Biodiversity

• Gene mutations

  A change in the base sequence of chromosomes

  • Arise spontaneously during DNA replication
  • Base deletion/substitution
• Degenerate

  More than one codon triplet codes for the same amino acid.
• Mutagenic agents can increase the rate of gene mutation
• Natural Selection

  1. Random mutations can result in new alleles of a gene
  2. Many are harmful but some, in certain environments, the new allele of a gene might benefit its possessor, leading to increased reproductive success.
  3. Advantageous allele is inherited by members of the next generation
  4. Over many generations, the new alleles increases in frequency in the population.
• Biodiversity

  The variety of organisms living in an area/habitat/ecosystem.
• Factors which impact biodiversity

  • Lower diversity/species of plants
  • Reduced variety of food sources
  • Reduced habitat
  • Fewer types of organisms able to live there
• Why maintain biodiversity?

  • Moral/ethical duty to prevent extinction
  • Potential source of medicines/useful resources
  • Financial importance
• Ecology

  The study of interrelationships between organisms and their environment

  • Biotic and Abiotic factors
• Population

  A group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed
• Ecosystem

  A community and the non-living components of its environment together
• Carrying Capacity

  The maximum size of a population of an ecosystem can support
• Community

  All the different species that live in one area and interact with one another.
• Habitat

  An area where one or more organisms live within an ecosystem
• Microhabitat

  A small area which differs somehow from the surrounding habitat with a microclimate
• Niche

  The role of a species within its community, consisting of its adaption both its biotic and abiotic factors
• Population sizes can vary as a result of:

  • Abiotic factors
  • Interactions between organisms: interspecific and intraspecific competition and predation
• Size of population can be estimated for slow moving or non-motile organisms

  Quadrats randomly placed; along a belt transect, grid coordinates.

  • Results reported as percentage cover or frequency
• Size of population estimated for motile organisms

  Mark-release-recapture
• Ecosystems are dynamic systems
• Wide range of variation in phenotypes within a population of a species

  Genetic and environmental factors
• Primary source of genetic variation is mutation

  • Meiosis and random fertilisation of gametes produces further genetic variation
• Biodiversity

  The variety of living organisms. Can be measured in terms of species, ecosystem and genetic diversity.
• Farming effects on species diversity

  Decreases species richness

  • Typically used for one species (monoculture)
  • Use of pesticides/herbicides
• Agriculture on genetic diversity

  Decreases

  • Farmers select for certain characteristics
  • Reduces number of different alleles in the population
• How to increase biodiversity in areas of agriculture

  1. Hedgerows instead of fences
  2. Grow different crops in same area; rotate crops around after a season
  3. Limit use of pesticides and herbicides
• 4 ways to compare genetic diversity between organisms

  • Frequency of observable characteristics
  • DNA base sequences
  • mRNA base sequences
  • Amino acid sequences
• Intraspecific

  Between individuals of the same species
• Interspecific

  Between individuals of different species
• Sampling

  Selecting a group of individuals to measure that will represent the whole target population
• How to achieve a random sample?

  • Create grid for sample area
  • Randomly generate coordinates where quadrant or transect can be placed
  • Repeat until required sample size is reached.
• 4 abiotic factors that affect population growth

  • Temperature
  • Light
  • pH
  • Water/Humidity
• Mark-release-recapture method

  • A sample is captured, marked, then released back into the same area they were caught.
  • After a certain period of time, another sample is captured and the number of marked organisms are counted.
• Assumptions in mark-release-recapture

  • Marked individuals distribute evenly
  • No net migration or immigration
  • No births or deaths
  • Marking does not affect survival
  • Mark does not come off
• Why are ecosystems dynamic?

  • Populations constantly rise and fall
  • Any small change can have a large effect
  • Biotic and abiotic factors may alter ecosystem conditions
• Primary succession

  Where an area previously devoid of life is colonised by a community of organisms
• Summarise process of primary successions

  • Pioneer species survive harsh conditions and colonise the area
  • Change abiotic factors of their environment (decomposition adds nutrients to the ground)
  • Over time, allows more complex organisms to survive.
• What is the climax community?

  The final stage of succession where the ecosystem is balanced and stable.
• How is the climax community reached?

  When the soil is rich enough to support large trees or shrubs, and the environment is no longer changing.
• How may a species alter the environment that develops during succession?

  May improve or worsen the environment for different species by making it more or less suitable for them.
• Conservation

  The protection and management of species and habitats, in order to maintain biodiversity.

  • Methods need to be adapted to the ecosystem.