Argentina C. Observations 4. Biogeography - Community Convergence

Argentina C. Observations 4. Biogeography - Community Convergence

Argentina C. Observations 4. Biogeography - Community Convergence In similar environments, there are organisms that fill similar ecological roles and they are morphologically similar.

Correlated patterns Australia C. Observations 4. Biogeography Island Faunas

C. Observations 4. Biogeography Island Fauna - Fauklands species same as mainland - Galapagos species different from mainland a. degree of isolation correlated with uniqueness of inhabitants.. Voyage of the Beagle Darwin (1845) "The natural history of these islands is eminently curious, and well deserves attention. Most of the organic

productions are aboriginal creations, found nowhere else; Flightless Cormorant there is even a difference between the inhabitants of the different islands; yet all show a marked relationship with those of America, though separated from that continent by an open space of ocean, between 500 and 600 miles in width.

Green Iguana Central and South America The archipelago is a little world within itself, or rather a satellite attached to America, whence it has derived a few stray colonists, and has received the general character of its indigenous productions. Considering the small size of the islands, we feel the more astonished at the number of their aboriginal

beings, and at their confined range. Galapagos Land Iguana, pallid species, only on Santa Fe island. Seeing every height crowned with its crater, and the boundaries of most of the lava streams still distinct, we are led to believe that within a period

geologically recent the unbroken ocean was here spread out. Hence, both in space and time, we seem to be brought somewhat near to that great fact -- that mystery of mysteries -- the first appearance of new beings on this earth. The Voyage of the Beagle Charles Darwin C. Observations

4. Biogeography Island Faunas a. Isolation correlates with uniqueness C. Observations 4. Biogeography Island Faunas a. Isolation correlates with uniqueness b. islands are dominated by dispersive forms

C. Observations 4. Biogeography Island Faunas a. Isolation correlates with uniqueness b. islands are dominated by dispersive forms c. there is even variation among islands - Finches

"Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends." - Mockingbirds - Mockingbirds

Darwin classified four varieties of one species: One species - Mockingbirds John Gould, the premiere ornithologist of the day, classified these as four species:

- Mockingbirds Darwin began to think could the variation WITHIN species eventually lead to variation BETWEEN species? Could organisms in a species become so different that they become different species? C. Observations

4. Biogeography Island Faunas - How did these animals get here? Everything points to migration from Americas C. Observations 4. Biogeography Island Faunas - How did these animals get here? Everything points to migration

- But if ancestors migrated from Americas, C. Observations 4. Biogeography Island Faunas - How did these animals get here? Everything points to migration - But if ancestors migrated from Americas, then the species must have changed over time

into the species we observe there today. Because they are not the same. C. Observations 5. Argument for Evolution as Historical Fact: P1: Species that are alive today are different from those that have lived previously. P2: Spontaneous Generation is refuted, so organisms only come from other

organisms. C1: Thus, the organisms alive today must have come from those pre-existing, yet different, species. C2: There must have been change through time (evolution). Corollary: The fossil record, vestigial organs, and homologies are all explicable and logical in this context, and inexplicable (even heritical) in some theological contexts (imperfection).

I. Darwins Contributions A. His Life B. Origin of Species C. Observations D. Hypothesis How Change Occurs D. Hypothesis How Change Occurs 1. Transitional Observations

a. Domesticated Animals D. Hypothesis How Change Occurs 1. Transitional Observations a. Domesticated Animals D. Hypothesis How Change Occurs 1. Transitional Observations

a. Domesticated Animals Humans can change the characteristics of a species by selecting for particular traits. This can lead to the expression of extreme variation, well beyond the original range of variation in the initial group. Selection can create. There are no wolves that are as small as Chihuahuas

D. Hypothesis How Change Occurs 1. Transitional Observations b. 1844: Darwin Reads Malthus - Essay On the Principle of Population (1798) Thomas Malthus (1766-1834) D. Hypothesis How Change Occurs

1. Transitional Observations b. 1844: Darwin Reads Malthus - Essay On Population P1: All populations have the capacity to over-reproduce P2: Resources are finite C: There will be a struggle for existence most offspring born will die before reaching reproductive age.

D. Hypothesis How Change Occurs 2. Natural Selection P1: All populations have the capacity to over-reproduce P2: Resources are finite C: There will be a struggle for existence P3: Organisms in a population

vary, and some of this variation is heritable D. Hypothesis How Change Occurs 2. Natural Selection P1: All populations have the capacity to over-reproduce P2: Resources are finite

C: There will be a struggle for existence P3: Organisms in a population vary, and some of this variation is heritable C2: Some organisms, as a consequence of their inherited traits, will be more likely to survive and reproduce than others. There will be differential

reproductive success. D. Hypothesis How Change Occurs 2. Natural Selection C2: Some organisms, as a consequence of their inherited traits, will be more likely to survive and reproduce than others. There will be differential reproductive success.

C3: So, adaptive traits will be passed on in a population at higher frequency than less adaptive traits. These adaptive traits will accumulate in a population. The population will change over time. LINEAGE EVOLUTION. D. Hypothesis How Change Occurs 2. Natural Selection C2: Some organisms, as a consequence of their inherited traits, will be more likely to survive and reproduce than others. There will be differential

reproductive success. C3: Over time, adaptive traits will be passed on in a population at higher frequency than less adaptive traits. These adaptive traits will accumulate in a population. The population will change over time. LINEAGE EVOLUTION. Corollary: Two populations, adapting to different environments, will become different from one another; perhaps so different that they are unable to mate, and are different species RADIATIONAL EVOLUTION.

E. Dilemmas 1. Evolution of complex traits E. Dilemmas 1. Evolution of complex traits E. Dilemmas

1. Evolution of complex traits - "we should be extremely cautious in concluding that an organ could not have been formed by transitional gradations of some kind. Numerous cases could be given in the lower animals of organs performing at the same time wholly distinct functions" E. Dilemmas 1. Evolution of complex traits

2. Where are the continuous sequences of transitional forms, both through time and at present (connecting existing species?) X X X

X X ? X X

X X E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional forms?

-the fossil record is incomplete not all species leave a fossil -Keep looking E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional forms?

1861: Archeopteryx Lithographica E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional

forms? - Connecting species: Adapted forms swamp intermediates, which are typically rare and are not as 'perfected' as adapted forms... E. Dilemmas 1. Evolution of complex traits

2. Where are the continuous sequences of transitional forms? 3. How are instincts evolved? E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional forms?

3. How are instincts evolved? close study demonstrates that instincts also vary; so selection can act on them if they are heritable like a morphological trait. E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional forms?

3. How are instincts evolved? 4. How do sterility barriers evolve? And how are sterile castes selected for??? E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional forms?

3. How are instincts evolved? 4. How do sterility barriers evolve? And how are sterile castes selected for??? 5. Source of heritable variation? E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional

forms? 3. How are instincts evolved? 4. How do sterility barriers evolve? And how are sterile castes selected for??? 5. Source of heritable variation? - Natural selection should weed out poorly adapted forms over time, making the organisms in the population more similar (less variation). Why is there still so much variation in natural populations?

E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional forms? 3. How are instincts evolved? 4. How do sterility barriers evolve? And how are sterile castes selected for???

5. Source of heritable variation? - and if heredity is governed by blending traits, then how is variation produced generation after generation? E. Dilemmas 1. Evolution of complex traits 2. Where are the continuous sequences of transitional forms?

3. How are instincts evolved? 4. How do sterility barriers evolve? And how are sterile castes selected for??? 5. Source of heritable variation? - Darwins explanations: - Lamarckian use and disuse - and gemmules

F. Darwinian Evolution 1. Darwins Model Sources of Variation Causes of Change ???????????????? VARIATION NATURAL SELECTION (use and disuse??)

F. Darwinian Evolution 2. A Summary of Darwin's Theories (from Mayr) - Evolution as such - change over time - Common Descent - not Lamarckian transformationalism - Gradualism - incremental, uniformitarian change - Populational Change in Frequencies of Traits not changes in individuals becoming perfect

- Natural Selection - changes due to differential reproductive success Post Darwinian Developments I. Physics A. The Age of the Earth 1. 1862 - William Thompson - "Lord Kelvin"

2. 1896 - Henri Becquerel - discovers emission of Uranium 3. 1903 - Pierre and Marie Curie - discover emission from new element - Radium 4. 1904 - Ernst Rutherford - "The discovery of the radio-active elements, which in their disintegration liberate enormous amounts of energy, thus increases the possible limit of the duration of life on this planet, and allows the time claimed

by the geologist and biologist for the process of evolution." Post Darwinian Developments II. Geology A. The Dynamic Earth Post Darwinian Developments

II. Geology A. The Dynamic Earth Continental Drift - 1915 - Alfred Wegener - Not accepted until the 1960s and 1970s, when sea floor spreading was observed, sonar was used to map the ocean, and paleomagnetism

demonstrated where continents had been in the past relative to magnetic north. - North and South Atlantic and Indian Ocean Basins. Post Darwinian Developments III. Paleontology

A. Intermediate Fossils FISH AMPHIBIANS Ichthyostega - Fins and gill covers (FISH)

- Feet (AMPHIBIANS) XXX - After fish, before amphibians (just where evolution predicts it should be) D. Devonian (417-354 mya)

- Placoderms - Sharks - Lobe-finned Fishes 365 mya 385 mya Archeopteryx

- Fingers, teeth, tail (Reptiles) -Feathers (birds) - After reptiles, before birds (just where evolution predicts it should be) REPTILES BIRDS

XXX Therapsids REPTILES MAMMALS

- Mammalian skeleton - Intermediate ear - scales XXX - After reptiles, before mammals (just where evolution predicts it should be)

Mammals from the Jurassic (185 mya) Therapsids from the Permian (280 mya) to the Triassic (200mya) Pelycosaur Reptiles of the

Carboniferous (300 mya) Australopithecines Australopithecus afarensis Legs

Australopithecines - bipedal (human trait) - chimp-sized cranial volume APES HUMANS - After apes, before humans (just where

evolution predicts it should be) XXX Post-Darwinian Facts I. Physics II. Geology/Paleontology III. Genetics

Post-Darwinian Facts I. Physics II. Geology/Paleontology III. Genetics - Genetic info is particulate (no blending) - Variation produced by new combinations of particles (crossing over and ind. assort.)

Post-Darwinian Facts I. Physics II. Geology/Paleontology III. Genetics IV. The Modern Synthesis 1940s The Modern Synthetic Theory of Evolution

Mutation Recombination - crossing over VARIATION Sources of Variation

- independent assortment So, if NO AGENTS are acting on a population, then it will be in equilibrium and WON'T change. Agents of Change N.S. Drift

Migration Mutation Non-random Mating Beyond the Synthesis 1. Peripatric Speciation (Mayr) Beyond the Synthesis

1. Peripatric Speciation (Mayr) 2. Punctuated Equilibrium (Eldridge and Gould 1972) - 1972 - Eldridge and Gould - Punctuated Equilibrium VARIATION 1. Consider a large, well-adapted population

TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium 1. Consider a large, well-adapted population VARIATION

Effects of Selection and Drift are small - little change over time TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium

VARIATION 2. There are always small sub-populations "budding off" along the periphery of a species range... TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium

2. Most will go extinct, but some may survive... X VARIATION X X

TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium 2. These surviving populations will initially be small, and in a new environment...so the effects of Selection and Drift should be strong... X

VARIATION X X TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium

3. These populations will change rapidly in response... X VARIATION X X

TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium 3. These populations will change rapidly in response... and as they adapt (in response to selection), their populations should increase in size (because of increasing reproductive success, by definition). X

VARIATION X X TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium

3. As population increases in size, effects of drift decline... and as a population becomes better adapted, the effects of selection decline... so the rate of evolutionary change declines... X VARIATION X

X TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium 4. And we have large, well-adapted populations that will remain static as long as the environment is stable...

X VARIATION X X TIME

- 1972 - Eldridge and Gould - Punctuated Equilibrium 5. Since small, short-lived populations are less likely to leave a fossil, the fossil record can appear 'discontinuous' or 'imperfect' X VARIATION X

X TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium 5. Large pop's may leave a fossil.... X

VARIATION X X TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium

5. Small, short-lived populations probably won't... X VARIATION X X

TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium 6. So, the discontinuity in the fossil record is an expected result of our modern understanding of how evolution and speciation occur... X VARIATION

X X TIME - 1972 - Eldridge and Gould - Punctuated Equilibrium 6. both in time (as we see), and in SPACE (as changing

populations are probably NOT in same place as ancestral species). X VARIATION X X

TIME Beyond the Synthesis 1. Peripatric Speciation (Mayr) 2. Punctuated Equilibrium (Eldridge and Gould 1972) 3. Evo-devo: the importance of developmental programs Evo-Devo the influence of developmental programs

1. Core Processes - Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED: - Many enzymes are more than 50% similar in AA sequence in E. coli and H. sapiens, though separated by 2

billion years of divergence. - Of 548 metabolic enzymes in E. coli, 50% are present in ALL LIFE, and only 13% are unique to bacteria. Evo-Devo the influence of developmental programs 1. Core Processes

- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED: - Many enzymes are more than 50% similar in AA sequence in E. coli and H. sapiens, though separated by 2 billion years of divergence. - Of 548 metabolic enzymes in

E. coli, 50% are present in ALL LIFE, and only 13% are unique to bacteria. - So the variation and diversity of life is NOT due to changes in metabolic or structural genes... we are all built out of the same stuff, that works the same way at a cellular level.

Evo-Devo the influence of developmental programs - Variation is largely due to HOW these processes are REGULATED... 300 cell types in humans, all descended from the zygote; all genetically the same.

- Best (and most fundamental) examples are HOX genes. These are 'homeotic genes' that produce a variety of transcription factors. The production and localization of these transcription factors are CRITICAL in determining the developmental compartments' of

bilaterally symmetrical animals. Evo-Devo the influence of developmental programs - Effects can be profound - 'Master Switches' that initiate downstream cascades that can be very different... like compound or vertebrate eyes.

Beyond the Synthesis VARIATION Recombination DEVELOPMENT

Mutation Agents of Change PHYSIOLOGY Sources of Variation

Selection Drift Mutation Migration Non-Random Mating

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