Evidence For Biological Evidence For Biological Change Across TimeChange Across Time

Paleogeologists use Fossils in StrataPaleogeologists use Fossils in Strata

The more deeply The more deeply buried the fossil, the buried the fossil, the more time has gone more time has gone by, and the older it is. by, and the older it is.

Layers of rock with Layers of rock with fossils show us their fossils show us their relativerelative age: which is age: which is older and which is older and which is more recent.more recent.

Fossils in Strata InferencesFossils in Strata Inferences

By looking at a By looking at a sequence of related sequence of related fossils and their fossils and their relative ages, relative ages, relationships and relationships and changes through time changes through time can be inferred.can be inferred.

Radiometric dating Radiometric dating provides more provides more accurate ages.accurate ages.

As gaps in the fossil record are As gaps in the fossil record are gradually filled, we see transitionsgradually filled, we see transitions

Evolutionary Biologists study Evolutionary Biologists study Homologous StructuresHomologous Structures

Similar body parts are Similar body parts are modified and used modified and used differently in different differently in different life forms.life forms.

Homologies give clues Homologies give clues to common ancestry.to common ancestry.

They must have They must have shared a common shared a common ancestor who had ancestor who had similar structuressimilar structures

And Vestigial StructuresAnd Vestigial Structures

If a body part changes If a body part changes in a way that it in a way that it becomes no longer becomes no longer used or useful, it is used or useful, it is called vestigial, or a called vestigial, or a “vestige” of the former “vestige” of the former structure.structure.

Developmental Biologists Developmental Biologists compare embryo developmentcompare embryo development

A = Cat B = Cow C = Horse D = Human

Which one is the Cat?Which one is the Cat?

Changes accumulate in DNA Changes accumulate in DNA over timeover time

By comparing DNA, we can see By comparing DNA, we can see how closely related life forms arehow closely related life forms are

Known rates of mutations allow us Known rates of mutations allow us to use DNA as a “molecular clock”to use DNA as a “molecular clock”

We can use it to make more accurate inferences We can use it to make more accurate inferences about common ancestorsabout common ancestors

Physical Anthropologists study Physical Anthropologists study changes in hominid anatomychanges in hominid anatomy

Observed Changes?

(A) Pan troglodytes, chimpanzee, modern(B) Australopithecus africanus, STS 5, 2.6 My(C) Australopithecus africanus, STS 71, 2.5 My(D) Homo habilis, KNM-ER 1813, 1.9 My(E) Homo habilis, OH24, 1.8 My(F) Homo rudolfensis, KNM-ER 1470, 1.8 My(G) Homo erectus, Dmanisi cranium D2700, 1.75 My(H) Homo ergaster (early H. erectus),

KNM-ER 3733, 1.75 My(I) Homo heidelbergensis, "Rhodesia man,"

300,000 - 125,000 y(J) Homo sapiens neanderthalensis, La Ferrassie 70,000 y(K) Homo sapiens neanderthalensis,

La Chappelle-aux-Saints, 60,000 y(L) Homo sapiens neanderthalensis,

Le Moustier, 45,000 y(M) Homo sapiens sapiens, Cro-Magnon I, 30,000 y(N) Homo sapiens sapiens, modern

Discovering Ardi: After school Discovering Ardi: After school “Movie Night” “Movie Night”

2:30-4:30, Wednesday: Up to 10 points extra credit2:30-4:30, Wednesday: Up to 10 points extra credit