Lecture 1- Global Patterns Of Biodiversity Flashcards
Define biodiversity
A measure of the VARIETY and VARIABILITY of life on earth. It is highly complex and has many attributes
What is the most common way of measuring biodiversity?
Species richness
What percentage of species on earth have been sampled, and what percentage of this are mammals?
15% sampled, 95 % mammals
On what gradient does species richness increase?
Latitudinal gradient, increasing towards the poles
Are the longitudinal and latitudinal gradients applicable to all species?
The latitudinal is widely accepted, the longitudinal is NOT
Define delta diversity
The change in species composition and abundance over wide geographical areas.
What are the lattitudinal and longitudinal gradients measures of?
Latitudinal gradient: delta diversity
Longitudinal gradient: climate diversity
Where does marine species richness peak?
Plu or minus 30 degrees o the equator
What gradients do coastal and oceanic species follow?
Oceanic species follow a latitudinal gradient, coastal species follow a longitudinal one
What are three three species that do not follow latitudinal gradients, and what are their alternative?
- Sea birds
Have northern distribution due to greater productivity in the northern hemisphere - Lichens
Max diversity in dry and cold regions - Microbes
Classed as cosmopolitan, so are found anywhere without geographical boundaries
What organism has no geographical boundaries to distribution?
Microbes
What are the five hypotheses for latitudinal gradients of species distribution?
- Geographical area
- Energy species richness
- Heterogeneity hypothesis
- Rapports rule
- Evolutionary speed
What are the two sub theories of the energy species richness hypothesis?
- Productivity hypothesis
2. Ambient energy hypothesis
Explain the geographical areas hypothesis
The greater land area at the tropics provides more habitats for species, meaning a greater number of individuals in each species can be maintained- which reduces the extinction risk.
Large areas also facilitate more speciation, which allows for the development of ore species.
Explain the energy species richness hypothesis
The amount of energy available directly influences the amount of co-existing species within an environment. This is measured via actual and potential evapotranspiration
how is energy species richness measured?
Actual and potential evapotranspiration
Describe the productivity hypothesis (part of energy species richness)
More resources means a greater plant biomass is supported, leading to more support for higher food chain levels and overall greater diversity.
What can greater resource availability lead to?
Paradox of enrichment, and competitive exclusion
Explain the ambient energy hypothesis
This is dictated by temperature, with it being physiologically costly for organism to live at high latitudes (temperatures are outside their optimal range), resulting in there being lesser species at the low temperatures found at high latitudes
Explain the heterogeneity hypothesis
The greater the heterogeneity (diversity) of habitats located at the tropic means that more species can exist in these difference niches, leading to greater species diversity
Explain rapports rule
At low latitudes, organism have small niches and partitioning occurs, meaning more organism can exist within a given habitat. At high latitudes, organism have very large niches, meaning that less species will exist in order to avoid their niches overlapping
Explain the evolutionary speed hypothesis
The species richness at the tropics is a result of:
- long evolutionary history allowing for more speciation to occur
- stable conditions leading to stable existence
- constantly warm temperatures
