Download Earth History: Organic Evolution

Earth History: Organic Evolution
Ideas Around the Time of Darwin
• Natural Theology: Philosophy that saw
adaptations in organisms as evidence that
God designed each species for a special
purpose.
Ideas Around the Time of Darwin
• Catastrophism: idea that boundaries in
rock strata correspond to catastrophic
events in Earth’s history.
– Purposed by Georges Cuvier
Ideas Around the Time of Darwin:
A Shift in thinking
• Paradigm Shift  a change from one
way of thinking to another.
– In the 18th century there was a shift from
catastrophism to gradualism
Ideas Around the Time of Darwin
• Gradualism: idea that profound change is
the cumulative product of a slow
continuous process
– Proposed by James Hutton
Ideas Around the Time of Darwin
• Uniformitarianism: The idea that the
same laws of nature and the same Earth
processes that affect the planet now, are
the same ones that have always affected
the planet.
Ideas Around the Time of Darwin
• Today most geologists combine catastrophist,
gradualist and uniformitarianist standpoints,
– They take the view that Earth’s history is a slow,
gradual story punctuated by occasional natural
catastrophic events that have affected Earth and its
inhabitants
Ideas Around the Time of Darwin
• Taxonomy: branch of Biology that
deals with naming and classifying
organisms
– Proposed by Carolus Linnaeus
• For Linnaeus, grouping organisms into
these taxons implied no evolutionary
relationship between them. He was
simply trying to reveal God's plan.
Ironically, Linnaeus's scheme does
indeed reflect the evolutionary kinships
of a great many plants and animals.
Ideas Around the Time of Darwin
• Lamarck’s Evolutionary Theory: During their
lifetimes, organisms arquire new characteristics
as a results of their interactions with the
environment.
– Looked at evolution as an accumulation traits that
were passed to offspring
– Ex: Giraffes’ necks
Ideas Around the Time of Darwin
• It was these ideas that facilitated Darwin’s
evolutionary theory
– Gradualism / Catastrophism
– Unifomaitrianism
– Taxonomy
– Lamarckian Evolution
Ideas Around the Time of Darwin
• Darwin made two points in his book, “The
Origin of Species”
– Present forms of species evolved from
ancestral species
– The mechanism for evolution was natural
selection
• Over time Darwin’s theory has been
modified / updated / etc.
Evolutionary Theory
• Evolution: change in a gene pool over
time
• Two Types
– Microevolution
– Macroevolution
Evolutionary Theory:
Microevolution
• Microevolution: generation to generation
change in a population’s gene pool
– Causes
– Small population size
– Isolation
– Mutation
– Nonrandom mating
– Natural Selection
Evolutionary Theory:
Microevolution
Small population size – in small populations
big changes can result by random chance
– The loss or gain of one individual has a big
impact on the gene pool
• Founder effect
• Bottleneck effect
Evolutionary Theory:
Microevolution
Isolation – no migration; no gene flow
• Behavioral, temporal, mechanical, etc
Evolutionary Theory:
Microevolution
Mutation – genes are altered
• Most mutations are lethal
• Beneficial mutations will proliferate
Evolutionary Theory:
Microevolution
Evolutionary Theory:
Microevolution
Nonrandom mating – certain traits are
picked above others
– Sexual selection
• Male-male contests
– Deer
• Mate choice
Evolutionary Theory:
Microevolution
Natural Selection – the environment
selects certain organism for survival
Evolutionary Theory:
Macroevolution
• Macroevolution: the accumulation of
small changes that eventually lead to new
species
– What is a species?
• Classified by physical appearance
• Classified by ability to interbreed and produce
viable fertile offspring
• Classified by DNA
• Other
Evolutionary Theory:
Macroevolution
• Speciation: origin of species due to
evolutionary process
– Causes:
• Geographical barriers
• Reproductive barriers
• Adaptive radiation
Evolutionary Theory:
Macroevolution
• Geographical barriers
– the most common form of speciation, occurs when populations of
a species become geographically isolated.
– When populations become separated, gene flow between them
ceases. Over time, the populations may become genetically
different in response to the natural selection imposed by their
different environments.
Evolutionary Theory:
Macroevolution
• Reproductive barriers
– Speciation occurs when populations of a
species that share the same habitat become
reproductively isolated from each other.
Different species of bowerbird construct elaborate bowers and decorate them with different colors in order to woo females. The
Satin bowerbird (left) builds a channel between upright sticks, and decorates with bright blue objects, while the MacGregor’s
Bowerbird (right) builds a tall tower of sticks and decorates with bits of charcoal. Evolutionary changes in mating rituals, such as
bower construction, can contribute to speciation.
Evolutionary Theory:
Macroevolution
• Adaptive radiation - Adaptive radiation
describes closely related species that look very different,
as a result of having adapted to widely different
ecological niches
Evolutionary Theory: Macro v.
Micro
• Microevolution – little debate
– Actually observed
• Ex: Antibiotic resistance
Evolutionary Theory:
Macroevolution
• Macroevolution – much debate
– Inferred from evidence
• Ex: Finches
Branching v. Linear Evolution
• Linear Evolution  one species evolves
into a new species
• Branching Evolution  all present day
species sharing a common ancestor
– Populations of species at some point are
isolated, experience different pressures from
the environment , and “branch off” from the
ancestral lineage
Branching Evolution
Branching v. Linear Evolution
Branching Evolution
It is generally thought the reason few
transition fossils are found is because
evolution takes place in “short” spurts
• Many years of no change followed by
relatively few years of rapid change.
Summary
• Vocabulary (handout)
– Population / natural selection / adaptation / isolation /
extinction
• Ideas around the time of Darwin
– Shift in thinking
• Evolution
– Micro
• Causes
– Macro
• Speciation
• Branching vs. Linear Evolution
– Punctuated Equilibrium