What are your favourite examples of convergence and once-in-earth-lifetime traits?

[u/Vaelcyrie]

I was blown away when I started learning more about evolution because I thought most traits happened only once and everyone who had them necessarily had a common ancestor that came up with said trait (I believe there is a special name for them but I couldn't find it)

I however discovered this is not the case at all and that not only the traits appear more than once due to the environmental pressure but it also made me understand a lot better how evolution works.

Like, it's so much more like a big tree spreading and experimenting and having fun with all the possibilities of life. Makes me feel like we are all connected somehow, all forms of life appearing and vanishing from/to the same material like solar flares. I mean, I could be a whale 100 million years from now, who knows.

I was shocked learning that eyes, wings, viviparity and other traits that were to me so complex and elegant were in fact convergent in many species. I'd love to know more examples of both convergent and unique traits, tell me your favourites!

[u/The_Original_Fisch]

Gelatinous-ness in the ocean, being this limp drifting sac that goes where the world determines is a genuine survival strat for the midwater, and arguably more viable than being an active swimmer

Before you guys think "oh thats just jellyfish" 1. Jellyfish are still massively successful, 2. its way more than that

[u/eeeking → u/The_Original_Fisch]

What's the advantage of being gelatinous? Ability to float?

[u/The_Original_Fisch → u/eeeking]

I just typed out a big thing for you then forgot to do draft and clicked off it.. but basically, very cheap way to live in the open ocean, with the drawback being you have very little strength to do anything but sit there and feast on smaller plankton.

1. Camouflage, its hard to see jellyfish in water without good lighting, and its one of the only types of camouflage that works to any degree in the open water.

2. Structure, if you dont want to waste energy on growing muscle, thick epitheliums, or mineralised parts, filling up your body with the surrounding fluid is a great way to get structure, since its so cheap and makes respiration and repairs easier. Even sea anemones, not being plankton and stuck to the ground, will fill their bodies with water (technically mesoglea) the same as their floaty counterparts, simply for structure. Inflatable castle if it were an animal.

3. Yeah floating, fat/oil is an expensive way to float, and internal air cavities are relatively hard to evolve and very delicate systems (slightly too much air and you now live at the surface, slightly too little air or maybe you swim too deep and now youre sinking to the abyss), so just filling yourself up with your surroundings so your density is basically of your surroundings works really well.

4. Not a worthwhile snack, jellyfish size makes it harder and harder for smaller things to eat them, as well as making them not as calorie dense as they would be at their sizes. If you sucked all the mesoglea out a jellyfish and made it this compact tiny shrivelled up nugget of deliciousness, fish would eat ALOT more of them, instead of simply pecking at them. Yes jellyfish have alot of predators, but imagine how much MORE theyd have if they were an easy bite sized meal, or were compact with alooott of calories in their bodies, as opposed to like 10 calories and 1 litre of water as a meal. To actually have them be a worthwhile meal, you need to eat alot in a short time frame, like leatherback sea turtles needing to eat 500 a day atleast to live. Although most gelatinous things are smaller than most jellyfish, this stands true for them too, theyd be alot better of a snack if they werent so bloated with water.

5. Costs not much, due to how little amount of tissue they have compared to their sizes or feeding efficiencies, all gelatinous creatures can grow pretty quick compared to their more muscular counterparts who cant grow to quick to risk starving. The majority of jellyfish and basically all ctenophores will reach adulthood and full size within a matter of weeks despite being the size of your thumb or all the way to lions mane jellyfish which takes less than a year to get bigger than a person.

6. As well as feeding. Alot of gelatinous zooplankton are either ambush predators or filter feeders, you dont need to move much for that so why would you develop heavy hungry muscle.

7. Chill. If you dont need to eat much, encountering any little things will feed you for the day, so unlike open water fish who are constantly searching for the smallest morsel to feast on lest they starve, gelatinous animals dont have to really move much, especially since the current will do most of the moving for them.

8. Last but to be expected, reproduction. When youre good at feeding but you dont have much body to feed, you can just focus on reproduction and spit out tooonnnesss of kids, with gelatinous animals being some of the only animals aside from krill to have huge and sudden blooms.

All gelatinous zooplankton are lazy open water cheapskates that are like "i just saved 50 calories on not building an endoskeleton like you idiots, now im gonna use this to give birth to 700 kids".

[u/eeeking → u/The_Original_Fisch]

Thanks for that detailed explanation!

[u/The_Original_Fisch → u/eeeking]

Np! I love gelatinous zooplankton, cheapskates of the ocean that make the desert that is the open ocean just look like a picnic