Population & Biodiversity

• Levels of Biological Organization

  • Organism
  • Population
  • Community
  • Ecosystem
  • Biosphere
• Organism


  • Survival and reproduction; the unit of natural selection
• Population


  • Population dynamics; the unit of evolution
• Community


  • Interactions among populations
• Ecosystem


  • Global processes Energy flux and cycling of nutrients
• Population Density


  Total Population / Total Area or Total Volume
• Abiotic Factors


  • Changes in temperature level
  • Humidity: amount of rainfall
  • Sunlight
• Population Range


  The area occupied by a population
• Biotic Factors


  • Presence of predators
  • Competitors
  • Parasites
• Population Dispersion

  • Clumped Distribution
  • Uniform Distribution
  • Random Distribution
• Carrying Capacity


  The maximum population an environment can support sustainably without depleting its resources
• Population Growth


  • Exponential Growth
  • Logistic Growth
• Birth Rate


  Number of births / Total Population x 1000
• Death Rate


  Number of deaths / Total Population x 1000
• Population Growth Rate

  How fast the number of members of a population increases
• Ecology is the study of the relationships between organisms and their environment
• The Law of Conservation of Energy states that energy can neither be created nor destroyed, it can only be transformed or transferred
• Types of Consumers

  • Herbivores
  • Carnivores
  • Omnivores
• Food Chains transfer matter and energy in the form of food from organism to organism
• Food Webs are complex interconnected food chains
• Plants are the considered producers (Autotrophs)
• Heterotrophs are organisms that cannot produce their own food and must consume other organisms
• Biodiversity (Biological Diversity)


  • Variations within and among life-forms
  • The total sum of all the living organisms that exist on earth
  • A product of millions of years of evolutionary history
  • Includes ecological complexes in which organisms live
• Biodiversity Hotspot


  • An area that hosts high biodiversity and may also experience the threat of biodiversity loss
  • Creates a stable environment
• Stability


  The ability of an ecosystem to resist change
• Keystone species


  Species that are more key to maintaining the current state of an ecosystem
• Diversity-stability Hypothesis


  Biologically diverse communities are more likely to contain resilient species that can benefit the ecosystem
• Insurance Hypothesis


  Different species vary their responses to environmental fluctuations and diseases, allowing more species which are more able to adapt to changes in the ecosystem
• Niche


  Each species occupying a specific role, habitat, and relationship with other species
• Effects of Biodiversity on Ecosystem Stability

  • Resistance to Invasion
  • Insurance Effect
  • Species resistance to diseases
  • Negative covariance effect
• Resistance to Invasion


  Comes from complementarities or competition (e.g. resources, niche), making it difficult for intruders to thrive
• Insurance Effect


  Allows more species which are more able to adapt to changes in the ecosystem, buffering against changes or disturbance
• Negative covariance effect


  More adaptable organisms in an ecosystem take the role of underperforming organisms, as more and more organisms come in resulting in overlapping capacities
• How humans disturb the ecosystem

  • Introduction of pollutants
  • Agricultural effects on nutrient cycling
  • Combustion of fossil fuels
  • Depletion of the ozone layer
  • Global warming
• How can we help protect the ecosystem

  • Use and manage materials wisely
  • Conserve nonrenewable resources
  • Reduce and save the amount of energy we use
  • Recycle, reuse, reduce, repurpose, repair (5 Rs)
  • Keep species in their natural habitat
  • Avoid chemically enhanced pesticides and fertilizers
• Population


  • A group of organisms of a single species living within a certain area
  • Directly shows the gene pool than observing the entire species
• Aspects of Population

  • Population Density
  • Population Dispersion
  • Population Growth
  • Population Range
  • Age Structure
  • Carrying Capacity
• Population Density (PD)


  Total Population / Total Area

  Total Population / Total Volume
• Growth Rate (r)


  Influenced by Density Dependent Limiting Factors (biotic factors like diseases, mates, predators) and Density Independent Limiting Factors (abiotic factors like forest fires, earthquakes, tsunamis)

  Calculated as: r = (B-D)+(I-E) / N
• Patterns of Population Distribution

  • Clumped
  • Random
  • Uniform