Fossils, Anatomy, and DNA

Evidence for Evolution

Three types of evidence:– Fossils– Anatomical– Molecular

Fossil Evidence

• Fossils- any traces of dead organisms– dinosaur bones– insects trapped in tree sap– leaf impressions– footprints

Paleontology

• Study of fossils is called Paleontology• A paleontologist is a scientist who studies

fossils.• Paleontology can be divided into 4

divisions of study

Four divisions of Paleontology

• Invertebrate Paleontology• Vertebrate Paleontology• Paleobotany• Micropaleontology

Types of Fossils

• Preserved original or altered hard parts of organisms (examples: shells of clams, oysters, snails. Teeth, bones)

• Molds or casts• Trace fossils (example burrows, tracks,

trails)

Method of Preservationdepends on three things:

• The original composition of the organism• It’s environment• The forces that affected the organic

remains after death

Fossil Evidence• Transitional species- species that have

been found in the fossil record that are intermediates between two other species in the evolutionary process.

– Radiometric dating- a dating technique that measures amount of radioactive material in a rock or fossil.

– Relative dating- a dating technique that estimates the date of a fossil by relating it to the age of the layers of rock around it.

Fossil Evidence

• To fossilize an organism must be buried by sediment. – In swamps, mud, tar

pits, or the ocean bottom.

– Hard stuff fossilizes (bones, nails).

– Radiometric and relative dating are used to find out how old the fossil is.

Relative Dating

RadiometricDating

Fossil Evidence• Fossils show:

– Life has been around for millions of years– Transitional species link older to newer species

– Darwin proposed the idea of transitional species, though he had no evidence

– Today we have evidence:• Archaeopteryx• Tiktaalik Fossil, etc.• Whales

Fossil Evidence-Archaeopteryx

BEAK

WINGS

Fossil Evidence

• Whales--60 million years of evolution–Descended from 4-legged wolf-like

animals that were also ancestors to cows and horses

–Fossil evidence shows slow loss of legs–Pelvis still remains with no rear legs

Fossil Evidence-Whales

Whale Video

Anatomical Evidence• Anatomical evidence- evidence for evolution

which is based on similarities and differences between the physical structures of different species.

• What can we tell about the relatedness of the three species below?

Anatomical Evidence• Homologous structures-Bone structure the

same (homo) but not function • Bird wing, dolphin fin, and a human arm

– Function these structures is not the same!

– Show that these species shared a common ancestor.

– Similar structures resulted from accumulated mutations and modifications.

Homologous Structures

Anatomical Evidence– Analogous structures- Bone structure different but

serve the same function.• Function = flight

Butterfly wing, bat wing, fly wing• These structures, although they have

the same function, are not built the same!

• Show different species evolved structures with similar function through different evolutionary pathways.

• EVOLUTION IS NOT RANDOM!

Anatomical Evidence

Anatomical Evidence• Vestigial structures-

• Structures that no longer serve a function

• These structures are the remnants of an evolutionary past and show common anatomy with other species

Evidence for Evolution• ***Mutations and sexual

reproduction are a cause of variation in a species’ DNA.

• DNAmRNAprotein– Transcription- copying the DNA

code into mRNA– Translation- converting the code

of mRNA into a long chain of amino acidsprotein

– Differences in DNA are seen in differences in protein

Molecular Evidence

• Molecular evidence- evidence concerning the comparison of DNA and protein molecules between species

• Ultimate tools for scientists studying evolution

• Same genetic basis for all organisms: A, C, T, and G shows we are all related

Molecular Evidence• Species with more similar

DNA are more closely related on the evolutionary tree—less time to accumulate mutations (and, therefore, differences)

• Common ancestor- any species in the past from which two or more species has evolved.

• Sharing a Gene Pool = speciation event = mutation

What evolution IS NOTBiological Evolution...• Is NOT an educated guess, it is a THEORY• Is NOT something one should believe in...(it's

based on science, not faith).• Is NOT just concerned with the origin of

humans...(no more than any other species).• Was NOT discovered or first explained by

Charles Darwin...

What evolution IS NOT

• Is NOT the same thing as natural selection…natural selection is the driving force that causes evolution

• Is NOT something that happened only in the past...

• Is NOT something that happens to individuals...(it happens to POPULATIONS).

• Is NOT an accidental…mutations that cause variation are

What evolution IS NOT

• Does NOT have any evidence against it• Was NOT contrived to undermine religion...(we

tried to make sense of observations of life in a testable way).

• Does NOT deny the existence of God; God is neither required nor eliminated. For all we know, evolution could be part of God's creation, but science cannot determine that.

If these popular misconceptions about evolution are all wrong, then what IS evolution?

What evolution IS

Biological Evolution is... • The genetic change of a population of species

over time. • The idea that new species develop from earlier

species by accumulated genetic mutations • It has been directly observed in some species,

and inferred in many others from evidence mainly in anatomy, embryology, paleontology, geology, and molecular biology.

What evolution IS

• The Theory of Evolution by Natural Selection holds the high status of near certainty: it’s a scientific theory

• There are no observations of life, living or extinct, that evolution cannot explain.

• Why is evolution controversial anyway?