Biodiversity

Hiya, Seen as we're off school because of Covid-19, I can at least have time to update this blog.
This one is on biodiversity and sampling types as well as plant and animal sampling.

I'm running out of my own images so here's a Costa Rican rainforest

Biodiversity is a measure of variation within the living world. Biodiversity can be measured using sampling techniques because recording every species and population would be too time consuming and very difficult to do. By sampling a habitat, an estimation of populations and biodiversity can be calculated. For example if you sampled 1/10 metres squared, then you would multiply your counted population by 10 to estimate for the whole 10 metre habitat.

Sampling can be random or non-random.

Random sampling is where a location within a habitat is random, for example, a random number generator can be used to generate coordinates for a transect area. Pro: It gives an unbiased result
Con: may not capture all of the species in the habitat, leading to an underestimate

Non- random sampling can be split into three main categories;

• Opportunistic; the researcher already knows about this habitat and selects an area which is known to be rich in biodiversity or a specific species. Pro: It's easier and faster than random sampling. Con: can lead to an overestimate in biodiversity and is very biased
• Stratified: the habitat is split into different appearing areas and sampled. Pro; ensures all areas are sampled. Con; leads to an overestimate of biodiversity, most areas not as rich
• Systematic; samples are taken at a specific interval e.g using a transect and transect belt. Pro; good for showing effects of a variable e.g moisture up a coastline. Con; can lead to an underestimate as some populations could be missed entirely

Sampling plants

Large plants and trees can often be counted individually as they're easy to see but with smaller plants, they are often too small or too numerous to count effectively without spending too much time on it. Like at GCSE, quadrats and transects are used to sample plants. Within a quadrat, either the number of each species is counted and this is applied to the whole area. Alternatively, the percentage cover of species in the quadrat can be calculated and then used to reflect the biodiversity. Using a point cover quadrat you can;

• Use simple random sampling by using a random number generator to place the quadrat in different places around the habitat
• Use line transect sampling by recording how many species touch the line along a habitat
• Belt transect sampling by placing a quadrat along a belt transect and recording percentage cover of the plants, this can be done across the whole transect or systematically (at set intervals)

Sampling animals

Animals are more difficult to capture than plants because they can move due to a variety of reasons, particularly when sensing danger. There are a few main methods of capturing animals, starting with invertebrates;

1. Sweep netting (and pooters); by waving about a sweep net in, often a forest, habitat, organisms can be captured and then released onto a white sheet to count and record the species present. Alternatively, and arguably more effectively, you can place a white sheet beneath or on some branches of a tree and use a stick to lightly 'tap' creatures onto the sheet. A pooter is  a piece of equipment that helps to collect the organisms to be counted.
2. Pitfall trap; a container is placed into the soil and a layer of matter/leaves covers the opening. Invertebrates fall into the pit and can be collected and counted before being released. For this 'trap' it needs to be protected in rain so it doesn't fill up, also paper or water needs to be placed in it so that the species can't escape.
3. Tullgren funnel; a container with a layer of leaves and matter on top of a screen above the jar. A light is above the matter, driving the creatures to dig downwards, falling through the screen and into the containing jar.
4. Light trap; a light inside a container, flies and insects fly towards it at nighttime and eventually fall into an alcohol container below. This kills the flies and insects- could cause some ethical issues
5. Longworth trap; used to trap small animals ethically (as there are legal issues when trapping animals) A trap is set and the animals caught are marked C1 and set free. After some time, a second sample are taken (in the same place) and marked C2  where the C1 that are counted again are now marked C3. This allows us to calculate the population, although it's important to note that animal behaviour can affect this for example an animal can learn these traps hold food or that they are dangerous and therefore behave differently.