Evolution Species change over time in part because

Evolution Species change over time, in part because of how they interact with their environment (ecology).

I. Darwin A. Evolution and Common Ancestry Concludes that species change over time, diverging from one another and their common ancestors as they adapt to new environments 1837 notebook Plate from The Origin of Species, 1859

I. Darwin A. Evolution and Common Ancestry As a consequence of: - stratigraphic patterns in the fossil record

I. Darwin A. Evolution and Common Ancestry As a consequence of: - stratigraphic patterns in the fossil record - evidence from morphology Homologous Structures: Same parts, but different uses in different environments (correlated pattern)

I. Darwin A. Evolution and Common Ancestry As a consequence of: - stratigraphic patterns in the fossil record - evidence from morphology Analogous Structures: Different parts, but same uses in same environment (correlated pattern)

I. Darwin A. Evolution and Common Ancestry Whale embryo w/leg buds As a consequence of: - stratigraphic patterns in the fossil record - evidence from morphology Vestigial and embryonic Structures: No used in one species but functional in others Haeckel (after Darwin)

I. Darwin A. Evolution and Common Ancestry As a consequence of: - stratigraphic patterns in the fossil record - evidence from morphology - evidence from biogeography Community Convergence: In similar environments, unrelated organisms play parallel roles and converge morphologically and ecologically

I. Darwin A. Evolution and Common Ancestry As a consequence of: - stratigraphic patterns in the fossil record - evidence from morphology - evidence from biogeography Island Communities: In isolated environments, colonists change in response to new conditions

I. Darwin A. Evolution and Common Ancestry B. Mechanism of Change: Natural Selection P 1: All populations have the capacity to ‘over-reproduce’ P 2: Resources are finite C: There will be a “struggle for existence”… most offspring born will die before reaching reproductive age.

I. Darwin A. Evolution and Common Ancestry B. Mechanism of Change: Natural Selection P 1: All populations have the capacity to ‘over-reproduce’ P 2: Resources are finite C: There will be a “struggle for existence”… most offspring born will die before reaching reproductive age. P 3: Organisms in a population vary, and some of this variation is heritable

I. Darwin A. Evolution and Common Ancestry B. Mechanism of Change: Natural Selection P 1: All populations have the capacity to ‘over-reproduce’ P 2: Resources are finite C: There will be a “struggle for existence”… most offspring born will die before reaching reproductive age. P 3: Organisms in a population vary, and some of this variation is heritable C 2: As a result of this variation, some organisms will be more likely to survive and reproduce than others – there will be differential reproductive success.

I. Darwin A. Evolution and Common Ancestry B. Mechanism of Change: Natural Selection P 1: All populations have the capacity to ‘over-reproduce’ P 2: Resources are finite C: There will be a “struggle for existence”… most offspring born will die before reaching reproductive age. P 3: Organisms in a population vary, and some of this variation is heritable C 2: As a result of this variation, some organisms will be more likely to survive and reproduce than others – there will be differential reproductive success. C 3: The population changes through time, as adaptive traits accumulate in the population.

I. Darwin A. Evolution and Common Ancestry B. Mechanism of Change: Natural Selection P 1: All populations have the capacity to ‘over-reproduce’ P 2: Resources are finite C: There will be a “struggle for existence”… most offspring born will die before reaching reproductive age. P 3: Organisms in a population vary, and some of this variation is heritable C 2: As a result of this variation, some organisms will be more likely to survive and reproduce than others – there will be differential reproductive success. C 3: The population changes through time, as adaptive traits accumulate in the population. Corollary: Two populations, isolated in different environments, will diverge from one another as they adapt to their own environments. Eventually, these populations may become so different from one another that they are different species.

I. Darwin Sources of Variation ? V A R I A T I O N Agents of Change Natural Selection

I. II. Darwin Genetics Sources of Variation Mutation Recombination - crossing over - independent assortment V A R I A T I O N Agents of Change Natural Selection Mutation Units of heredity (genes) don’t blend together; they are ‘particulate’ and are passed in new combinations to offspring. In a diploid species, each parent makes 2 n combinations of chromosomes in their gametes, without accounting for crossing-over!

I. Darwin II. Genetics III. Population Genetics and The Modern Synthesis A. Model Sources of Variation Mutation Recombination - crossing over - independent assortment V A R I A T I O N Agents of Change Natural Selection Mutation Drift Migration Non-Random Mating Rates of mutation are low; mutation is important as a source of new genes, but doesn’t change frequencies much. Selection and drift are major agents of change.

I. Darwin II. Genetics III. Population Genetics and The Modern Synthesis A. Model B. Drift - two patterns related to population size

- “Genetic Bottleneck” If a population crashes (perhaps as the result of a plague) there will be both selection and drift. There will be selection for those resistant to the disease (and correlated selection for genes close to the genes conferring resistance), but there will also be drift at other loci simply by reducing the size of the breeding population. European Bison, hunted to 12 individuals, now number over 1000. Cheetah have very low genetic diversity, suggesting a severe bottleneck in the past. They can even exchange skin grafts without rejection… Fell to 100’s in the 1800 s, now in the 100, 000’s

- “Founder Effect” and Huntington’s Chorea HC is a neurodegenerative disorder caused by an autosomal lethal dominant allele. The fishing villages around Lake Maracaibo in Venezuela have the highest incidence of Huntington’s Chorea in the world, approaching 50% in some communities. By comparing pedigrees, she traced the incidence to a single woman who arrived 200 years ago. When the population was small, she had 10 children who survived and reproduced. Folks with HC now trace their ancestry to this lineage.

I. III. IV. Darwin Genetics Population Genetics and The Modern Synthesis Modern Evolutionary Theory A. Peripatric Speciation

I. III. IV. Darwin Genetics Population Genetics and The Modern Synthesis Modern Evolutionary Theory A. Peripatric Speciation B. Punctuated Equilibrium Niles Eldridge Stephen J. Gould

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

B. Punctuated Equilibrium – Eldridge and Gould 1. Consider a large, well-adapted population VARIATION Effects of Selection and Drift are small - little change over time TIME

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

B. Punctuated Equilibrium – Eldridge and Gould 2. Most will go extinct, but some may survive. . . X VARIATION X X TIME

B. Punctuated Equilibrium – Eldridge and Gould 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

B. Punctuated Equilibrium – Eldridge and Gould 3. These populations will change rapidly in response. . . X VARIATION X X TIME

B. Punctuated Equilibrium – Eldridge and Gould 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

B. Punctuated Equilibrium – Eldridge and Gould 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

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

B. Punctuated Equilibrium – Eldridge and Gould 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

B. Punctuated Equilibrium – Eldridge and Gould 5. Large pop's may leave a fossil. . X VARIATION X X TIME

B. Punctuated Equilibrium – Eldridge and Gould 5. Small, short-lived populations probably won't. . . X VARIATION X X TIME

B. Punctuated Equilibrium – Eldridge and Gould 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

B. Punctuated Equilibrium – Eldridge and Gould 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

I. III. IV. Darwin Genetics Population Genetics and The Modern Synthesis Modern Evolutionary Theory A. Peripatric Speciation B. Punctuated Equilibrium C. Genes and Development: “Evo-Devo” …explain changes like this? Can changes like this….

C. Genes and Development: "Evo-Devo" …explain changes like this? Can changes like this…. Differences correlate with what they make (different proteins make them different colors) Differences don’t correlate with what they make; they are pretty much the same stuff, just in a different shape.

C. Genes and Development: "Evo-Devo"

C. Evo-Devo – the influence of regulatory genes .

Antennules detect chemicals secreted by predatory fish Stimulate release of dopamine in the brain Brain releases juvenile hormone (growth hormone in inverts) Growth of particular body parts continues, creating a sharp “helmet” and longer “spine” that reduce predation. Selection for an inducible developmental pathway Without Fish With Fish

IV. Modern Evolutionary Theory A. Peripatric Speciation B. Punctuated Equilibrium C. Genes and Development: “Evo-Devo” D. Model Sources of Variation Mutation Recombination - crossing over - independent assortment D E V E L O P M E N T V A R I A T I O N Agents of Change Natural Selection Drift Mutation Migration Non-random Mating