes?

Use a linear scale that spreads the data over at least half of the available graph paper, and label each axis with the quantity and unit.