mammals

1. Blue whale.


http://en.wikipedia.org/wiki/Blue_Whale

2. No idea! Not sure if there ARE mammals anywhere else in the universe, just for starters!

3. Just lucky, I guess.

4. Since the blue whale is a baleen whale, and therefore its diet mainly consists of tiny krill, and plankton, it is very unlikely any of its prey could hurt it.

I think blue whales have been found bearing the scars of giant squid attack, I would imagine these might sometimes prey upon them.

Sharks and orcas might be able to prey on young, injured, or very weak blue whales, I would think.

I think we can say with a high degree of certainty (based on our understanding of evolution and genetics) that there are no other mammals in the Universe, and there never will be, unless the genetic line is exported (or has been exported) from Earth where they obviously evolved.

I thought about that....but some form of spine, internal nurturing of young for a bit, warm bloodedness, exuding stuff to feed young, and some form of fur seem not impossible to co-evolve on different planets.

I agree

Not likely for there to be mammals per se, but mammal like species? I think it's very possible on an earth-like planet elsewhere in the universe.

While I don't believe life can only exist on an earth-like planet, obviously earth-like life can only exist on an earth-like planet.

There aren't an infinite number of forms life can take on an earth-like planet.

Physical factors like gravity, atmospheric chemistry, temperature ranges etc frame the possibilities for life forms, and it's likely that within an earth-like frame, earth-like species will evolve.

Life forms that might exist on a gas giant planet (jupiter-like), are never going to be found on an earth-like planet, and visa versa.

Early speculation on extraterrestrial life was certainly earth centric, but the next wave of thinking on the subject was too determined to exclude the possibility of terrestrial-like life forms.

No reason I can think of why there might not be millions of earth-like species populating a near infinite universe.

That's true, with enough planets, virtually anything could be possible.

However, the entire mammalian line started with mammal-like reptiles back before the dinosaurs even got started and in all that evolutionary time, no other line of creatures ever became even remotely mammal "like".

If those first mammal-like reptiles had been eliminated, it seems that nothing even remotely like a mammal would exist on this planet today.

And while it's possible that existence of mammals filled a niche which prevented any other lines from becoming mammal-like, it's also possible that the range of potential morphology is simply so vast that almost everything that ever develops is virtually unique.

The first microbe we ever discover off-planet (*IF* we ever find one) is going to tell us a lot about the potential range of variation of life, especially if it's not even based on DNA.

Fun to speculate, though, eh?

Mammals have been pretty successful here...so I guess the design has some promise.

Though without that asteroid....

Yes indeed.