Experimental methods using quadrats and transects

• It is important to estimate the number of organisms in a population to better understand the relationships in a community
• This information is useful for monitoring the impact of conservation projects that aim to conserve endangered species
• Animals that are close to extinction because of their low numbers are considered endangered species
• It is almost always impossible to count all of the organisms in a population, so sampling is used to draw conclusions about the rest
• Sampling involves counting the numbers of organisms within a sample site and then multiplying the results to estimate the total number in the entire habitat
• Large animals and plants can often simply be counted, while smaller animals like insects and smaller mammals need to be trapped first for counting
• Methods for sampling small animals include pitfall traps, sweep netting, kick-sampling, and using pooters to suck up small insects safely
• Quadrats are square frames of wire used for sampling the abundance and distribution of slow or non-moving organisms
• When using quadrats to look at plants, sampling methods include counting the number of individual species, recording species richness, and estimating percentage cover
• Random sampling using a quadrat is common, but systematic sampling can be used if there is a trend or pattern across the habitat
• Systematic sampling is used when investigating linear changes, such as the growth of seaweed depending on the distance from the tide on the seashore
• Transects are imaginary lines along which sampling occurs, and systematic sampling is used along transects to link changes in species to abiotic factors
• Results from transects can be drawn into kite diagrams to show the distribution of individuals observed at different points along the transect