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
  1. mark out a grid on the grass using tape measures
  2. use random numbers to determine coordinates
  3. 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 
• 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
• 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
• 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