Biodiversity Flashcards
Recognise that biodiversity includes the diversity of species and ecosystems
Biodiversity is a measure of the number of different types (richness) and the relative abundance of populations (evenness) within a community.
Species Richness
Species Richness (D): measures the number of species in an area.
To account for sample size sometimes
Species richness is also calculated using the Menhinick Index where the number of species (s) is divided by the square root of the number of individuals in the sample (N).
Menhinick Index for Species Richness (D) = s /√N
Percentage Frequency
Percentage Frequency refers to the number of times a plant species is present within a given number of samples.
% Frequency= (number of quadrats in which the species is found/ total number of quadrats) X 100
Simpson’s Diversity Index
Used to determine species diversity of a group of organisms.
Low SDI (numbers close to 0) suggests:
relatively few successful species in the habitat
the environment is quite stressful with relatively few ecological niches and a few organisms that are well adapted to that environment
food webs which are relatively simple
change in the environment would have quite serious effects
High SDI (numbers close to 1) suggests:
A greater number of successful species and a more stable ecosystem
More ecological niches are available and the environment is less hostile
Complex food webs
Environmental change is less likely to be damaging to the ecosystem
SDI= 1- (sum of n(n-1)/N(N-1)
where N= total number of organisms of all species
n= number of organisms of all species
Species Evenness
Relative spread of species abundance
Percentage Abundance
Refers to the number of a species present in relation to the total number of species present.
% abundance= (Number of individuals in a species present/total number of individuals for all species present) X 100
Percentage Cover
Refers to the percentage of space a species occupies in a given area. (Note: Percentage cover is often useful to use when looking at diversity of plants ( animal diversity is better estimated by looking at abundance / numbers of individuals). Total percentage cover can be over 100% because often plants of different species overlap in their distribution.)
Spatial and temporal scales
Spatial scale, looks at how communities change over space / distance whereas, a temporal scale looks at how communities change over time
Species Indices
Simpsons Diversity Index
Menhinick Index
Species Interactions
Predation
Competition
Symbiosis (Mutualism, Commensalism, Parasitism)
Disease: Temporal and spatial factors will affect how these pathogens or parasites can be spread. Organisms living in close proximity to each other to each other will allow the spread to occur faster. Seasonal variations can also affect the ease at which a pathogen or parasite can be spread.
Abiotic Factors
Climate: tropics vs poles, or how the microclimate changes as you move from the tide line up the beach
Substrate: eg at the beach consider sand, rock, wood or soil substrate
Size/depth of area: comparing the size of different rainforests in two completely different countries, the depth of any aquatic environment, from rock pools to trenches
Abiotic factors vary along spatial gradients to produce environmental gradients
Each species in an environment has a range of abiotic conditions most suitable for its survival and reproduction… Therefore, these gradients are important determinants in patterns of species distribution.
Biotic Factors
Intraspecific relationships (same species)
May increase surviving an attack by a predator
Compete for limited resources such as food, shelter, water, a mate etc…
Interspecific relationships (between different species)
Predation: predator kills prey and eats it
Competition for limited resources
Symbiosis: two or more species living closely together for a long time. At least one organism benefits
Line Transects
Strengths: Line transects are good to use as they can be quick and also can be used to collect abiotic data and to visualise change in the distribution of species along gradients.
Limitations: Line transects do not provide good data on species density (or estimating moving animal population)
Belt Transects
Strengths: Belt transects allow the collection of abiotic data, species distribution and species density / abundance to be determined across a range of strata along a gradient.
Limitations: Belt transects are very time consuming and do not provide good data on moving animal populations
Quadrats
Strengths: good for estimating the population size / density of stationary organisms (plants, fungi, sedentary animals).
Limitations: if randomly placed may not sample all strata well and quadrats are not good for counting moving animals. Smaller quadrats should be used for smaller organisms.
can be time consuming, can be discrepancies in method used to count organisms (eg. counts vs percentage cover) and quadrats are not good methods for counting moving animals. Smaller quadrats should be used for smaller organisms.
‘Systematic sampling’ involves placing quadrats at regular intervals (eg. along a transect line) whereas, ‘Random sampling’ involves using randomly selected sampling points.
