Evolution and Genetics Come Together Flashcards
problem #1 of Darwin’s Natural selection
- blending inheritance suggests that offspring will resemble their parents
- would new variants be swapped and disappear before natural selection could act?
- didn’t think natural selection was possible as there would be no organisms that resemble their parents as they would all move toward uniformity
- why is there variants
problem #2 of Darwin’s Natural selection
- all the variance that came along with early genetics suggested that most variation was bad
- how could it produce variance that was a benefit to the organism?
problem #3 of Darwin’s natural selection
- Is the earth and sun too young for Darwin’s slow process of natural selection to have produced the different species we see today?
- Kelvin suggested this
problem #4 of Darwin’s natural selection
- why do fossils form a progressive series from lower to higher strata
- natural selection does not have directionality apart from continuous selection in one direction
- evolution may occur for long periods in one direction but otherwise doesn’t
- maybe there is another type of evolution that could explain the things seen in the fossil record
problem #5 of Darwin’s natural selection
-why are there gaps and jumps in the fossil record
What book did Hugo de Vries write
Mutation Theory
Hugo de Vries observations
- found 2 strains of a plant
- when he self-pollinated them they bred true, when he crossed them they produced offspring of different sizes
- thought that he had created a new species that couldn’t be crossed back to produce parents
- ** called these one generation transformations “mutations”
Hugos de Vries model
- new species evolve in single generation jumps
- abrupt changes, not incremental
What is Saltationism?
- model of evolution through big jumps
- this answered many of the objections to the Darwinian evolution (natural selection)
What questions about Darwinian evolution did Saltationism (De Vries’ mutation theory) answer?
- Swamping of new variants?
- creates variability so great that it justifies the naming of new species - How are there good variations?
- natural selection was perhaps just elimination of bad traits, and rather mutationism generated new variety - Young Earth?
- abrupt changes. Earth does not have to be old to support intense variation and biodiversity - Fossils in progressive series?
- inherent progression to de vries model which makes the progressive fossil record understandable - Gaps in the fossil record
- large changes
Problem with De Vries model
- oenothera lamackiana is weird plant
- many unique chromosomal things that happen and cannot be inferred with another species
- could not replicate this work
More recent example of Saltational evolution
Richard Goldschmidt
-believed that microevolution does not lead to macroevolution and that large genetic jumps are needed to explain speciation
Richard Goldschmidt’s thoughts
- thought you needed jumps to explain speciation
- thought there were special variants that were more extreme than the normal variation you see in organisms
- thought that there was a disconnect between micro and macro evolution to produce speciation
What did Richard Goldschmidt call his ‘jumps’
- ‘hopeful monsters’ that may have an advantage
- sometimes this kind of thing occurs through hybridization and can be mistaken as an evolutionary jump
- sometimes dramatic phenotypic changes occur but it is not always beneficial
what does orthogenesis suggest?
- internal propulsion to evolve, not natural selection
- lineages can experience growth, development, and death under the weight of an evolutionary momentum that natural selection cannot reverse
- evolution todya does not agree with this
What was Neo-Lamarckism
- revival of the idea of “acquired characteristics”
- idea that traits can be passed to offspring
- when not watering plants, leaves get thicker. These thick leaves are passed to offspring
What approach did Hardy and Weinberg take?
population approach
-asked how frequencies of Mendelian factors increase or decrease in a population over time
who was GH Hardy
English Mathematician
Who was Wilhelm Weinberg
German Physician
Who’s evolutionary biology and genetics were very strong in the 1920’s and 1930’s
Soviets – excelled at agricultural genetics and the study of genetic variation of natural populations
What did modern synthesis demonstrate
-that the principles of the new genetics were sufficient to explain Darwinian evolution
What were the principles of new genetics?
- No inheritance of acquired characteristics
- cutting off mice tails, all offspring mice had long tails - Persistence of recessive variants
- no intermediates when blending a uniform organism - Recombination
- generates variability that evolution can act upon
- not all recombination is good - Gene interactions
- interaction of genes causes creation of unique phenotype - Quantitative Traits can be explained by particulate inheritance
- No blending inheritance at the level of the gene
- sometime the phenotype appears blended but the genotypes do not.
What did modern synthesis show?
- selection doesn’t have to be large to be important
- process can occur due to small variation over a long time
What did modern synthesis enlarge?
- enlarged the causes of evolution
- genetic drift is random and populations can change due to sampling error when populations are low
- migrations can significantly alter the structure of a population
What did modern synthesis argue?
- no barrier between microevolution and macroevolution
- macroevolution is due to additive microevolution
- seen on the genetic level where small changes over time create new species.
