3.1.1 Measuring Biodiversity

IB Knowledge Statements

3.1.1 Biodiversity is the total diversity of living systems and it exists at several levels.

3.1.2 The components of diversity contribute to the resilience of ecological systems.

3.1.7 Species diversity in communities is a product of richness and evenness.

3.1.8 Simpson’s reciprocal index is used to provide a quantitative measure of species diversity, allowing different ecosystems to be compared and for change in a specific ecosystem over time to be monitored.

3.1.9 Knowledge of global and regional biodiversity is needed for the development of effective management strategies to conserve biodiversity.

This section focuses on:

Defining terminologies of biodiversity and the three types of biodiversity
Outlining the measure of species diversity
Applying Simpson's Index to evaluate a site

Part 1: Defining Biodiversity

Mt. Kinabalu is one of the most important biodiversity hotspots in the world. It has more than 600 species of fern. The whole Africa only has 500 species of fern

Mt. Kinabalu from the entrance gate

Biodiversity

Diversity is a measure of both the number of species in an area and their relative abundance.

Biodiversity is the total diversity of living systems and exists at several levels. It is a result of habitat diversity, species diversity and genetic diversity

Habitat diversity

Range of different habitats in an ecosystem or biome. It is often associated with the variety of ecological niches. For example, woodland has a high habitat diversity because it contains many different habitats, including rivers, soil, trees, shrubs, ground vegetation, leaf litter, fallen dead trees and so on. In contrast, a desert has a low habitat diversity because it only contains a few habitats such as sand and occasional vegetation

Species diversity

Variety of species per unit area. It includes both the number of species present and their relative abundance. The higher the species diversity of a community or ecosystem is, the greater the complexity. Areas of high species diversity, such as primary rainforest, are more likely to be undisturbed. Species diversity within a community is a component of the broader description of the biodiversity of an entire ecosystem. Figure above shows complex marine ecosystem

Genetic diversity

Gene pool refers to all the different types of gene found within every individual of a species. A large gene pool leads to high genetic diversity and a small gene pool leads to low genetic diversity. The term genetic diversity normally refers to the diversity within one species. However, it can also be used to refer to the diversity of genes in all species within an area. Figure above shows cheetah having low genetic diversity

Part 2: Measure of Species Diversity

Species Diversity

Richness and evenness are components of biodiversity
High evenness = complex ecosystem - a lots of different niches that support a wide range of different species
Low evenness = low complexity and smaller number of potential niches - community where one or a few species dominate

Richness

Richness = number of species in an area

Left or right is more rich?

Evenness

Evenness = relative abundance of all species

Left or right is more even?

Communities can be described and compared using indices such as Simpson's index, D value (described below)
- High D value indicates that the system is stable. Many niches support each other and contribute to the resilience of the system towards external factors/disturbances
- Small disturbances may not have an impact on the system
When doing this, we can compare similar communities for example in two different ponds that show the same or similar communities (in general niches)
- Low diversity may be due to pollution or recent colonisation
Biologists assess the effect of disturbance (pollutions or colonisation) using diversity indices, such as the Simpson’s index.
This quantification of biodiversity is important to conservation efforts so that areas of high biodiversity are identified, explored, and conserved.
Areas that are high in biodiversity are known as hotspots.
- Home for large numbers of endemic species (species not found anywhere else),
- The measures of biodiversity are essential in identifying areas that should be protected against damaging human activities.
- Example:
  - Tumbes-Chocó-Magdalena - an area that includes the forests of the South American Pacific coast (from Panama to Peru)
  - Galápagos Islands.
  - Borneo rainforest of Malaysia
  - Atlantic Forest of Brazil

Part 4: [Skills] Simpson's Index

Simpson's index can be used to monitor the complexity of two different areas that home the same or similar communities
The following activity is a field visit and investigation of biodiversity using Simpson's index and quadrat
The placement or quadrat i.e the sampling location must be randomised to eliminate bias in the investigation
The quadrat is use to find the number of individuals for each species present per unit area

Simpson's index, D, is identified using the above formula. To simplify, use the following manual to use Simpson's index

Simpson’s Index Manual.pdf

Activity 1

Note: This kind of activity also qualifies for ESS and biology internal assessment in the IBDP curriculum

Research Question
- How does distance from a coal and fossil fuel power plant affect plant diversity in the surrounding field within 10km radius measured using Simpson's index

Introduction to the investigation
- Due to the increase in electricity demand in country A, a new power plant has been built in area near a forest. This new electricity plant deforested a large area and burning coal and fossil fuels to generate electricity
- On daily basis, the power plant releases tonnes of carbon diaxide to the air. As the plant also uses coal and fossil fuels, it releases the gasses containing sulfur such as sulfur dioxide (SO2). This has caused acid rain
- The acid rain has a direst impact on the soil pH in the nearby forests.
- Over the course of a year, the soil pH and the plant biodiversity was monitored to assess the impact of the power plant. The government tried to mitigate some observable impacts of the power plant by enforcing the requirement of hydrodesulfurisation to remove sulfur from the fossil fuels prior to the combustion.
- Tensions occur between the firm and the government as this technology would require high cost for installation and maintenance considering that only 40% of the energy source can be applied with hydrodesulfurisation.

Hypothesis
- The more acidic the soil, the lower the plant diversity in the area
- Acidic soils stunt plant growth in many ways
  - Wet deposition causes soil to become more acidic
  - This causes the soil to dissolve extra metal cations in the soil (minerals).
  - These cations can be absorbed by the plants as they take in water.
  - As the result, plant could absorb toxic level of metal cations such as mangenese and aluminium
  - The plant growth will be stunted. Green leaves may not be formed and eventually plants will die
- Acid soils inhibit seed germination for new plant to emerge
  - Acidic soil deactivate and destroy enzymes that are needed for seed germination.

Variables
- Independent variable: Distance of sampling from the power plant to the forest
  - Distances are: 2km, 4km, 6km, 8km and 10km of the surrounding field

- Dependent variable:
  - Plant biodiversity measured by Simpson's index

- Controlled variables
  - Elevation: This was maintained at below 500m. The field surrounding the power plant was flattened and therefore, the elevation was controlled
  - Time of the year: The sampling was done in summer as this enable precipitation and the effect of pH to act on the soil and plants in the field. All sampling was also done around the same time in a day to increase the accuracy and precision of the quantitative data
  - Randomised sampling: Using quadrat that are randomly placed at different points of each km internal
  - Species monitored: The sampling only focuses on 5 plant species (P, Q, R, S and T) in the field. Other species are not recorded

- Uncontrolled variables
  - Plants' mutation rate: Some plants may mutate at different rate in a selected area. This may increase their chance to adapt to the external factors
  - Distribution of rain: Rain distribution in the field may be uneven and hence some areas in the same km internal may have different acidity.
  - Wind and diffusion of dry deposition: The movement of dry air particles containing acidic substance cannot be controlled. It follows the wind movement in general

Methodology

Using a drone, a photograph was taken of the 10km radius within the power plant
A randomiser was used to select 5 different areas in each 2 km internal
Once the 5 areas was selected for the first 2km radius, a quadrats were place in the precise areas
The number of individuals of each of the 5 selected species (P, Q, R, S and T) was recorded in each of the 5 quadrats
Step 2 and 3 were repeated for radius between 2 km and 4 km. Then the same steps were used for the next 2 km radius until the sampling reaches 10km radius
All data were recorded and organised into new table for Simpson's index

Quantitative Data
- This is needed for IAs. However, for the same of this activity, we will skip this for now. In general, this should focus on quality only such as heat, colour, state of appearance, beahviour etc
Qualitative Data
- Complete the table in the Google Sheet by recording the data shown in the Powerpoint
- Describe the change in D values as the sampling was done further away from the power plant. Explain possible reasons for the observed pattern

Simpson's Index Activity.pptx

3.2 Simpson's Index

Count the number of individuals for each species. Record the data on the Google Sheet. Comment on the D values as the sampling was done futher away from the power plant

Importance of Biodiversity

Each component of biodiversity (species diversity, habitat diversity and genetic diversity) contributes to the resilience of ecosystems.
- Resilience = ability of a system to maintain equilibrium and avoid tipping points.
In communities with high species diversity give complex food webs.
- The loss of one species (unless it is a keystone species) does not adversely affect the community.
Species diversity is reflected by habitat diversity.
- Many different habitats = many niches to co-exist
- This enhances species diversity.
Species that are genetically diverse are more likely to survive than populations with low genetic diversity
- One gene can have different versions, each of which has a slightly different genetic code – these different forms of the same gene are called alleles.
- Genetic diversity = number of different alleles for different genes in a population.
- Greater the genetic diversity = greater the ability of a population to survive periods of adversity.
Genetically diverse populations have greater resilience than ones that show a small range of alleles for any given characteristic.

Activity 2

Notes

3.1 Defining and Measuring Biodiversity.pptx

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