Tracing Phylogeny

What is Phylogeny?

• The evolutionary history of a species or group of related species
• Greek word derivation:
  • Phylon: tribe
  • Genesis: origin
• You can think of it as “genealogy on steroids!”
• It is the “ultimate family tree.”

The Tracing of Phylogeny Leads to Phylogenetic Trees

Figure 25.11, page 479, Campbell's Biology, 5th Edition

What is Systematics?

• The goal of systematics is to have the classification of biodiversity reflect its evolutionary history.
• If this is done well two things will occur:
  • The phylogenetic trees we see will accurately represent evolutionary relationships between species.
  • The way organisms are classified will accurately represent how closely they are truly related.

What Allows Us To Trace Phylogeny?

• Fossil Record: preserved remains and traces of what were once living organisms provide a wealth of information.
  • This is raw evidence of the relatedness of organisms.
• Radiometric Dating: using our understanding of the radioactive decay of certain elements, we are able to determine the age of certain rocks and therefore place fossils in an accurate timeline.
• Molecular Data: using a variety of techniques looking at DNA, RNA, and proteins, scientists have been able to show relatedness of organisms and determine their evolutionary histories.

The Ultimate Phylogeny

Figure 26.3, page 493, Campbell's Biology, 5th Edition

Geological Time Scale: “Recent History”

Table 25.1, page 467, Campbell's Biology, 5th Edition

The Cambrian “Explosion” and the Burgess Shale

• Animal life first diversified rapidly and radically about 550 million years ago.
• Evidence: the Burgess Shale in the Canadian Rockies

Unknown source

Two Important Influences on the Evolution of Life

Plate Tectonics

• Earth is dynamic; the crust is broken into plates that ride on a “sea” of partially molten rock.
• This helps explain the distribution of life on the planet, especially the existence of marsupials in Australia.

Figure 25.4, page 470, Campbell's Biology, 5th Edition

Asteroid/Comet Impacts

• It is becoming clear that these may be driving forces of evolutionary change, due to the rapid changes in the environment that they cause.
• The major breakthrough in this area of research was the discovery of the impact crater in the Yucatán Peninsula that led to the demise of the dinosaurs 65 million years ago.

Figure 25.6, page 473, Campbell's Biology, 5th Edition