Chapters 11 and 12Chapters 11 and 12

The Origin of Life?

And Evolution

Life on Earth?

Extraterrestrial origin?No solid proof.

Divine Creation?Cannot be tested scientifically.

Spontaneous Origin?Can be tested scientifically! • Many scientists try to prove the spontaneous

origin theory.

An Evolutionary Timeline:

Earth is estimated to be 4.5 billion4.5 billion years old!

The earliest fossils are about 3.5 billion3.5 billion years old.

How could life have arisen?Theories:

Creation, Primordial soup model, and micelles.

Primordial Soup Model1920’s – A.I. Oparin proposed that organic molecules could have formed in Earth’s early oceans if energy were added.

1953 – Harold Urey and Stanley Miller tested this hypothesis.

Urey and Miller’s Experiment

The following substances were believed to be in Earth’s early atmosphere and oceans.

Nitrogen

Hydrogen

Water

Methane

Ammonia

Miller and Urey’s Experiment

Electrical energy was added to the compounds to simulate lightning.The following compounds were formed:Amino AcidsFatty AcidsHydrocarbonsSignificance?

These are the basic units of life!!

How Were Cells Formed?

Microspheres – proteins and lipids tend to aggregate in water. These form phospholipids (cell membranes).Cannot be considered

living until it can pass on hereditary information.

DNA or RNA

Life is still a mystery scientifically!!!Life is still a mystery scientifically!!!

Theory of EvolutionEvolution – Change in the genetic make-up of a population or species over time.Charles Darwin – conducted studies of populations all over the Earth while traveling on his ship, the Beagle.

He studied the living things that lived in the Galapagos Islands.

Theory of EvolutionVariation exists in genes of all species.Some individuals are better suited for survival. This leads to natural selection, or survival of the fittest.Over time, change within a species leads to a new species (speciation) and the extinction of an old species.Adaptation – the changing of a species that results in its being better suited for its environment.Fossils show species have evolved from ancestral forms.

Early Theories of Evolution

Jean-Baptiste Lamarck – Believed evolution resulted by acquired characteristics. This idea stated that individuals changed and passed these adaptations on to their offspring. Example: Giraffes stretching their necks to reach leaves led to longer-necked offspring.Lamark’s theory was wrong!

Darwin’s Theory:

Darwin found that finches on the Galapagos Islands closely resembled the finches on the mainland, but developed (adapted) special modifications for survival(natural selection). Over time, the birds became so different that they could no longer interbreed. This led to the formation of a new species, or speciation.

Types of Speciation:

Geographical isolation – Groups are physically separated.

Ecological isolation- Groups occupy different habitats.

Temporal isolation- reproduce at different times of the day.

Behavioral isolation- no attraction.

Mechanical isolation- structural differences.

Reproductive failure- no fertile offspring.

Microevolution- a shift within a species gene frequency over time.

Does NOT constitute a new species.Examples:Broccoli and CabbagePeppered moth – 1850 in Europe during the industrial revolution.Sickle-cell anemia – high in African populations, helps with malaria.

Peppered Moth- normal and dark

Pollution caused the

Trees to become dark.

Which moth variation

would survive?

The chart and map show

The selection for dark-

Colored moths.

Macroevolution – a new species being formed because the small changes have accumulated and made the groups too different to interbreed.

Example: Dinosaurs were replaced by mammals. Evidence:FossilsAmino acid sequencesHomologous structuresVestigal structures