REVIEW: Historical Geology
Classification of Marine Organisms
• Planktonic – floaters such as diatoms, radiolarians, foraminifera, and graptolites
• Nektonic – active swimmers such as nautiloids and fishes
• Benthic – fixed on the seafloor (sessile) such as brachiopods, corals, and
archaeocyathids or moving along seafloor (mobile) such as trilobites and snails.
Four Basic Feeding Groups
• Suspension feeders – consume microscopic plants and animals, as well as
dissolved nutrients in water such as archaeocyathids
• Herbivores – plant eaters
• Carnivore-scavengers – meat eaters such as anomalocaris
• Sediment-deposit feeders – ingest sediment and extract nutrients from it such
as trilobites and starfishes
Trophic Levels of the Marine Ecosystem
• Primary Producers – the autotrophs capable of producing organic compounds
from light energy or chemical energy through photosynthesis or by
chemosynthesis, respectively.
• Primary Consumers – feeds on primary producers
• Decomposers – organisms that break down dead or decaying organisms; they
carry out decomposition, a process possible by only certain kingdoms, such as
fungi.
The Precambrian is the earliest of the geologic ages, which are marked by different
layers of sedimentary rock. Laid down over millions of years, these rock layers contain a
permanent record of the Earth's past, including the fossilized remains of plants and
animals buried when the sediments were formed.
The Phanerozoic, the eon of visible life, is divided into three major spans of time largely
on the basis of characteristic assemblages of life-forms: the Paleozoic (541 million to
252 million years ago), Mesozoic (252 million to 66 million years ago), and Cenozoic
(66 million years ago to the present) eras.
The Cambrian period, part of the Paleozoic era, produced the most intense burst of
evolution ever known. The Cambrian Explosion saw an incredible diversity of life
emerge, including many major animal groups alive today. Among them were the
chordates, to which vertebrates (animals with backbones) such as humans belong.
, The Mesozoic Era, also called the Age of Reptiles and the Age of Conifers, is the
second-to-last era of Earth's geological history, lasting from about 252 to 66 million
years ago and comprising the Triassic (251.902 to 201.3 million years ago), Jurassic
(201.3 to 145 million years ago), and Cretaceous (145 to 66 million years ago) Periods.
Cenozoic Era (Age of Mammals), third of the major eras of Earth's history, beginning
about 66 million years ago and extending to the present. It was the interval of time
during which the continents assumed their modern configuration and geographic
positions and during which Earth's flora and fauna evolved toward those of the present.
The Cenozoic is divided into three periods: the Paleogene, Neogene, and Quaternary;
and seven epochs: the Paleocene, Eocene, Oligocene, Miocene, Pliocene,
Pleistocene, and Holocene.
Proterozoic
• from the Greek word proteros meaning ‘first’ and zoon meaning ‘life’
• approximate dates: 2.5 BYA to ~541 MYA
• Some notable occurrences: formation of stable continents, Great Oxidation
Event, first multicellular organisms, global glaciation and Snowball Earth,
Ediacaran Fauna, Formation and Breakup of Rodinia and Pannotia
• Archaean: beginning of transformation from oxygen-poor to oxygen-rich
• Early atmosphere contained only very small amounts of free oxygen
• Single-celled algae and cyanobacteria are photosynthesizing
• Evolution of life and organisms
• At the beginning of Proterozoic, organisms were exclusively primitive, single-
celled prokaryotes
• Multicellular animals
• Ediacaran Fauna (~600 MYA)
• Almost all soft-bodied and preserved impressions in sandstone
• Others unlike any known organisms and cannot be classified
Cambrian
• Notable occurences: Cambrian Explosion, appearance of skeletonized animals,
early animal diversification, diversification of trilobites, Burgess Shale Fauna
• Abrupt appearance of animals with skeletons in the fossil record at the beginning
of the Paleozoic Era
• Newly evolved skeletons allowed Cambrian animals to become fossilized more
easily
• Cambrian records showed first examples of predation in the fossil record
• Early Cambrian Life: The First Shelled Animals
Classification of Marine Organisms
• Planktonic – floaters such as diatoms, radiolarians, foraminifera, and graptolites
• Nektonic – active swimmers such as nautiloids and fishes
• Benthic – fixed on the seafloor (sessile) such as brachiopods, corals, and
archaeocyathids or moving along seafloor (mobile) such as trilobites and snails.
Four Basic Feeding Groups
• Suspension feeders – consume microscopic plants and animals, as well as
dissolved nutrients in water such as archaeocyathids
• Herbivores – plant eaters
• Carnivore-scavengers – meat eaters such as anomalocaris
• Sediment-deposit feeders – ingest sediment and extract nutrients from it such
as trilobites and starfishes
Trophic Levels of the Marine Ecosystem
• Primary Producers – the autotrophs capable of producing organic compounds
from light energy or chemical energy through photosynthesis or by
chemosynthesis, respectively.
• Primary Consumers – feeds on primary producers
• Decomposers – organisms that break down dead or decaying organisms; they
carry out decomposition, a process possible by only certain kingdoms, such as
fungi.
The Precambrian is the earliest of the geologic ages, which are marked by different
layers of sedimentary rock. Laid down over millions of years, these rock layers contain a
permanent record of the Earth's past, including the fossilized remains of plants and
animals buried when the sediments were formed.
The Phanerozoic, the eon of visible life, is divided into three major spans of time largely
on the basis of characteristic assemblages of life-forms: the Paleozoic (541 million to
252 million years ago), Mesozoic (252 million to 66 million years ago), and Cenozoic
(66 million years ago to the present) eras.
The Cambrian period, part of the Paleozoic era, produced the most intense burst of
evolution ever known. The Cambrian Explosion saw an incredible diversity of life
emerge, including many major animal groups alive today. Among them were the
chordates, to which vertebrates (animals with backbones) such as humans belong.
, The Mesozoic Era, also called the Age of Reptiles and the Age of Conifers, is the
second-to-last era of Earth's geological history, lasting from about 252 to 66 million
years ago and comprising the Triassic (251.902 to 201.3 million years ago), Jurassic
(201.3 to 145 million years ago), and Cretaceous (145 to 66 million years ago) Periods.
Cenozoic Era (Age of Mammals), third of the major eras of Earth's history, beginning
about 66 million years ago and extending to the present. It was the interval of time
during which the continents assumed their modern configuration and geographic
positions and during which Earth's flora and fauna evolved toward those of the present.
The Cenozoic is divided into three periods: the Paleogene, Neogene, and Quaternary;
and seven epochs: the Paleocene, Eocene, Oligocene, Miocene, Pliocene,
Pleistocene, and Holocene.
Proterozoic
• from the Greek word proteros meaning ‘first’ and zoon meaning ‘life’
• approximate dates: 2.5 BYA to ~541 MYA
• Some notable occurrences: formation of stable continents, Great Oxidation
Event, first multicellular organisms, global glaciation and Snowball Earth,
Ediacaran Fauna, Formation and Breakup of Rodinia and Pannotia
• Archaean: beginning of transformation from oxygen-poor to oxygen-rich
• Early atmosphere contained only very small amounts of free oxygen
• Single-celled algae and cyanobacteria are photosynthesizing
• Evolution of life and organisms
• At the beginning of Proterozoic, organisms were exclusively primitive, single-
celled prokaryotes
• Multicellular animals
• Ediacaran Fauna (~600 MYA)
• Almost all soft-bodied and preserved impressions in sandstone
• Others unlike any known organisms and cannot be classified
Cambrian
• Notable occurences: Cambrian Explosion, appearance of skeletonized animals,
early animal diversification, diversification of trilobites, Burgess Shale Fauna
• Abrupt appearance of animals with skeletons in the fossil record at the beginning
of the Paleozoic Era
• Newly evolved skeletons allowed Cambrian animals to become fossilized more
easily
• Cambrian records showed first examples of predation in the fossil record
• Early Cambrian Life: The First Shelled Animals
