EVOLUTION:

EVIDENCE AND

THEORY

But first, a very quick cartoon

show.

NOTHING IN BIOLOGY MAKES SENSE EXCEPT

IN THE LIGHT OF EVOLUTION

-THEODOSIUS DOBZHANSKY (1900-1975)

The Fossil Record

Nature of fossils

Archaeopteryx

Lucy

Ida

Famous Fossils

Distribution of fossils• RELATIVE AGE

Distribution of fossils• LAW OF SUPERPOSITION

Distribution of fossils• ABSOLUTE AGE

• WHEN SCIENTISTS USE RADIOMETRIC DATING, THEY USE A MASS SPECTROMETER TO ANALYZE THE ISOTOPES PRESENT IN THE MATERIAL, BOTH OF THE OLD MATERIAL AND OF THE NEW, DECAYED ISOTOPE. USING THE KNOWN HALF-LIFE OF MATERIALS (FOR EXAMPLE, THE HALF-LIFE OF CARBON-14 IS 6,000 YEARS), SCIENTISTS CAN COMPARE HOW MUCH OF EACH TYPE OF ISOTOPE (THE ORIGINAL ISOTOPE, KNOWN AS THE PARENT, AND THE DECAYED ISOTOPE, KNOWN AS THE DAUGHTER ISOTOPE) IS PRESENT IN THE MATERIAL. USING THIS INFORMATION, HIGHLY ACCURATE DATING CAN BE ESTABLISHED FOR EVEN VERY OLD OBJECTS.

READ MORE: HOW DOES RADIOMETRIC DATING WORK? | EHOW.COM HTTP://WWW.EHOW.COM/HOW-DOES_5185123_RADIOMETRIC-DATING-WORK_.HTML#IXZZ1ELXIKT6D

Absolute Aging

Distribution of fossils

• SUCCESSION OF FORMS

Extinction

Distribution of fossils• MASS EXTINCTION

K-T

K-T Permian

• VIDEO• dramatization

immediate6 months

10 years

50 years

65 million years

Video

Theories of

Evolution

• MODERN BIOLOGY CHAPTER 15.2

Lamarck’s Explanation• FIRST TO PROPOSE A

UNIFYING THEORY ABOUT SPECIES MODIFICATION–SIMILAR SPECIES

DESCENDED FROM A COMMON ANCESTOR

–RELATED FOSSILS TO EXTANT ORGANISMS BASED ON PHYSICAL CHARS.

Lamarck’s Explanation

Lamarck’s Problem– ACQUIRED TRAIT– FIERCELY ATTACKED, PRIMARILY BY

SCIENTISTS WHO WERE VIOLENTLY OPPOSED TO THE IDEA OF EVOLUTION

The beginning of modern evolutionary thought

• NATURAL SELECTION: ORGANISMS BEST SUITED TO THEIR ENVIRONMENTS ARE BETTER ABLE TO SURVIVE AND THEREFORE REPRODUCE MORE, LEAVING MORE OFFSPRING

• POPULATION: A GROUP OF INTERBREEDING INDIVIDUALS WITHIN A SPECIES

Charles Darwin• BORN IN 1809• MEDICAL SCHOOL AND

CLERICAL SCHOOL• H.M.S. BEAGLE

A 5-Year Tour

Darwin’s Beginnings• Analysis of Darwin's data

– Returned to England in October, 1836 with thousands of specimens, each carefully documented

– 13 similar, but distinctly different species of finches• Young islands

The Finches• Similar but not the same• Identify the island

Darwin’s Beginnings• Publication

– Wallace’s move – On the Origin of Species By Means of Natural

Selection • Was published in 1858 • Sold out on its first day

Darwin’s theories• Evolution: defined by Darwin as “descent

with modification”– Newer forms are refined forms of earlier fossils– All must have developed from a few common

ancestors– Accounts for the similarities in organisms in a

geographical area and the fossils found there

Darwin’s theories• Natural selection: defined by Darwin as the

“means of evolution”– Competition– Some individuals are better able to survive– Eventually the frequency of that trait changes

in the population

Lamarck v. Darwin

Darwin’s theories• Survival of the fittest

– Not always true– Fitness means ability to reproduce, not

healthiest– Oversimplification

Evolution

“A CHANGE IN THE FREQUENCY OF ALLELES WITHIN A POPULATION OVER GENERATIONS”

Requirements for natural selection

• If these are present, selection will occur.– Differential selection– Variation– Heritability

Evolution in Process

Evidence of Evolution• Homologous structures

– Same origin; different function

Evidence of Evolution• Analogous structures

– Same function, different origin

Evidence of Evolution• Vestigial structures

– “Left-overs”

Evidence of Evolution• Macromolecule comparison

– All organisms have the same dna structure and the same amino acids

– Many related organisms have very similar proteins

Patterns of evolution• CO-EVOLUTION

Patterns of evolution• Convergent evolution

– Different origins similar characteristics– Similar environment similar solution

Patterns of evolution• Divergent evolution

– Similar background– Different environment; different solution– Adaptive radiation

http://apod.nasa.gov/apod/image/0010/PangeaUltima_scotese_big.jpg

Patterns of evolution• Divergent evolution

– Speciation – Artificial selection

“… when the last individual of a race of living things

breathes no more, another heaven and another earth

must pass before such a one can be again."

--William Beebe