3. Life Processes in the Biosphere

• Taxonomy 


  • The science of grouping organisms according to their similarities
  • A taxonomic group is called a taxon
  • Increasingly based on phylogeny
• Species 


  • A group of organisms that naturally breed and produce fertile offspring
  • Most organisms can't breed due to anatomical, behavioural and genomic difference
  • Species are named using Binomial Nomenclature
• Evolution 


  • The process that changes the gene pool of a species
  • It is driven by an increased chance of survival and reproduction
  • If populations become isolated, they may eventually form a new species
• Habitat 


  The area or location where a species or community lives
• Niche


  • The ecological niche of a species is the role that it plays in its habitat
  • In a single habitat, two species cannot occupy exactly the same niche
• Population


  All of the individuals of a single species that live in a particular area
• Community 


  All the members of all species that live in an area
• Ecosystem


  • The biotic and abiotic features of an area
  • This includes the community of species, their inter-relationship and their relationships with the physical environment
• Biome 


  • A large geographical region with specific climate conditions within which a characteristic community of species lives
  • They are often defined by the most prominent organism
• Process of evolution

  1. All organisms must be adapted to a range of biotic and abiotic conditions in their habitat in order to survive
  2. Those that are better adapted have increased chances of survival
  3. Better adaptations occur through random mutations
• Range of tolerance

  • Organisms have a range of tolerance
  • For any abiotic factor, an organism can survive in a narrow range
  • The larger the gene pool, the more likely a population will survive environmental changes
  • Some individuals will adapt to the new conditions
• Ecological Succession 


  Changes to an ecological community over time. All species colonize new habitats. Once the colonization has taken place, the organism may alter the habitat. This can make the habitat more/less suitable for other species. Each stage of the succession is called a Sere.
• Pioneer species 


  The first species to colonize an area
• Climax community 


  When the community no longer changes
• Plagioclimax 


  Human activities that prevent a climax community forming
• Secondary succession 


  the changes in ecological communities over time, on a previous colonised area
• Simpsons Diversity Index 


  Diversity index = Total no of individuals(total no of individuals - 1)/ Sum of no of individuals per species(no of individuals per species - 1)
• Populations 


  finding the exact no of individuals in a population is difficult. Population sizes are estimated
• Population regulation 


  Population sizes change overtime. If, reproduction rate > death rate, then the population will increase. if reproduction rate < death rate, then the population will decrease
• Conservation aims to maximise factors causing population growth and minimise factors that cause population decline e.g. minimise birth = evolution, Minimise death = environment
• r selected species 


  Species adapted to low survival rates. Often reach sexual maturity quickly, produce many young, and disperse widely e.g. rabbits
• k selected species 


  Species adapted to high survival rates. Reach sexual maturity slowly, produce few young e.g. whales and elephants
• Maximum Sustainable Yield (MSY)

  Population = initial population + (births + Immigration) - (deaths + emigration)
• Mortality rates 


  Dependent on:

  • Density independent factors e.g. droughts, floods, volcanic activity
  • Density dependant factors e.g. food, shelter, disease
• Carrying Capacity 


  The greatest population that an area can support indefinitely, without damaging the environment
• Artificial population control 


  If a population is not naturally regulated, artificial regulations may be put in place. This includes conservation measures and culling