Módulo 2 de 3 · Texto
Biodiversity
Biodiversity
- Importance = essential for maintaining a balanced ecosystem for all organisms --> they provide food, oxygen and other materials for us to survive
- Measuring a baseline for the biodiversity of an area means you can work out how much of an effect a change has had/ will have on the area
- Habitat biodiversity = number of different habitats found within an area
- each habitat will have different numbers of different species so the higher the habitat diversity the higher the biodiversity
- Species biodiversity has two compononents:
- species richness --> number of different species living in a particular area
- species evenness --> comparison of the number of individuals of each species in a community
- overall species diversity can be different even if it has the same number of species, it also depends on the evenness
- Genetic biodiversity = variety of genes that make up a species
- many of the genes are the same for all individuals in the species but alleles do exist and they cause the genetic variation within and between species
- genetic biodiversity can result in different characteristics being exhibited (dogs can be big or small, round or pointy eared)
- greater genetic biodiversity within a species allows for better adaptation to a changing environment
- Sampling = taking measurements of a limited number of individual organisms within a particular area
- Used to estimate the number of organisms in an area aka the abundance of the organisms
- Also used to measure a particular characteristic of an organism (average height of crop)
- Random sampling = selecting individuals by chance
- each population has equal chance of being recorded
- mark out a grid on the grass using tape measures
- use random numbers to determine coordinates
- take a sample from each randomly generated coordinte pair
- Non-random sampling = sample is not chosen at random
- opportunistic --> weakest form of sampling as it is not representative of the whole population (uses organisms that are conveniently available)
- stratified --> some population can be divided into sub-groups based on a particular characteristic, a random sample is then taken from each of the groups proportional to its size
- systematic --> areas are identified within a habitat that are then sampled separately --> usually with line (line along the ground and take samples from specified points) or belt transect (two parallel lines marked and samples taken in the area between them)
- Reliability
- Sample is never entirely representative because:
- sampling bias --> may be by accident or deliberate (you choose an area because you know it'll give you good numbers for certain species)
- chance --> the organisms selected may not be representative of the whole population --> can never be removed but its effects can be minimised with large sample sizes
- Sample is never entirely representative because:
- Sampling animals
- pooter to catch insects
- sweep nets to catch insects in long grass
- pitfall traps for small invertebrates
- tree beating for invertebrates that live in trees or bushes (shake it over a white cloth to catch them)
- kick sampling for organisms in a river (the riverbed is "kicked" for a while before to disturb the substrate then a net catches anything that's disturbed downstream)
- Estimating animal population size
- capture-mark-release-recapture technique
- capture as many as you can
- mark them all and then release them
- time is allowed for the organisms to redistribute themselves
- repeat the capture process and compare the numbers that are new or recaptured
- the greater the marked individuals recaptured the smaller the population size
- Sampling plants
- point quadrat --> frame with a horizontal bar, at set intervals a pin is pushed through to the soil and each plant that touches the pin is recorded
- frame quadrat --> sqaure frame divided into a grid, the type and number of species and individuals within each section is recorded
- used to measure:
- density --> if plants can be seen clearly, counting how many are in one quadrat shows the density of the plant per metre <-- not an estimate
- frequency --> used where individuals of a species are hard to count --> count the number of squares the species is present within to work out an estimated percentage (clover in 65 of 100 squares means they are in 65% of the area)
- percentage cover --> used for speed when collecting data --> used when a species is abundant but hard to count --> estimate by eye of the area within the quadrat that the plant is present within
- for best results, quadrats should be used in random sampling but often aren't)
- Measuring species richness
- make a list of all the species identified then a total number can be calculated
- identification keys are used when sampling
- Measuring species evenness
- compare the numbers for the individuals in each species
- Measuring abiotic factors
- abiotic factors = non living components in a habitat
- wind speed
- light intensity --> light meter
- relative humidity --> humidity sensor
- pH --> pH probe
- temperature --> temperature probe
- oxygen content of water --> dissolved oxygen probe
- can be measured quickly and accurately so that:
- rapid changes can be detected
- human error in taking reading is reduced
- high degree of precision
- data can be stored and tracked
- Calculating biodiversity
- use the Simpson's Index of Diversity to take both species evenness and richness into account
- values always between 1 and 0 --> closer to 1 means higher biodiversity
- organisms in a low biodiversity habitat are usually highly adapted to survive there
- Genetic diodiversity
- differences in alleles create genetic biodiversity
- species with greater genetic biodiversity are more likely to adapt and survive as it is likely that some organisms carry the advantageous alleles
- increased by:
- mutations in the DNA
- interbreeding between different populations as the alleles are transferred between the groups aka gene flow
- decreased by:
- selective breeding where organisms are only selected to breed if they have desirable traits
- captive breeding programmes in zoos and conservation centres as new alleles are rarely introduced
- rare breed where they have been selectively bred but then go out of fashion so numbers and allele numbers drop dramatically
- artificial cloning
- natural selection --> organisms evolve to only carry the advantageous alleles
- genetic bottlenecks --> few individuals survive an event or change so the gene pool is reduced
- genetic drift due to random nature of alleles being passed from parent to offspring (more pronounced in populations with small gene pools)
- Measuring genetic biodiversity
- measure polymorphism (polymorphic genes have more than one allele like immunoglobulin which codes for blood type)
- most genes are monomorphic where only a single allele exists (ensure the basic stucture of a species stays the same)
- proportion of genes that polymorphic can be measured by:
- number of polymorphic gene loci / total number of loci
- the greater the proportion of polymorphic genes, the greater the genetic biodiversity in a population
- Factors affecting biodiversity
- deforestation
- can occur naturally but it is mostly deliberate by humans
- affects biodiversity by:
- directly reduces the number of trees in an area
- specific species are sometimes targeted so it reduces species biodiversity
- destroys the habitats for animals so their numbers fall too
- animals are forced to migrate to ensure their survival
- agriculture
- selection of only a few species reduces the biodiversity of the area
- much of the methods used by farmers reduces biodiversity:
- deforestation to create area for planting
- removal of hedgerows
- use of pesticides and herbicides
- monoculture
- climate change and global warming
- melting of the polar ice caps would lead to the extinction of the plants and animals in these regions
- rising sea levels from the melting caps and thermal expansion of the seas would lead to flooding
- higher temperatures and less rainfall would result in droughts and some plant species dying out + xerophytes would become more dominant --> less food for some animals so the ones who eat xerophytes would be more common
- insect life cycles and populations would change as they adapt to the new climates --> as key pollinators they would effect the plants as well
- slow climate change would give time for species to adapt and as this would lead to the loss of native species, biodiversity wouldn't be lost
- deforestation
- Reasons for maintaining biodiversity
- aesthetic reasons:
- different plants and animals enrich out environments and lives
- natural world provides inspiration for the arts
- patients recover more quickly from stress if they're surrounded by plants
- economic reasons:
- soil erosion may occur as a consequence of deforestation so there would be a drop in land available for crops and animals
- important to conserve the organisms we use to make things (hardwood timber) to prevent industries breaking down
- protect species with potential economic importance --> undiscovered medicines
- continuous monoculture depletes the soil which would lead to smaller crop yields and less money
- high biodiversity protects against abiotic stresses so crops are more likely to survive
- economic income from areas of natural beauty
- plant varieties are needed for cross-breeding to make more profitable and successful crops
- ecological reasons:
- the removal of one species could have a serious effect on the others in its ecosystem - including us!
- keystone species have a disproportionally large effect on their environments so its essential to protect them so other species don't also disappear
- aesthetic reasons:
- Human activity vs biodiversity
- in many countries the natural habitat is created and maintained by human intervention by farmers and landowners
- Maintaining biodiversity
- In situ conservation = within the natural environment
- maintains the genetic diversity and the evolutionary adaptations
- preserves interdependent relationships therefore interlinked species are also protected
- wildlife reserves:
- controlled grazing
- restricted human access
- controlling poaching
- feeding animals
- reintroduction of a species
- removal of invasive species
- halting succession
- marine conservation zones:
- less well established
- vital in preserving species-rich areas
- aim is to create areas of refuge where populations can build up and repopulate adjacent areas
- Ex situ conservation = outside of the natural environment
- botanic gardens:
- plant species actively maintained to provide optimum conditions
- roughly 1500 worldwide holding 35,000 plant species
- majority of species aren't conserved though
- many wild species are unrepresented
- seed banks:
- store of genetic material
- seeds are carefully stored so new plants can be grown in the future
- dried and stored at -20C
- don't work for all plants, some seeds die when dried and frozen (mostly the seeds from rainforests)
- captive breeding programmes:
- often run and managed by zoos and aquatic centres
- scientists help to create a stable, healthy population of the species so it can be gradually reintroduced to its natural habitat
- provide the animals with shelter, food, no predators and vets
- suitable breeding partners or semen can be imported from other zoos to increase the gene pool
- maintaining genetic biodiversity can be difficult as interbreeding happens often
- sometimes they cant't be reintroduced because:
- loss or resistance to a disease
- may not have learned the correct behaviours to survive
- genetic make up of the captive species may be too different from wild ones
- in many cases the natural habitat must first be restored
- conservations agreements
- International Union for Conservation of Nature (IUCN) assist in securing agreements between nations
- established the Convention of International Trade in Endangered Species (CITES) which regulates the trade of wild plant and animal specimens (protects 35,000 species)
- the Rio Convention of 1992 --> 172 nations agreed on :
- Convention of Biological Diversity (CBD) requires them to develop national strategies for sustainable development
- United Nations Framework Convention on Climate Change (UNFCCC) agreed to take steps to stabilise greeenhouse gases
- United Nations Convention to Combat Desertification (UNCCD) aims to prevent desertification of fertile land
- botanic gardens: