BIO E121 Lecture Notes - Lecture 9: Stephen Jay Gould, Cambrian Explosion, Speciation
Document Summary
Difficult to observe directly: patterns in fossil record, 2 models to explain fossil record, punctuated equilibrium, niles eldredge and stephen jay gould, 1972. Speciation occurs in rapid bursts followed by stasis. Triggered by environmental change: low environmental diversity > few resources/niches available > Low species diversity: high environmental diversity > many niches available > high species diversity, low environmental diversity > high environmental diversity > Rapid diversification: environmental change > change in selective pressures > Slow constant change: rare in fossil record, requires correct conditions for fossilization for long time, conditions not always right for preservation record incomplete. Takes a long time for speciation to occur: range of data 4,000 years to 40 million years, average is approx 6. 5 million years, only very rarely less than 500,000. Basics of phylogenetics: interpret phylogenies, cc types of groups. Constructing phylogenies: seq making phylogenies, cc homologous/analogous. Study of diversity of organisms and evolutionary relationships.
