Defining Biodiversity
Biodiversity is defined by the Convention on Biological Diversity (1992), as ‘the variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems.’
- In other words, biodiversity is the amount and assortment of biological life forms; that are found in a particular area; and its changes over time
- It includes variety within, and between, species and ecosystems
- Ecosystems are communities of living organisms (biotic - plants and animals), sharing the environment, with the non-living (abiotic - light, water, soil etc.) components
- Each ecosystem is unique at a local level
- Biodiversity varies on a local scale:
- Natural habitats will have higher biodiversity than agricultural land
- Biomes are very large ecosystems on a global scale; such as tropical rainforests, savannahs, deserts etc.
- Each biome share similarities but differ at the local level
- Tropical rainforests share general features such as climate and overall appearance
- However, each tropical rainforest's biodiversity will differ, along with its composition and interactions
- Ecosystems are dynamic systems and develop through distinct succession from a 'sterile' area to a climatic climax community
- Plant succession affects food chains, biomass, species diversity and size of organisms
Measuring biodiversity
- Biodiversity is measured through:
- Indicator species
- Certain species are used as an indication of environmental conditions
- Often used as evidence in planning and conservation of an area
- Species richness
- Provides a direct link between biodiversity and the number of species
- Measures the total number of the species in a community
- Difficult to produce a complete inventory of all the species present in a location as living organisms are dynamic and areas change
- Living Planet Index (LPI)
- This measures the state of the world's biological diversity - the health the world's ecosystems
- Based on average changes in the population of vertebrate species from terrestrial, freshwater and marine habitats
- Population number
- The amount of a genetically distinct population within a particular species
- E.g. Butterflies as a species, but Red Admiral as a genetically distinct population
- Evenness indices
- Shows how evenly spread individuals are in a community of different species
- Genetic diversity
- This is the total amount genetically different information found within a species
- Genetic differences allow species to adapt to its changing environment
- Also known as natural selection
- Indicator species
Exam Tip
- Biodiversity is vital to the healthy functioning of ecosystems and is the foundation to a healthy life on Earth
- Make sure you can relate the concept of biodiversity at a local and global scale
Distribution of biodiversity
- Biodiversity is not equally distributed within ecosystems or biomes
- Biodiversity decreases further away from the equator (north and south)
- Approximately 50% of global biodiversity lives within tropical rainforests
- This is due to the climate being wetter, warmer, with little seasonal variation; making it a reasonably stable climate that supports continuous plant growth
- Which, in turn, supports greater biodiversity along the food chain
Worked example
Explain the link between global ecosystems (biomes) and biodiversity.
[4 marks]
- Show the examiner that you understand what biodiversity and biomes mean
Answer:
- Biodiversity is the amount, variety and differences of living organisms [1] in and amongst species in a particular area known as an ecosystem. [1] Ecosystems are part of the global system that make up biomes. [1] The link is that biodiversity shows how changes occur from one location to another. [1]