biodiversity Flashcards
biodiversity
Biodiversity describes the number of species (species richness) and number of individuals of each species (species evenness) in a given area.
The more biodiverse an area is, the more types of species and individuals there are.
Biodiversity on the planet varies spatially; it increases going from the poles towards the equator.
reasons why biodiversity increases going from the poles towards the equator ??
More UV light causes a higher rate of mutation and therefore more rapid evolution.
More species types means there are more habitats (places to live) and niches (food types).
A more stable temperature range and water availability means conditions are more favourable for survival.
With more species and individuals, competition is high, leading to more specialized and narrower exploitation of niches, making it more difficult to move out of the area.
biodiversity varies over time…
throughout evolutionary history there have been mass extinctions caused by climate change. These have been followed by rapid expansion and diversification of species.
A good example of this is the extinction event for dinosaurs followed by the rapid expansion and diversification of mammals. It is feared that human activities are currently driving a sixth mass extinction event with a massive loss of biodiversity.
investigating the biodiversity in a habitat
To investigate biodiversity in a habitat, the number of different species (species richness) and the numbers of individuals of each species (species evenness) must be counted.
The area is sampled, either by gridding or by sampling along a line (transect). Gridding is used where two areas are to be compared, for example a mown and unmown area of grassland. Transects are used where there is a gradual change in the environment, for example moving from under a tree into the open.
importance of random sampling
Random sampling is important as it avoids unconscious sampler bias, increasing the reliability of the data. Random number tables are used to generate random co-ordinates for a gridded area and the quadrats placed at those co-ordinates only. Sampling along a transect is often done at a fixed distance, e.g. every 2 metres.
how is biodiversity measured in a terrestrial ecosystem and aquatic?
In terrestrial ecosystems a quadrat is placed; this is a grid of known area inside which plants can be counted. Many samples are taken to improve reliability.
In aquatic ecosystems the method of collection in each area is standardised. This could include time for collection or mesh size of net. Kick sampling is also used in aquatic ecosystems.
risk assessment; main hazards in field work
Biting and stinging insects and stinging or thorny plants - the risk is scratches or allergic reaction, and these are controlled by wearing insect repellent and protective clothing.
Different ecosystems have different hazards, e.g. the tide is a hazard on a seashore. The risk is being cut off, and the control would be to utilise tide tables and choose an appropriate time for the work.
Slippery surfaces can be a hazard causing risks of strains and sprains - appropriate footwear with grip should be worn.
Simpson’s Diversity Index
a calculation that reduces the data about numbers of species and individuals of each species to a single number. This number can be used to compare biodiversity in two different areas or ecosystems.
As the calculation is “1-…” the number is always between 0 and 1. A higher value indicates that the biodiversity is higher.
D=1− N(N−1) /
∑n(n−1)
