Chapter 4 & 5Organic Evolution

Before Darwin

Jean Baptiste LamarckLamarckism: inheritance of acquired characteristicsTransformational view of evolutionNot supported. 1744-1829

Sir Charles LyellUniformitarianismLaws of physics and chemistry remain the sameNatural processes which acted in the past will continue to act. 1797-1875

Thomas MalthusConcerned with human population growthPeople tended to reproduce faster than their food supply, and are forced to compete for existence. 1766-1834

Charles DarwinNaturalist who combined the ideas of Malthus, Lyell and others to form the theory of evolution. 1809-1882

DARWINS THEORY OF EVOLUTION A sea voyage helped Darwin frame his theory of evolutionOn his visit to the Galpagos Islands Charles Darwin observed many unique organisms0

Darwins main ideas can be traced back to the ancient Greeks

Aristotle and the Judeo-Christian culture believed that species are fixed0

In the century prior to Darwin the study of fossils suggested that life forms change

Geologists proposed that a very old Earth is changed by gradual processes0

While on the voyage of the HMS Beagle in the 1830s Charles Darwin observed similarities between living and fossil organisms and the diversity of life on the Galpagos Islands0North AmericaEuropeGreat BritainAfricaEquatorAsiaAustraliaTasmaniaNew ZealandPACIFIC OCEANATLANTIC OCEANPACIFIC OCEANPACIFIC OCEANThe Galpagos IslandsSouth AmericaTierra del FuegoCape HornCape of Good HopeAndesPintaMarchenaGenovesaEquatorSantiagoIsabelaFernandinaFlorenzaEspaolaSan CristobalSanta CruzSanta FePinznDaphne Islands40 miles40 km0 0

Darwins experiences during the voyage of the Beagle helped him frame his ideas on evolution0

Evolution

EvolutionChange over time: Organic or biological evolution is a series of changes in the genetic composition of a population over time.

Adaptation

AdaptationOccurs when a heritable change in a phenotype increases an animals chance of successful reproduction.

AdaptationOccurs when a heritable change in a phenotype increases an animals chance of successful reproduction.Likely to be expressed when an organism encounters a new environment.

AdaptationOccurs when a heritable change in a phenotype increases an animals chance of successful reproduction.Likely to be expressed when an organism encounters a new environment.Not every characteristic is an adaptation to some kind of environmetal situation.

AdaptationOccurs when a heritable change in a phenotype increases an animals chance of successful reproduction.Likely to be expressed when an organism encounters a new environment.Not every characteristic is an adaptation to some kind of environmetal situation. A No No: evolutionary adaptations lead to perfection.

Darwinian Evolutionary Theory: The Evidence 1) Perpetual change

2) Common descent

3) Multiplication of species

4) Gradualism

5) Natural selection

I. Perpetual ChangeDarwin noticed fossils of extinct marine organisms thousands of feet above present day sea level.

The Burgess Shale

Before the Scientific MethodPeople based their beliefs on their interpretations of what they sawWithout testing their ideas

Rather, their conclusions were based on untested observations.

Snakestones!

Some fossils you can not refute.

The Baltic amber deposits range between 35 to 40 million years old and is the largest source of amber yet discovered.

So What do these Fossils tell us?

Geological TimeLong before the earths age was known, geologists divided its history into a table of succeeding events based on the ordered layers of sedimentary rock.

The fossil record reveals that organisms have evolved in a historical sequence0

Evolutionary trendsThe fossil record allowed Darwin to view evolutionary change across the broadest scale of time.

Animal species typically survive approximately 1 million to 10 million years, before going extinct.

I. Perpetual ChangeDarwin noticed fossils of extinct marine organisms thousands of feet above present day sea level.

Darwin also worked on the change of animals under domestication by humans (artificial selection).

Darwin found convincing evidence for his ideas in the results of artificial selectionThe selective breeding of domesticated animals0

I. Perpetual ChangeDarwin noticed fossils of extinct marine organisms thousands of feet above present day sea level.

Darwin also worked on the change of animals under domestication by humans (artificial selection).

He combined these two observations to form the idea that organisms are constantly changing through time.

II. Common DescentWhereas Lamarck believed in multiple origins of life, Darwin believed that all life originated from a single common ancestor.

Darwin proposed that living species are descended from earlier life forms0Thousands to millions of years of natural selectionAncestral canineAfrican wild dogCoyoteWolfFoxJackal

Hi There How are You!!!

6-11, p 110

How many species of horses are there?

Grevy's Zebra (Equus grevyi) Burchell's Zebra (Equus burchelli) Mountain Zebra (Equus zebra)

Asiatic Wild Asses - Kulan and Onager (Equus hemionus) - Kiang (Equus kiang)

African Wild Asses - African Wild Ass (Equus asinus)

Przewalski's Horse (Equus caballus)

So what do these horse fossils suggest?

Throughout the history of all forms of life, evolutionary processes generate new characteristics that are then inherited by subsequent generations.

II. Common DescentWhereas Lamarck believed in multiple origins of life, Darwin believed that all life originated from a single common ancestor.The evidence Darwin used was homology:

HomologiesHomologies: Anatomical structures within different organisms which originated from a structure or trait of their common ancestral organism.

Vestigial Structures

What are these animals?

Analogous StructuresThe evolution of superficially similar structures in unrelated organisms is called convergent evolution.

So What?

Theory of Common Descent is TestableLike all good scientific theories, common descent makes several important predictions that can be tested and potentially used to reject it.According to this theory, we should be able to trace the genealogies of all modern species backward until they converge on ancestral lineages shared with other species, both living and extinct.

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