Why is Darwin s Theory of Evolution by Natural Selection controversial? Or is it?

Why is Darwin s Theory of Evolution by Natural Selection controversial?

Why is Darwin s Theory of Evolution by Natural Selection controversial? Darwin: species change and form from existing species by natural causes vs. species were created as is by supernatural causes and if new species form by natural causes, does that mean human moral and rational faculties are the result of natural causes? -> humans descended from monkeys

Why is Darwin s Theory of Evolution by Natural Selection controversial? Darwin: if new species can form, then given a lot of time, the many diverse forms of life could descend from a common ancestor vs. the earth is about 8,000 years old Darwinian evolution accepts (requires) the conclusion of geologists and physicists that the earth is very old.

How old is the earth and life on earth?

a. Simple eukaryotes b. prokaryotes Place these events on the timeline of earth s history d. c. Cambrian explosion major animal groups e.

A brief overview of the earth s history Earth forms Carbon isotope (first evidence of life) First fossil microbes Oldest eukaryotic fossil Animal diversity begins Period of heavy bombardment Oxygen accumulates in atmosphere dinosaurs hominids 4 3 2 1 today Time - billions of years ago

Why is Darwin s Theory of Evolution by Natural Selection controversial? Evolution is just a theory, and is has not been proven (nor can it be proven because we can t go back in time to observe it). A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method, and repeatedly confirmed through observation and experimentation. As with most (if not all) forms of scientific knowledge, scientific theories are inductive and they aim for predictive and explanatory force. Cell theory, germ theory, big bang theory, theory of relativity, molecular orbital theory, transition state theory some theories are discarded when evidence contradicts: Lamarkianism, Spontaneous generation of life, miasma theory of disease A scientific law is a statement based on repeated experimental observations that describes some aspect of the world. Laws differ from scientific theories in that they do not posit a mechanism or explanation of phenomena: they are merely distillations of the results of repeated observation. Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Newton's law of universal gravitation states that any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Hooke's law is a principle of physics that states that the force needed to extend or compress a spring by some distance is proportional to that distance. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but cannot be created or destroyed.

Applying the scientific method Problem: How did the many diverse forms of life originate? Note: this is not the same as how did life originate (e.g. molecules to man ) Hypothesis: 1. New species come from previously existing species, and 2. divergent life-forms descended from a common ancestor. Mechanism: New species come from previous species by descent with modification (evolution by natural selection) 1. Organisms in a population are born with heritable variation of traits 2. The number of offspring outnumber resources, therefore there is a struggle to survive/reproduce 3. Individuals with some traits will survive/reproduce more than others 4. Over time, the population will change to have more individuals with the traits that promote survival/reproduction, and hence the population will change to become adapted to its particular environment

Problem: How did the many diverse forms of life originate? Hypothesis: 1. New species form from previously existing species, and 2. divergent life-forms descended from a common ancestor Mechanism: New species form from previous species by descent with modification (evolution by natural selection) If so, then:?? Applying the scientific method

Applying the scientific method Problem: How did the many diverse forms of life originate? Hypothesis: 1. New species form from previously existing species, and 2. divergent life-forms descended from a common ancestor Mechanism: New species form from previous species by descent with modification (evolution by natural selection) If so, then: 1. We should be able to see transitional forms gradually accumulating modifications of traits over time. 2. We might expect to directly observe species changing over time. 3. Species related by descent from a common ancestor should share traits they inherited from that common ancestor. 4. Closely related species live near one another, while more distantly related species are more geographically separated: Species living near each other should be more similar (share more traits) because they are more closely related, while species isolated from each other should have less traits in common because they are more distantly related.

Problem: How did the many diverse forms of life originate? Alternate Hypothesis: 1. New species are created as is and do not change. Mechanism: Supernatural causes If so, then:?? Applying the scientific method

Problem: How did the many diverse forms of life originate? Alternate Hypothesis: 1. New species are created as is and do not change. Mechanism: Supernatural causes Applying the scientific method If so, then: 1. Fossils of all organismal types should be present at all geographic levels (ages) 2. And these fossils should not show signs of progression or change between levels. 3. Traits in organisms reflect the acts of the creator, without historical traces. Note: Evolution addresses the origins of the diversity of life, not the origins of the first living organisms. Scientist are still trying to understand how living organisms could originate from non-living chemicals but scientific explanations require reproducible observations (processes that follow natural laws) and not super-natural causes.

The Evidence for Evolution 1. We should be able to see transitional forms gradually accumulating modifications of traits over time. 2. We might expect to directly observe species changing over time. 3. Species related by descent from a common ancestor should share traits they inherited from that common ancestor. 4. Closely related species live near one another, while more distantly related species are more geographically separated: Species living near each other should be more similar (share more traits) because they are more closely related, while species isolated from each other should have less traits in common because they are more distantly related. What is found? Fossils exist and fossil forms are unlike species living today 1. Fossil Sequence? When fossils are arranged according to their age, they show successive evolutionary change 2. Fossil Intermediates? Transitional fossils have been found between: Amphibians & reptiles, reptiles & birds, reptiles & mammals, apes and humans

The fossil Record is Incomplete Why is that?

The fossil Record is Incomplete At the time of Darwin, the fossil record was VERY scanty. A great deal of progress has been made since, but it is far from finished. The fossil record is relatively incomplete for several reasons: 1. Soft tissues are rarely preserved 2. Movement of the earth's crust has obliterated and/or covered many fossils 3. Fossilization takes place only in certain types of habitats and favorable environments 4. Paleontologists have not dug up every place on earth

The Evidence for Evolution 1. We should be able to see transitional forms gradually accumulating modifications of traits over time. 2. We might expect to directly observe species changing over time. 3. Species related by descent from a common ancestor should share traits they inherited from that common ancestor. 4. Closely related species live near one another, while more distantly related species are more geographically separated: Species living near each other should be more similar (share more traits) because they are more closely related, while species isolated from each other should have less traits in common because they are more distantly related. Natural Selection: antibiotic resistance in bacteria beak length in soapberry bug

The Evidence for Evolution 1. We should be able to see transitional forms gradually accumulating modifications of traits over time. 2. We might expect to directly observe species changing over time. 3. Species related by descent from a common ancestor should share traits they inherited from that common ancestor. 4. Closely related species live near one another, while more distantly related species are more geographically separated: Species living near each other should be more similar (share more traits) because they are more closely related, while species isolated from each other should have less traits in common because they are more distantly related. Homologous structures: bones of the forelimb The underlying design of each structure is similar despite their functional differences

The Evidence for Evolution 1. We should be able to see transitional forms gradually accumulating modifications of traits over time. 2. We might expect to directly observe species changing over time. 3. Species related by descent from a common ancestor should share traits they inherited from that common ancestor. 4. Closely related species live near one another, while more distantly related species are more geographically separated: Species living near each other should be more similar (share more traits) because they are more closely related, while species isolated from each other should have less traits in common because they are more distantly related. Homologous structures in embryos indicate common ancestry Homologous structures in adults develop from homologous groups of cells in embryos (they share developmental pathways)

The Evidence for Evolution 1. We should be able to see transitional forms gradually accumulating modifications of traits over time. 2. We might expect to directly observe species changing over time. 3. Species related by descent from a common ancestor should share traits they inherited from that common ancestor. 4. Closely related species live near one another, while more distantly related species are more geographically separated: Species living near each other should be more similar (share more traits) because they are more closely related, while species isolated from each other should have less traits in common because they are more distantly related. Vestigial structures an interesting kind of homologous structure Features that have no apparent function Typically have an important function in related species reflect history of change Ex: Hindlimb joints in whales. What other animal has vestigial hindlimbs?

Vestigial Structures in Humans Tailbone Wisdom Teeth Appendix

Vestigial Structures in blind cave fish

The Evidence for Evolution 1. We should be able to see transitional forms gradually accumulating modifications of traits over time 2. We might expect to directly observe species changing over time 3. Species related by descent from a common ancestor should share traits they inherited from that common ancestor. 4. Closely related species live near one another, while more distantly related species are more geographically separated: Species living near each other should be more similar (share more traits) because they are more closely related, while species isolated from each other should have less traits in common because they are more distantly related. Homologous molecular structures in all life: Central dogma (DNA -> mrna -> protein) Universal codon table Protein sequences are similar: hemoglobin DNA polymerase cytochrome oxidase, and thousands more

The Evidence for Evolution 1. We should be able to see transitional forms gradually accumulating modifications of traits over time. 2. We might expect to directly observe species changing over time. 3. Species related by descent from a common ancestor should share traits they inherited from that common ancestor. 4. Closely related species live near one another, while more distantly related species are more geographically separated: Species living near each other should be more similar (share more traits) because they are more closely related, while species isolated from each other should have less traits in common because they are more distantly related. Species that are extremely similar to one another tend to be clustered geographically, for example: Darwin s finches Hawaiian honeycreepers The law of succession: Living species are more similar to fossil species in the same geographic area than they are to living species in other areas.

Geographic Distributions Wolves are native to North America, North Africa, and Eurasia Hares and rabbits are native to North America, Africa, and Eurasia Cactuses are native to North America

Geographic Distributions Wolves are native to North America, North Africa, and Eurasia Hares and rabbits are native to North America, Africa, and Eurasia Cactuses are native to North America Tasmanian wolf Patagonian hare African spurge

Convergent Evolution

Homology vs. Analogy Natural selection appears to have favored similar adaptations independently in distantly related organisms living in similar environments --> these are analogous structures homologous structures: have similar structure (because of common ancestry), but do not necessarily have similar function (because the organisms adapted differently by divergent evolution). analogous structures: have similar function (because of similar selective pressures), but the structures are only superficially similar (because each adaptation evolved independently by convergent evolution)