Transcript Devonian Period

Speciation, Extinction, and
Biodiversity
How Species Evolve


Speciation
Geographic isolation

Reproductive isolation
Fig. 5-7 p. 94
Extinction

When Environmental changes occur, species must evolve to adapt.
If not…

Background extinction – slow rate
Mass extinction – quickly, large groups

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99% of species that have existed on earth are now extinct.
Changes in Earth’s biodiversity – has leveled off during the last
1.8 million years. Is this due to human influence?
Extinction
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Adaptive radiation – after mass extinctions,
numerous new species evolve to fill vacated
niches. Takes 1-10 million years for adaptive
radiation to rebuild biodiversity.
Human impacts – accelerated extinction
http://en.wikipedia.org/wiki/Image:Geologica_time_USGS.png
Evolution: Periods of the
Earth

The age of the Earth is difficult to determine
with absolute certainty

It is thought to be about 4.57 billion years old

This age is based on
dating of both the oldest
terrestrial minerals on
Earth and of meteorite
and lunar samples,
which provide estimates
of the age of the solar
system
http://en.wikipedia.org/wiki/Image:Asaphiscuswheelerii.jpg
How old is the Earth?
• This estimate is based on a
combination of radiometric dating of
the oldest terrestrial minerals on the
planet (small crystals of zircon found
in western Australia), and estimates
by astronomers of the age of the
solar system, based on radiometric
dating of meteorite and lunar
samples.
• The Earth is believed to have formed
early on in the formation of the solar
system.

Technique known as radiometric dating

Rocks are made up of chemical elements

These elements decay at a constant rate over
time into radioactive
isotopes

The ratio of
radioactive to nonradioactive isotopes
provides an
estimate of age
http://en.wikipedia.org/wiki/Image:DirkvdM_rocks.jpg
How do we Age Rocks?
•All matter, including rocks, is made up of chemical
elements. When a rock is first crystallized, it
contains elements in their “normal” state or
isotope.
• However, over time, changes take place in the
elements that make up the rock, and radio-active
isotopes begin to accumulate in the rock at a
constant rate of disintegration.
• These radioactive products remain in the rock
along with what is left of the original material. The
ratio of radioactive to non-radioactive isotopes give
us a gauge as to the age of the rock.
• Uranium was one of the first elements used in
radiometric dating. Argon and potassium are now
usually used.
Geological Time Scale
Eon is the largest sub-division of geological time

First three eons (Hadean, Archean, Proterzoic)
are collectively known as the Precambrian eon

Eons are sub-divided into eras
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Eras are sub-divided into periods
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Periods are sub-divided into epochs
http://en.wikipedia.org/wiki/Eon_%28geology%29
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Paleozoic (543 to 250 million
years ago), divided into six
periods
CENO
-ZOIC
Phanerozoic eon is divided into
three eras:
Cretaceous
65
MYA
Jurassic
Permian
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Mesozoic (250 to 65 million
years ago), divided into three
periods
Cenozoic (65 million years
ago to present), divided into
two periods and seven
epochs
Present
Tertiary
Triassic
PALEOZOIC

Quaternary
MESOZOIC
Phanerozoic Eon – Ancient Life
250
MYA
Carboniferous
Devonian
Silurian
Ordovidan
Cambrian
543
MYA

542 to 488 Million years ago

Sudden appearance in the fossil record of many new
phyla (Cambrian explosion)
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Fauna included:
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Earliest animals with a notochord (Pikaia spp.)
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Abundant marine invertebrates
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Primitive marine algae
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Brachiopods
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Arthropods
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Echinoderms
Pikaia gracilens
http://park.org/Canada/Museum/burgessshale/NK20.GIF
Cambrian Period
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488 to 444 Million years ago
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Diversity of marine invertebrates, including molluscs,
coelenterates, graptolites, trilobites, euryptids
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Earliest vertebrates appeared (ostracoderms)
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The first plants
invaded land
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A major extinction
event in which 60%
of marine species
were wiped out
ended the
Ordovician period
http://en.wikipedia.org/wiki/Image:Ordovician_Sea.jpg
Ordovician Period
http://universe-review.ca/I10-29-placoderm.jpg
Silurian Period

443 to 416 Million
years ago

Coral reefs became
abundant

First jawed fish
appeared
(Placoderms)

First freshwater
fish appeared

First vascular plants appeared on land

Myriapods (a type of arthropod) became the first animals
to colonise land
Placoderm

416 to 360 Million years ago

First fish evolved into tetrapods and invaded land

Cartilaginous fish (sharks) became dominant

Trees and forests colonized the land

Terrestrial invertebrates
invaded the land

Another major extinction
of marine fauna ended
the Devonian period
http://universe-review.ca/I10-72-Eusthenopteron.jpg
Devonian Period – “age of the
fish”
Devonian Period: Leaving the
water
Devonian Period: Leaving the
water
Devonian Period: Leaving the
water
Leaving the Water:
Terrestrialization
Why make the transition to an aquatic
ecosystem?
 Terrestrialization may be a secondary event.

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Water bodies may have had low oxygen content,
and thus may have favored air ‘gulpers.’
abundant arthropod and plant resources may
have been close to shore.
Terrestrialization

What problems exist for a ‘fish’ design on
land?
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Integumentary water loss.
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Thick dermis, but thin epidermis.
Presence of 2 types of glands (mucous and poison)
Temperature control?
Respiration?
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Bucal pump, skin, lungs. (Lungs were already present
in the osteichthys. Lungs actually preceed swim
bladders.
Terrestrialization
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Skeletal support
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organization of myomeres in fishes
water acts as an external skeleton in fish.
Locomotion
Hearing
Terrestrialization
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Feeding
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Once the pectoral girdle is free from the skull,
greater mobility is possible in the skull, permitting
greater feeding. This is enhanced by the
architecture of the 2 occipital condyls and the
presence of the atlas. The snout and jaws
become elongated (seen as a relative shortening
of otic-occipital region). There is improved
articulation of the jaw, and expansion of the
primary palate.
Terrestrialization
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Smell
Reproduction
Circulation with multiple respiratory
structures.
Skeletal solutions to terrestrialization.

Pectoral girdleis divorced from back of skull
(implications for sound conduction)
Terrestrialization
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Skeletal Sol’n. Cont.
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undulatory locomotion
suspension of vertebral column
regionalization of vertebral column
organization of amphibian vertebrae.
Suspension of internal organs.
Reorganization of the skull.

360 to 299 Million
years ago

Climate became drier

The first conifers
appeared
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Extensive forests
appeared with prolific
insect life, including
the first winged insects
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The first reptiles evolved from amphibians
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The first ammonites evolved
http://universe-review.ca/I10-68-Carboniferous.jpg
Carboniferous Period

299 to 250 Million years ago
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Major transition in vegetation
from ferns to more advanced
conifers and ginkgo trees
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Deserts were established
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Amphibians became larger in size
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Insects continued to radiate, with the appearance of
Coleoptera (beetles) and Diptera (flies)
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Reptiles thrived and began their radiation
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Ended with the largest extinction event on record – 96%
of animal species disappeared

This also marked the end of the Paleozoic era
http://www.copyrightexpired.com/earlyimage/prehistoriclifebeforekt/dimetrodon.jpg
Permian Period

250 to 200 Million years ago
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Conifers continued to expand

Ammonites recovered from
their near extinction to
co-dominate the seas with
bony fish
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Reptiles returned to the seas
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The ancestors of snakes and
lizards evolved
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Beginning of the radiation of dinosaurs
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End of the Triassic marked with another extinction event
http://universe-review.ca/I10-33-Triassic1.jpg
Triassic Period

200 to 145 Million years ago
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Warm climate and high sea
levels
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Cone-bearing plants covered
the land
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First small mammals
appeared
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First evidence of feathered
birds (Archaeopteryx)
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In addition to land and water,
reptiles also radiated into the
air (pterosaurs)
http://en.wikipedia.org/wiki/Image:SArchaeopteryxBerlin2.jpg
Jurassic Period
Archaeopteryx

145 to 65 Million years ago

Continents began to move into
their present-day positions
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First flowering plants appeared
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Mammals evolved into three
forms (monotreme, marsupial,
placental)
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A meteorite impact caused a
major extinction, which ended
the Cretaceous period – all
dinosaurs and all ammonites,
along with many other species,
became extinct
http://universe-review.ca/I10-68-flowering.jpg
Cretaceous Period

65 to 1.8 Million years ago

Paleocene epoch: flowering
plants became abundant
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Eocene epoch: many orders
of mammals appeared
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Oligocene epoch: primitive
apes; first elephants
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Miocene epoch: kelp forests
and grasslands appeared,
many grazing animals

Pliocene epoch: First ancient
hominids arose
http://universe-review.ca/I10-36-oldesthominid.jpg
Tertiary Period

1.8 Million years ago to present

Pleistocene epoch: modern humans evolved; ended with
the Ice Age that saw the extinction of mammoths and
other animals

Holocene epoch: human civilization spread throughout
the globe and humans became the dominant form of life
http://universe-review.ca/I10-37-Quaternary.jpg
http://www.primates.com/homo/homo-sapiens.jpg
Quaternary Period
In a group of 2 or 3:
Imagine a species that came into being during the
Cambrian Explosion and some form of this
species survived through all eras to our modern
time.
Draw and describe your species and adaptations
through each period (11 total)
Each Period should have:
a drawing
a description of how it survives
a description of a new adaptation for the
changed environment (land, water, temperature,
predators, etc)