Darwin Flashcards
FitzRoy
Captain of the H.M.S. Beagle
Henslow
A natural theologian and one of the most influential people in Darwin’s life
Darwin became the Naturalist for the H.M.S. Beagle (1831-1836)
- 5 year circumnavigation of the earth
- Darwin would get dropped on land as hydrographic survey was carried out
Components of the hydrographic survey
- Geological mapping
- Fossil survey and collection
- Plant & animal description and collection
- Shapes Darwin’s understanding of human variation
Darwin’s ideas developed during trip, but he reworked them following his return…
Darwin returns to a celebrated reputation
- meets and befriends Lyell and many other naturalists
- Presents papers to Zoological and Geological Societies of London
Begins to seriously doubt “Fixity of Species”
- transmutation of species
How did the Whig political party influence Darwin?
Overpopulation as the source of poverty
Opposition to social welfare
In 1838, what book did Darwin read that influenced his thought process about “evolution”?
Malthus’s An Essay on the Principle of Population
- Population grows at a faster rate than the food supply
- Famine is a necessary outcome of the difference in growth rate
Darwin’s first diagram of an evolutionary tree from his Notebook B on Transmutation of Species (1837)
Proposes branching evolution
Vestiges of the Natural History of Creation (John Churchill in 1844)
Laid out a hypothesis of common descent
- God is the programmer of natural laws
People HATED it
- Theologists condemned it
- Scientists critiqued and enumerated errors
Darwin did not publish his ideas for decades… so what pushed him to publish?
He was about to get scooped by Alfred Russel Wallace– a naturalist and explorer working in Indonesia
Who independently comes up with the idea of natural selection?
Alfred Russel Wallace
- On the Tendencies of Varieties to depart Indefinitely from the Original Type (1858)
On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life
1st edition of Origin of Species was published in 1859 by Charles Darwin
Darwin’s 2 Big Ideas?
1.) All living things descend from one or a few original life forms
2.) Natural Selection is the mechanism
Darwin’s observations
1.) Populations have the potential to increase exponentially
2.) But they generally maintain a stable size
3.) Resources are limited
(struggle for existence)
4.) Variation in all species
5.) Variation is heritable
(Variation makes some individuals more successful in the struggle; those that survive and reproduce will leave offspring that have those same variants
Evolution by natural selection
Observations summarized
1.) There is variation in all species
2.) Variation is heritable
3.) Struggle for existence
- potential for exponential increase
- populations generally have stable sizes
- resources are limited
Some individuals are more likely to reproduce than others because of heritable traits…
So the next generation has a greater frequency of individuals that possess those specific traits
Fitness
Describes how much more likely (to reproduce)
- a number that measures the reproductive output of an organism with a given trait
“Survival of the Fittest”
Coined by Herbert Spencer in 1864
- incorporated by Darwin only in the 5th edition of Origin
- this phrase has created some misconceptions
Misconceptions of “Survival of the Fittest”
1.) Survival isn’t really the important part
2.) Physical fitness isn’t the same as Darwinian fitness (where focus is more on reproductive success)
3.) It is necessary to decouple social values from the idea of fitness
Common descent
All living things descend from one or a few original forms of life
- New/different forms of life appear by natural selection playing out over geological timescales
What can change the relative frequency of a trait in a population?
Natural selection
- results in population divergence
Darwin’s theory has implications for interpreting biological similarity
- Similarity indicates recent divergence (two life forms shared a more recent common ancestor)
- Dissimilarity indicates more distant ancestors with many differences accumulating in that length of time
Did Darwin ever use the word “evolution” in first edition of Origin?
NO!
- instead he used phrase “descent with modification” or “transmutation”
-“Evolutionist” was a bad word because of historical association with criticized ideas
- the roots of the word evolve and how it is used colloquially today
- Reasons why that word wasn’t a good fit for Darwin’s idea:
* There is no progress in evolution
* Change does not happen wholesale
Darwin’s theory of natural selection provides the framework for interpreting:
1.) Correspondence between species and their environment (adaptation)
2.) Similarity/dissimilarity among species (length of time since divergence)
Important things about evolution!
1.) There is NO PROGRESS in evolution
2.) Individuals do NOT evolve, only populations
