Week 7

Precambrian: Archean, Lecture Materials + ch 8

Proterozoic: Ediacara Fauna, Lecture  Materials + ch 9


alligator gar: Lepisosteus osseus, Cretaceous to Recent
Reading Assignment:  Chapters 9, and 10
 Middle Paleozoic

Unit (Chapter) Plan:
(unit topics)
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Abilities Acquired
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Visit this web site: UCMP    to review the History of Life of  this interval of time

Contents (course topics):

Phanerozoic Eonothem The Middle Paleozoic
Chronstratigraphic Divisions: Silurian System || Devonian System
  The Silurian System
            Biological Features:
          The Evolutionary Processes of Phanerozoic Biota; From Eukaryotes to Animalia
                Life recovered and expanded in aquatic habitats (textbook ch 10, p. 150-151)
                Paleoecology: || Types of marine environments (Textbook ch 10, p. 133-150)
                        Spectacular Reefs of corals and stromatoporoids
                Significant biological events in the Silurian:
                        New swiming invertebrates
                        Marine Predators: Ammonoids and Fishes
           Geological features:
                Paleogeography || LandmassesLaurentia and Baltica collide
           Paleoentological features:
          Divisions of time
                Fossil types:
               Silurian faunas
              The Invertebrate radiation:  Bivalves || Brachiopoda || snails || crinoids || trilobite
                    The vertebrates: Jawless fishes || earliest jawed fishes (textbook, ch 10, p.186-190)
                    First millipedes at the end of the Silurian
Plants: Early land plants (textbook, ch 13, p.193-198)
   The Devonian System: Age of Fish
            Biological Features:
                Coral-strome reefs
                New swimming invertebrates: ammonoids (cephalopods) Texbook ch 12, p. 182-186)
                Animals move ashore: the amphibians Tiktaalik (textbook ch 13, p. 198-204)
            Geological features:
      Paleoentological features:
                 Faunas: Classification of Fishes (textbook, ch 10, p.186-190)
                    Jawless fishes: ostracoderms
                    Fishes with jaws: acanthodians
                        sharks and ray-finned fishes
                    Fishes with lungs
                Plants invaded the land (textbook ch 13, p. 193-195; ch. 14, p. 205-218)
                    Vascular plants
                    Spore plants
                    Seed plants

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Activities (things you must do):
Read Chapters nine and ten  of your textbook
Review the story of plate tectonics
For a more simplistic model visit this site <http://www.pbs.org/wgbh/aso/tryit/tectonics>
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Abilities Acquired (what you learned):

By the end of this chapter you should be able to:

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Phanerozoic Eonothem

Chronostratigraphic  Division of the Paleozoic Eratherm
Eonothem Phanerozoic
Erathem Paleozoic
Permian System
Carboniferous System
Devonian System
 Silurian System
Ordovician System
Cambrian System


Phanerozoic Eonothem:

This Eonothem is often referred to as the tine of "Visible Life". Organisms with skeletons or hard shells appeared by the first time in the geological record. The Phanerozoic Eonothem spans from 543 mya  through today. The Phanerozoic is divided into three Erathems, from older to younger: Paleozoic, Mesozoic, and Cenozoic.
ThePaleozoic Erathem: 543 to 248  mya
The Paleozoic is delimited by two of the most important events in the history of life. At its beginning, members of Eukarya (multicelled  animals) underwent a dramatic "explosion" in diversity, and almost all living animal phyla appeared within a few millions of years. At the other end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species. The causes of both these events are still not fully understood and the subject of much research and controversy. Roughly halfway in between, animals, fungi, and plants alike colonized the land, the insects took to the air, and the limestone shown in this picture was deposited near Burlington, Missouri

The Paleozoic took up over half of the Phanerozoic, approximately 300 million years. During the Paleozoic there were six major continental land masses; each of these consisted of different parts of the modern continents. For instance, at the beginning of the Paleozoic, today's western coast of North America ran east-west along the equator, while Africa was at the South Pole. These Paleozoic continents experienced tremendous mountain building along their margins, and numerous incursions and retreats of shallow seas across their interiors. Large limestone outcrops, like the one shown above, are evidence of these periodic incursions of continental seas.

Many Paleozoic rocks are economically important. For example, much of the limestone quarried for building and industrial purposes, as well as the coal deposits of Western Europe and the eastern United States, were formed during the Paleozoic.

The Middle Paleozoic = Siluarian + Devonian Systems
 The Middle Paleozoic is an informal division of the Paleozoic Erathem which includes the lower two systems: the Silurain and the Devonian. See Chronostratigraphic Chart
Summary of Middle Paleozoic Events:

Silurian System: 438 to 408  mya . From Latin Silures, an ancient people of southwest Wales, where the rocks were first identified. It is characterized by: the first terrestrial plants and animals.  The first jawed fishes and  uniramians  (like insects, centipedes and millipedes) appeared during the Silurian (over 400 million years ago). First vascular plants (plants with water-conducting tissue as compared with non-vascular plants like mosses) appear on land (Cooksonia  is the first known). High seas  worldwide.Brachiopods , crinoids, corals.

The Silurian was a time when the Earth underwent considerable changes that had important repercussions for the environment and life within it. The Silurian witnessed a relative stabilization of the earth's general climate, ending the previous pattern of erratic climatic fluctuations. One result of these changes was the melting of large glacial formations. This contributed to a substantial rise in the levels of the major seas.

Coral reefs made their first appearance during this time, and the Silurian was also a remarkable time in the evolution of fishes. Not only does this time period mark the wide and rapid spread of jawless fish, but also the highly significant appearances of both the first known freshwater fish as well as the first fish with jaws. It is also at this time that our first good evidence of life on land is preserved, including relatives of spiders and centipedes, and also the earliest fossils of vascular plants.

Biological Features:
The Silurian is a time when many biologically significant events occurred. In the oceans, there was a widespread radiation of crinoids, a continued proliferation and expansion of the brachiopods, and the oldest known fossils of coral reefs.

Horn and honeycomb corals were common. By mid-period, these same corals were building reefs in the warm seas.

The time period also marks the wide and rapid spread of jawless fish, along with the important appearances of both the first known freshwater fish and early jawed fish. Other marine fossils commonly found throughout the Silurian record include trilobites, graptolites, conodonts, corals, stromatoporoids, and mollusks.

Numerous brachiopods, worms, and shrimp lived on the muddy bottoms. The larger scorpions (eusarus) and sea scorpions (ptertogus) were less numerous but dominated the scene because of their larger size.

It is also in the Silurian that we find the first clear evidence of life on land. While it is possible that plants and animals first moved onto the land in the Ordovician, fossils of terrestrial life from that period are fragmentary and difficult to interpret. Silurian strata have provided likely ascomycete fossils (a group of fungi), as well as remains of the first arachnids and centipedes.

Perhaps most striking of all biological events in the Silurian was the evolution of vascular plants, which have been the basis of terrestrial ecology since their appearance. Most Silurian plant fossils have been assigned to the genus Cooksonia, a collection of branching-stemmed plants which produced sporangia at their tips. None of these plants had leaves, and some appear to have lacked vascular tissue. The Silurian was a time for important events in the history of evolution, including many "firsts," that would prove highly consequential for the future of life on earth.

Devonian System: "The Age of Fishes" 408 to 360 mya . Devonian period (div?'n?un) [key], fourth period of the Paleozoic era of geologic time between 408 and 360 million years ago (see Geologic Timescale, table). It was named (1838) by the geologists Sir Roderick Impey Murchison and Adam Sedgwick for Devonshire, England, where they first investigated rocks formed during the period.
The Devonian period was a time of great tectonic activity, as Laurasia and Gondwanaland drew closer together.First amphibians, ammonites, fishes abundant. Fish and land plants become abundant and diverse. First  tetrapods  appear toward the end of the period. First amphibians appear. First sharks, bony fish, and ammonoids. Many  coral reefs, brachiopods, crinoids. New insects, like springtails, appeared. Mass extinction (345  mya) wiped out 30% of all animal families) probably due to  glaciation  or meteorite impact.
Biological Features:
By the Devonian Period life was well underway in its colonization of the land. Before this time, there is no organic accumulation in the soils, causing these soil deposits to be a reddish color. This is indicative of the underdeveloped landscape, probably colonized only by bacterial and algal mats.

The vegetation of the early Devonian consisted primarily of small plants, the tallest being only a meter tall. By the end of the Devonian, ferns, horsetails and seed plants had also appeared, producing the first trees and the first forests in swampy areas.

By the beginning of the Devonian  early terrestrial vegetation had begun to spread. These plants did not have roots or leaves like the plants most common today, and many had no vascular tissue at all. They probably spread largely by vegetative growth, and did not grow much more than a few centimeters tall. These plants included the now extinct zosterophylls and trimerophytes. The early fauna living among these plants were primarily arthropods: mites, trigonotarbids, wingless insects, and myriapods, though these early faunas are not well known.

Insects appeared during the middle of the system and were common by the end of the system. Most were small, but a few grew to sizes larger than the largest insects known today. Fossil remains include cockroaches up to 10 centimeters (4 inches) long and dragonflies with wingspans about 74 centimeters (29 inches) wide. Scorpions, spiders, and centipedes also were among the more than 400 species found as fossil remains.

Plants: By the Upper Devonian, lycophytes, sphenophytes, ferns, and progymnosperms had evolved. Most of these plants have true roots and leaves, and many are rather tall plants. The progymnosperm Archaeopteris was a large tree with true wood. In fact it is the oldest such tree known, and produced some of the world's first forests. This rapid appearance of so many plant groups and growth forms has been called the "Devonian Explosion". Along with this diversification in terrestrial vegetation structure came a diversification of the arthropods.

Also during the Devonian, two major animal groups colonized the land. The first tetrapods, or land-living vertebrates, appeared during the Devonian, as did the first terrestrial arthropods, including wingless insects and the earliest arachnids. In the oceans, brachiopods flourished. Crinoids and other echinoderms, tabulate and rugose corals, and ammonites were also common. Many new kinds of fish appeared.

In warm seas, corals had become the dominant form of live. At least 700 different species of brachiopods lived on the ocean floor with lily-like crinoids which were scattered everywhere.

The Devonian seas were dominated by brachiopods, such as the spiriferids, and by tabulate and rugose corals, which built large bioherms, or reefs, in shallow waters. Encrusting red algae also contributed to reef building. In the Lower Devonian, ammonoids appeared, leaving us large limestone deposits from their shells. Bivalves, crinoid and blastoid echinoderms, graptolites, and trilobites were all present, though most groups of trilobites disappeared by the close of the Devonian.

The Devonian is also notable for the rapid diversification in jawed and bony fish. Benthic armored fish were common by the early Devonian. These early fish are collectively called "ostracoderms", and include a number of different groups. By mid-Devonian, placoderms, the first jawed fish, appear. Many of these grew to large sizes and were fearsome predators. Of the greatest interest to us is the rise of the lobe-finned fish, which eventually produced the first tetrapods just before the end of the Devonian. The lungfish developed the ability to breathe air at the surface. Some lungfish still survive today in Africa. The first amphibians developed from this group of animals by the end of the period. The footprint of a primitive salamander-like amphibian was found in Pennsylvania.

The Evolutionary Process of Phanerozoic Life
Major groups of animals are already present in the Phanerozoic, at the beginning  of the Cambrian System, thier phylogenetic development is shown in the following diagrams as shown below: 


See Biological Principles for a review of these concepts

Schizocoels: A group of animal phyla, including Bryozoa, Brachiopoda, Phoronida, Sipunculoidea, Echiuroidea, Priapuloidea, Mollusca, Annelida, and Arthropoda, all characterized by the appearance of the coelom as a space in the embryonic mesoderm.

Lophophore: A horseshoe-shaped ciliated organ located near the mouth of brachiopods, bryozoans, and phoronids that is used to gather food.

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Fishes are a member of a large, heterogeneous group of VERTEBRATES, living in a wide variety of aquatic habitats.
There are slightly more species of fishes than of all other vertebrates combined.

Kingdon Animalia
Phylum Chordata
Subphylum Vertebrata
Class Agnatha: Jawless fish, includes the living lampreys and hagfish, and the extinct Ostracoderms. Cambrian-Recent.
     1. Myxini [Hagfishes]
     2. Petromyzontida [Lampreys]
Class Acanthodii: Primitive jawed fish with numerous spiny fish (Silurian-Permian)
Class Placodermii: Primitive armored jawed fish (Silurian-Permian)
Class Chondrichthyes: Cartilaginous fish such as sharks and rays. Devonian-Recent
Class Osteichthyes: Bony fish
    Subclass Actinopterygi: Ray-finned fish. Devonian to Recent. eg, SALMON, PERCH, FLATFISHES,
    Subclass Sarcopterygi: Lobe-finned, air-breathing fish. Devonian-Recent. eg, coelacanths and lungfishes, and also including the tetrapods,
                                i.e, amphibians to mammals, since tetrapods are thought to have evolved from sarcopterygian fishes.

Most bony fish belong to the “ray-finned” group.There are approximately 50 species of jawless fish, 600 species of cartilaginous fish and more than 30,000 species of bony fish. There are approximately 70 fish orders known to biologists.

Classificaction of Plants
Kingdom Plantae
Photosynthetic eukaryotes
Division (=Phylum) Bryophyta: Liverworts, mosses, hornworts- (Devonian-Recent)
Divisiion Psilophyta: small, primitive vascular plants (Silurian-Recent)
Division Lycopodophyta: Paleozoic lycopsids (Devonian to Recent)
Division Sphenophyta: Horsetails, eg., Carboniferous Clamites (Devonian-Recent)
Division Pteridophyta: Ferns (Devonian-Recent)
Division Pteridospermophyta: Seed ferns (Devonian-Jurassic)
Division Coniderophyta: Conifers or cone-bearing gymnosperms (Carboniferous-Recent)
Division Cycadophyta: Cydads (Triassic-Recent)
Division Ginkophyta: Maidenhair tree (Triassic-Recent)
Division Angiospermophyta: Flowering plantas and trees (Cretaceous-Recent)

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