BILD 3 Chapter Notes - Chapter 27: Body Plan, Lophotrochozoa, Eumetazoa
30 May 2016
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Current evidence indicates that animals evolved from single-celled eukaryotes similar to present- day choanoflagellates. Biologists have named more than 1. 3 million species, and estimates of the actual number run far higher - nearly 8 million species according to one recent study. Researches have unearthed 710 million year old sediments containing the fossilized remains of steroids that today are primarily produced by a particular group of sponges. Suggests that animals had arisen by 710 million years ago. One recent molecular clock study estimated that sponges originated about 700 million years ago. Also consistent with molecular analyses suggesting that the common ancestor of all extant animal species lived about 770 million years ago. The first generally accepted macroscopic fossils of animals date from about 560 million years ago. First discovered from the ediacara hills of australia. Filter out food particles suspended in the water as they draw it through their body.
