What Is Symbiosis?

Symbiosis is the "long-term living together of unlike organisms". Here we explore how symbiotic relationships evolve over time.

Subjects: Biology, Evolution


People often associate symbiosis with mutualism – the cooperation of 2 species which enhance the survival and reproduction of each other. In reality, the term “Symbiosis” is classically defined as the “Long-term living together of unlike organisms”. Symbiosis encompasses an entire continuum of relationships from mutualism to parasitism.

As animals evolve and adapt to each other’s presence, their relationships can shift along the symbiotic continuum, even turning enemies into allies.

This animation explores the symbiotic relationships between a variety of organisms including squirrels and oak trees, opossums and ticks, and your own relationship with bacteria in your gut!

Our understanding of the evolution of symbiosis is helping researchers discover how parasites spread and what can be done to make them less harmful to their hosts.

Explore Further

Video lecture by Jon Perry on his second channel, Stated Casually, where he goes over the research that this animation was based on in much greater detail:

Scientific papers on interactions between plants and seed predators:

Scientific paper on interactions between ticks and opossums:

Scientific paper on the evolution of aggressiveness in cholera strains:

TED talk on the evolution of aggressiveness in cholera strains


Our videos benefit from guidance and advice provided by experts in science and education. This animation is the result of collaboration between the following scientists, educators, and our team of creatives.

  • Jon Perry
  • Anthony Danzl
  • Jordan Collver
  • Johana Revel, PhD


Squirrels Vs Trees: Evolutionary Arms Race
Ticks and Opossums
Cholera Evolve Toward Commensalism