Introduction to Ecosystems APES 1.1 Introduction to Ecosystems

The Niche Describes an organisms use of resources and functional role in a community. Includes: Habitat Food eaten Reproduction (how and when) Interactions with other organisms Example: A large part of a spider’s niche is to prey on food that is caught in its web.

The Niche The Niche can be affected by an organism’s tolerance It’s ability to survive and reproduce under changing environmental conditions. Specialist: very restricted tolerance range Ex: Giant Panda, Koala Generalist: Wide tolerance range, can live in a wide variety of places with a wide variety of resources Ex. Rat, mouse, cockroach

The Nice Organisms with similar roles in the environment compete when they seek the same limited resources. Competitive Exclusion can occur in rare cases when one species can entirely exclude another from using the resources.

The Niche Fundamental Niche: When a species fulfills all its roles and uses all of the resources possible. Realized Nice: Resources and roles fulfilled by a species competing with other species (adjusted)

Resource Partitioning: When species divide (partition) the resource they use in common by specializing in different ways. Ex: One bird may eat in the morning while one eats at night. Or, types of food they eat from the same resource. The Niche

Competition Species Interactions When organisms of the same or different species attempt to use a limited resource in the same place at the same time. Ex: Lions and hyenas compete for the same prey such as zebras Ram Fight

Predation Species Interactions One organism (the predator) captures and feeds on another organism (the prey)

Species Interaction Predation can cause cycles in predatory and prey population sizes. Why?

Species Interactions Predation & Evolution Likewise, individuals predators that are better at hunting will likely be more successful than less skilled hunters so natural selection leads to evolution of characteristics that enable predators to be better hunters Prey that are better at defending themselves will be more successful and pass these traits onto their offspring.

Symbiosis Species Interactions A close relationship between two different species. Parasitism Mutualism commensalism

Parasitism Species Interactions One organism benefits at the expense of another the other is harmed

Mutualism Species Interactions Both organisms benefit from the relationship

Commensalism Species Interactions One organism is benefiting and the other is neither harmed nor benefited