Biodiversity and Ecosystems

• The Earth's biosphere is the sum total of all living organisms on earth.
• Abiotic factors

  Non-living components
• Ecosystems


  • A community forms an ecosystem by its interactions of the abiotic environment
  • Abiotic factors have a large influence on the ecosystem
• Ecologists study both the biotic components of an ecosystem, and the interactions between biotic and abiotic factors

  Ecosystems
• Populations

  • A group of organisms of the same species, living in the same location at the same time
  • If two populations of the same species are geographically isolated, they are unlikely to breed with each other
• Ecosystem


  A community of interacting organisms and their physical environment
• Post-Zygotic Barriers

  • Hybrid Inviability: If fertilisation does occur producing a zygote, the embryo may not develop as the genes from the parents are too different
  • Hybrid Sterility: If two species differ in chromosome type and number, the hybrid offspring will be sterile
  • A horse and a donkey will produce a mule
• Pre-Zygotic Barriers

  • Temporal isolation: The species mate and reproduce during different seasons
  • Behavioural Isolation: The mating recognition behaviour of one species may be sufficiently different so they are not interested in other species
  • Mechanical Isolation: Anatomical differences in genitals may prevent the transfer of genetic material
  • Gamete Isolation: If gametes are transferred fertilisation is prevented
• Species Interactions

  • Positive: Mutualism, Commensalism
  • Negative: Parasitism, Competition, Predator-prey
• Adaptations


  • Characteristics that help species survive and reproduce
  • Structural, Physiological, Behavioural
• Species


  • A group of organisms that are alike and can reproduce to produce fertile offspring in their natural environment
  • Have similar physiological and morphological characteristics
  • Are genetically distinct from other species
  • Have a high similarity within their genetic sequences
• Gene pool


  The total set of genes found in an interbreeding population
• Competition


  • Interaction where each species have a harmful influence on each other
  • No two populations have identical requirements but when overlap occurs, there is competition for resources
• Biotic factors

  Living components
• Interactions between organisms can be between members of the same species or members of different species in the community
• Predation

  • One species (a predator) benefits at the expense of the other species (the prey)
  • Predation shapes the community as it affects the size of the population, biodiversity
• Communities

  • A group of populations living and interacting with each other
  • All species in a community are dependent on each other for their survival
• Symbiosis


  Any type of a close and long-term biological interaction between two different biological organisms
• Symbiosis types

  • Mutualism
  • Commensalism
  • Parasitism
• Predation


  When one organism feeds on another live organism to obtain energy
• Predation

  Shapes the community as it affects the size of the population, biodiversity in the community, and evolution in species
• Symbiosis

  Relationships between organisms of two different species
• Parasitism

  One species (a parasite) benefits at the expense of the other species (host)
• Parasitism


  • mosquitos feed on human blood
  • mistletoe attach to the vascular system of a host tree
• Predation


  • sharks feed on sea lions
  • lions feed on antelope
• Predation

  One species (a predator) benefits at the expense of the other species (the prey)
• Mutualism


  • flowering plants produce nectar to attract bees
  • termites have bacteria in their gut to help digest cellulose
  • bacteria in a cow’s stomach provide enzymes to break down cellulose eaten by the cow
• Keystone Species in Australia

  • Ecological niche
  • Role in ecosystem maintenance
  • Status
• Commensalism

  • Barnacles ride on whales so they can feed on plankton
  • Egret eats insects as the grazing animals disrupt the grass
• Commensalism

  An interaction that benefits one species while the other is unaffected
• Genetic Diversity


  The variety of genes and phenotypes that occur within a particular species
• Keystone Species


  Species with an essential role and a large influence on the relationships within the ecosystem, despite low numbers
• Species Diversity


  The number of individual organisms in a population and the number of species in a given community
• Genetic Diversity


  Variation in the number and types of genes that are expressed by individuals of a population or species
• Genetic Diversity
• Keystone Species in Australia

  • Grey-headed flying fox
  • Grey nurse shark
• Biodiversity levels

  • Genetic diversity
  • Species diversity
  • Ecosystem diversity
• Keystone Species


  Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether
• Species Diversity
• Genetic Diversity

  • The koala species have low genetic diversity which could account for the high incidence of chlamydia in the population
  • Tasmanian devil population are all affected by face tumour disease due to low genetic diversity