EE1/7/26 How species interact

Competition in Ecosystems

  • All organisms compete for food resources.

  • Competition can occur within a species or between different species.

    • Example: Two animals consuming the same plant are in direct competition.

    • Within a species, niches may overlap, leading to increased competition.

Predation

  • Defined as the relationship between a predator and its prey.

    • Predator: An organism that feeds on another organism.

    • Prey: The organism that is consumed by the predator.

  • Examples of predation:

    • Sharks eating fish.

    • Bats consuming insects.

    • Wolves preying on deer.

  • Changes in populations often mirror the predator-prey relationship:

    • Example: The relationship between snowshoe hares and lynx in the North.

    • Lynx are the predators; snowshoe hares are the prey.

    • Population dynamics observed:

      • When lynx populations are low, hare populations increase due to decreased predation.

      • Conversely, as lynx populations rise, hare populations decline as predation increases.

    • This creates cyclical population fluctuations over time.

Parasitism

  • A relationship that occurs between a parasite and its host.

    • Parasite: An organism that lives on or within another organism, feeding off it.

    • Host: The organism that provides nourishment to the parasite.

  • Key difference from predation: Parasites typically do not kill their hosts; they rely on them for survival.

  • Examples of parasites include:

    • Ticks

    • Fleas

    • Tapeworms

Mutualism

  • A close relationship between two species where both benefit from the interaction.

  • Notable examples include:

    • Bacteria in the human intestines:

    • Humans benefit by processing food and nutrients.

    • Bacteria benefit from the environment and nutrients available in the intestine.

    • Acacia trees and ants: Ants protect the tree from herbivores, while the tree provides shelter and food for the ants.

Commensalism

  • A relationship in which one species benefits while the other is neither helped nor harmed.

  • Example of commensalism:

    • Pilot fish swimming alongside a shark or sea turtle:

    • Pilot fish consume debris and parasites from the shark's skin.

    • The shark remains unaffected by the presence of the pilot fish.

Symbiosis and Coevolution

  • Symbiosis: A broad term for any close, long-term interaction between two different species. It includes:

    • Parasitism

    • Commensalism

    • Mutualism

  • Coevolution: The process by which two species evolve in response to changes in each other, often to maintain a successful symbiotic relationship.

  • Symbiotic relationships can promote or necessitate coevolution among species.