-Some populations grow exponentially until the reach the carrying capacity of the environment.  Populations may exhibit slow growth that tends to approach the carrying capacity with minor flucuations, rapid growth that tends to expand exponentially, and then expierence massive die-backs, or fall somwhere inbetween.

 

-Density-dependent factors such as disease and food supply, and density-independent factors such  as weather, have effects on populations size.  Interactions among organisms such as predation, competition, stress, and crowding also limit population size.

 

Section 4.1

Define-carrying capacity-

           -density dependent factors-

           -density independent factors-

           -exponential growth-

4.1 Outline-

  -defined as an increase in the size of the population over time-

  -many ways of finding out how fast a population grows-

 -How fast do populations grow?-

  -unlike growth of other things-

  -not linear growth, but exponential growth-

  -exponential growth- as a population gets larger it also grows faster-

  -carrying capacity- the amount of a certain organism a biosphere can hold-

  -if under carrying capacity you will see births > deaths-

  -if over carrying capacity you will see deaths > births-

 -Patterns of population growth-

  -why don't populations become stable all at once-

  -because different organisms have different reproductive patterns-

  -some organiams are slow to reproduce, but have long lives-

  - other organisms are fast to reproduce, but have short lives-

  -short lived organisms live in constantly changing worlds-

  -long lived organisms live in stable worlds-

  -unpopulated areas see fast growth-

  -densely populated areas see slow growth-

 -Environmental limits to population growth-

  -limiting factors regulate the size of a population-

  -density dependent factors-  include disease, competition, food and parasites-

   -disease goes faster through tighly packed areas-

  -density independent factors- includes natural disasters mainly-

 -Organisms interactions limit population size-

  -predations affects population size-

  -when kills > births, population size decreases-

  -predator-prey relationships seem to flucuate over time-

  -when population #'s are low, resources are plentiful-

  -when population #'s are large, resources are scarse-

   -some organisms may kill each other for food, or some may die of starvation-

 -The Effects of crowding and stress-

  -disease spreads quicker the tighly packed areas-