2007-08-22 19:12:54 · 8 answers · asked by kt 1 in Science & Mathematics ➔ Zoology
Animals are technically defined as any multicellular eukaryote that consumes other organics as its source of energy. Among living animals, sponges are at the bottom of the evolutionary tree, and they originated about 1.2 billion years ago (+/-).
That said, single-celled eukaryotes (eukaryotes are non-bacteria if you will...) first evolved about 2.7 billion years ago (though the evidence for these is indirect). They aren't alive today, and since the evidence for them (sterols) is indirect, we know little about them other than that they were single celled and consumed other things through phagocytosis.
I hope this helps.
2007-08-23 01:32:11 · answer #1 · answered by Dr. Evol 5 · 1⤊ 0⤋
Who? Fish and birds on the 5th day of Creation
2007-08-23 02:18:56 · answer #2 · answered by Anonymous · 2⤊ 1⤋
Uhhh...Jebus? That or aliens came and deposited single-cell organisms on Earth
2007-08-23 02:20:28 · answer #3 · answered by ? 4 · 0⤊ 1⤋
Itty-bitty-tiny thing of a cell or two that could move a bit unlike a plant the same size.
2007-08-23 02:19:26 · answer #4 · answered by Mike1942f 7 · 1⤊ 3⤋
Not an animal it was an organism (cells) called Algie, they produce Oxygen.
2007-08-23 02:15:26 · answer #5 · answered by Anonymous · 1⤊ 3⤋
The creatures of the sea (Fish)
IT WAS NOT THE SNAKE
2007-08-23 02:19:07 · answer #6 · answered by 7 Habits 3 · 2⤊ 1⤋
amphibian
2007-08-23 06:32:00 · answer #7 · answered by surendra 1 · 0⤊ 1⤋
paramecium (unicellular organisms?)
2007-08-23 02:20:27 · answer #8 · answered by Mars 4 · 1⤊ 2⤋