1. Interactions Between Organisms

2. Predator/Prey Relationships:
Predation, or the act of one organism killing another for food, is very common throughout ecosystems.
ex.—Lions eat zebras, spiders eat flies and other insects, etc.

3. Symbiotic Relationships:
Symbiosis is where two or more species live together in a close, long-term relationship or association.
Symbiotic relationships can be beneficial or harmful, may not affect one of the organisms at all.

4. Types of Symbiotic Relationships:
Mutualism benefits both organisms.
ex.—Flowers and their pollinators—the flower gets fertilized and the insect receives nectar.
Commensalism benefits one organism while the other is unaffected.
ex.—Clown fish and anemones—the anemone protects the clownfish, while it is unaffected by Nemo’s presence.
Parasitism benefits one species, while the other is harmed.
ex.—A tick feeding of the blood of a dog.

5. Regardless of the ecosystem, competition for resources such as food, space, water, nutrients, etc. is ever present.
The carrying capacity, of a species in an ecosystem is the population size of the species that the environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment.
These limiting factors determine the amount of organisms that can live in an ecosystem.