# Biodiversity

Biodiversity

(b) explain how biodiversity may be considered at different levels; habitat, species and genetic.

• Habitat – The range of habitats in which different species live. Each habitat will be occupied by a range of organisms.
• Species – The differences between species. This could be structural differences (between a tree and an ant) or functional differences (between bacteria that cause decay and those that help to digest food).
• Genetic – Genetic variation between individuals belonging to the same species, ensures that they do not all look alike.

(c) explain the importance of sampling in measuring the biodiversity of a habitat

In order to measure the biodiversity of a habitat, you need to observe all the species present. However, observing the whole habitat is time-consuming and difficult. Sampling involves taking a small portion of the habitat and studying the area carefully. You can then multiply up the numbers of individuals of each species found, on order to estimate the number in the whole habitat.

Sampling is a balance of ease and accuracy. To improve the accuracy of the estimation, repeated samples are taken and also the sample size must be large.

(d) describe how random samples can be taken when measuring biodiversity

Where do you sample?:

1. Random Sampling– A basic way to do this is to stand within the area, and just throw the quadrat, however, it is not truly random. A better way is to use a calculator to generate random numbers, to get coordinates of where you will place your quadrat. The first number is the x coordinate and the second number is the y coordinate.
2. Systematic Sampling– In some situations, you may want to sample more systematically. In this case, you could sample along a transect. A transect is a line taken across a habitat. You stretch a tape measure across the habitat and take samples along the line. You can use a:
• Line Transect – recording each organism which is touching the line at suitable, regular intervals.
• Belt Transect – placing a quadrat against the line, recording its contents, then placing the next quadrat immediately touching the first one, repeating this along the transect.
• Interrupted Belt Transect – placing quadrats at regular intervals along the transect.

Sampling Plants:

Quadrats are square frames used to define the size of the ample area. It’s important to choose the right size of the quadrat (normally 50cm or 1m quadrats are used) depending on the size of the area. The quadrat is placed randomly and the abundance is measures. You could:

• Habitat – The range of habitats in which different species live. Each habitat will be occupied by a range of organisms.
• Species – The differences between species. This could be structural differences (between a tree and an ant) or functional differences (between bacteria that cause decay and those that help to digest food).
• Genetic – Genetic variation between individuals belonging to the same species, ensures that they do not all look alike.

(c) explain the importance of sampling in measuring the biodiversity of a habitat

In order to measure the biodiversity of a habitat, you need to observe all the species present. However, observing the whole habitat is time-consuming and difficult. Sampling involves taking a small portion of the habitat and studying the area carefully. You can then multiply up the numbers of individuals of each species found, on order to estimate the number in the whole habitat.

Sampling is a balance of ease and accuracy. To improve the accuracy of the estimation, repeated samples are taken and also the sample size must be large.

(d) describe how random samples can be taken when measuring biodiversity

Where do you sample?:

1. Random Sampling– A basic way to do this is to stand within the area, and just throw the quadrat, however, it is not truly random. A better way is to use a calculator to generate random numbers, to get coordinates of where you will place your quadrat. The first number is the x coordinate and the second number is the y coordinate.
2. Systematic Sampling– In some situations, you may want to sample more systematically. In this case, you could sample along a transect. A transect is a line taken across a habitat. You stretch a tape measure across the habitat and take samples along the line. You can use a:
• Line Transect – recording each organism which is touching the line at suitable, regular intervals.
• Belt Transect – placing a quadrat against the line, recording its contents, then placing the next quadrat immediately touching the first one, repeating this along the transect.
• Interrupted Belt Transect – placing quadrats at regular intervals along the transect.

Sampling Plants:

Quadrats are square frames used to define the size of the ample area. It’s important to choose the right size of the quadrat (normally 50cm or 1m quadrats are used) depending on the size of the area. The quadrat is placed randomly and the abundance is measures. You could:

• Count the number of individuals of each species.
• Estimate the percentage cover of each species – this is the proportion of the area within the quadrat which it occupies.
• Use an abundance scale, such as the ACFOR scale, by estimating which one of these best describes the abundance of each species within the quadrat.
• A point quadrat may be used. This is a frame holding a number of long needles or pointers. You lower the frame into the quadrat and record any plant touching the needles. It can also be useful for measuring the height of plants.
Sampling Animals:

(f) use Simpson’s Index of Diversity (D) to calculate the biodiversity of a habitat, using the formula

D = 1-[Σ(n/N)2]

Simpson’s index of diversity is a measure of the diversity of a habitat. It takes into account both species richness and species eveness. It is calculated by the formula:

(g) outline the significance of both high and low values of Simpson’s Index of Diversity

A high value of Simpson’s Index indicates a diverse habitat, which provides a place for many different species and many organisms to live in. Small changes to the environment would only affect one species. If the species is only a small part of the habitat, the total number of individual affected is a small proportion of the total number present. Therefore the effect on the whole habitat is small. The habitat tends to be stable and able to withstand changes.

A low value of Simpson’s Index indicates a less diverse habitat, which provides a habitat for only a few different species. A small change to the environment that affects one of those species could damage or destroy the whole habitat. Such a small change could be a disease or predator, or even something that humans have done nearby.

(h) discuss current estimates of global diversity

Estimates of global diversity varies across the world. One estimate includes:

• 4,000 bacteria, 70,000 fungi, 80,000 protocista, 300,000 plants, 130,000 invertebrates and 40,000 vertebrates
• 2 million species in the world – 100,000 in the UK

These figures are estimates because

• We cannot be sure we have found all the species.
• New species are being found all the time.
• Evolution and speciation are continuing
• Many species are becoming endangered or extinct.