Transcript Slide 1
EVOLUTION POPULATIONS, SPECIATION AND ADAPTIVE RADIATION Population – a group of interbreeding organisms Gene pool – the sum of all of the genetic components in a population Speciation – the origin of new species Species – a collection of populations within which there is free flow of genes EVOLUTION POPULATIONS, SPECIATION AND ADAPTIVE RADIATION Geographic barriers (Allopatric speciation) Kaibab Squirrel (left) Aberts Squirrel (right) EVOLUTION POPULATIONS, SPECIATION AND ADAPTIVE RADIATION Adaptive radiation Hawaiian honeycreepers EVOLUTION POPULATIONS, SPECIATION AND ADAPTIVE RADIATION Adaptive radiation also occurs at other taxonomic levels Adaptive radiation of mammals at beginning of Cenozoic Era Evolution above the species level is macroevolution THE FOSSIL RECORD Phyletic gradualism Phyletic gradualism is the gradual progressive change by means of an almost infinite number of small, subtle steps THE FOSSIL RECORD Phyletic gradualism THE FOSSIL RECORD Punctuated equilibrium Punctuated equilibrium is sudden changes interrupting long periods of little change Periods of little change are called stasis Most change occurs over a short period of time THE FOSSIL RECORD Punctuated equilibrium THE FOSSIL RECORD Punctuated equilibrium Punctuated equilibrium suggests that evolution occurs in isolated areas around the limits of a populations geographic range Groups in these areas are peripheral isolates and rapid speciation may occur here Also known as allopatric speciation When the new species expands into its original territory, it is seen as a sudden appearance THE FOSSIL RECORD Allopatric speciation THE FOSSIL RECORD Allopatric speciation THE FOSSIL RECORD Allopatric speciation THE FOSSIL RECORD Phylogeny Phylogeny is the sequence of organisms placed in evolutionary order THE FOSSIL RECORD Phylogeny Diagrams are used to illustrate ancestor-descendent relationships. Phylogenetic Tree THE FOSSIL RECORD Phylogeny Branches on the diagram are called clades THE FOSSIL RECORD Phylogeny Cladograms are diagrams drawn to show ancestordescendent relationships based on characteristics shared by organisms Do not include information on time or geologic ranges THE FOSSIL RECORD Phylogeny - Cladogram THE FOSSIL RECORD Sequential Evolution THE FOSSIL RECORD Homology Homology is the similarity of body parts in regards to origin, history and structure, without reference to function Homologous organs and bone configurations have a common origin and ancestry THE FOSSIL RECORD Homology THE FOSSIL RECORD Fossils and Stratigraphy Principle of Fossil or Faunal Succession William Smith Used for Age Correlation THE FOSSIL RECORD Fossils and Stratigraphy The geologic range of an organism is the interval between its first and last occurrence. THE FOSSIL RECORD Paleontologic Correlation Cosmopolitan species are found almost everywhere; they are not restricted to a single geographic location in their environment. Endemic species are confined to a restricted area in the environment in which they live. Cosmopolitan species are most useful in correlation because they have a geographically widespread distribution. Fossils found only in limited environments (endemics) are not as useful in matching up rock layers that are far apart. THE FOSSIL RECORD Paleontologic Correlation Appearances and disappearances of fossils may indicate: Evolution or Extinction Changing environmental conditions that cause organisms to migrate into or out of an area THE FOSSIL RECORD Index Fossils Index fossils or guide fossils are useful in identifying time-rock units and in correlation. They are: oabundant owidely distributed (cosmopolitan) oorganisms with short geologic ranges (rapid evolution rates) THE FOSSIL RECORD Biostratigraphic Zones Biozone = a body of rock that is identified only on the basis of the fossils it contains. They are the basic unit for biostratigraphic classification and correlation (much as the formation is the fundamental unit for lithostratigraphy). THE FOSSIL RECORD Biostratigraphic Zones Range Zone = the part of the stratigraphic column containing the total geologic range of a species or other taxon THE FOSSIL RECORD Biostratigraphic Zones Assemblage Zone = the part of the stratigraphic column containing an assemblage or set of several associated fossils that coexist THE FOSSIL RECORD Biostratigraphic Zones Concurrent Range Zone = the rock where the ranges of two (or more) taxa overlap