Biology 1001A Lecture Notes - Lecture 18: Distant Relatives, Odd-Toed Ungulate, Pedigree Collapse

• School: Western University
• Department: Biology
• Course: Biology 1001A
• Professor: Scott Mac Dougall- Shackleton

Document Summary

Most recent common ancestor (mrca) for a given group(s), given a phylogenetic tree. Co(cid:373)(cid:373)o(cid:374) a(cid:374)(cid:272)estr(cid:455) (cid:449)as the (cid:373)ai(cid:374) poi(cid:374)t i(cid:374) dar(cid:449)i(cid:374)"s origins. All cellular life has the same genetic code and can be traced back to find that there is a point at which we all shared a common ancestor (bacteria, archaea, eukarya). This is called luca- last universal common ancestor for a group of organisms. This shows the degree of relatedness (eg. humans and bacteria are not closely related as you have to go back far for the mrca). Branching points on the tree called (cid:862)re(cid:374)dez(cid:448)ous(cid:863) poi(cid:374)ts. Wh(cid:455) the idea that (cid:862)hu(cid:373)a(cid:374)s are des(cid:272)e(cid:374)ded fro(cid:373) (cid:272)hi(cid:373)ps(cid:863) is i(cid:374)a(cid:272)(cid:272)urate. Our most recent common ancestor was not human but not chimp either. Why some traditional groupings of orga(cid:374)is(cid:373)s (cid:894)(cid:862)reptiles(cid:863), (cid:862)fish(cid:863)(cid:895) do (cid:374)ot refle(cid:272)t evolutionary relationships. Therefore, the group (cid:862)(cid:373)o(cid:374)ke(cid:455)s(cid:863) does (cid:374)ot represe(cid:374)t e(cid:448)olutio(cid:374)ar(cid:455) relatio(cid:374)ships. ~18000 new species of life discovered each year.