12. Biodiversity Flashcards
(36 cards)
What is biodiversity
a general term used to describe the variety of living organisms in a community/habitat.
It includes species diversity and genetic diversity.
What is a habitat
the place where an organism lives
What is a community
all the organisms (of different species) in a habitat
What is species richness
Counting the number of different species in a habitat
What is the species diersity index
A single number that describes species diversity. it relects:
-The number of different species present
-The number of individuals in each species
Enables us to make an objective assessment of diversity in any community
How is the species diversity index calculated
D = N(N-1) / E n(n-1)
N = total number of organisms of all species
n = total number of organisms of a particular species
why is it more useful to calculate diversity index rather than just record the number of species present.
measures number of individuals in each species as well as the number of species
takes into account the fact that some species may be present in very low or high numbers
When is the diversity index used
to compare the diversity of different habitats, or of the same habitat over time
What does the diveristy index indicate
A High value of D indicates a stable and ancient site with a diverse community.
A low value of D suggest agricultural management, a recently deforested site or a polluted area. These are only generalisations.
What does a low D valuve explain about the environment
Harsh environment
-Few species present and ofter populations are small
-Generally abiotic factors determine which species are present
-Ecosystmes are usually unstab;e
Only few species are adapted to survive the harsh conditions
What does a high species index value explain about the environment
Favourable environment
-Many species present and populations are large
-Biotic factors determine which species are present
-Ecosystmes are stable
-Complex food webs so a change in population of one species is less likley to affect other populations
How may organimsms be distributed in an area
Ranodm
Regular
Clumped
What is the only method of gaining an unbiased measure of the species present
Sample the area randomly to avoid bias
e.g chosing a palce that is easy to get to or are more obvious is biased
How do you radom sample
· Quadrat laid out across the sample area using tape measures.
·random numbers are generated to provide coordinates on the grid. These are the sample points where a quadrat is placed.
· Within each quadrat the community is sampled, in this case each organism in the quadrat is identified and the number of each species is counted.
· As any one sample point is unlikely to be representative of the area, a large number of randomly placed quadrats are used.
How many quadrats are needed to give a representative sample
a rule of thumb you need to take at least 20 quadrats to be able to do any statistical analysis of the results.
What is intensive farming
intensive farming usually involves the removal of existing vegetation and the growth of one crop species, a system called monoculture
aim is to provide ideal conditions for the crop to grow and supply a high yield.
How does agriculture provide ideal conditions for crop photosynthesis and growth
· Fertilisers added to provide minerals for growth.
· Fields irrigated so there is enough water.
· The crop species are specially selected to grow well in the conditions provided and to provide high yields of useful product.
How are weeds and pest species removed
Weeds can be physically picked out or chemical herbicides used which kill the weeds but not crop plants.
Animal pesticides are toxic chemicals which kill a wide range of similar species.
Removing hedgerows and field boundaries, unprofitable pockets of woodland and draining marshy areas make maximum use of land for crops, and remove sources of pests and disease
Why will so few species exist, and therefore species diversity be so low in the fields
· A lower variety of habitats/ niches
· Fewer plant species because just one crop species grown and most weeds removed or killed by herbicides.
· Few species of herbivores as so little variety of plant food types.
· Fewer types of carnivore species because so few herbivore species to feed on.
· Use of pesticides will reduce diversity of insect species
What conservation techniques are used to increase species and habitat diversity, without raising food costs or lowering yields.
· Maintain existing hedgerows at the most beneficial height and shape.
· Plant hedges rather than erect fences as field boundaries.
· Maintain ponds and where possible create new ones
· Leave wet corner of fields rather than drain them.
· Plant native tree species on land with a low species diversity rather than in species-rich areas.
· Reduce the use of pesticides – use biological control or genetically modified organisms that are resistant to pests.
· Use organic fertilisers.
· Use crop rotation that includes a nitrogen-fixing crop, rather than fertilisers, to improve soil fertility.
· Create natural meadows and use hay rather than grasses for silage.
· Leave the cutting of verges and field edges until after flowering and when seeds have dispersed.
· Introduce conservation headlands – areas at the edge of fields where pesticides are used restrictively so wild flowers and insects can breed.
How do hedgerows increase biodiversity
contain several plant species which will provide a greater variety of habitats and food for animals.
may be habitats for predators of pests. An increase in the number of these should increase the yield and reduce the need for using pesticides.
habitats for pollinating species. An increase in these would also improve the crop yield
What are disadvantages to hedgerows
take up a lot of room, reducing the land area available for growing crops
Habitats for pests, so may lead to an increase in pest populations and reduce crop yields.
Crops will face increased competition for resources,
What is genetic diversity
the number of different alleles of genes in a population.
Why does genetic diveristy matter
If a population has many different alleles for a particular gene, then the population is said to be genetically diverse.
The bigger the gene pool, the greater the variation within that species and the greater the genetic diversity.
The greater the genetic diversity the better the survival chances as they are more likely to be able to adapt to a change in the environment.
Creates variation within a population.
Which specific alleles will increase over time and which decrease is dependent on if they cause differential changes in survival and reproduction.
