Flashcards in History of Evolution Deck (40):
what is essentialism? who thought it?
- the physics world and is life forms are fixed
- all members of a class share unchanging properties that define the class
*most controversial aspect of what Darwin proposed, was that species were NOT fixed in form
what is scala naturae?
the "great chain of being"
- life arranged hierarchically, culminating in divinity
who was Linnaeus?
father of modern taxonomy
- binomial nomenclature
- hierarchical taxonomy embodied scala naturae
who was Louis Leclerc?
- recognized that the differences between related species living in different parts of the world reflect the different environments they inhabit
- after migrating organisms have to somehow change to suit their new environment
- plants that live in desserts look like they should live in the desert and have characteristics that will allow them to live there
who was Lamarck? what was his theory?
- lineages persist forever but change in form
- vague mechanism of "internal force"
- no extinction or branching of lineages
- first explicit scientific treatment of evolution
- he proposed a mechanism that is incorrect: some internal "force" causes parents to produce offspring slightly different from themselves which accumulates changes over time so species transform into another one
who was Cuvier? what was his theory?
who did he disagree with? why?
- disputed Lamarck's claim that forms change gradually over time
**correlation of parts: organisms are so integrated in form and function that any changes would lead to death
- first to establish extinction as fact
- attributed extinction to discrete catastrophic events
- reconstructed fossils
who was Hutton? what was his theory?
earth's physical features gradually changed due to slow geological processes
who was Lyell? what was his theory?
historical changes result from uniform geological process that STILL occur today (erosion, sedimentation, volcanism)
supplanted geological catastrophism
what is the difference between Hutton and Lyell?
Lyell: geological changes are occurring
Hutton: the geological processes are STILL going on so the impacts that people saw 100 years ago are still happening now
what are the implications of Hutton and Lyell's theories?
- the earth is very old and is always slowly changing
- the past can inform the present and vice versa!
the complexity of the Earth's history can be explained in terms of the processes that are observed today
what were the thoughts on evolution before darwin?
1) essentialism was dominant
- most people thought that species did not change
2) there was no satisfactory theory for biological diversity
- those who favored evolution like Lamarck has incorrect views of the process (transforms) and the mechanism
3) extinction and branching
- Cuvier demonstrated that extinction happened but even those who favored evolution didn't think that species could split
4) uniformitariansim was promoted
- geologists like Hutton/Lyell argued that the Earth is old and constantly changing, not static like the essentialists thought
what was Darwin's mechanism for evolution?
descent with modification is the outcome of evolution
what is evolution?
descent with modification
what lead Darwin to his ideas about evolution?
- modern species resemble fossils
- modern domesticated animals can be made to vary through intentional selection (artificial selection)
- creatures in the archipelagos vary from island to island
- organisms may have very complex modifications that are necessary for their survival
what traits do domesticated varieties of species have?
- unlike wild species, most varieties are freely inter-fertile
- closely related varieties show more pronounced morphological differences that closely related wild species
what do people think is the cause of domesticated varieties?
each variety is descended from a unique ancestral species
domesticated varieties arose form wild ancestors that had the same or similar characteristics as the domesticated variety
what is artificial selection?
new varieties arise by preferentially breeding individuals showing specific desirable traits
- this process occurs over many generation, not in a single step
- improvement of breeds is a continual process resulting in the accumulation of fairly significant modifications in a relatively short period of time
what was Darwin's idea on wild species?
wild species also undergo selection!
rather than accumulating large modifications over several generations, natural species accumulate many TINY changes over a VERY long period of time
what species did Darwin observe the most? what did he write?
"The Origin of Species"
the finches in the Galapagos islands
who did further research on the finches in the Galapagos? what did he conclude?
John Gould made a descriptive account of the Galapagos collections, with the conclusion that the finches belonged to the SAME family
what were the types of finches and what differences did they have?
the size and shape of their beaks (correlated to eating preferences)
ground finches: seed eaters and cactus flower eaters
tree finches: insect eaters and bud eaters
the 13 species of finches found on the island comprise the sade number of feeding types as 9 families of birds in south america
what characteristics related beaks and eating preference?
rounded beaks were seed eaters
pointed beaks were insect eaters
what kind of climate did the Galapagos Islands have?
harsh, arid climate characterized by extended periods of severe drought
who is Malthus?
"Essay on Population"
his idea: left unchecked, human reproduction rates will rapidly outpace resource production, leading ultimately to crime, disease, war and vice (these being "natural" checks on population growth)
according to Malthus, what happens at the point where population size outstrips resource production?
1) find the means to expand the resource pool
how is the finches survival correlated to the Malthusian dilemma?
in periods of drought favorable resources like soft buds and seeds are quickly depleted, leaving only hard tough seeds
only those birds with beaks capable of breaking the tough food items can survive
deaths of "unfavorable" birds readjusts population size to the available resource pool
what are the reproductive consequences of the malthusian dilemma?
"favorable" beak morphologies are passed on to offspring
very small morphological changes accumulate over a long period of time leading to eventual morphological divergence of populations
widely different morphologies gradually become reproductively incompatible
what is adaptive radiation?
Adaptive radiation is usually due to a lack of competition for space and food sources there’s all new food sources and habitats for these birds to use and variation in the birds can make then better suited for certain habitats and become isolated and turn into their own species
what are Darwin's four postulates of natural selection?
individuals within species are variable
some of these variations are passed on to offspring
3) differential survival:
in every generation more offspring are produced than can survive
survival and reproduction of individuals is not random, those who survive and reproduce are those with the most favorable variation
what four concepts does Darwin propose?
1) common descent
2) gradual change over time
3) population differentiation
4) natural selection
what is common descent?
all living things are part of a community of descent
organisms that are more closely related have a more recent common ancestor
what is gradual change over time?
differences among organisms have accumulated in small increments over a long time
outgrowth of his "uniformitarianist" perspective
what is population differentiation?
changes in species reflect changes in the proportion of individuals in a population bearing certain hereditary traits
changes in species take place at the level of individuals within a population
not a sudden origin of new species or transformation of individuals
VARIATION, NOT TRANSFORMATION
what is natural selection?
population differentiation caused by differential reproductive success of individuals bearing particular traits
individuals that have more success are those better able to use resources in a particular habitat
same principles independently derived by Alfred Wallace
who is Alfred Wallace?
wrote a paper on natural selection and sent it to Darwin and then a year later Darwin published "Origin of the Species"
what was Darwin's particular concept of evolution?
based on lineage splitting, NOT inherently "progressive" towards higher forms
Darwin's mechanism of natural selection? what was its flaw?
generally rejected by scientists
one flaw was the lack of a mechanism for heredity
what was Darwin's theory on inheritance?
for lack of a better alternative, Darwin favored blending inheritance
red and white roses make pink
summary of Darwin's ideas
there are naturally existing differences in a population (variation)
more offspring are produced than can survive
organisms with favorable variation will be preserved = have offspring
accumulation of differences over time leads to adaptive radiation