Biology 1001A Lecture Notes - Lecture 9: Polyphyly, Tetrapod, Mosaic Evolution

• School: Western University
• Department: Biology
• Course: Biology 1001A
• Professor: Tom Haffie

Document Summary

Reasons why the fossil record is incomplete: be(cid:272)ause there (cid:449)as a(cid:374) (cid:862)e(cid:454)plosio(cid:374)(cid:863) i(cid:374) the di(cid:448)ersit(cid:455) of groups of a(cid:374) orga(cid:374)is(cid:373), a(cid:271)out 600 mya, this marked the beginning of the cambrian. It is often difficult to assign some of these fossil animals to any living group: two other explosions have occurred, land plants in the devonian period, flowering plants in the cretaceous. Importance of animal skeletons to the fossil record: the development of skeletons increases the abundance of the fossils since hard tissues are subject to mineral fossilization subject to mineral fossilization whereas soft tissues are fossilized as moulds. 1. 2 million species that we have already discovered -> eukaryotes. There are about 8. 7 million species in total, therefore we only know about 10% of the eukaryote species on earth: all life on earth is related to all other life on earth is what darwin believed. By 30 generationgs, 230 ancestors (> 1 billion)