Chapter 22. Darwin’s origin of species challenged long-standing Western ideas, especially those of...
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Transcript of Chapter 22. Darwin’s origin of species challenged long-standing Western ideas, especially those of...
Chapter 22 Darwin’s origin of species
challenged long-standing Western ideas, especially those of the Christian church
Earth only a few thousand years old
unchanging forms of life made individually during single week by Creator
Chapter 22Plato (427 – 347 BC) 2 worlds:
(1) ideal & eternal real world(2) world of imperfection that we
perceive through our senses thought evolution would be counter-
productive in world already populated by perfect species
Aristotle (384 - 322 BC)
all living things arranged on scale of increasing complexity
each form had rung on ladder, with every rung filled
species are permanent and perfect
natural theology
dedicated to discovering Creator’s plan by studying nature
adaptations seen as evidence that the Creator designed each and every species for a particular purpose
Linnaeussought to discover order in the diversity of life “for the greater glory of God”
specialized in taxonomy(developed binomial nomenclature)
clustering of species implied no evolutionary kinship
fossils (sedimentary rocks)
layers show that a succession of organisms has populated Earth throughout time
paleontology
developed by Cuvierdocumented succession of
fossils in Paris Basinadvocated catastrophism:
each boundary corresponded with a catastrophe of some kind(flood, drought, etc.)
Hutton
explain current landforms by looking at mechanisms currently operating in the world(Ex. canyons formed by river)
gradualism: profound change is cumulative product of slow, but continuous change
Lyell
incorporated Hutton’s ideas into uniformitarianism
geologic processes have not changed throughout the history of the Earth
Lamarck
oversaw invertebrate collection at Natural History Museum of Paris
could see lines of descent when comparing current species with fossils
Lamarck’s ideas
use & disuse Ex. blacksmith hammering, giraffe stretching
inheritance of acquired characteristicschanges during lifetime could be acquired by offspring
Darwin—HMS Beagle
goal was to chart unknown S. American coastline
Darwin observed adaptations of plants and animals
many characteristics were distinct from those of Europe
Darwin—Galapagos species found nowhere else in the
world read Lyell’s “Principles of Geology” began to believe that the Earth
was very old and constantly changing
considered link between origin of new species and adaptation to environment (Ex. finches)
Darwin—theories
saw evolution as an explanation for life’s unity and diversity
developed concept of natural selection to explain adaptive radiation
Darwin—Natural Selection and Adaptation 1. natural selection is differential
success in reproduction 2. natural selection occurs through
an interaction between the environment and the variability inherent among the individual organisms making up a population
3. the product of natural selection is the adaptation of populations of organisms to their environment
Natural Selection—related ideas Malthus essay on human population connection between natural
selection (struggle for existence) and capacity of organisms to “overproduce”--many eggs laid, young born, and seeds spread, but few leave offspring
(potential offspring are eaten, freeze, starve, diseased, etc.)
Natural Selection—related ideas
in each generation, environmental factors filter heritable variations favoring some over others--differential reproduction results in favored traits being disproportionately represented in the next generation
Natural Selection—related ideas
power of selection seen in artificial selection (breeding)--Darwin thought the same process could be just as powerful over 100s and 1000s of generations--slight advantages accumulate over generations (gradualism)
Natural Selection—SUMMARY
1. diverse forms of life have arisen by descent with modification from ancestral species
2. mechanism of modification has been natural selection (working over tremendous time periods)
population
group of interbreeding individuals belonging to a particular species and sharing a common geographic area--individuals do not evolve--evolution can only be measured in populations
population--examples insecticide-resistant insects
--initial use kills 99% of insects--subsequent sprayings are less effective--natural selection is cause
HIV strains resistant to medication(these cases are rapid enough to be
observed in short period of time…)
evidence of evolution HOMOLOGY
--similar characteristic resulting from common ancestry* anatomical
(a) mammal forelimb(b) remodeling / retrofitting(c) vestigial organs
* embryological: Ex. pharyngeal pouch* molecular: Ex. DNA & RNA codes
evidence of evolution HOMOLOGY
--form a layered pattern, with all life sharing the deepest layer and each smaller group adding fresh homologies to those they share with larger groups--tools of molecular biology have corroborated evolutionary trees
(Ex. Amino acid sequences of hemoglobin)
evidence of evolution BIOGEOGRAPHY
--geographic distribution of species--species tend to be more closely related to other species from the same area than to other species with the same way of life, but living in different areas--islands provide models for this idea
evidence of evolution FOSSIL RECORD
--oldest known species are prokaryotes (supports chemistry, molecular, and cell biology evidence)--chronology: Ex. Fossil fish predate all other vertebrates--transitions: signs of change should be seen in fossil record (Ex. changes in shape of human skull)