Lecture 4: Biodiversity
How many species are there?
• 18.7 million.
• 1.2 million species of eukaryote identified.
• Many more species that have not been described than those that have.
Most recent common ancestor (MRCA) for a given group(s), given a phylogenetic tree:
• Only one LUCA.
• Many MRCAs.
• MRCAis only 3000 years old.
Why the idea that “humans are descended from chimps” is inaccurate:
• Chimps and Bonobos are our closest living relatives.
• We are not descended from chimps (not our ancestors...more like cousins).
Order of main branching events in tree of life (dates not testable):
3. Orangutans (Asian GreatApe)
5. Old World & New World Monkeys
7. Lemurs & Lorises
***End- Cretaceous mass extinction, 65 million years ago***: about 50% of the species on earth
8. Rodents & Rabbits 2000 rodent species 9. Laurasiatheres (hippos, hoofed mammals)
10.Marsupials *(kangaroo, koala etc.)
11.Monotremes (platypus, echidna, po