Historically Important Scientists Historically Important Scientists and the History of Evolutionary and the History of Evolutionary

ThoughtThought

Linnaeus, Carolus (1707-1778)Linnaeus, Carolus (1707-1778)

Botanist, TaxonomistBotanist, Taxonomist

Founder of Founder of taxonomy taxonomy (system of naming and classifying (system of naming and classifying organisms) invented the system of organisms) invented the system of Binomial NomenclatureBinomial Nomenclature

Believed in Creation & Fixity of SpeciesBelieved in Creation & Fixity of Species

Cuvier, George (1769-1832)Cuvier, George (1769-1832)

Vertebrate Zoologist, largely Vertebrate Zoologist, largely responsible for developing responsible for developing paleontologypaleontology..

First to use Comparative Anatomy to First to use Comparative Anatomy to develop a system for classifying develop a system for classifying animalsanimals

"only needed single bone to describe "only needed single bone to describe organism”organism”

staunch supporter of creation & fixity staunch supporter of creation & fixity of speciesof species

Cuvier Cuvier

Explained how between layers strata unique fossils were found Explained how between layers strata unique fossils were found unlike those above and belowunlike those above and below

Suggested that after each in a series of catastrophes, mass Suggested that after each in a series of catastrophes, mass extinctions and repopulations made it appear that speciesextinctions and repopulations made it appear that specieschanges over time – changes over time – CatastrophismCatastrophism. These were localized and . These were localized and the result of special creation.the result of special creation.

Most crucial and longest-lasting contribution to biology was Most crucial and longest-lasting contribution to biology was establishing extinction as a fact.establishing extinction as a fact.

Lamarck, Jean Baptist de (1744-1829)Lamarck, Jean Baptist de (1744-1829)

Invertebrate ZoologistInvertebrate Zoologistimpressed by changes in impressed by changes in

species associated with species associated with geological stratageological strata

Proposed an evolutionary Proposed an evolutionary theory:theory:Theory of Inheritance Theory of Inheritance of Acquired of Acquired Characteristics:Characteristics:

Lamark - Inheritance of Acquired Lamark - Inheritance of Acquired CharacteristicsCharacteristics

More complex organisms are descended from less complex onesMore complex organisms are descended from less complex ones

Plants and animals adapt to the environment during their Plants and animals adapt to the environment during their lifetimeslifetimes

Adaptations are passed to offspringAdaptations are passed to offspring..((Inheritance of Acquired CharacteristicsInheritance of Acquired Characteristics))

e.ge.g. Giraffes stretch for food Their necks elongate Longer necks . Giraffes stretch for food Their necks elongate Longer necks are passed to offspringare passed to offspring

Lamark: Use/Disuse: Lamark: Use/Disuse: structures that structures that are used extensively become are used extensively become larger/better than those that are not larger/better than those that are not used. used. A change in the environment causes changes in the needs of A change in the environment causes changes in the needs of

organisms living in that environment, which in turn causes organisms living in that environment, which in turn causes changes in their behavior. changes in their behavior.

Altered behavior leads to greater or lesser use of a given Altered behavior leads to greater or lesser use of a given structure or organstructure or organ

use would cause the structure to increase in size over several use would cause the structure to increase in size over several generationsgenerations

disuse would cause it to shrink or even disappeardisuse would cause it to shrink or even disappear

BUT now BUT now we know there is no mechanism to permit this - cells we know there is no mechanism to permit this - cells that form gametes are separate from those in the rest of thethat form gametes are separate from those in the rest of thebodybody

Lyell, Charles & Hutton, JamesLyell, Charles & Hutton, James

Both were geologists (Lyell's book Both were geologists (Lyell's book [[Principle’s of GeologyPrinciple’s of Geology] ] described Hutton's ideas)described Hutton's ideas)

Earth was dynamic, not static. Earth was dynamic, not static.

Earth was subject to Earth was subject to continuouscontinuous cycles of erosion and uplift = cycles of erosion and uplift = UniformitarianismUniformitarianism Theory Theory

Examples of ProcessesExamples of Processes

Erosion puts sediments into waterErosion puts sediments into water

Forms sedimentary rock in which fossils are foundForms sedimentary rock in which fossils are found

Uplifting of rocks forms land Uplifting of rocks forms land

Modern view is that such geological changes are periodic.Modern view is that such geological changes are periodic.

Darwin, CharlesDarwin, Charles

Darwin, Charles (1809-1882)

After his 1831-1836 voyage on HMS Beagle, Charles Darwin was chronically ill, having contractedwhat was eventually termed Chagas Disease.

April 19th, 1882 he had a fatal heart attack and died.

Buried in Westminster Abbey along with Newton, Lyell, and Faraday.

Darwin theories on evolution influenced by Lyell and Thomas Malthus (population explosions occur unless acted on bylimiting factors).

Published 19 books including, “On the Origin of Species by Means of Natural Selection”

DARWIN’S THEORY OF NATURAL SELECTIONDarwin’s theory of evolution through natural selection explains

how adaptations can lead to achange in a population over time.

The population (group of interbreeding organisms of the same species in a geographicarea) is the smallest unit that can evolve over time.

Evolution (change) is measured as a change in allele frequency within alarge population (next chapter).

These changes would be the result of differential survival rates of members of the populationthat are better adapted to their environment.

DARWIN’S THEORY OF NATURAL SELECTION1. In most species the number of individuals in a

generation that survive and reproduce is relatively small.

2. Variations among individuals of a population exist. Everyone is unique.

3. Limited resources within an environment and large numbers of individuals of any given species leads to a “struggle for existence”

3a. Individuals with favorable adaptations are more likely to survive and reproduce.

4. Inherited favorable characteristics become more common from one generation to the next.

Adaptive radiation of Adaptive radiation of finchesfinches

Natural Selection Observed

Insecticide-resistance in insects

Drug-resistant HIV viruses

3TC interferes with reverse transcriptase of HIV

3TC, instead of cytosine, is inserted in DNA produced from HIV RNA

Resistant HIV can discriminate between 3TC and normal cytosine

EVIDENCES USED BY BIOLOGISTS TO SUPPORT DARWINIAN EVOLUTION

BIOGEOGRAPHYTHE FOSSIL RECORDCOMPARATIVE ANATOMYCOMPARATIVE EMBRYOLOGYMOLECULAR BIOLOGY

BIOGEOGRAPHY

Study of the distribution of organisms.Related organisms are found living close to

one another.Island species are related to the species

found on the nearest continent. Due to changes in the population as they are

under different environmental pressures from mainland species. (eg. Galapagos Is, Indonesian Islands)

THE FOSSIL RECORD

provides evidence that the variety of species that has inhabited the earth has changed over time

What is a fossil ?

remains of organisms that have been buried quickly so that decomposition has stopped or slowed

Geological processes form layers of rock = strata

each stratum has its own type of fossils

Fossils at the lowest level are the oldest and get younger with each layer as you move upward

Dating of FossilsDating of Fossils

Dating using strata called Relative Dating and uses the Principle of Superposition.

boundaries between layers show transitions -- many are mass extinctions - and form basis for dividing time.

Actual dates are estimated from the decay of radioactive isotopes and the measurement of half-life to determine the Absolute Dating.

COMPARATIVE ANATOMY

•Comparing structures of various organisms leads to system of classification that indicates evolutionary relationships.

•Similar structures indicate that organisms may have descended from a common ancestor and that the structure has changed due to specific environmental pressures that have been selected for

Homologous StructuresHomologous Structures

•Have the same structure but a different function.

•Evolution used one structure and modified it to fit a new situation. (Common Ancestory).

•Commonly used example: forelimb of human, bird, whale, dolphin, bat, etc.

Homologous StructuresHomologous Structures

Analogous StructuresAnalogous Structures

• Have same function but different structure. • The result of unrelated groups adapting to a

similar environment. (Different Ancestory).• Natural selection has taken similar

environmental roles and modified them in a similar manner.

• This is called Convergent Evolution.• Commonly used example: flying structures

of insects and vertebrates; lungs of mammals and trachea of insects.

Vestigial StructuresVestigial Structures

• Structures that functioned in an ancestral organisms, but that are reduced (in structure and function) in the descendant.

• Serve little or no purpose in an extant (currently or actually existing) species but may have in an ancestor.

• Natural selection (not Lamarkian Use and Disuse) has selected for organisms within the population that have reduced or absent forms of the structure.

• Commonly used examples: nictating membrane of eye, caudal vertebrae of coccyx, appendix of intestines, muscles that move the ears, vestigial hind legs of whales and snakes

Vestigial StructuresVestigial Structures

COMPARATIVE EMBRYOLOGY• Comparing the general appearance of

embryos from different species at various stages in development shows them to be quite similar.

• Certain embryonic structures are shared by all chordates, but show interesting structural and functional changes during development.

• e.g. notochord (develops into jointed vertebral column in higher vertebrates), gill slits (used for gas exchange in fishes, jaw support and other functions in higher vertebrates), aortic arches (becomes heart)

MOLECULAR BIOLOGY

•a comparison of DNA and amino acid sequences in proteins of various species

•closely related species should have more similar DNA & more similar sequences in certain proteins (like cytochrome C; electron carrier of ETC and hemoglobin molecules)

Molecular BiologyMolecular Biology