ge 15 - community ecology

• Habitat


  All of the biotic and abiotic factors in the area where an organism lives
• Lemurs


  • Spend most of their time in trees, with the exception of the ringtail lemur
  • Active during the day
  • Live in groups

  
• Niche


  The unique position occupied by a species, both in terms of its physical use of its environment and its function in an ecological community
• Beavers


  • Live in riparian systems
  • Keep these systems healthy and in good repair
  • Cut down trees to maintain a reliable pool of water for many species
  • Create a small wetland
  • Clearing out trees allows young trees to grow
  • Their lower branches give easier access to many species
• Aspects of a species' niche


  • Food
  • Abiotic conditions
  • Behavior
• Aye Aye


  • Omnivorous, eats grubs, fruit, leaves, nectar, and fungi
  • Lives in Madagascar, preferring canopy of the tropical rainforest
  • Nocturnal, mostly solitary, though their home ranges often overlap
  • Dedicated mothers, will play 'peek-a-boo' with their babies
• Fundamental niche


  The entire range of conditions where an organism or species can survive
• Realized niche


  The actual niche a species occupies
• Competitive exclusion


  • Competition between two species that use the same niche
  • When resources are scarce--someone has to die or move on
  • No two species can occupy the same niche
• Symbiosis


  The relationship between different species living in close association with one another
• Types of symbiosis


  • Predation
  • Parasitism
  • Competition
  • Mutualism
  • Commensalism
• Predation


  • When one organism hunts and kills another organism for food
  • Predator captures, kills, and consumes another individual
  • Prey is the individual that is killed
• Adaptations for predators


  • Rattlesnakes have acute smelling and heat-sensitive pits
  • Spiders build webs
  • Carnivores have sharp teeth
  • Tigers have striped camouflaged coat
• Adaptations for animal prey


  • Poisonous and warn predators with bright colors
  • Mimicry: a harmless species resembles a poisonous or distasteful one
  • Stay in herds; run away
  • Camouflage
• Adaptations of plants


  • Physical defenses (sharp thorns, spines, sticky hairs, tough leaves)
  • Chemical defenses (secondary compounds that can be irritating, bad-tasting, or toxic)
• Parasitism


  • One organism is harmed (the host) while the other organism benefits (the parasite)
  • Usually does not result in death
  • Two types: ectoparasites (external) and endoparasites (internal)
• Competition


  • Results from fundamental niche overlap
  • Two or more species use the same limited resource
  • Competitive exclusion: one species is eliminated from a community
  • Interspecific competition occurs when two different species compete for a limited resource
  • Intraspecific competition is when members of the same species compete for limited resource
• Competition


  • Bear vs. Bald Eagle
• Resource partitioning


  A pattern of resource use in which species reduce their use of shared resources
• Character displacement


  Evolution of anatomical differences that reduce competition between similar species
• Ecological equivalents


  • Poison Dart Frog of South America and Mantella Frog of Madagascar
• Mutualism


  Cooperative relationship in which both species derive some benefit
• Mutualism


  • Acacias provide shelter and nectar for ants, ants protect the plant
  • Bees pollinate plants and get pollen and nectar
• Commensalism


  Interaction in which one species benefits; the other is neither helped nor harmed
• Commensalism


  • Cattle Egret feeds on prey disturbed by grazing animals
• Species richness


  The number of species a community contains
• Species diversity


  An index combining the number and relative abundance of different species in a community
• Interactions between organisms and the number of species in an ecosystems add to the resiliency of an ecosystem
• Patterns of species richness

  Species richness varies with latitude, with more species closer to the equator
• Species-area effect


  Larger areas usually contain more species than smaller areas
• Species interactions promoting richness


  • Predators can prevent competitive exclusion among their prey
• Keystone species


  A species that is critical to an ecosystem, affecting the survival and number of many other organisms
• Keystone species


  • Grizzly bears in salmon-bearing rivers
• Community stability


  How a community responds to a disturbance
• Species richness improves a community's stability
• Succession


  The gradual, sequential re-growth of species in an area
• Types of succession


  • Primary succession
  • Secondary succession
• Pioneer species


  The first species to colonize a new habitat, tend to be small, fast-growing, and fast-reproducing
• Primary succession


  Development of a community in an area that has not previously supported life, proceeds slowly due to lack of soil
• Secondary succession


  Occurs where an existing community has been cleared by a disturbance, but the soil has been left intact