We have a small pond on our property. Most years it retains a small amount of water all year long. Last year, after an extended drought, it went dry. This year we had ample spring rains, and it filled with water again. However, we have had another extended dry spell, and the pond has gone dry again. Here is what the surface looks like:
As I wandered along the crunchy surface I saw something move. It was a small frog, and it jumped into one of the cracks in the mud.
It is a northern cricket frog.
I saw some tiny shells–fingernail clams, I think. Then I found two halves stuck tightly together. Is there a living organism inside?
Hard to tell.
I found some snail shells:
This seems to be in the family Physidae.
This appears to be a different species, but also likely in Physidae.
I have not worked through the aquatic snails yet (give me time!), so my ID skills leave something to be desired.
This snail seems to be in the family Planorbidae.
All of these organisms either survived in the dried up mud of the pond last year, or were able to repopulate the pond from another location this spring, based on their conditions and locations. How do they do it?
The roused bear 
A testament to the durability of wild creatures. That’s why when us humans are a footnote in the history of the earth there’ll be a pair of frogs somewhere saying to each other “Come on, we’ve got some repopulating to do”. I hope.