A4.2 Conservation of Biodiversity

What is biodiversity, and its levels?

Definition: The total variety of life on Earth

• Three levels influence how ecosystems function, adapt, & sustain life:

  • Ecosystem diversity

  • Species diversity

  • Genetic diversity

Define and explain ecosystem diversity [2]

Definition: The variety of ecosystems within a region or globally

• It is measured by physical characteristics & organisms they support 

Define and explain species diversity (measurement, significance) [6]

Definition: Number and variety of species in an ecosystem or globally 

• Measured by:

  • Species richness - Total number of species in an area 

  • Species evenness - Relative abundance of individuals among different species 

• Significance: Every species has a specific ecological role that stabilises ecosystems

  • Predators - Prevent overpopulation of prey species

  • Decomposers - Fungi & bacteria recycle nutrients, maintaining soil health

Define and explain the significance of genetic diversity [5]

Definition: Variation of genes within populations of a species 

Significance: Crucial for species’ survival & adaptability

• Disease resistance

• Adaptation to changing environmental conditions 

• Reduced inbreeding - prevents genetic disorders & reduced fertility 

Explain factors that create uncertainty in determining species number on Earth [3]

• Inaccessible habitats - Many species live in deep ocean or rainforest canopy, 

• Cryptic species - Look identical to known species but differ genetically

• Unculturable microbes - Most microorganisms cannot yet be grown in a lab, so diversity is largely unknown 

Describe how past extinctions have affected biodiversity & its recovery [4]

• In the past, Earth has had five mass extinctions:

  • First four due to volcanic activity, changes to atmosphere & climate 

  • Fifth extinction: Cretaceous Period (~66 mya) - Massive asteroid collision wiping out non-avian dinosaurs 

• Biodiversity tends to recover through the evolution of new species 

[CS] North Island Giant Moa - Describe its extinction cause [3]

• Terrestrial bird originally found in New Zealand 

• With no natural predators, moa populations were highly sensitive to hunting 

  • Hunted for food by Maori until extinction, in less than 200 years 

[CS] Caribbean Monk Seal - Describe its extinction cause [4]

• Native to waters of Caribbean Sea and western Atlantic 

• It was declared extinct in 2008, which was driven by: 

  • Overhunting - Hunted for blubber, which was rendered into oil

  • Overfishing - Loss of coral reefs, a primary food source → starvation

Explain anthropogenic causes of extinction [5]

1) Overharvesting - Species exploited at faster rate than reproduction 

2) Habitat destruction - Agricultural development & urbanisation overtake breeding & feeding areas  

3) Invasive species - Drives native species to extinction by predation, spreading of pests & diseases, or resource competition 

4) Pollution - Release of pollutants & substances intoxicate atmosphere & contaminate land 

5) Climate change - Rapid changes in temperature & rainfall make it difficult to adapt & migrate in time 

Explain anthropogenic causes of ecosystem loss [7]

1) Agriculture development - Forests & grasslands are cleared, wetlands drained → habitat loss

2) Urbanisation - Residential & industrial buildings, & infrastructure take up natural land

3) Water management - Reservoirs created by dams can flood natural ecosystems + extraction of water for domestic/industrial use can reduce river flows 

4) Overexploitation - Poaching, overfishing, unsustainable fuel wood harvesting → decline in natural resources & species 

5) Mining & smelting - Opencast mines generate waste that pollute & damage rainforests

6) Leaching - Washing of fertilisers into rivers & lakes causes eutrophication & algal blooms → loss of oligotrophic ecosystems 

7) Anthropogenic climate change

[CS] Dipterocarp Forest - background, causes, and consequences of ecosystem loss

• Trees from the Dipterocarpacae family used to dominate large areas of rainforest in Southeast Asia 
  

Causes of loss:

1. Logging - Trees chopped for timber extraction

2. Agricultural expansion - Nutrient-rich soils cleared for oil palm plantation

Consequences of loss:

1. Biodiversity loss - Deprives habitats of endangered species 

2. Carbon emissions - Following land conversion, peatland decomposition released stored carbon, intensifying climate change

3. Flooding & erosion - Forest loss destabilises soil & alters water cycles, increasing flood risk

[CS] Aral Sea - background, causes, and consequence of ecosystem loss [9]

• A lake located between Kazakhstan & Uzbekistan

• It was fed by rivers but had no outflows

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Causes of loss:

1960 - Water management scheme 

1) Desertification 

• Diverted two major rivers feeding Aral Sea to irrigate an area of desert 

  • This reduced water flow, eventually drying up 

2) Salinisation 

• As water volume decreased, salinity of remaining lake increased

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Consequence of loss:

Biodiversity loss - Conditions became inhabitable for endemic species, including extinction of 24 fish species & invertebrates

What is a biodiversity crisis?

The accelerated loss of species & ecosystems

How is evidence for a biodiversity crisis collected, and what are they used to track? [4]

• Evidence can be gathered by conducting surveys, which are only reliable if repeated:

• They can be used to track variables for changes in:

  • A species

  • An ecosystem

What aspects can surveys track of a species?

1) Numbers in species populations 

2) Genetic diversity

3) Range of the species

What aspects can surveys track of an ecosystem?

1) Species diversity

2) Richness & evenness of biodiversity

3) Area occupied

4) Extent of ecosystem degradation

What is the biggest root of the biodiversity crisis, and reasons why? [4]

The exponential growth of the human population, driving an increase in:

a. Demand for resources (e.g. food, water, energy)

b. Space consumption

c. Industrial activity

What are other direct/indirect causes of the biodiversity crisis? [6]

Causes

Over-exploitation

Urbanisation

Deforestation & land clearance → habitat loss

Pollution

Invasive alien species + pests

Diseases

What constitutes effective conservation?

• No single method can address the numerous threats to biodiversity 

• Effective conservation combines two approaches:

  • In situ conservation

  • Ex situ conservation 

Define and explain In situ conservation [6]

Definition: Protecting species within their natural habitat

• Establish a protected area (e.g. national park or nature reserve), shielding ecosystems from harmful human activity 

• They require active management, e.g. removing alien species, control of population size & human access 
  

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• For damaged ecosystems, rewilding & reclamation are required 

  • Rewilding - Reintroducing keystone species & letting natural processes take over 

  • Reclamation - Repairing damaged or degraded ecosystems 

Define and explain Ex situ conservation [6]

Definition: Protecting species outside their natural habitat 

• Retain species in zoos, aquariums, & botanical gardens to prevent extinction in the wild

• Techniques like captive breeding & germplasm storage are used

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Captive breeding -

Limitations: 

1. May lose genetic diversity over generations → less adaptable to environmental shifts & selection pressures

2. Many lose survival behaviours (e.g. predator avoidance) 

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Germplasm - Genetic material (e.g. seeds, embryos, tissues) stored for future use 

• Seed banks with cold, dry conditions are used to preserve plant diversity 

  • Protects against climate & disease-related extinction, increasing food security 

• For animals, cryopreservation of sperm, eggs, & embryos serve a similar purpose

Explain what are EDGE species, and their purpose [5]

• Refers to species that meet the following criteria:

  • Evolutionarily Distinct - Few or no close relatives, possessing unique traits, & sole surviving members of ancestral species

  • Globally Endangered - Serious risk of extinction due to declining populations, restricted geographical range, & human threat

• Losing one of these species = losing entire evolutionary tree

• Due to limited conservation resources, EDGE helps focus efforts where evolutionary loss is most severe