Phylogeny and Systematics

Fossil record – Provides information about ancient organisms Figure 25.1

The Fossil Record Sedimentary rocks – Richest source of fossils – Deposited into layers called strata Figure Rivers carry sediment to the ocean. Sedimentary rock layers containing fossils form on the ocean floor. 2 Over time, new strata are deposited, containing fossils from each time period. 3 As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion reveals strata and fossils. Younger stratum with more recent fossils Older stratum with older fossils

The fossil record – Based on the sequence in which fossils have accumulated in such strata – Fossils reveal ancestral characteristics

Figure 25.4a–g (a) Dinosaur bones being excavated from sandstone (g) Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice (e) Boy standing in a 150-million-year-old dinosaur track in Colorado (d) Casts of ammonites, about 375 million years old (f) Insects preserved whole in amber (b) Petrified tree in Arizona, about 190 million years old (c) Leaf fossil, about 40 million years old

Convergent Evolution Similar environmental pressures & natural selection Produce similar (analogous) adaptations Figure 25.5

Peppered Moths Dark vs. light variants Year% dark% light

The Universal Tree of Life Divided into 3 great clades (domains): Bacteria, Archaea, and Eukarya The early history of 3 domains is not yet clear Figure BacteriaEukaryaArchaea 4 Symbiosis of chloroplast ancestor with ancestor of green plants 3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes 2Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells 1Last common ancestor of all living things LUCA Billion years ago Origin of life