Descent with Modification: A Darwinian View of Life Click on Picture

Evolutionary history

Historic Context Plato and Aristotle believed that organisms were perfectly formed and adapted to the world Judeo Christian theology believed: that the world is 6,000 years old species were created individually Natural Theologians searched for God’s plan through the study of nature

Carolus Linnaeus founder of taxonomy and binomial nomenclature Clustered similar organisms into categories, he did not assume any evolutionary relationship based on this classification scheme

Principles of Populations Thomas Malthus (1798) published that populations increase faster than environment can handle Capacity to over-reproduce is seen in all species Eventually populations stop increasing in size and reach a steady state (carrying capacity)

Geology Hutton ( 1795) theory of gradualism that major changes are the result of slow small changes Lyell (1830) geological changes throughout time have been subjected to the same forces Conclusions: If geological changes are slow earth is older than 6,000 years old the slow changes can build and result in profound environmental changes over time

Sir Charles Lyell (1797 – 1875) Born in Scottland Attended Oxford University -> mathematics and geology Knighted for scientific accomplishment Principles of Geology (12 editions). action of the rain, sea, volcanoes and earthquakes explained the geological history of more ancient times. http://www.mnsu.edu/emuseum/information/biography/klmno/lyell_charles.html

Relating geological evolution to biological evolution: Theories of biological evolution begin in the late eighteenth century Lamarck was the first to propose a mechanism that related environment to biological changes (1809) Use and Disuse Inheritance of Acquired Characteristics

Jean-Baptist Lamarck (1744 -1829) -> French zoologist -> ignored or attacked during his lifetime -> Lamarck proposed a different mechanism for evolution than Darwin, but the predicted result is the same

Jean-Baptist Lamarck First Law -> change in the environment changes the needs of animals -> causes a change in their behavior -> altered behavior leads to greater or lesser use of structures or organs -> structures increase/decrease in size over generations Second Law -> such changes are inheritable

Georges Cuvier (1769 – 1832) French anatomist and father of paleontology History of life is recorded in geological strata containing fossils He noticed that species appear and disappear in the fossil record He did not use this to support evolution, but developed catastrophism Fossils -> essential for understanding evolutionary relationships -> connection between past and present

Riddles… => Some fossils do not resemble existing species! => Some seashells can be found on mountaintops

Stratification Placing fossils in a historical sequence Deeper strata are older

Scientists influencing Darwin

Darwin Sails on Beagle at 22 Noted that flora and fauna of islands off of SA were more like continental species than those of other islands with similar climate and habitats Contributions of Lyell and Malthus along with his observations lead him to his mechanism for evolution

Galåpagos Islands Darwin Wolf Pinta Marchena Genovesa Santiago Isabela Darwin Wolf Pinta Marchena Genovesa Fernandia Santiago Bartolomé Råbida Pin zon Seymour Baltra Santa Cruz Santa Fe Tortuga Española San Cristobal Floreana EQUATOR Galåpagos Islands

Marine Iguana Land Iguana

Evolution Click On Picture For More November 24, 1859 Evolution: the change over time of the genetic composition of populations Natural selection: populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others (differential reproductive success) Evolutionary adaptations: a prevalence of inherited characteristics that enhance organisms’ survival and reproduction November 24, 1859

Descent with Modification, I 5 observations: 1- Exponential fertility 2- Stable population size 3- Limited resources 4- Individuals vary 5- Heritable variation

Descent with Modification, II 3 Inferences: 1- Struggle for existence 2- Non-random survival 3- Natural selection (differential success in reproduction)

Mechanism : Natural Selection Fact 1: Over-reproduction occurs in nature Fact 2: Populations do not increase exponentially Fact 3: There are limited natural resources (food, shelter) These facts are seen in Malthus’ works on populations

Fact 4: Variation exists in populations Inference 1: struggle for survival ensues Fact 4: Variation exists in populations Fact 5: Much of the variation is heritable Fact 4 was physically observed. Darwin’s weakness was the 5th fact Inference 2: Organisms with the best variations survive the struggle for life Inference 3: Unequal survival of organisms with different variations leads to favorable variations accumulating over time

Key Concepts What is the raw material necessary for the mechanism of Natural Selection? Heritable variations What is the smallest unit of evolution? Populations Darwin incorporated Lyell’s gradualism into biological evolution combined with Malthus’ observations regarding populations

Evidence for Evolution Artificial selection Island biogeography Fossil record Taxonomy Comparative Anatomy Vestigial Structures Comparative Embryology Molecular Biology

Natural selection process by which individuals that are better suited to their environment survive and reproduce most successfully. Adaptation is an inherited characteristic that increases an organism’s chance of survival.

Evolution evidence: Biogeography Geographical distribution of species Examples: Islands vs. Mainland Australia Continents

…can lead to reproductive isolation, divergence of gene pools and speciation.

Evolution evidence: The Fossil Record Succession of forms over time Transitional links Vertebrate descent

Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis.

The Fossil Record

Evolution evidence: Comparative Anatomy Homologous structures (homology) Descent from a common ancestor Vestigial organs Ex: whale/snake hindlimbs; wings on flightless birds The ZOO OF YOU…Click on Picture

Evolution evidence: Comparative Embryology Pharyngeal pouches, ‘tails’ as embryos

Evolution evidence: Molecular Biology Similarities in DNA, proteins, genes, and gene products Common genetic code

Final words…... “Absence of evidence is not evidence of absence.” Review… Evolution In your Life… Sexual Cannibalism? Modern View of Evolution