Controversies (Evolution) Flashcards
controversy to Darwin’s theory of evolution through natural selection
no major controversies
natural selection is able to explain everything
disagreement in the understanding of evolution
two schools of thought
- gradualism
- punctuated equilibrium theory
gradualism
new species arise at a consistent rate
species evolve slowly over time through minor changes
aren’t able to observe speciation because it takes so long
history of the earth is long enough to explain the amount of diversity
frequency of speciation events
around a handful every 10,000 years
gaps in the fossil record
can be a gap of 50 million years
gradualism explanation for gaps in the fossil record
it can be very difficult for a fossil to form
requirements for the formation of a fossil
organism must die in a location that is relatively protected from the elements
bones cannot be broken or too badly shattered
bones have to acquire minerals from the surrounding ground over millions of years
buried deep and under significant pressure for millions of year
cannot be disturbed (floods, glaciers, volcanoes, earthquakes, erosion)
millions vs. billions of years for the formation of fossils
billions of years under that much pressure can cause too much distortion for the fossil to be recognizable
taphonomy
study of how fossils are formed
paleontological digs
very expensive
have to have strong evidence or be very sure before they dig
limited by funding
“missing links”
part of gradualism theory
where there are gaps in the fossil record
evolutionary phylogeny
scientists aren’t trying to find the missing links- have enough to support the theory of evolution through natural selection
finding all the fossils in the world
would require digging all over the world
fill in the missing links
determining the relations between organisms
based on shared characteristics
don’t need the whole ancestral lineage of a species
uniformitarianism vs. gradualism
not the same
gradualism supports natural selection
uniformitarianism: species are always changing uniformly over time making changes to fill needs
similarities: evolution happened slowly over time at the same rate throughout history
punctuated equilibrium theory
different explanation for gaps in the fossil record
difficult to prove because the evidence is based on lack of evidence
lack of evidence accounts for gaps in transitional fossils
catastrophists
19th century
believed the world was very old
went against uniformitarianism
gaps in fossil record caused by a series of catastrophes that cause the eradication or near eradication of life on earth
catastrophes caused Creation events to occur
Adam and Eve was an example of a Creation event
catastrophism vs. punctuated equilibrium theory
not the same
punctuated equilibrium theory supports natural selection
similarities: evolution hasn’t happened at the same rate throughout history
equilibrium
when a species doesn’t have to adapt to survive
doesn’t have to change appreciably as long as no major changes happen to the species
small genetic variations that don’t hinder the species’ ability to survive and reproduce
punctuated equilibrium theory and speciation
ex of peripatric speciation:
sub-population moves somewhere else and they can survive there because of a genetic variation from the original population
eventually a new species arises and they reach equilibrium
transitional period is the reason for gaps in fossil record
Stephen Jay Gould and Niles Eldredge
first to propose the theory of punctuated equilibrium
late 1970s
Stephen Jay Gould
essayist
illustrated biology to general public using lit, history, language, poetry, art, architecture, music
