BIODIVERSITY

Biodiversity

• A measure of the variation found in the living world

What is a habitat

• Where an organism lives
• Sand dunes, woodlands, meadows and streams
• Each occupied by a large range of organisms

Species biodiversity

• A species consists of individual organisms that are very similar in appearance, anatomy, physiology, biochemistry and genetics
• Individuals in a species can interbreed freely to produce fertile offspring
• The range of organisms found in a habitat contributes to the species biodiversity
• Two habitats may have an equal number of different species, but they may not be considered equally diverse. For example wild meadow is more diverse than grass
• The number of plant species is the species richness
• The degree to which the species are represented is known as the species evenness

Genetic biodiversity

• The variation between individuals belonging to the same species
• Can create breeds within a species
• Ensures we do not look all identical

Using samples to measure biodiversity

• Need to observe all the species present, identify them, and count how many individuals of each species there are
• This is not practical as it would be impossible to count all the fungi, bacteria and other single-celled organisms
• Some microorganisms can be cultured on a nutrient medium in the laboratory to gain an estimate of numbers, but not all will grow like this
• Instead, you can sample a habitat - you select a small portion and study that carefully
• Then you can multiply up the numbers of individuals of each species found, in order to estimate the number in the whole habitat
• Its important samples are representative of the habitat

Random sampling

• Sample sites inside the habitat are randomly selected
• You can do this by deciding where to take samples before you study any area in detail
• This can be achieved by using randomly generated numbers as coordinates for your samples, or possibly selecting coordinates from a map and using a portable global-positioning satellite system to find the exact position inside the habitat
• Advantages - ensures that the data are not biased by selective sampling
• Disadvantages - may not cover all areas of a habitat equally. Species with a low presence may be missed, leading to an underestimate of biodiversity

Non-random - opportunistic

• This is when the researcher makes sampling decisions based on prior knowledge or during the process of collecting data
• The researcher may deliberately sample an area that he or she knows contains a particular species
• Advantages - easier and quicker than random sampling
• Disadvantages - data may be biased, the presence of large and colourful species may entice the researcher to include that species. This may lead to an overestimate of its importance and therefore an overestimate of biodiversity

Non-random - stratified

• Dividing a habitat into areas which appear different , and sampling each area separately
• For example, patches of bracken in heathland might be sampled separately from the heather or gorse patches
• Advantages - ensures that all different areas of a habitat are sampled and species are not under-represented due to the possibility that random sampling misses certain areas
• Disadvantages - possibility that this may lead to over-representation of some areas in the sample - i.e. a disproportionate number of samples are taken in small areas that look different

Non-random - systematic

• When samples are taken at fixed intervals across the habitat
• Line transects and belt transects are systematic techniques
• Advantages - particularly useful when the habitat shows a clear gradient in some environmental factor such as getitng drier further from a pond
• Disadvantages - only the species on the line or within the belt can be recorded. Other species may be missed' leading to an underestimate of biodiversity

Sampling a habitat - preparation

• suitable clothing
• suitable footwear
• apparatus needed to carry out the sampling
• clipboard, pen and paper
• appropriate keys to identify plants
• camera or smartphone to record specimens and grid locations

Sampling a habitat - at the site

• Best to use a range of techniques
• Random sampling but if the habitat is not homogeneous (even) it may be helpful to modify the technique
• Combine sampling methods
• Any sampling should cause as little disturbance as possible

Sampling plants

• generate random numbers and use them as coordinates to place quadrats
• Inside the quadrat you'll need to identify the plants found and then calculate the percentage cover as a measure of their abundance
• Point frame - frame with a number of long needles or pointers
• Best to use point frame at regular intervals across the quadrat (systematic sampling within the randomly placed quadrat)

Using a transect

• A transect is a line taken across the habitat
• You stretch a long string or tape measure across the habitat and take samples along the line
• In a large habitat, you might use a line transect
• In this case you would record the plants touching the line at set intervals along it
• There's also an interrupted bell transect, where a quadrat is used at set intervals along the line, providing quantitative data at intervals across the habitat
• A continuous belt transect is when a quadrat is placed beside the line and is moved along the line so you can study a band or belt in detail, again providing quantitative data

Sampling animals by observation

• Many animals are not easy to spot and are more difficult to count
• Larger animals may hide from human eye
• Obtaining quantitative data on animals is difficult
• Can note the presence of many larger animals by careful observation - looking for signs that they have left behind (footprints, droppings etc)
• DNA sequencing can distinguish droppings from different individuals, this provides a more accurate way to calculate the population size

Catching invertebrates

• Sweep netting - walking through the habitat with a stout net. You sweep the net through the vegetation in wide arcs. Any small animals will be caught, you can then identify them. A pooter can collect animals before they have a chance to fly away. This type of sampling is suitable for low vegetation that is not too woody, a similar technique can be used to take samples in water
• A sweep net will not work as well when collecting from trees, here it's better to spread a white sheet out under a branch and knock the branch with a stout stick. The vibrations dislodge any small animals, which then drop on to the sheet
• A pitfall trap is a trap set in the soil to catch small animals. It consists of a small container buried in the soil so that its rim is just below the surface. Any animals moving through the plants or leaf litter on the soil surface will fall into the container
• A tullgren funnel is a device for collecting small animals from leaf litter. The leaf litter is placed in a funnel. A light above the litter drives the animals downwards as the litter dries out and warms up. They fall through the mesh screen to be collected in a jar underneath the funnel
• A light trap can be used to collect flying insects at night. Consists of a UV light that attracts the insects. Under the light is a collecting vessel containing alcohol, insects and moths attracted to the light eventually fall into the alcohol

Trapping small animals

• The Longworth trap is a humane trap that needs to be monitored regularly to release any trapped animals. This kind of trap allows the population size to be calculated using the mark-and-recapture technique
• First you need to capture a sample of animals
• Mark each individual in a non harmful way, number captured = C1
• Release the marked animals and leave the traps for another period of time
• The number captured on this second occasion will be C2, the number of already captured animals will be C3
• total population = C1 x C2 divded by C3
• Estimate can be affected by animals who learn the trap is harmless and contains food, or by animals who keep away from the trap after the first time