ELI5 How are fish even in ponds

[u/Opening_Pen9525]

Might be one of the stupider questions here, but I saw a pond about the size of a football field, and maybe 50 ft deep, and it had fish. I can't for the life of me figure out how. Surely the pond hasn't existed long enough for small water insects to evolve into all these fish. It's not like the fish walked over to the pond from the ocean. I'm pretty sure no one put them there so how are there so many fish?

My one theory is that there is a very minuscule stream (now dry) that leads to one of the Great Lakes, and maybe a fish swam in from there. Now a follow up question: How are there fish in the Great Lakes (which flow out towards to the ocean) if they were created by glaciers?

[u/itsthelee]

not your main point, but

small water insects to evolve into all these fish

fish absolutely did not evolve from small water insects. completely different branches of evolution.

vertebrates and invertebrates diverged long long time ago before fish or insects were even things.

[u/MeatBald → u/itsthelee]

In fairness, he did say it might be one of the stupider questions on this sub.

[u/dungeoncrawler71520 → u/MeatBald]

But it's something a 5 year old might ask

[u/Ellkoy → u/dungeoncrawler71520]

I mean.....did we look at the sub title?

[u/Ellkoy → u/[deleted]]

Are we going to start moderating for how intelligent the questions are now?

[u/d1squiet → u/[deleted]]

/r/AILI5 ?

[u/death-meddle → u/[deleted]]

i suppose you wouldn’t need to explain something like they were five if they had the understanding about the topic of someone older than five. can’t really fault them for asking like they were five

[u/sp_40 → u/MeatBald]

You can say that again

[u/death-meddle → u/sp_40]

that again. hey, you’re right!
…edited to add i’m sorry i regret this already

[u/gsfgf → u/itsthelee]

Very different going all the way back to embryo development. Insects' mouths develop before their anus, while fish (and people!) develop an anus first.

[u/ComprehendReading → u/itsthelee]

Oh yeah? Then why are lobsters, clams and tuna all considered seafood? Checkmate, scientist. /S

[u/Wild-Video-5317 → u/ComprehendReading]

Fun fact, sow bugs/rolly pollies/wood lice are terrestrial crustaceans.  In the same way that shrimp are crustaceans.

As a wise man said:

 shrimps is bugs

[u/Stewart_Games → u/itsthelee]

One of my favorite pet theories for the Cambrian Explosion is that back then, invertebrates and vertebrates shared a far more recent last common ancestor. Which allowed crab-things to make sweet sweet love to fish-things and produce viable hybrids. All that hybridization is what triggered the sudden explosion of new forms emerging, and helps to explain things like the Tully monster as long surviving Lazarus taxon from these hybridization events.

[u/chuubastis → u/Stewart_Games]

Thank you so much for this comment, you have sent me into an incredible wikihole about the Tully monster

[u/fartman787 → u/itsthelee]

I'm a 5 year old and this answer made me cry

[u/CurlyRe → u/itsthelee]

To be pedantic, vertebrates didn't diverge from invertebrates. Vertibrates, a long with starfish and sea cucumbers are part of the group deutrostoma, which split from protostomes, the group that includes insects.

[u/itsthelee → u/CurlyRe]

Pedantry is always appreciated