EVOLUTION -POPULATIONS, SPECIATION AND ADAPTIVE RADIATION

Population – a group of interbreeding organisms

Gene pool – the sum of all of the genetic componentsin a population

Speciation – the origin of new species

Species – a collection of populations within which thereis free flow of genes

EVOLUTION -POPULATIONS, SPECIATION AND ADAPTIVE RADIATION

Geographic barriers (Allopatric speciation)

KaibabSquirrel (left)

AbertsSquirrel (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 ofCenozoic Era

Evolution above the species level is macroevolution

THE FOSSIL RECORDPhyletic gradualism

Phyletic gradualism is the gradual progressive change by means of an almost infinite number of small,subtle steps

THE FOSSIL RECORDPhyletic gradualism

THE FOSSIL RECORDPunctuated equilibrium

Punctuated equilibrium is sudden changes interruptinglong periods of little change

Periods of little change are called stasis

Most change occurs over a short period of time

THE FOSSIL RECORDPunctuated equilibrium

THE FOSSIL RECORDPunctuated equilibrium

Punctuated equilibrium suggests that evolution occursin isolated areas around the limits of a populationsgeographic 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 RECORDAllopatric speciation

THE FOSSIL RECORDAllopatric speciation

THE FOSSIL RECORDAllopatric speciation

THE FOSSIL RECORDPhylogeny

Phylogeny is the sequence of organisms placed inevolutionary order

THE FOSSIL RECORDPhylogenyDiagrams are used to illustrate ancestor-descendent

relationships.

Phylogenetic Tree

THE FOSSIL RECORDPhylogenyBranches on the diagram are called clades

THE FOSSIL RECORDPhylogeny

Cladograms are diagrams drawn to show ancestor-descendent relationships based on characteristicsshared by organisms

Do not include information on time or geologic ranges

THE FOSSIL RECORDPhylogeny - Cladogram

THE FOSSIL RECORDSequential Evolution

THE FOSSIL RECORDHomology

Homology is the similarity of body parts in regards toorigin, history and structure, without referenceto function

Homologous organs and bone configurations have acommon origin and ancestry

THE FOSSIL RECORDHomology

THE FOSSIL RECORDFossils and Stratigraphy

Principle of Fossil or Faunal SuccessionWilliam Smith

Used for

Age

Correlation

THE FOSSIL RECORDFossils and Stratigraphy

The geologic range of an organism is the interval between its first and last occurrence.

THE FOSSIL RECORDPaleontologic 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.

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 RECORDPaleontologic Correlation

THE FOSSIL RECORDIndex 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 RECORDBiostratigraphic 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 RECORDBiostratigraphic Zones

Range Zone = the part of the stratigraphic column containing the total geologic range of a species or other taxon

THE FOSSIL RECORDBiostratigraphic Zones

Assemblage Zone = the part of the stratigraphic column containing an assemblage or set of several associated fossils that coexist

THE FOSSIL RECORDBiostratigraphic Zones

Concurrent Range Zone = the rock where the ranges of two (or more) taxa overlap