A4.2

• Biodiversity


  The total number of different species living in a defined area or ecosystem
• Three levels of biodiversity

  • Ecosystem diversity
  • Species diversity
  • Genetic diversity
• Ecosystem diversity


  Range of different habitats/ number of different ecological niches per unit area
• Species diversity


  • Variety of different species that live per unit area
  • Richness = number of species
  • Evenness = relative abundance of each species
• Genetic diversity


  • Range of genetic material in a gene pool
  • A large gene pool = high genetic diversity
  • A small gene pool = low genetic diversity
• Evenness


  If a habitat has similar abundance for each species present, the habitat is said to have evenness
• The total number of organisms that exist is unknown, but it's thought to be around 9 million species (estimates vary from 5-100 million)
• Only 1.8 million species have been identified and described
• Splitters


  Split organisms based on differences and place into smaller groups
• Lumpers


  Place species into few larger groups based on similarities
• The Earth is entering its 6th Mass extinction
• Mass extinction


  A significant proportion (at least 75%) of the earth's species become extinct within a short geological time frame (less than 2 million years) over a large geographical area
• Unlike previous mass extinctions the 6th one is the result of human activity
• Causes of the current biodiversity crisis

  • Human population growth
  • Hunting and other forms of over-exploitation
  • Urbanization
  • Deforestation and clearance of land for agriculture with consequent loss of natural habitat
  • Pollution and spread of pests, diseases and invasive alien species due to global transport
• Anthropogenic


  Caused by human related activities
• Case studies of anthropogenic species extinction

  • North Island giant moas
  • Caribbean monk seals
• Causes of ecosystem loss

  • Areas cleared of natural forests, wetlands and grasslands for farming
  • Urban areas have doubled since 1992. Natural ecosystems destroyed to build housing and infrastructure to accommodate growing populations
  • Extraction and processing of minerals destroy areas of natural ecosystem
  • Extraction of water for irrigation results in loss of river and lake ecosystems
  • Increased pollution/ gas emissions result in climate change. This can change an ecosystem's abiotic factors such as rainfall and temperature and can result in the loss of an entire ecosystem
  • Draining water to change land use (e.g. building housing estates) results in loss of swamps and wetlands
• Ecosystem services


  The processes and outputs of the ecosystem that directly or indirectly benefit humans
• Keystone species


  A species that plays a critical role in maintaining the structure and functioning of an ecosystem. The presence or absence can significantly impact the overall biodiversity and stability of the ecosystem
• Case study: Mixed Dipterocarp forest in South East Asia


  • Ecosystem: Tropical Rainforest
  • Keystone Species: Dipterocarps (The dominant family with 695 species)
  • Threat: deforestation. Trees prized for timber and to clear land for Palm oil plantations
  • Importance of Species to ecosystem: Supports other organisms/ forms of life (high species diversity with 20% species endemic to Borneo), Food source, Decomposition of leaves returns nutrients to soil, Roots hold soil, Home to arboreal animals, birds and epiphytic plants, Canopy shelters lower layers from heavy rain, Carbon store to help fight climate change
  • Impact of loss: increased CO2 emissions and changes to weather patterns, Loss of habitat for endangered animals e.g. Orang utan and elephant, Loss of biodiversity
• Case study: Great Barrier Reef - Queensland


  • Ecosystem: Coral Reef
  • Keystone Species: Coral Polyps
  • Threat: multiple threats. Pollution (from land-based activities), climate change, ocean acidification, invasive species, overfishing
  • Importance of Species to ecosystem: Provide habitat and food for many other species, Produce oxygen, Absorb carbon dioxide, Protect coastlines from erosion
  • Impact of loss: Loss of biodiversity, Loss of coastal protection, Loss of tourism revenue
• Ecosystem


  • Presence or absence of keystone species can significantly impact the overall biodiversity and stability of the ecosystem
• Keystone species


  A species that plays a critical role in maintaining the structure of an ecological community and whose impact on the community is greater than would be expected based on its relative abundance or biomass
• Case studies


  • Mixed Dipterocarp forest in South East Asia
  • Great Barrier Reef - Queensland
• Mixed Dipterocarp forest in South East Asia is a Tropical Rainforest ecosystem
• Keystone Species in Mixed Dipterocarp forest

  Dipterocarps (The dominant family with 695 species)
• Threat to Mixed Dipterocarp forest is deforestation. Trees prized for timber and to clear land for Palm oil plantations.
• Importance of Dipterocarps to Mixed Dipterocarp forest ecosystem

  • Supports other organisms/ forms of life (high species diversity with 20% species endemic to Borneo)
  • Food source
  • Decomposition of leaves returns nutrients to soil
  • Roots hold soil
  • Home to arboreal animals, birds and epiphytic plants
  • Canopy shelters lower layers from heavy rain
  • Carbon store to help fight climate change
• Impact of loss of Mixed Dipterocarp forest: increased CO2 emissions and changes to weather patterns, Loss of habitat for endangered animals eg Orang utan and elephant, Loss of biodiversity
• The Great Barrier Reef is a Coral Reef ecosystem
• Keystone Species in Great Barrier Reef

  Coral Polyps
• Threats to Great Barrier Reef

  • Pollution (fertilizer run off/ sewage)
  • Over-fishing (and irresponsible fishing practices)
  • Loss of natural habitat due to coastal development
  • Unsustainable tourism
  • Climate change (resulting in increased ocean temperature and ocean acidification)
• Impact of loss of Great Barrier Reef: Impacts all other species that depend on the reef, Loss of habitat and biodiversity, Disrupt food chains, Decrease in population sizes of many fish species (due to loss of habitat/ food source/ migration), Increased temperatures cause the coral polyps to expel the algae leading to bleaching of the coral
• Importance of Coral Polyps to Great Barrier Reef ecosystem

  • Home to 25% of worlds marine species
  • Sustain food webs
  • Provide food for people
  • Sources of new medicine
  • Protect coastline from erosion and storms
• The biodiversity crisis is the unprecedented loss of ecosystems, species and genetic diversity
• IPBES


  Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, founded in 2012 by 94 countries, strengthens link between scientific information and policy decisions
• Data gathered by IPBES

  • Population size of species
  • Range of species (location)
  • Diversity of species (number of species – Simpson's reciprocal index)
  • Richness and evenness of biodiversity
  • Area occupied by an ecosystem
  • Extent of degradation of an ecosystem
  • Number of threatened species within a taxonomic group
  • Genetic diversity within a species
• Simpson's reciprocal index


  D = N(N-1) / Σ n(n-1), where N is the total number of organisms of all species, and n is the number of organisms of a single species. It takes into account both richness and evenness. The greater the biodiversity the higher the value of D.
• Sample A has a Simpson's reciprocal index of 1.87, while Sample B has a slightly higher index of 2.0, indicating Sample B has higher biodiversity
• Conservation approaches


  • In-situ (in its natural habitat)
  • Ex-situ (away from its natural habitat)