Transcript Evolution - treshamurphy

Evolution
http://www.youtube.com/watch?v=
7hUNBhRiKCI
Origins and History of Life
• Earth was formed ~ 4.6 billion yrs ago
• Formation of Earth: Current theory
suggests that pieces of debris were
attracted to one another and provided
precursors for biochemical molecules
• Early atmosphere was very different from
today - H, methane, ammonia
Where did the first living things
come from?
Abiogenesis:
• Originally, spontaneous generation (Redi and
Pasteur)…..
Miller and Urey
• Stanley Miller and Harold Urey (1950’s)
tried to simulate early Earth
• Hoped experiments would give rise to
biological molecules that could have
developed into the first living organisms
• Essentially, carbon (from methane) was
converted to amino acids
• According to many, this experiment and its
downfalls actually did more to disprove
abiogenesis than support the theory
• Abiogenesis- living things come from
nonliving
• Biogenesis- living things come from other
living things (ex: spider lays eggs that
develop into a spider)
Primitive Organisms
• Fossil evidence suggests that the first unicellular
organisms existed more than 3.5 billion years
ago
• These organisms evolved in the absence of
oxygen
• Over time, Bacteria became common (could
photosynthesize and make oxygen as product)
• Atmospheric oxygen levels increased
• Those org. who could use oxygen evolved
Origin of Eukaryotes-The
Endosymbiotic Theory
• Thought to have
evolved from large
prokaryote cells that
ingested other free
floating prokaryotes
• Two most important
organelles developed:
mitochondria (c.r.)
and chloroplasts
(photo.)
Fossils
Fossil Records
• Fossils are the preserved remains of an
organism that lived many years ago
• Fossils can be dated with a relationship to
the layers of rock within which they can be
found
Fossils, cont.
• Relative datingyoungest layer on top,
oldest on bottom
• Absolute datingprovides a specific
date or numerical age
of a fossil
Fossils are important to study because…..
Originally, we thought….
• Inheritance of acquired characteristics:
characteristics acquired during lifetime,
• i.e.: if you cut off your finger cutting wood,
all of your offspring would be missing the
same finger…..hmmmm….
• This theory also
called the Use and
Disuse Theory (by
french naturalist
Lamarck)
• Organisms acquired
or lost characteristics
during their lifetime
based on whether
they needed the trait
or not
We can use fossil records to show
similarities among organisms…
• the same bones in the
same relative positions
are used in primate
hands, bat wings, bird
wings, pterosaur wings,
whale and penguin
flippers, horse legs, the
digging forelimbs of
moles, and webbed
amphibian legs.
• All of these characters
have similar structures
that perform various
different functions.
Evolution Notes, cont.
• Char. of a theory:
physical explanation
of large sets of
observations, based
on physical evidence;
must yield
hypotheses that can
be tested and results
are consistent; it must
be revisable
The Modern Theory of Evolution
• Charles Darwin- Theory of Evolution by
Natural Selection; he proposed that new
species could develop by a process of
natural selection
• A.k.a- survival of the fittest
• Wrote “Origin of Species”
• Studied the Galapagos Islands
Modern Theory Of Evolution
Summary of Darwin’s Theory
• Individual organisms differ, some
variations are heritable
• Organisms produce more offspring than
can survive, and many that do survive
don’t reproduce
• Organisms compete for resources
Darwin’s Theory cont.
• Individuals best suited for environment
survive and pass heritable traits to their
offspring. Others die or leave less
offspring.
• Species change over time due to natural
selection
• Species today are descended with
modification from ancestral species.
Evolution
• Produces patterns in living organisms that
include:
– Variation- of org. due to random genetic
mutations, deletions, etc. on chromosomes
– Natural selection- severe competition exists
and those that have the genetic variations that
are suited to the enviro. survive
– Adaptation- group of organisms that inherit
variations that lead to survival
Terms, cont.
• Adaptive radiation- related species that
look very diff. b/c have adapted to diff.
enviro.
• Speciation- if enviro. changes over time, or
org. are separated in some way, changes
may proceed in diff. directions for diff.
groups; over time, the groups change so
much, they can no longer interbreed, and
they become separate species
• Convergent evolution- different species adapt
similar traits as a result of enviro.
• Divergent evolution- related species evolve diff.
traits
• Directional selection- the enviro. favors a
particular phenotype
• Disruptive selection- org. at extremes are
favored
• Genetic equilibrium- org. is not evolving
• Punctuated equil.- sexually reprod. org. show
little change, and if it does, it is little and rapid
Evidence of Evolution
• Closely related org. have similar structures
(homologous structures)
• Structures in org. that are useless and appear to
be leftovers from ancestors (vestigial structures)
• Intermediate org. can be found in the layers of
the earth and currently in existence
• DNA sequences btwn org. are closely related
(2% diff. btwn humans and chimps)
• Closely related org. have sim. Behaviors
• Geographic distribution (isolation)