Biology

• Species


  A group of organisms with similar morphological and physiological features, which can interbreed to produce fertile offspring and are reproductively isolated from other species
• Ecosystem


  A relatively self-contained, interacting community of organisms, and the environment in which they live and with which they interact. Consists of biotic and abiotic parts
• Niche


  The role of an organism in an ecosystem (how an organism fits into the ecosystem)
• Biodiversity


  The variety of species in an area along with their variation within species and the genetic diversity between them
• Levels of biodiversity


  • Variation in ecosystems or habitats
  • Number of different species in the ecosystem and their relative abundance
  • Genetic variation within each species
• Uses of maintaining biodiversity

  • Maintains stability of ecosystem; preventing extinction
  • Maintains large gene pool (genetic diversity)
  • Ecosystems provide 'services' for humans
  • Species can be source of new medicines
  • Resource such as food and wood
  • Leisure for humans to see in zoos; ecotourism
  • Climate stability
• Genetic diversity


  The diversity of the alleles within the genes in the genome of a single species
• Species diversity


  • The number of species in a community is known as species richness
  • Species diversity takes species richness into account, but also includes evenness of abundance of each species
• Random sampling


  1. Decide size of quadrat and number of samples

  2. Mark a specific area

  3. Samples are taken randomly eg by using random number generator to give coordinates of sampling points in the area to avoid any bias and increase accuracy of estimate

  4. Take measurement of abundance of specific species
• Species frequency


  The measure of the chance of a particular species being found in any one quadrant
• Species density


  A measure of how many individuals there are per unit area
• Mark-release and recapture


  1. As many individuals possible are caught

  2. Each individual is marked in a way that would not affect its chance of survival or reproduction

  3. The marked individuals are counted and returned to their habitat to mix randomly

  4. After enough time elapses for mixing to take place, capture another sample

  5. Number of marked and unmarked counted and used to calculate estimate of population
• Systematic sampling


  1. Using transacts: to detect changes in community composition along a line across one or more habitats

  2. Line transect: The number of organisms found at regular points along a line are noted

  3. Belt transect: The abundance of organisms within quadrats placed at regular intervals
• Drawing a kite diagram

  1. Find the highest value from the table

  2. Give each species 6 spaces on y axis

  3. Draw a straight line of 0 through the middle

  4. Divide the number you are plotting by two, plot it above and below the line (from 0)
• Correlation coefficient (r)


  Determine whether there is a linear relationship and its strength (ie how close the points are to the line)

  
• Pearson's linear correlation


  1. Interval data that must be distributed normally

  2. Must have linear correlation

  3. The two variables can be on either axis

  4. Quantitate data as measurements or counts

  
• Spearman's rank correlation


  Used to find out if there's a correlation when data is not normally distributed
• Spearman's rank correlation


  1. Rank both species (where the highest data is ranked 1 and so on)

  2. Calculate the difference in rank in each quadrat, D

  3. Square the difference

  4. Find the sum of D^2, and proceed with formula
• Simpson's Index of Diversity

  Used to calculate the diversity of an area after abundance of species is calculated
• Viruses are not classified in the 3 domain classes as they are considered dead (they don't undergo MRS GREN), also they do not have any of the features that are used in the classification
• Viruses


  • Structure only visible by electron microscope
  • Acellular- they do not have cellular structure like bacteria and fungi however they have particles made of proteins and nucleic acids similar to cellular organisms
  • Infectious but have no metabolism when they are free
  • When they infect cells, they use the biochemical machinery of the host cells to copy their nucleic acids and make their proteins destruction of host cell
  • Energy for these processes is obtained by host cells' respiration
• Taxonomic system for viruses

  • Is based on the diseases which they cause
  • Type of nucleic acid they contain (DNA or RNA)
  • Whether nucleic acid is double/single stranded
• Five major threats to biodiversity

  • Habitat loss and degradation of environment
  • Climate change
  • Excessive use of fertilizers and industrial and domestic forms of pollution
  • Over exploitation and unsustainable use of resources
  • Alien species
• Habitat loss


  The process in which habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced, habitats get divided into smaller areas (habitat fragmentation) or destroyed, reducing biodiversity and leading to extinction in extreme cases
• Deforestation


  Due to farming, urbanisation etc leads to severe land degradation as a result of soil erosion
• Climate change


  • Plants and animals affected as they may not be able to adjust
  • Major cause is greenhouse gas emission from eg organic waste (methane) and factories (CO2). It traps more heat, causing global warming and a rise in sea levels
  • As the earth gets warmer, organisms at high altitudes find it difficult to adapt
  • Acidification/temp rise of the oceans can destroy aquatic life such as coral reefs, algae and molluscs
• Coral reefs


  An example of key stone species ie species that play a central role in the ecosystem, and whose existence effects the entire community. They have been destroyed due to overfishing, mining, fertilizer run-off, and high temperatures (leading to coral bleaching ie when coral becomes white as algae leaves coral which supply O2 to coral)
• Pollution


  • Substances such as polychlorinated biphenyl (PCBs) enter our food chains, effects our immune systems and reduces fertility
  • Non-biodegradables such as plastic can be eaten by turtles
  • Fertilizers can drain into rivers causing eutrophication, killing all species in that ecosystem
  • Air pollution causes acid rain, affecting aquatic life and vegetation
• Over exploitation


  Hunting and poaching for eg ivory, and overfishing due to overpopulation
• Alien species


  • Invasive species that moved from one ecosystem to another by trading animals and used to control pests
  • Increase in disease: alien species could introduce diseases
• Why does biodiversity matter?

  • Moral and ethical: some people/cultures believe we have no right to cause extinction of other species
  • Ecological: ecosystems are more stable when biodiversity is high. They also add direct value to us eg medicinal herbs must be protected so that species beneficial to us are not lost
  • Nutrient cycles and food chains are
• Substances such as polychlorinated biphenyl (PCBs) enter our food chains, effects our immune systems and reduces fertility
• Non-biodegradables such as plastic can be eaten by turtles
• Fertilizers can drain into rivers causing eutrophication, killing all species in that ecosystem
• Air pollution causes acid rain, affecting aquatic life and vegetation
• Over exploitation: hunting and poaching for eg ivory, and overfishing due to overpopulation
• Alien species: invasive species that moved from one ecosystem to another by trading animals and used to control pests
• Increase in disease: alien species could introduce diseases
• Moral and ethical


  Some people/cultures believe we have no right to cause extinction of other species
• Ecological


  Ecosystems are more stable when biodiversity is high. They also add direct value to us eg medicinal herbs must be protected so that species beneficial to us are not lost