Unit 8 AP BIO: Ecology

KEY IDEAS: keystone species, idea of increasing fitness, competitive exclusion principle


  • Behavior might be linked to changing seasons (migration) changes, darkness, light, circadian rhythms, lunar cycles

  • Animals communicate using visual, chemical, tactile, and auditory signals

  • Cooperative behaviors = increases fitness 

    • Kin Selection: organisms are more likely to perform an altruistic (selfless) behavior for organisms that are their close relatives

  • Endothermic: generate heat by metabolism, have basal metabolic rate

  • Ectothermic animals gain heat from external sources such as sun, have standard metabolic rate

    • Aggregation = crowding with other individuals

  • Metabolic rate is the amount of energy an animal uses in a unit of time; determined by:

    • animal’s heat loss

    • amount of oxygen consumed or carbon dioxide produced

  • Reproductive diapause = temporary suspension of development/reproduction during environmentally unfavorable conditions

  • Chemosynthesis captures energy in the form of small inorganic molecules

  • Cycles: water, carbon, nitrogen, phosphorus, sulfur 

  • Density-dependent factors: produced due to increased population density, biotic

    • Competition, stress, toxic wastes, disease

  • Density-independent factors: abiotic

    • natural disasters, pollution, temperature changes, nutrient availability 

  • Simpson’s Diversity Index calculates ecosystem’s diversity, accounts for number of species and relative abundance (proportions of different populations in community)

    • A value of 1 = infinite diversity and a value of 0 = no diversity

    • More ecosystem diversity = more resilient 

  • commensalism = one benefits and the other has no change

  • mutualism = both benefited 

  • Parasitism = one benefits at expense and harm of the other

  • competitive exclusion principle = two species competing for the same, limited resource, cannot coexist in the same place

    • resource partitioning

  • Keystone species = typically small population with large effect on ecosystem, without them it may collapse