ECOSYS

• Community


  • Includes all organisms inhabiting a particular area
  • An assemblage of all the populations of organisms living close enough together for potential interaction
• Community structure


  • Species composition, number of species, relative abundance, feeding relationships
• Community dynamics


  • The variability or stability in the species composition of a community caused by biotic and abiotic factors
• Community ecology is necessary for: Conservation of endangered species, Management of wildlife, Controlling diseases such as malaria, Zika, and Lyme disease that are carried by animals, Agriculture application, By controlling the species composition of communities they have established
• Interspecific interactions


  Relationships with individuals of other species in the community that greatly affect population structure and dynamics
• Interspecific interactions classified according to the effect on the populations concerned

  • Helpful (+)
  • Harmful (-)
• Interspecific competition


  Occurs when populations of two different species compete for the same limited resource
• Interspecific competition


  • Desert plants competing for water
  • Squirrels and black bears competing for acorns in temperate broadleaf forest in autumn
  • Plants in tropical rainforest competing for sunlight
  • When acorn production is low, the nut is a limited resource for which squirrels and bears compete
• Predation


  Interactions in which one species exploits another species
• True predation


  One species (predator) kills and eats another species (prey)
• Herbivory


  Consumption of plant parts or algae by an animal
• True predators help control the size of prey populations, especially when a predator preys on just one species. Generally, the predator-prey relationship keeps the population size of both species in balance

  
• As the prey population increases


  The predator population starts to rise. With more predators, the prey population starts to decrease, which, in turn, causes the predator population to decline. This pattern keeps repeating. There is always a slight lag between changes in one population and changes in the other population
• Symbiosis


  Living together, any type of a close and long-term biological interaction between two different biological organisms
• Types of symbiotic relationships

  • Mutualism (both species benefit)
  • Commensalism (one species benefits while the other species is not affected)
  • Parasitism (one species (parasite) benefits while the other species (host) is harmed)
• Symbiotic relationships


  • Lichens (association of fungus and algae)
  • Barnacles attach themselves to whales to get a "free ride"
  • Intestinal worms
• Ecological niche


  The sum of its use of the biotic and abiotic resources in its environment
• Ecological niche of Virginia's warbler

  • Nest sites and nest building materials
  • Insects it eats
  • Climatic conditions (precipitation, temperature, humidity)
• Interspecific competition occurs when the niches of two populations overlap and both populations need a resource that is in short supply
• Ecologists can study the effects of competition by removing all the members of one species from a study site. When researchers removed either species, the remaining species was significantly more successful in raising their offspring. Interspecific competition has a direct effect on reproductive fitness. Competition lowers the carrying capacity for competing populations because the resources used by one population are not available to the other population
• Adaptations of predators and prey

  • Both predators and prey have adaptations to predations. Prey populations have numerous adaptations for predator avoidance that have evolved through natural selection
• Camouflage (disguise)


  One way is to blend in with the background. Another way is to look like a different, more dangerous animal
• Mimicry


  Using appearance to "mimic' another animal
• Camouflage and mimicry


  • The moth on the left mimics the owl on the right. The moth has markings on its wings that look like the eyes of an owl. When a predator comes near, the moth suddenly displays the markings, startling the predator and giving the moth time to fly away
• Mechanical defenses


  • Sharp quills of a porcupine or hard shells of clans and oysters. Animals usually have bright color pattern (yellow, orange, or red in combination with black) that predators learn to associate with undesirable consequences (noxious taste, painful sting) and avoid potential prey with similar markings
• Chemical defenses


  Toxins in plants that tend to be distasteful, and herbivores learn to avoid them
• Chemical defenses in plants

  • Strychnos toxifera (poison strychine)
  • Tobacco (nicotine)
  • Opium poppy (morphine)
  • Peyote cactus (mescaline)
  • Tannins (variety of plants)
  • Brussels and cabbage (sulfur compounds)
• The vegetables we eat are not toxic. The amount of chemicals in them has been reduced by crop breeders. Chemical companies have taken advantage of the poisonous properties of plants, such as chrysanthemum used to produce a pesticide called pyrethrin
• Coevolution


  A series of reciprocal evolutionary adaptations in two species. Occurs when a change in one species acts as a new selective force on another species, and the resulting adaptations of the second species in turn affect the selection of individuals in the first species
• Coevolution


  • The rough-skinned newt produces a strong toxin, and common garter snakes have evolved resistance to the toxin. This leads to an evolutionary "arms race" with newts evolving higher toxin levels and snakes evolving higher resistance
  • Passiflora produces toxic chemicals that protect its leaves, but Heliconius caterpillars have digestive enzymes that break down the toxins. Passiflora has evolved false egg spots on its leaves to deter Heliconius from laying eggs
• Trophic structure


  A pattern of feeding relationships consisting of several different levels
• Trophic levels


  • 1st Trophic Level: Producers (make their own food)
  • 2nd Trophic Level: Primary consumers (consume producers)
  • 3rd Trophic Level: Secondary consumers (consume primary consumers)
  • 4th Trophic Level: Tertiary consumers (consume secondary consumers)
• Food chain


  The sequence of food transfer up to the trophic levels. This transfer of food moves chemical nutrients and energy from organism up through the trophic levels in a community
• Components of a food chain

  • Producers (autotrophs)
  • Primary consumers (heterotrophs)
  • Secondary consumers (carnivores, insectivores)
  • Tertiary consumers
  • Quaternary consumers
  • Decomposers (prokaryotes and fungi)
  • Scavengers (large animals such as crows and vultures)
  • Detritivores (diet is made up primarily of decaying organic material)
• Food web


  A more realistic view of the trophic structure of a community. A network of interconnecting food chains
• Keystone species


  A species whose impact on its community is much larger than its abundance or total biological mass would indicate. Removal of a keystone species has a drastic effect on its prey population
• Keystone species


  • Some sea star species are keystone species in coral reef communities. If sea stars are removed, mussel and sea urchin populations would have explosive growth, driving out most other species and destroying the reef community
• Disturbances


  Events such as storms, fires, floods, droughts, or human activities that change biological communities by removing organisms from it or altering the availability of resources
• Ecological succession


  Occurs following a disturbance that creates unoccupied areas for colonization. The first colonizer species are called pioneer species, which change the environment and pave the way for other species to move in
• Primary succession


  Occurs in an area that has never been colonized before, such as bare rock from a volcanic eruption or glacier retreat