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Summary Biodiversity- International A-Level Geography notes including AS-Level
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International A-Level Geography notes including AS-Level
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A- level Biodiversity,Defining biodiversity
The different ways of defining biodiversity in terms of genetic, species and ecosystem diversity and the
merits of each.
Biodiversity refers to plant (flora) and animal (fauna) species found in ecosystems
The variety of plant and animal life in the world or in a particular habitat, a high level of which is
usually considered to be important and desirable.
Number of species in particular areas as well as genetic diversity and the diversity of ecological
niches in an area
Ecosystems- Communities of plants and animals (biotic) interacting with non-living (abiotic)
components of their environment (air, water, soil) working as a natural system. The biotic and abiotic
components are linked together through nutrient cycles and energy flows
Different biomes of the world:
● Ice sheet and polar desert
● Tundra
● Taiga
, ● Montane (alpine tundra and montane forest)
● Mixed deciduous forest
● Tropical rainforest
● Steppe
● Savana
● Desert
● Mediterranean vegetation
Genetic diversity- The genetic variability within one species (within)
Species Diversity- The number of different species within an area (between)
Ecosystem Diversity- The range of different ecosystems, habitats and niches in an area (over an
area)
Biodiversity often used as a measure of health of biological systems
The biotic and abiotic components are linked together through nutrient cycles and energy flows- in an
ecosystem
Advantages Disadvantages
Genetic - Genetic variation prevents the whole - It can also cause some undesired
diversity species to wipe out effects like genetic disorders,
- Due to Variation, organism can be diseases, etc.
developed to survive in adverse
conditions, more resistant to diseases, - Needs high level biological skills
also it creates diversity to analyse DNA
- Accurate picture of diversity
- Explains how isolated groups have
adapted
Species - Small disturbances natural or manmade - There is a lot of pressure for food
Diversity do not affect the ecosystem. and energy on the ecosystem.
- Survival rate of species is very high. - Organisms become prone to
predators as the number of
- Good general measure individuals is very high.
- Better if a range of indicator species
used - Areas needs to be of similar size
- Better to use taxonomic diversity - Many undiscovered species may
be microscopic and might skew
biodiversity index based on species
numbers
, Ecosyste 1) By having more biodiversity the 1) More biodiversity means more animals
m environment can be conserved and will more and plants hence the population and living
Diversity easily recover from disturbances of ecosystem of humans can be restricted
2) More plants means a better environment and 2) Excess of wild animals can harm
lesser effect of greenhouse gases or temperature humans or each other. There will be more
rising. conflicts over territory or water.
3) The biodiversity helps to maintain the food 3) The establishment of the forest or an
web circle , while disturbing it can result in the acceptable environment for so many
scarcity of food. different animals may be costly.
- Complex as needs to measure - Difficult to place boundaries
interaction of species in their - Need consistent set of criteria
environment and with each other
- Useful when assessing areas to protect
as has wider focus
Factors affecting biodiversity
The processes and factors that influence biodiversity (climate limiting factors, isolation and the role
of endemism, age and area, human activity and actions)
Global distribution of biodiversity:
- Unevenly distributed. Equator- Humidity is a key factor and mostly tropical rainforest
biomes. Still exists mid latitudes- humidity and high precipitation levels and low pressure
- Travel towards the poles lower diversity, and sub saharan africa and altitude have low
diversity
Factors:
● Latitude
● Altitude
● Climate- main limiting factor
● Temperature
● Amount of light
● Rate of nutrient cycling
● Endemism- species only found in one location
○ Endemism is the ecological state of being unique to a particular location. e.g. many
species of lemur are endemic to the island of Madagascar.
○ Cosmopolitan Distribution is the ecological state of being found almost anywhere
around the world.
○ Endemism is the ecological state of being unique to a defined geographic location,
such as an island, nation or other defined zone, or habitat type.
● Growth of human population- the bigger the population, the more in competition we are for
space and resources
● Hunting and direct exploitation of flora and fauna- big impact if it focuses on one species
● Size of the area and topography- the bigger the area more space for species
● The level of recording of species within the region
● Anthropogenic effects such as pollution, clearance for agriculture- often monoculture
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