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You are responsible for reading these chapters…we will be
discussing these slides in class, however, we will not be going
slow enough for students to copy word-for-word
 This PowerPoint combines Darwin information from
both texts
 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.
 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 =
 Fossils/Their Dating
 Fossil Record/Geologic
Time Scale
 Continental
 Mass Extinctions
 Formed from remains of organisms buried by
sediments, dust, or volcanic ash
 Soft body parts – usually decay rapidly
 Hard body parts (shells, bones, or teeth) – may become
preserved; long-lasting
 Hard body parts are hardened more
 Minerals dissolve in groundwater
 Seep into tissues of dead organisms and replace its
organic material
 Plant/animal becomes petrified
 Some rare fossils contain
organic material
 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
 Sometimes an
organism happens to
die in a place where
bacteria and fungi
cannot decompose the
 Ice
 Plant sap
 Fossil record is a “rich storehouse of information”
about macroevolution
 Geologic Time Scale
 Precambrian
 Paleozoic
 Mesozoic
 Cenozoic
 Periods are divided into epochs
 Boundaries between eras are marked by a major
change in forms of life and possibly mass extinctions
 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
 Measurement of certain radioactive isotopes in objects
 Every isotope has a fixed rate of decay
 Number of years for 50% of original sample to decay =
 Unaffected by temperature, pressure and other
environmental conditions
 Used to date rocks
 Fossils can sometimes be dated as well
 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
 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
 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
 Matching fossils in totally different locations
 Differing plants in locations that became isolated
 1. 250 million years ago, near end of Paleozoic Era
 Plates moved = 1 supercontinent = Pangea
 Variety of changes
 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. 180 Million years ago = Continental Drift
 Pangea broke up
 Each continent became isolated
 Species on each continent diverged in their evolution
and adapted and diversified based on new, separate
 Long periods of relative stability broken by brief
periods of great species loss
 Extinction of dinosaurs (end of Cretaceous Period
– 65 million years ago)
 Climate was cooling
 Shallow seas receding
 Large meteor hit Yucatan Peninsula in Mexico during
same time, sending dust into the atmosphere
 Blocked sunlight
 Reduced food production by photosynthesis
 Adaptive radiation of
 In aftermath, biological
diversity increased again
 Gives surviving organisms
new opportunities
 Rise of mammals may have
resulted from the void left by
the extinction of dinosaurs
 Identification, naming, and classification of species
 Common names cause confusion
 Common name can refer to many different species
 Doesn’t reflect organism
 Universal scientific name needed for all scientists to
clearly communicate
 Binomial Nomenclature = two-part Latin naming
system for naming each species
 Also a hierarchy of species into broader and broader
 Genus + species (Ex. Panthera pardus)
 Closely related species are grouped into same genus
 Phylogenetic Tree reflects the hypotheses of
evolutionary relationships
 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
 Not all structures are inherited from common ancestor
 Unrelated species from similar environments have
adaptations that seem very similar = analogous
 Wings of insects and birds = evolved independently
despite both are flight equipment and built from
entirely different structures
 Early 1800’s
 Jean Baptiste Lamarck attempted to explain Buffon’s
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)
Voyage of the Beagle
 December 1831
 Mission – chart poorly known stretches of the S.
American coastline for the British navy
 Charles Darwin, 22, was on the ship
 Interested in studying geology, plants, animals encountered
on voyage
 Pivotal trip in that it changed the thinking of many
Darwin’s Observations
 Darwin spent a lot of time on shore while ship’s crew
 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’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
 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
Ideas from Geology
 Darwin read a lot despite puking
 Read from Lyell’s writings
 Proposed that gradual and observable geologic processes
(erosion) could explain the physical features of today’s Earth
 River erosion = deep, river-carved canyon
 Mountain range rises = earthquakes
 Ideas from Geology (cont.)
 Darwin personally experienced an earthquake in Andes
 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. Slow processes of mountain building and erosion suggested an
Earth that must be very cold
2. These slow and gradual processes occurring over vast spans of
time could cause enormous change on Earth
 Darwin was at sea for 5 years
 Over this time he sent letters and specimens back to
 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.
 Thomas Malthus (wrote essay few decades before
 Contended that much of human suffering was due to the
human population’s potential to grow
 Populations grow IF food supplies and other resources can be
 If this does not happen = it is a struggle for existence
This helped Darwin to propose a mechanism of evolutionary
 Darwin’s essay (1844)
 200 pages
 Didn’t release it to the public
 Colleagues urged Darwin to publish before someone else
 Alfred Wallace (1858) came to same conclusion and
wrote to Darwin explaining his findings
 Within a month, both had findings presented to public
 Darwin published The Origin of Species about a year
 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. Life has a history of change
2. Descendants of the earliest organisms spread into various
habitats over millions of years
1. Accumulated different modifications = “Descent with
2. Accounts for diversity of life
 Darwin’s 2nd point
 His argument for natural selection was the mechanism
for evolution
 Natural selection can cause a population to change over
 Result = adaptation
 Homologous vs. Analogous Structures (evidence of
 Homologous = similar features that originated in a
shared ancestor (see page 289 in your text)-orcomplete online activity 14.2 in Exploring Life
 Look different but have similar skeletal structure
 Derive from same structures in embryo
 Analogous = serve identical functions and look
somewhat alike
 Very different embryological development
 Just keeping you on your toes!!!!!
 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
 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
 Coevolution – change of 2 or more species in close
association with each other
 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
 Adaptive radiation
 Artificial selection
Page 321…differences between human and ape
 Anthropoid Primate
 Prosimian Primate
 Marmosets
 Lemurs
 Monkeys
 Lorises
 Apes
 Tarsiers
 Humans
 Movable fingers and toes
 Most have flattened nails rather than claws
 Some have prehensile hands (grasping)
 Color vision (due to activity during day)
 Anthropoids
 Ex. Gibbon
 Well-developed
 Rotating shoulder joints
 Partially rotating elbow
 Opposable thumb
 Similar dental formula
 Large brains
 Humans
 Specific anthropoid
 Bipedal
 Cup-shaped pelvis
 S-shaped spine
 Larger brain
 Bipedalism defines first hominid line
 1974 Donald Johanson found “Lucy” in the Afar Valley
region of Africa…very well preserved
 Cranial capacity size of chimpanzee
 Originally thought that bipedalism and large
brain evolved at same time, but the “Lucy”
find proved that upright walking…
• “Lucy” was given this name
• Means “southern ape of Afar Valley”
• About 3.2 million years old
Dates from about 2.3 – 3 million years ago
Probably descended from A. afarensis
Taller and heavier than “Lucy”
Had a slightly larger cranial capacity
Australopithecus boisei
 May have descended
 May have descended
from “Lucy” but were
probably not ancestral to
modern humans
from “Lucy” but were
probably not ancestral to
modern humans
• In 1995, Tim White discovered fossils
that may
Predate earliest known
australopithecines by
200,000 years
• Unsure whether it is ancestral to
Found with stone tools
“Handy Human”
Between 1.6-2.5 million years old
Region of the brain essential to speech
may have existed
• Tool marks on animal bones found
near fossils suggest H. habilis ate
“Upright human”
1.8 million – 50,000 years ago
Thick skull
Large brow ridges
Low forehead
Large, protruding teeth
Average brain size 2/3 that of modern humans
Adults could easily have been as tall as modern
• Charred bones found near fossils indicate H.
erectus were hunters who used fire (cooking and
• In colder climates, may have lived in caves
 Neanderthals
 230,000 – 30,000 years ago
 Heavy bones, thick brow ridges,
protruding teeth
Cranial capacity slightly larger than
modern humans
Stone tools led scientists to believe
that they wore animal skins
Not ancestral to modern humans
Disappeared approximately same
time as modern H. sapiens arrived
(killed off Neanderthals or killed by
 Modern Homo sapiens
 Fossils about 35,000 years old
 Found in southwestern France
 Cro-Magnons
 Cranial capacity equal to that of modern humans
 High forehead
 Lack of protruding brow ridge and teeth
 Taller than Neanderthals
 Oldest are 100,000 years old
 Parallel populations of H. sapiens evolved from different
H. erectus populations around the world
 Modern H. sapiens evolved in Africa and spread
throughout the world, replacing populations of H.
erectus and early H. sapiens
 RNA molecules can take on a great variety of shapes (t-
shaped tRNA)…dictated by H bonds between particular
 Much like the shape of the protein depends on the H
bonds between particular a.a.
 Speculation that some RNA molecules might actually
behave like proteins and catalyze chem. rxns.
 Thomas Cech
 Ribozyme…act as an enzyme
 Early Earth had little or no O, so first cells must have
been anaerobic; fossils indicated that they were
prokaryotes and probably heterotrophs
 Chemosynthesis…CO2 serves as C source for assembly of
organic molecules…many archaebacteria (live in extreme
and harsh conditions) obtain E this way
 Photosynthesis and Aerobic Respiration
 O was damaging to some unicellular organism
 Early function of aerobic may have been to prevent the
destruction of essential organic compounds by O
 Believed that between 2.0 and 1.5 billion years ago a type
of small aerobic prokaryote entered (endosymbiosis)
and began to live and reproduce inside larger, anaerobic
 Lynn Margulis proposed that “invasion” turned mutually
beneficial = giving way to mitochondria
 Second invasion may have been related to
cyanobacteria…eventually gave rise to chloroplasts