Biodiversity and sampling

• Biodiversity is the variety of organisms living in an area
• Species are a group of similar organisms, that can have similar anatomy,physiology,genetics,appearance, bio-chemistry
• A habitat is a place where organisms live

You need to observe all the species present in a habitat to measure the biodiversity, this can be done by counting the amount of species present and how many of each species are present. The abundance of species is known as species richness and the variety of species presence is known as the species evenness.

The coral reefs in Australia has a lot of Biodiversity

Sampling plants

You need to randomly choose the position of where you take your samples inside the habitat. It can be done in 3 ways, for example:

• take samples at regular distances across the habitat
• use random numbers, generated by a computer or a random number table to plot co-ordinates within the habitat
• select co-ordinates from a map of the area and use a portable global positioning satellite system to find the exact position inside the habitat

The amount of samples you take will depend on the time you have and the size of the habitat, you need to also take into account how diverse the habitat is.

There are different ways that plants can be sampled as listed below:

Using random quadrats

• its a square frame used to define a sample area
• you can place the quadrats at random in the habitat
• place the quadrat on the co-ordinates generated from the random numbers
• then you identify the plants found within that frame
• then you measure the abundance of plant species in one of 3 ways

A quadrat sample device, used to measure the percentage cover of certain grasses. (Photo credit: Wikipedia)

Abundance scale

• Abundant
• common
• frequent
• obvious
• rare

Estimate the percentage cover

Point frame

• record any plants touching the needles
• if the frame has 10 needles, use it 10 times
• you will have 100 readings
• therefore with a point frame with 10 needles and 10 samples every time a plant touches a sample it has 1% coverage
• as one needle may touch several plants, it is possible to have greater than 100% coverage

Using a transect

• take rope or tape measure across the habitat
• take samples across the line
• larger habitats use a line transect
• and record the plants that touch the line at several intervals along it
• you can place quadrats along the set intervals
• using a quadrat gives an interrupted belt transect which makes it a quantitative measure
• they are good for awkward shaped habitats
• and for habitats that change over distance

Sampling animals

There are things that need to be considered when sampling for animals. Such as

• Do animals move
• how large are they
• how large is the  population likely to be
• where do they live
• will the animal’s habitat be disturbed

The best technique usally is to either catch or trap , however you would not do it to large animals as they would be observed. Therefore you should estimate the numbers from the trapped organisms or estimate their numbers from what they leave behind…..

Animal dropppings are often looked at when sampling animals….

Catching animals can be done in many ways, examples of these methods include:

sweep netting

• sweep net through vegetation
• animals caught in net
• empty contents onto white sheets
• take care as animals crawl away
• can also use a pooter

 collecting from trees

• a net is swept through the tree
• spread a white sheet under the tree to collect the small animals that are dislodged
• must be quick to identify

pitfall traps

• Set below surface of the soil
• any animals moving through the leaf litter will fall into the trap
• trap should contain water or scrucned up paper to stop animal from crawling out

tullgren funnels

• collects small animals from leaf litter
• place leaf litter in a funnel
• the light drives animals downwards
• animals are collected in the collecting pot

Light trap

• UV light attracts insects
• under the light is the collecting vessel
• contains alcohol

You need to be aware of the mark and recapture method, the formula for this is:

Total population = (C1 x C2)/C3

C1 = no. caught on the 1st occasion

C2 = no. caught in the 2nd occasion

C3 = no. recaptured

We need to sample the habitat to determine what effect human acitvity is having on the habitat. Environment impact assessment reports also sample the habitat and hey are essential to the development in habitats.