APES 1: Organism Interactions & Feedback

4 ways organisms interact

• competition
  • compete for available resources (food, mating partners, etc.)
  • occurs between both the same and different kinds of organisms
• predation
  • hunt and kill other organisms to supply their energy needs
  • occurs between different kinds of organisms,
• cooperation
  • live together and help each other
  • occurs between the same kind of organisms
  • ex) herds, packs, colonies, families, etc.
• symbiosis
  • live in close association with another kind of organism
  • occurs between different kinds of organisms,

resource

• anything needed by an organism for life
• ex) nutrients, water, light, space

limiting factor

• a nutrient in short supply or one that cycles slowly
• this LIMITS the growth of the population

symbiosis

• %%mutualism%%
  • a relationship where both organisms benefits
  • ex) insects transfer pollen between plants as they gather nectar for food
• commensalism
  • a relationship where one organism benefits; the other is neither harmed nor helped
  • hermit crabs make homes in shells abandoned by snails
• ==parasitism==
  • a relationship where one organism benefits; and the other is harmed in some way
  • ex) ticks feed on dog’s blood

feedback

• any process that increases or decreases a change to the system

feedback loop

• a feedback process where an output of matter, energy, or information is fed back into the system as an input and leads to changes in that system

positive feedback loop

• causes systems to change further in the same direction
• increases change to a system
• ex) melting of a polar ice cap, increased erosion due to decreasing vegetation

negative feedback loop

• causes systems to change in the opposite direction
• decreases change to a system
• ex) reproduction, overgrazing, less reproduction