In depth analysis on how to make creatures and their evolutionary lines

School has me bored and I watched Avatar (Blue people) the other day, so I'm going to do a "seminar" of sorts on how to write/create realistic though still bizarre fantastical creatures. If you want to pitch in some ideas or ask any questions, go ahead, this is entirely open. I ALSO think it's entirely ok to make magical creatures with magical origins (Like in Harry Potter), as well as creatures never observed by science (Like how star wars has Silicone based organisms) , as long as they're not TOO out there (Although sometimes "out there" is the best choice, like in Adventure Time, one of my favorite cartoons in history). I will be going over all of these things over the course of possibly a few weeks/months, or I might give up on it halfway through, who knows. Have fun making creatures!

So first, we start with the basics, what are your origins of life? Are we doing primordial soup or magical/divine intervention? A little of both? Let's go over these and some examples of them. Let's start with the primordial soup. It is a well recorded and accepted theory that life on earth sprouted from molecular (mostly carbon, hydrogen, nitrogen, and oxygen) components floating in water that combined to form nucleic acids, which then in turn joined together to create a living system. Now, for your story, if it's going to be realistic fiction or sci fi, you'll have to go in depth into thought on how these systems formed and survived and created energy, if you want to form a cohesive family of creatures or evolutionary line. You will have to go step by step. The first step would be to ask yourself, how would each different organism type produce energy, autotrophically or heterotrophically, meaning on it's own, or by consuming other creatures. Autotrophs have two forms of producing energy, through chemicals or through sunlight (Chemosynthesis vs. Photosynthesis), while Heterotrophs have many, though we generally use the term primary and secondary consumers, primary being those that consume autotrophs and secondary being those that consume other heterotrophs. For my example, my first species will be autotrophs, chemotrophs to be exact, and I'll call them Chemospheres. They're small spheres formed by many different microorganisms clumped together, they float above underwater volcanoes to collect the chemicals that rise up from it, such as phosphorus.

Heterotrophs are harder to make, because they require movement, even from their earliest stage, so you have to start with a base body, and continue with limbs, forms of consumption and forms of respiration. My first heterotrophic creature will be call the Yelenapod (meaning yelena footed as a tribute to Yelena Belova, my fav Marvel character). It has six underdeveloped limbs on it's elliptical narrow body, four of the limbs, placed at it's sides are used for paddling and walking on the ocean floor while the other two, placed at the back, are for steering. It has no eyes yet. It has a large gaping mouth at the front bottom of it's base (the pseudo-head), which it uses to suck in Chemospheres, as well as to take in water to breath (oxygen) which it releases from a small hole on it's near rear. Now that I have a primary heterotroph, the other heterotrophs (Both primary and secondary) have to evolve from this simple build, while the rest of the autotrophs will evolve from my primary autotroph.

They're both entirely microscopic, so they have a long process to go.

https://docs.google.com/drawings/d/17EdHuVDucmTDqOuW-CrCihTtQJlz97h0rnitc5wCBpA/edit?usp=sharing
Rough diagram of Yelenapod and Chemosphere

From the Yelenapod, we can assume that the basal heterotroph form will most likely have 6 legs/limbs. Unless during the pre-skeletal phase, those legs seperate into more legs. This will not happen after forming a skeletal structure, though it CAN lose legs after forming a skeleton, like how whales have lost their back limbs through evolution (we know this due to their vestigial thigh bones). Eventually, the Yelenapod will seperate into many different creatures, macropredators and microorganisms alike, as all heterotrophs will be related to this ancient ancestor.

(Following and taking notes, I hope you continue to add to this! ^^)

(I will! I'm glad people are reading this~ I feel learning about creatures from different world's are so interesting)

(I agree!!)

From the Yelenapod, we can assume that the basal heterotroph form will most likely have 6 legs/limbs. Unless during the pre-skeletal phase, those legs seperate into more legs. This will not happen after forming a skeletal structure, though it CAN lose legs after forming a skeleton, like how whales have lost their back limbs through evolution (we know this due to their vestigial thigh bones). Eventually, the Yelenapod will seperate into many different creatures, macropredators and microorganisms alike, as all heterotrophs will be related to this ancient ancestor.

Remember that you don't have to mention any of this "background" in your story, but there SHOULD be similarities in your creatures, especially macro-heterotrophs. Like how a Rhino and a Lion share a front facing mouth, four limbs, two eyes, a tail, eyes above the mouth, a nose above the mouth, and many other features, even though ultimately they look distinct. Even a lungfish and a human (who are both distantly related tetrapods) share MANY features. Realistically, an 18 legged macropredator with 15 eyes can't have a (close) common ancestor with a 2 legged herbivore with no eyes. It's implausible, though, it would be feasible in a magical setting.

You may also use a realistic but rarely or never before seen trait in your fictional universe, such as bitrophy, which is a creature that uses both autotrophy and heterotrophy to produce energy. There are very few examples of this in the real world, some being Carnivorous plants like the Venus Flytrap, and others being animals that photosynthesize like the Green Sea Slug. Another one of these "plausible but rare or unseen" examples are plants that move by their own will. One such fictional example being the Knobby White Spider from Star Wars, which is actually a plant that migrates from place to place to plant it's roots and lay "eggs" (which are actually just seeds). The movie avatar also uses a "plausible" method of nature, which is the connection between different species neural pathways to influence and create relations between one another, which could be plausible in an alien species (though not on earth. At least not for another billion years).

Now, after we establish the basic common factors in ur species, we gotta continue the evolutionary pattern, which animals take which niches. To do this, we first have to establish our autotrophs' evolutionary pattern. They will always take the lowest position on the food web, meaning they are the base of most other creatures evolutionary patterns. I'll say some Chemospheres adapt to an environment near the surface of the water, where they eat the chemicals in the air, and they evolve into a flatter bigger form to have as much surface area as possible to consume, lets call them Chemoplanas . This leads to some Yelenapods travelling to the surface of the water to eat those chemoplanas, but because their mouth are on their bottoms, they can;t eat them, so some of them evolve to have top mouths, and to swim to the surface, they develop fins rather than pods. Let's call this new species Pinnatheria (Pinnatheres meaning finned beasts). Because of their time on the surface actually searching for food, their nerves on their heads develop light sensors, forming primitive eyes. They have five of these, two on either side of their head and one on the top center.

https://docs.google.com/drawings/d/1PrxvGXjUNVn9_4VVEC8BMUaFVyHM6qKFk5FKE1Ig9wk/edit?usp=sharing
A rough diagram of the Chemoplanas and the Pinnatheres

(I love this sort of thing, I kind of throw it out the window in my fantasy stuff but the science behind biology and evolution is always so fascinating! Your analysis is excellent and very interesting to read through!)

(Thanks! I'm glad you like it!)

So from here, we can assume that throughout the years these creatures and autotrophs adapt to terrestrial forms of living, in which the descendants of the Chemoplanas would take different niches, such as seeding plants, bacteria and fungi-like niches. The descendants of the Yelenapod and the Pinnatheres would definitely take a lot more njches though. One such niche is the predator. Due to the Pinnathere's increased senses, size and mobility, we can assume that some predator niches would be filled by their descendants, probably beginning with feeding on the smaller Yelenapods and other creatures. Yelenapods would possibly also become carnivores, but mostly scavenging or deep sea hunting. I'm going to make it so that Yelenapods and their descendants never leave the oceans, but Pinnatheres will, having them colonize the planet.

Now let's assume that some herbivorous, omnivorous and carnivorous pinnatheres eventually colonize the terrestrial part of the planet, they would evolve into different niches, forests, tundras, deserts, savannas, jungles and more. I'm going to make my story set in the desert of this foreign planet, where human scientists landed in the year 15017, so they could study wildlife in foreign planets (like Avatar hehe). In this desert biome there are 6 major niches, large herbivores, small herbivores, flying carnivores, small carnivores, small omnivores and pseudo-insects. There will be a few species filling out these niches, competing with each other for food and containing a lot of genetic diversity. Over the course of this week and the next I'll be doing a full summary of each species and which specific niche they fill.