Chapter 15
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This PowerPoint combines Darwin
information from both texts
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It provides a lot of background information that
should better help you understand the development
of Darwin’s theories as well as give you a more
thorough foundation of the history of Earth.
These PowerPoints will be online…please pay
close attention in class as we will move quickly
through them
Plate Tectonics and Continental
Drift Theory
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Complete the Chapter 15 WebQuest:
ContinentalDriftQuest (located on the Biology:
Exploring Life site
Try to explain how Plate Tectonics and
Continental Drift influenced evolution and
biodiversity
You will need to read "On the
Move...Continental Drift and Plate Tectonics."
–this is linked on that site = VERY USEFUL!
The Fossil Record
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Fossils/Their Dating
Fossil Record/Geologic
Time Scale
Continental
Drift/Macroevolution
Mass Extinctions
Fossils
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Formed from remains of organisms buried by
sediments, dust, or volcanic ash
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Soft body parts – usually decay rapidly
Hard body parts (shells, bones, or teeth) – may become
preserved; long-lasting
Hard body parts are hardened more
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Minerals dissolve in groundwater
Seep into tissues of dead organisms and replace its organic
material
Plant/animal becomes petrified
Fossils (cont.)
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Some rare fossils contain
organic material
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Found as thin films
Pressed between layers of
sand stone or shale
Ex. Idaho – plant leaves
millions of years old that are
still green with chlorophyll
Other Fossils: footprints,
animal burrows, sediment
impressions
Preserved specimens
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Sometimes an organism
happens to die in a place
where bacteria and
fungi cannot decompose
the corpse
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Ice
Plant sap
Fossil Record/Geologic Time Scale
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Fossil record is a “rich storehouse of
information” about macroevolution
Geologic Time Scale
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Precambrian
Paleozoic
Mesozoic
Cenozoic
Geologic Time Scale
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Periods are divided into epochs
Boundaries between eras are marked by a
major change in forms of life and possibly
mass extinctions
Dating Fossils
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Know age of fossils based on location in
sediment
Relative Ages = reflect the order in which
groups of species existed compared to one
another
Absolute Ages = Actual ages in years
Radiometric Dating
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Measurement of certain radioactive isotopes in
objects
Every isotope has a fixed rate of decay
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Number of years for 50% of original sample to
decay = half-life
Unaffected by temperature, pressure and other
environmental conditions
Used to date rocks
Fossils can sometimes be dated as well
Figuring out age of Fossils
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Could contain isotopes of elements that
accumulated in the organisms when they were
alive
When organism dies, intake of isotopes stops,
but radioactive decay continues
Carbon Dating
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Dinner and a movie usually works! Just
kidding.
Can only be used to find the age of recent
fossils due to half-life of C-14 = 5,600 yrs
Any fossil older than 50,000 must be estimated
using the surrounding rocks that contain
Uranium-238 and other radioactive isotopes
that have longer half-lives
Continental Drift
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Continents aren’t locked into place
Landmasses on different plates change
position relative to each other as a result of
continental drift
Solution to many biological puzzles
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Matching fossils in totally different locations
Differing plants in locations that became isolated
2 Major Events
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1. 250 million years ago, near end of Paleozoic Era
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Plates moved = 1 supercontinent = Pangea
Variety of changes
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Shoreline reduced
Sea levels dropped
Shallow coastal seas were drained, destroying shallow water
environments and inhabiting species
Continental interiors influenced as well
Isolated, evolving species came together and competed = cause
mass extinctions
2 Major Events (cont.)
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2. 180 Million years ago = Continental Drift
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Pangea broke up
Each continent became isolated
Species on each continent diverged in their
evolution and adapted and diversified based on
new, separate continents
Mass Extinctions
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Long periods of relative stability broken by brief
periods of great species loss
Extinction of dinosaurs (end of Cretaceous Period –
65 million years ago)
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Climate was cooling
Shallow seas receding
Large meteor hit Yucatan Peninsula in Mexico during same
time, sending dust into the atmosphere
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Blocked sunlight
Reduced food production by photosynthesis
The Positive to Mass Extinction:
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Adaptive radiation of
survivors
In aftermath, biological
diversity increased again
Gives surviving organisms
new opportunities
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Rise of mammals may have
resulted from the void left by
the extinction of dinosaurs
Taxonomy Relfects Evolutionary
History
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Identification, naming, and classification of
species
Common names cause confusion
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Common name can refer to many different species
Doesn’t reflect organism
Universal scientific name needed for all
scientists to clearly communicate
Linneus
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Binomial Nomenclature = two-part Latin
naming system for naming each species
Also a hierarchy of species into broader and
broader groups
Genus + species (Ex. Panthera pardus)
Closely related species are grouped into same
genus
Classification and Evolution
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Phylogenetic Tree reflects the hypotheses of
evolutionary relationships
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Homologous structures
Basic underlying similarities if evolved from
single structure in a common ancestor
Greater number of homologous structures = more
closely the species are thought to be related
Convergent Evolution
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Not all structures are inherited from common
ancestor
Unrelated species from similar environments
have adaptations that seem very similar =
analogous structures
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Wings of insects and birds = evolved
independently despite both are flight equipment
and built from entirely different structures
Theories of Evolution
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Early 1800’s
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Jean Baptiste Lamarck attempted to explain
Buffon’s observations
Proposed that life evolves/changes
Species are not permanent
Evolution is a process of adaptation
Today – unfairly remembered for mistaken
explanation of how adaptations evolve (make sure
you know what these are – pg. 293)
Darwin
Voyage of the Beagle
 December 1831
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Mission – chart poorly known stretches of the S.
American coastline for the British navy
Charles Darwin, 22, was on the ship
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Interested in studying geology, plants, animals
encountered on voyage
Pivotal trip in that it changed the thinking of many
Darwin (cont.)
Darwin’s Observations
 Darwin spent a lot of time on shore while
ship’s crew surveyed
 Collected many species of plants and animals
 Documented everything in extensive journals
(observations, studies, personal thoughts)
 Journals documented Darwin’s thoughts from
before the journey until he returned to port in
England
Darwin (cont.)
Darwin’s Observations (cont.)
 Noticed that plants and animals all had definite S.
Am. Character
 Distinct from species in Europe
 Deduced that species in S. Am. descended from
ancestral species on that continent
 Intrigued by life on Galápagos Island
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Species were similar to plants and animals on nearest
mainland (not exactly same)
Allowed Darwin to suggest that species that left the
mainland adapted to new lives on islands
Darwin (cont.)
Ideas from Geology
 Darwin read a lot despite puking
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Read from Lyell’s writings
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Proposed that gradual and observable geologic
processes (erosion) could explain the physical features
of today’s Earth
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River erosion = deep, river-carved canyon
Mountain range rises = earthquakes
Still Darwin…
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Ideas from Geology (cont.)
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Darwin personally experienced an earthquake in
Andes Mountains
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He collected fossils of ocean organisms high in the
Andes
Concluded that (based on Lyell’s work) that the
earthquakes gradually lifted the rock.
2 conclusions:
1.
2.
Slow processes of mountain building and erosion suggested an
Earth that must be very cold
These slow and gradual processes occurring over vast spans of
time could cause enormous change on Earth
Darwin (cont.)
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Darwin was at sea for 5 years
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Over this time he sent letters and specimens back
to England
This established his reputation with other scientists
Left as young graduate
Returned as a famous naturalist
After analysis of his data, he became convinced that
Earth was ancient and that species change through
time.
Darwin (cont.)
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Thomas Malthus (wrote essay few decades
before Darwin)
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Contended that much of human suffering was due
to the human population’s potential to grow
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Populations grow IF food supplies and other resources
can be produced
If this does not happen = it is a struggle for existence
This helped Darwin to propose a mechanism of
evolutionary change.
Darwin (cont.)
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Darwin’s essay (1844)
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200 pages
Didn’t release it to the public
Colleagues urged Darwin to publish before someone else
did
Alfred Wallace (1858) came to same conclusion and wrote
to Darwin explaining his findings
Within a month, both had findings presented to public
together
Darwin published The Origin of Species about a year later
Darwin’s 2 Points
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Darwin made 2 main points in his book
1.
He argued from evidence that the species of
organisms living on Earth today descended from
ancestral species
1.
2.
Life has a history of change
Descendants of the earliest organisms spread into
various habitats over millions of years
1.
2.
Accumulated different modifications = “Descent with
Modification”
Accounts for diversity of life
Darwin’s 2 Points (cont.)
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Darwin’s 2nd point
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His argument for natural selection was the
mechanism for evolution
Natural selection can cause a population to change
over time
Result = adaptation
Evolution in Process
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Homologous vs. Analogous Structures (evidence of
evolution)
Homologous = similar features that originated in a
shared ancestor (see page 289 in your text)-orcomplete online activity 14.2 in Exploring Life
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Look different but have similar skeletal structure
Derive from same structures in embryo
Analogous = serve identical functions and look
somewhat alike
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Very different embryological development
Look at t his picture…
Other Evidence of Evolution
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Vestigial Structures – features seem to serve
no useful function now (human’s tailbone) but
may have done so historically
Similarities in Embryology – See page 291,
Figure 15-9
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Ernst Haeckel – embryological development
repeats evolutionary history! (slightly exaggerated;
similarities fade as development proceeds)
Similarities in Macromolecules - homologous
proteins; RNA and DNA; amino acid sequence
is similar between different species
Patterns of Evolution
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Coevolution – change of 2 or more species in close
association with each other
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Predators and their prey; parasites and hosts; plant-eating
animals and their chosen plant
Convergent Evolution – Organisms appear to be
similar but are not closely related at all – analogous
structures are similar adaptations that result from this
Divergent Evolution – 2 or more related populations
become more and more dissimilar
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Adaptive radiation
Artificial selection
Adaptive Radiation
Artificial selection…