When designing an organism living on another planet, on Earth in a distant future or in an alternative timeline, it's important that each of its characteristics is well-adapted to the environment it lives in, without resorting to simply remake a living analogue, or throw in unlikely features for the sake of esthetics. Still, the ways real life forms survive, move, process energy and reproduce do offer excellent starting points: let's see, function by function, how an imaginary organism might work.
See main article: Speculative biomechanics
This article concerns the shape of speculative organisms, their body structure and organization, the way they mantain them and the way they move.
See main article: Speculative bioenergetics
This article concerns how organisms extract energy from the environment and how they store and use this energy.
See main article: Perception
This article concerns how organisms perceive the environment around them.
Offense and defense
See main article: Offense and defense
This article concerns how organisms can attack and kill other organisms or prevent being attacked and killed by them.
See main article: Reproduction
This article concerns the means by which organisms produce copies of themselves, perpetuating their genes.
See main article: Behaviour
Also see: Intelligence
This article concerns how organisms behave, react to the environment or work together to survive.