Lecture 2: History of Evolution Flashcards
Biological essentialism
a viewpoint that attributes certain characteristics, behaviors, or roles to individuals based on their biological makeup, particularly their sex or gender
What was the pre-Darwinian view?
Variation is accidental imperfection
Uniformitarianism
The same geological processed operated in the past as in the present. Geological data can be explained by causes that we now observe
Who championed uniformitarianism?
James Hutton and Charles Lyell
Catastrophism
Sudden, violent and short-lived events were responsible for the current state of the earth
What did Georges Cuvier believe?
He recognized that fossil forms were likely extinct. He established extinction as a fact
What theories did Lamarck, Jean-Baptiste Pierre, and Antoine de Monet develop?
Theories of phenotypic evolution and speciation
Theory of phenotypic evolution
Traits acquired during the course of an individual’s lifetime were passed on to offspring.
Ex: lengthening of giraffe’s necks, thickening of blacksmith’s arms
Which theory addresses the inheritance of acquired characteristics?
Lamarck’s theory of phenotypic evolution
Lamarck’s hypothesis for giraffes
Giraffes evolved long necks because individuals in ancestral giraffe populations stretched their necks to reach higher leaves on trees. This stretching led to the elongation of their necks, and this acquired trait was then passed on to their offspring. Over time, this process resulted in the evolution of giraffes with long necks.
Darwin hypothesis for giraffes
Giraffes with longer necks were more likely to survive and reproduce because they could access more food from taller trees. Over successive generations, the genes for longer necks became more common in the population through the process of natural selection
Theory of speciation
Species originate from spontaneous generation and have not originated from common ancestors
Where are the species and common ancestor on a bifurcating tree of life?
Species: tips
Common ancestor: root
How does natural selection play a role in the Peppered Moths example?
In the 18th century, the white form of the moth was the only form known.
In 1848, dark moths were discovered as they were camouflaged on trees where soot from coal-burning had darkened tree bark.
After coal-burning decreased in the 1960s, the white form became prevalent again
What are the 5 components of Darwin’s Origin of Species?
1) Evolution
2) Common descent
3) Gradualism
4) Population change
5) Natural selection
What is common descent?
Tree of life
What is gradualism?
Slow incremental change with intermediate forms
What is population change?
Evolution occurs by changes in the proportions of individuals within a population that have different inherited characteristics
What is natural selection?
Changes in proportion of individuals with different characteristics are caused by differences in their ability to survive and reproduce
Who independently conceived natural selection?
Alfred Russell Wallace
What did Alfred Russell Wallace spur Darwin to write?
The Origin of Species
Who is the father of biogeography?
Alfred Russell Wallace
What is Wallace’s Line?
Major biogeographic barrier between Australasia and Asia
What does Wallace’s Line tell us?
Many groups of organisms are found only north or south of this line
What is the Wallace Effect?
Natural Selection can contribute to reproductive isolation of incipient species (recently derived species) by creating barriers to breeding and geneflow between populations and ultimately leading to speciation
What is mutationism?
Discretely different organisms arose via mutation and natural selection is not required for the origin of new species
What was Richard Goldschmidt’s idea named?
Hopeful monsters
What does the Hopeful Monsters idea say?
Sudden drastic changes reorganize the heritable material in an organism and create “hopeful monsters” – most of this massive genetic change would be deleterious and the individuals wouldn’t survive, but some would and this would lead to speciation
Mendel’s pea plant experiment led to what laws
The laws of phenotypic characters, also known as Mendelian genetics
What is the Modern Synthesis?
A combination of Darwin’s evolution and Mendel’s genetics
What is the product of the Modern Synthesis?
Neo-Darwinism
What is Neo-Darwinism?
Adaptive evolution is caused by natural selection on mendelian genetic variation
Who were the 4 big players in the Modern Synthesis?
Ronald A. Fisher
J. B. S. Haldane
Sewall Wright
Ernst Mayr
Raw material of natural selection
Mutation is not an alternative to natural selection, but rather it’s raw material
Founder effect
Occurs when a subset of individuals of a population “move to an isolated island,” forming a founding population
Genetic drift
Random genetic changes that can cause evolution
What were Ernst Mayr’s 3 major contributions?
1) Biological species concept (BSC)
2) Theory of geographic (allopatric) speciation
3) Theory of founder effect speciation
What is the biological species concept (BSC)?
Species are groups which are reproductively isolated from other groups. They do not exchange genes from other groups
What are two ways that diverging species could become reproductively isolated?
1) Premating isolating mechanism, such as phenotypic preference
2) Postmating isolating mechanism, such as infertility
What is the theory of geographic (allopatric) speciation?
New species form when populations become geographically isolated, and thus can undergo genetic divergence
What is the theory of founder effect speciation?
Drastic reductions in population size promote speciation
What are the 4 causes of evolution within species?
1) Mutation (creation of new variants)
2) Geneflow/migration (movement of genes or variants of genes)
3) Natural selection (differential reproductive success of phenotypic variants)
4) Genetic drift (random effects such as founder events that cause changes in gene frequencies over time)
Phenotype vs Genotype
Phenotype: observed characteristics
Genotype: set of genes in an individual’s DNA
Reproductive isolation
species with barriers to genetic exchange and interbreeding
Great tree of life/common ancestor
All organisms form a great “tree of life” or phylogeny. All forms of life have descended from a single common ancestor in the remote past
Which 3 people are credited with the discovery of DNA’s stucture?
Watson, Crick, Rosalind Franklin
Who published the Neutral Theory of Molecular Evolution?
Motoo Kimura
What is the Neutral Theory of Molecular Evolution?
Most of the evolution of DNA sequences occurs by genetic drift rather than natural selection
Wobble Position
Mutations on the third position won’t change the amino acid. These mutations are silent as the phenotype doesn’t change
Who were two important players in Sociobiology?
William D. Hamilton and Robert Trivers
Cooperation
Organisms work together for common benefits
Kin selection
An animal risks its survival to help relatives, an example of altruistic behavior
3 examples of Conflict
Parent vs offspring
Sibling vs sibling
Male vs female
What are genomics and phylogenomics being used for?
Understanding individual genetic variants across genomes and populations that yield phenotypic variations
What were genomics and phylogenomics used to sequence?
The entire genome of the virus that causes COVID-19
What did Thomas Malthus believe?
The rate of human population growth is higher than the rate of increase in food supply, leading to famine
What is an intermediate fossil?
A fossil that shows an intermediate state between an ancestral trait and that of its later descendants
What is geneflow?
The movement of genes or variants of genes
What was the major gap in Darwin’s theory?
It didn’t explain heritability
