Here is an example of how @Buckly’s method of dealing with organs can look in game.
DIGESTIVE SYSTEMS
As Buckly suggests, a player will be able to create a digestive system by adding organs to their creature’s metaballs. The player must first place a gastrointestinal tube on a metaball.
Once this gastrointestinal tube is placed, the player will then be able to place more advanced digestive organs on their gastrointestinal tube, and otherwise modify their tube, to make a more advanced digestive system. More advanced organs require the basal digestive tube to be evolved first.
Incomplete Digestive System
Incomplete digestive systems only have one hole through which food goes through and waste is excreted from. It is referred to as an “incomplete” digestive system because the gastrointestinal tube doesn’t go all the way through the organism into an anal opening.
Incomplete digestive systems are found in most diploblastic organisms, such as jellyfish, and the most simple triploblastic organisms, such as flatworms.
Pros
- Simple. Requires relatively less energy/resources, so is good enough for simple and low-energy lifeforms.
- Easier to Circulate Resources. Incomplete digestive resources can also serve roles similar to the circulatory system, which makes the secondary system not as necessary. This is also due to the relative simplicity of organisms with incomplete digestive systems, however.
Cons
- Limited Storage Capabilities. Because both food and waste are released through the same hole, organisms can’t really afford to mix the two. This requires a more constant input of food.
- Weak Waste Management. Organisms with incomplete digestive systems oftentimes need to get rid of undigested food due to a buildup of waste, reducing efficiency of the digestive system as a whole.
Complete Digestive System
Complete digestive systems have both a mouth and an anal opening. The gastrointestinal tube runs completely throughout the entire organism, allowing enhanced compartmentalization and specialization within the digestive system.
Complete digestive systems are found in most triploblastic organisms, such as the arthropods, vertebrates, and molluscs
Pros
- Efficient. Because waste and food are processed well separately in complete digestive systems, more nutrients are absorbed.
- Allows Greater Specialization. Advanced organs, such as intestines and stomach cavities, now make sense to evolve, as food can now be stored separately from waste. More storage and digestive versatility can be applied to an organism.
Cons
- Less Circulatory Capabilities. Although partially due to the advanced nature of most organisms which have complete digestive systems, complete digestive systems require a more well-developed circulatory system to pick up the slack.
- More Resource Intensive. With greater specialization comes more tasks to fuel. Complete digestive systems usually need greater amounts of energy to maintain, although they can atleast store food more efficiently for future consumption.
In Thrive
In Thrive, a digestive system is incomplete if a player doesn’t extend their digestive tract completely through the organism. An incomplete system will have somewhat bumped circulation stats, but will have limited digestion stats due to its inefficiency. Players will have to spend the MP needed to get their gastrointestinal tube completely throughout their entire organism to have a complete digestive system.
A complete digestive system can be unlocked in Thrive when a player spends the MP needed to fully extend their gastrointestinal tube throughout the entire organism, resulting in an anal opening. Digestion will be bumped significantly, while circulation will be slightly reduced, incentivizing the development of a circulatory system.
A complete digestive system will also allow the player to develop more advanced digestive organs, opening up more parts that will allow broader diets and greater storage.