Biodiversity Threats

• humans are currently the biggest threat to biodiversity
• humans threaten biodiversity by the over use of resources and direct damage to ecosystems
• over use of resources example

  • vegetation cleared for urban development and mining for fossil fuels
• direct damage example

  • intorduction of non-native species
  • pollution of harmful chemicals
• three major types of habitat alteration:

  • habitat destrcution
  • habitat degregation
  • habitat modification
• habitat degregation occurs because of factors sucuh as pollution , invaisive species and over exploitation of resources
• habiatat fragmentation is the process of breaking up a habitat into smaller pieces, which can lead to the loss of biodiversity
• the rate of deforestation increases as the earth's population increases
• reforestation efforts cannot match the pace at which forests are cut down
• increase in population increases the demand for food
• non-native species have a two fold impact:

  • they compete with native species for ecological niches, dominating resources required by other species
  • they prey upon native populations
• global warming is a gradual rise in the overall atmospheric temperature, leading to an increasing frequency of extreme weather events
• loss of habitat and exploitation of resources leads to the creation and isolation of small populations from within a pre-existing larger area
• decline in population fitness is called inbreeding depression, it lowers genetic diversity
• the creation of smaller populations lead to:

  • genetic drift
  • demographic variation
  • genetic swamping
• organisms seek to exist in as wide a niche as possible which requires dispersal
• dispersal is important for any species because:

  • a population restricted to one small area risks becoming extinct if conditions become unfavourable
  • dispersal reduces inbreeding and the loss of evolutionary adaptability
• two aspects of dispersal is important for reproduction:

  • dispersal over distances away from the parent
  • dispersal in time
• pollinator habitat has been lost to agriculture, human development and mining
• physical barriers to dispersal consist of landscape features that prevent organisms from relocationg
• anthropogenic barriers (roads, farming) can disrupt movement patterns of species
• habitat loss = occurs when natural habitats are converted to human uses
• habitat degragation = when the condition of a natural habitat decliines
• habitat modefication = where native habitat is changed in some way
• climate change = refers to the alterations in long-term weather patterns
• alleles = forms of a gene
• symbiosis = a relationship between two organisms that live in close association with each other
• prasitism = a relationship which one species derives a benefit to a harm of the host
• commensalism = one species benefits with no expense or benefit to the other organism
• mutualism = a relationship where two species benefit
• bioaccumulation = the gradual collection of chemical substances in an organism
• biomagnification = the rise in concentration of a toxin in an organism at higher levels of a food chain
• edge edge effect = changes in population or community structures that occur at the boundary of two or more habitats