4.6 Biodiversity within a community Flashcards
Biodiversity within a community can be measured using…
species richness and an index of diversity
Species richness is…
a measure of the number of different species in a community
An index of diversity describes…
the relationship between the number of species in a community and the number of individuals in each species
Index of diversity (d) can be calculated from the formula:
d=N(N-1) / SUM of n (n-1)
where N = total number of organisms of all species
and n = total number of organisms of each species.
Farming techniques reduce biodiversity. How?
Technique #1: Habitat removal
INVOLVES:
Clearing woodland
Draining wetlands and filling ponds
Removing hedgerows
LEADS TO:
Fewer niches
Fewer food sources
Fragmented populations (smaller gene pools) that are so small as to be vulnerable to (local) extinction
Farming techniques reduce biodiversity. How?
Technique #2: Chemical use
INVOLVES:
Pesticides
Herbicides
Fertilizers
Effluent (livestock urine and faeces)
LEADS TO:
Pesticides kill ‘pests’, which are usually insects. Many insects are pollinators, predators and/or prey, so reducing their numbers affects the wider community.
Herbicides kill ‘weeds’ which are just other plants that aren’t the crop. These plants were also producers in the community food chain.
Fertilizers leach into waterways causing eutrophication
Farming techniques reduce biodiversity. How?
Technique #3: Monoculture
INVOLVES
1 Growing the same crop (or livestock) over and over again in the same place
2 Selective breeding
LEADS TO
1 Soil depletion (loss of nitrates, phosphates) or overgrazing (which leads to erosion)
2 Reduced genetic diversity
The balance between conservation and farming. What is conservation?
Conservation is the sustainable management of ecosystems / habitats with the aim of improving or maintaining biodiversity for the long term. Conservation, like farming, is a way to manage the environment. The aim of conservation is to halt, and ideally reverse, the local, national and global decline in biodiversity.
The balance between conservation and farming. What are the 4 reasons to conserve?
ETHICAL
The current mass extinction is our responsibility.
Prevent extinction / loss of populations / reduction in populations
Prevent loss of habitats
Save organisms for future generations
ECOLOGICAL
The community in an ecosystem is interdependent - reducing the population of some species will affect many others, often in unpredictable ways
The more biodiversity (at habitat, species and genome levels) in an ecosystem the more resilient that ecosystem is to change
ECONOMIC
Medical / pharmaceutical potential: most drugs are discovered in plants
Reducing soil depletion (that happens during continuous monoculture)
Tourism
Saving local forest communities
Other undiscovered commercial potential eg genes that could be genetically engineered into other commercially valuable species / biomimetic engineering
CULTURAL
Wild spaces are good for mental and physical health.
Aesthetic value
5 examples of farming techniques that improve biodiversity:
Replanting hedgerows and leaving unfarmed margins around fields increases number of niches and food sources, and provides ‘wildlife corridors’ linking otherwise fragmented populations.
Planting native species (rather than than introducing non-native species which other species in the community might not be able feed on / nest on / pollinate)
Farming rare breeds improves genetic diversity - keeps a gene pool or rarer alleles which could be reintroduced into other crops / livestock
Planting more than one variety of crop increases the number of niches and food sources, and crop rotation with nitrogen-fixing plants improves fertility of soil
Biological Control instead of pesticides - pesticides reduce population for all insects in the habitat. Introducing a predator (eg ladybirds) means fewer insect species are predated (eg not pollinators)
