Biodiversity within a community Flashcards
What is a species?
They are capable of breeding to produce living, fertile offspring.
This means that, when a species reproduces sexually, any of the genes of its individuals can be combined with any other.
What is biodiversity?
The term used to describe variety in the living world.
It refers to the number and variety of living organisms in a particular area.
What is species diversity?
The number of different species and the number of individuals of each species within any one community.
What is genetic diversity?
The variety of genes possessed by the individuals that make up of population of a species.
What is ecosystem diversity?
The range of different habitats, from a small local habitat to the whole of earth.
What is species richness?
A measure of species diversity.
It is the number of different species in a particular area at a given time (community).
Two communities may have the same number of species but the proportions of the community made up of each species may differ markedly.
What is diversity index?
d = N(N-1) / Σn(n-1)
d = index of diversity.
N = total number of organisms of all species.
n = total number of organisms of each species.
Σ = the sum of.
What are natural ecosystems?
As natural ecosystems develop over time, they become complex communities with many individuals of a large number of different species. These communities have a high index of diversity.
What are agricultural ecosystems?
They are controlled by humans and are different.
Farmers often select species for particular qualities that make them more productive.
As a result, the number of species and the genetic variety of alleles they possess is reduced to the few that exhibit the desired features.
What is the impact of agriculture?
To be economic, the number of individuals of these desirable species needs to be large.
Any particular area can only support a certain amount of biomass.
If most of the area is taken up by one species that the farmer considers desirable, there is only a smaller area available for all the other species.
The other species have to compete for the little space and resources available, and many will not survive this competition.
Even if species evolved to adapt to the changes, their population would be considerably reduced.
What is the impact of pesticides?
Pesticides are used to exclude these species because they compete for the light, mineral ions, water and food required by the farmed species.
The overall effect is a reduction in species diversity.
The index of diversity is therefore low in agricultural ecosystems.
How has farming affected diversity?
In the UK, food production has doubled in the last 40 years.
This has been achieved by the use of improved genetic varieties of plant and animal species, greater use of chemical fertilisers and pesticides, greater use of biotechnology and changes in farm practices.
This led to larger farms and the conversion of land supporting natural communities into farmland.
This has diminished the variety of habitats within ecosystems and consequently reduced species diversity.
What practices have directly removed habitats and directly reduced species diversity?
Removal of hedgerows and grubbing out woodland.
Creating monocultures, for example replacing natural meadows with cereal crops of grass for silage.
Filling in ponds and draining marsh and other wetland.
Over-grading of land, for example, upland areas by sheep, preventing regeneration of woodland.
What practices have had an indirect effect on diversity?
Use of pesticides and inorganic fertilisers.
Escape of effluent from silage stores and slurry tanks into water courses.
Absence of crop rotation and lack of intercropping or under sowing.
What management techniques are there for diversity?
These techniques can increase species and habitat diversity, without unduly raising food costs or lowering yields.
However these practices will make food slightly more expensive to produce, and therefore to encourage farmers there are a number of financial interventions from the Department For Environment, Food and Rural Affairs (DEFRA) and the European Union.
Maintaining biodiversity is important, if it is reduced the global living system becomes increasingly unstable and we all rely on the global system for food and other resources.
