Midterm EnviSci

• Population


  A group of individuals that belong to the same species and live in the same area
• Black bear


  found in forested areas throughout North America. It has 16 differently distinct populations.
• Natality


  number of individuals added to the population through reproduction
• sexual reproduction


  A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents
• asexual reproduction


  Process by which a single parent reproduces by itself
• Mortality


  the number of deaths in a population
• Survivorship curve


  shows the proportion of individuals likely to survive of each age
• sex ratio


  Relative number of males and females in a population
• 1.2 percent


  rate of increase in world population
• Famine


  extreme scarcity of food
• Political unrest


  seen in areas with great disparities in the availability of resources
• Environmental degradation


  caused by poor agricultural practices and the destructive effects of exploitation of natural resources
• Air pollution


  caused by human need to use energy for personal and industrial applications
• Extinction


  caused by people converting natural ecosystems to managed agricultural ecosystems
• ecological footprint


  measure of the land area required to provide the resources and absorb the waste of a population
• Demography


  the scientific study of human populations
• fertility rate


  number of children born per woman
• replacement fertility


  total fertility rate of 2.1
• economically developed countries has

  low fertility rate

  low population growth rate
• less developed countries

  high fertility rate

  high population growth rate
• 90%


  rate of energy lost in the original plant (human energy pyramid)
• succession


  The concept that communities proceed through a series of recognizable, predictable change in structure over time
• climax community


  a stable, long lasting community that is the result of succession
• primary succession


  begins with a total lack of organisms and bare mineral surfaces or water
• secondary succession


  begins with the destruction or disturbance of an ecosystem
• pioneer stage


  The first stage of primary succession. Bare rock or sand is very inhospitable places to live.
• pioneer community


  first to colonize bare rocks
• Lichens


  common organisms in many pioneer communities
• Intermediate stage


  the thin layer of soil produced by the pioneer community is the key to this stage
• wet meadow


  term for successional stage in aquatic primary succession
• Desert


  found where the rainfall was low; humans have little impact due to harshness of the climate
• Temperate grassland


  known as prairies or steppes, distributed over temperate parts in the world
• Savanna


  characterized by extensive grasslands spotted with occassional trees
• Mediterranean shrublands (chaparral)


  located near oceans and dominated by shrubby plants
• tropical rainforest


  biome that is heavy influenced by seasonal rainfall; have greater diversity of species more than any other biome
• epiphytic plants


  plants that live on the surface of other plants
• temperate deciduous forest


  have a winter-summer change seasons and have trees that lose their leaves
• nurse trees


  when a tree dies from the ground, it rots in place and serves a site for establishment of new trees
• Taiga (Boreal Forest)


  short, cool summers and long winter with abundant snowfall
• Tundra


  Temperatures are below freezing most of the year