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Intro To Biology > 4.4 Fossils and the History of Life > Flashcards

4.4 Fossils and the History of Life Flashcards

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1
Q

Fossil

A

Preserved remains of an organism, or an impression, trace, or track of that organism

Typically mineralized tissues (bones, teeth, shells, exoskeletons)

Soft tissues under the right conditions

Most dead organisms don’t fossilize

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2
Q

Permineralization

A

Most common method of fossil formation

Dissolved minerals in groundwater permeate soft tissues, then crystallize, to form rock that is shaped like the organism. Hard tissues are left behind.

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3
Q

Replacement

A

Similar to permineralization, except that hard tissues are dissolved and replaced by minerals

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4
Q

Compression

A

Heat and pressure cause the release of hydrogen and oxygen from the remains of an organism, leaving behind only a thin layer of carbon residue.

Occurs more often with plants than animals

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5
Q

Encasement

A

Entire body of organism can be preserved if frozen, dried, or trapped in tar or resin that hardens into amber.

Soft tissues still degrade and decompose

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6
Q

Impression (casts and molds)

A

Rigid outer surface of an organism can form an imprint in sediment as it decomposes

Internal molds can form if the specimen is hollow

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7
Q

Trace fossils

A

An organism moving over soft sediment leaves tracks or trails which are preserved if the sediment hardens or is covered by another layer

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8
Q

Molecular fossils

A

Organic molecules left behind by an organism

Most can be found in kerogen

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9
Q

Kerogen

A

Solid, water-insoluble organic matter embedded in roc

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10
Q

Chemical fossils

A

Traces of organic chemicals that indicate former life

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11
Q

Relative dating

A

Estimates age of a feature based on the other layers around it

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12
Q

Absolute dating

A

Uses quantitative, lab-based techniques to determine age of an object or feature

Typically focus on radioactive elements or changes in Earth’s magnetic field

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13
Q

Index fossils

A

From organisms known to have lived in a specific time period and in many places

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14
Q

Law of superposition

A

Lower strata are older than the layers deposited on top of them

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15
Q

Cross-cutting relationships

A

Geological principle stating that the geological feature that intrudes into another is younger than the feature it intrudes into

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16
Q

Biostratigraphy

A

Branch of science that uses index fossils to understand the relative ages of rock layers from different geographic regions

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17
Q

Principle of faunal succession

A

Principle that fossil species appear and disappear from individual layers in a certain order and that extinct species don’t reappear in younger layers of rock

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18
Q

Radiometric dating

A

Based on decay of radioactive isotopes of elements

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19
Q

Paleomagnetism

A

Measures changes in the magnetic field of the Earth

Magnetic minerals in newly formed volcanic deposits orient towards the Earth’s magnetic field as they cool

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20
Q

Isotopes

A

Different forms of the same elements that have different number of neutrons

Some are unstable and undergo radioactive decay

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21
Q

Radioactive decay

A

Ejecting matter and energy from their nuclei to reach a stable state

Occurs at a constant rate and can be used to determine age of materials

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22
Q

Half-life

A

Length of time it takes for half of the radioactive elements in sample to decay

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23
Q

Carbon-14

A

Used in radio metric dating, decays into Nitrogen-14

Half-life of 5,730 years

Useful for dating organic materials formed within the past 70,000 years

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24
Q

Potassium-40

A

Decays into 40Ar

Useful for dating rocks and minerals 1,000 to billions of years

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25
Q

Uranium-234

A

Decays into 40Ar

Useful for dating rocks and minerals 1,000 to billions of years

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26
Q

Ecological time

A

Used to discuss how an environment changes over time and how that influences the species in that environment

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27
Q

Geologic time

A

Considers the entire history of the earth

Begins with formation of earth about four to five billion years ago

Divided into eons, eras, periods, and epochs

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28
Q

Eons

A

Largest unit of geologic time

Hadean, Archean, Proterozoic, Phanerozoic

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29
Q

Phanerozoic

A

Current eon beginning 542 million years

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30
Q

Precambrian Super Eon

A

Hadean, Archean, and Proterozoic Eons

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31
Q

Hadean Eon

A

No life on earth

4.6-4 billion years ago

Earth still forming

No solid crust until 4.3 or 4.4 billion years ago (evidenced by zirconium crystals in Western Australia)

Oceans did not exist (water vaporized)

Not divided into eras or smaller geologic times

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32
Q

Archean

A

Formation of earliest rocks (granite) marked the start of this eon

4-2.5 billion years ago

Earth’s crust cooled enough to form continents and oceans

Large amount of volcanic activity

Atmosphere lacked oxygen

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33
Q

Earliest evidence of life

A

3.7 billion year old rocks in Greenland containing graphite created through biological process

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34
Q

Earliest fossils

A

3.5 BYO microbial mats formed by Cyanobacteria

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35
Q

Earliest evidence of bacterial life on land

A

3.2 BYA

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36
Q

Neoarchean

A

Final era of Archean eon

About 2.8 BYA microorganisms started releasing oxygen molecules into air as byproduct of photosynthesis, making evolution of aerobic life possible

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37
Q

Proterozoic

A

Evolution of photosynthetic Cyanobacteria marks beginning of this eon

Began 2.5 BYA-541 MYA

Glaciers first formed

Entire surface of the Earth may have frozen at some point during this eon

Oxygen crisis occurred

Origin of nucleus and endoplasmic reticulum

Origin of mitochondria and chloroplasts 2.1-1.6 BYA

True multicellular organisms arose during end of this eon

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38
Q

Oxygen Crisis

A

AKA Great Oxidation Event

During the Proterozoic eon

About 2.4-2.0 BYA atmospheric oxygen levels significantly increased

Extinction of enormous numbers of anaerobic microorganisms

39
Q

Phanerozoic

A

Initiated by the Cambrian Explosion about 541 MYA

Appearance of trilobites and corals marks boundary between this eon and the Proterozoic eon

Appearance of and plants, insects, fish, tetrapods

Tectonic plates formed Pangea which broke up later in the eon

40
Q

Cambrian explosion

A

Event of evolutionary radiation occurring over about 20 million years

Resulted in evolution of most animal phyla

41
Q

Era

A

Unit of geologic time spanning about one hundred million to a few hundred million years

42
Q

Phanerozoic eras

A

Paleozoic, Mesozoic, Cenozoic

43
Q

Paleozoic

A

Era occurring 541-251 million years ago

Aquatic invertebrates, mollusks, arthropods, fish, amphibians, and reptiles diversified with transition from aquatic to terrestrial environments aided by evolution of land plants

Massive conifer forests covered planet allowing evolution of gigantic insects in an oxygen rich environment

Ended with the catastrophic Permian extinction

44
Q

Permian extinction

A

Volcanic activity in Siberia wiped out around 90 percent of species at the end of the Paleozoic era

45
Q

Mesozoic

A

AKA “Age of the Reptiles”

Further increase in biodiversity

Appearance of dinosaurs, small mammals, birds, and flowering plants

Pangea began to slowly split apart

Temperatures were variable and higher than present day

Ended with a mass extinction

Climate hot and humid, forests found at the poles, sea levels higher

46
Q

Cenozoic

A

Era occurring 66 MYA to present

Mammals diversified

Continents moved to current positions

Climate dried and cooled around time the Himalayan mountains formed due to exposed rock reacting with CO2 in air, reducing greenhouse gases

Continued cooling caused a series of glacial and interglacial periods (ice ages)

47
Q

Most recent ice age

A

115,000 - 11,700 years ago

48
Q

Period

A

Span tens of millions of years

49
Q

Tertiary period

A

Used to collectively refer to the Paleocene and Neogene periods

50
Q

Paleozoic periods

A

Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian

51
Q

Cambrian

A

Period of the Paleozoic era starting 541 MYA

Warming climate

Diversification of many invertebrates

Biofilms and microbial mats

Trilobites

Earliest vertebrates

52
Q

Ordovician

A

Period of the Paleozoic era starting 488 MYA

Warming climate before later cooling and glaciation

Evolution of fishes

Filter feeders and marine invertebrates

First terrestrial plants

53
Q

Silurian

A

Period of the Paleozoic era starting 443 MYA

Stable, warm temperatures

Vascular plants

Moss forests

Terrestrial invertebrates

Bony fish

54
Q

Devonian

A

Period of the Paleozoic era starting 416 MYA

Warm temperatures

First seed-bearing plants

Diversification of fish

Placoderms rule the sea

Earliest insects

55
Q

Carboniferous

A

Period of the Paleozoic era starting 416 MYA

Warm temperatures

First seed-bearing plants

Diversification of fish

Placoderms rule the sea

Earliest insects

56
Q

Permian

A

Period of the Paleozoic era starting 299 MYA

Formation of Pangea

Variable climate with warm and cool cycles, relatively drier

Diversification of amniotes into mammals and reptiles

Reemergence of corals after large extinction

End of Permian marked by worst mass extinction in history

57
Q

Mesozoic periods

A

Triassic, Jurassic, Cretaceous

58
Q

Triassic

A

Period of the Mesozoic era starting 251 MYA

Warm and dry with seasons

Diversity recovered by mid-period

First mammals, dinosaurs, and crocodiles

Evolution of lichens

Conifer forests dominant

59
Q

Jurassic

A

Period of the Mesozoic era starting 200 MYA

Breakup of Pangea

Conifers and cycads (palm trees) abundant

Larger, iconic dinosaurs

First birds (Archaeopteryx)

60
Q

Cretaceous

A

Period of the Mesozoic era starting 146 MYA

Relatively warm, humid climate

Many shallow inland seas

Spread of flowering plants

Dinosaurs at peak diversity

Insects diversifying

Radiation of diatoms

61
Q

Cenozoic eras

A

Paleogene, Neogene, Quaternary

62
Q

Paleogene

A

Period of the Cenozoic era starting 66 MYA

Warm temperatures shifting to a cooler climate

Diversification of mammals

Adaptive radiation of birds

Increase in grasses

Decline in tropical plants

63
Q

Neogene

A

Period of the Cenozoic era starting 23 MYA

Seasonal climate

Cooling and drying

Evolution of mammals and birds into modern forms

Increase in grasslands

64
Q

Quaternary

A

Period of the Cenozoic era starting 2.6 MYA

Cycles of glaciation and ice sheet formation

Large mammals

Evolution of humans and their culture

65
Q

Epoch

A

Last about 5-20 million years

66
Q

Paleogene epochs

A

Paleocene, Eocene, Oligocene

67
Q

Paleocene

A

Epoch of the Paleogene Period starting 66 MYA

Subtropical/tropical climate

Temperate poles

Diversification of mammals

68
Q

Eocene

A

Epoch of the Paleogene Period starting 56 MYA

Maximum temperature reached for Cenozoic before cooling

Placental mammals

First prosimians (primates)

69
Q

Oligocene

A

Epoch of the Paleogene Period starting 33.9 MYA

Antarctic ice sheet formed

Increase in open landscapes

Mass extinction that replaced many European species with Asian ones

70
Q

Miocene

A

Epoch of the Neogene period starting 23 MYA

Continued cooling

Expansion of grasslands and plains

First apes

71
Q

Piocene

A

Epoch of the Neogene period starting 5.3 MYA

Continued cooling (2-3°C warmer than today)

Elevational changes

Formation of land bridge between Alaska and Siberia

First bipedal hominids

72
Q

Pleistocene

A

Epoch of the Quaternary period starting 2.6 MYA

“Ice Age”

Arctic ice cap formed

Cyclical glaciation

Large mammals such as mammoths, mastodons, and giant sloths

First modern humans

Extinction of Neanderthals

Formation of Yellowstone caldera (the most recent eruption of the Yellowstone super volcano was 630,000 years ago)

73
Q

Holocene

A

Epoch of the Quaternary period starting 11,000 years ago

Began with the last retreat of the glaciers; expansion of modern humans

Some critics argue that it is arbitrarily defined since it continues the cycles of glacial and interglacial periods typical during the Pleistocene

74
Q

Anthropocene

A

This existence of this epoch is debated within the scientific community

Characterized by human-mediated changes to the Earth

Would have begun post-WWII during the Atomic age

Demarcated by an increase in carbon dioxide and dusting of abnormal radioisotopes across the planet

75
Q

Phyletic gradualism

A

Postulates that speciation occurs at constant rate, slowly/gradually over time

No differentiation between ancestor and descendants unless two different species evolve from one

76
Q

Punctuated equilibrium

A

Several descendant species quickly arise from single ancestor at roughly same point in geologic time due to:

Sudden break-up of populations

Exploitation of different niches

Mass extinctions

77
Q

Biotic potential

A

Max capacity of an organism to reproduce under ideal environmental conditions

78
Q

Coevolution

A

Two or more species are interdependent in ways that affect each other’s evolution such as:
- Predators and their prey
- Plants and herbivores
- Hosts and parasites
- Flowering plants and pollinators

79
Q

Homeostasis

A

Ability to maintain a constant state of internal conditions that differs from the outside environment

80
Q

Origin of life

A

Scientists agree that life originated through abiogenesis

Most scientists believe that life spontaneously arose from a primordial soup

Disagreement about whether life arose near the ocean’s edge, in hydrothermal vents deep in the sea, far beneath Earth’s crust, or somewhere else

Debate about exact composition of the atmosphere and oceans

81
Q

Primordial soup

A

Hot water, carbon dioxide, methane, ammonia, hydrogen sulfide, hydrocarbons, and other simple molecules

82
Q

Alexander Oparin and J.B.S. Haldane

A

Developed theory of origin of life from a primordial soup in the 1920s

83
Q

Reducing atmosphere

A

Atmosphere in which oxidation can’t take place

84
Q

Panspermia

A

Theory postulating that the precursor molecules for life or life itself may not have originated on earth at all but from meteors carrying organic molecules

Could have worked alongside other ongoing processes on ancient earth

85
Q

Abiogenesis

A

Life originating from nonliving materials

86
Q

Stanley L. Miller and Harold C. Urey

A

Miller-Urey experiment in 1953 simulated hypothetical conditions of early Earth

Wanted to determine what if any organic molecules may have existed

Boiling water placed below a reducing atmosphere consisting of water vapor, carbon dioxide, methane, ammonia, and hydrogen gas

Sparking electrodes where positioned in the simulated atmosphere to create “lightning”

Water vapor would rise from the ocean, pass through the atmosphere, condense and return to the ocean

Repetition of this cycle created formaldehyde (CH2O), hydrogen cyanide (HCN), formic acid (HCOOH), urea (CO(NH2)2) as well as the amino acids glycine, alanine, and aspartic acid

Recreations of this experiment have found that other amino acids as well as adenine could be generated under these conditions

87
Q

Protocells

A

Bubble of lipids containing inorganic and organic molecules at higher concentrations than the external environment

88
Q

Coacervate

A

Earliest protocells

Microdroplets of lipids and amino acids or nucleic acids suspended in aqueous solutions

Not alive

Accumulated molecular material

Reproduced through fragmentation

89
Q

RNA world

A

Hypothesis based on the dual function of RNA in storing genetic information and catalyzing enzymatic reactions

RNA molecule would be capable of creating a duplicate of itself

Over time RNA molecules would have begun interacting with amino acids in the primordial soup creating polypeptides and eventually a ribosome

These molecules could have been gathered by protocells and served as a precursor to life

90
Q

Evolution of eukaryotic cells

A

Evolved form prokaryotic cells about 2.1 billion years ago as a chimera of a host cell and an alpha-proteobacterium in endosymbiosis, evident by

Mitochondria possess own circular genome, ribosomes, and tRNAs resembling prokaryotes

Mitochondrial genes for respiration (though sometimes relocated to eukaryotic genome) are very similar in sequence to genes of alpha-proteobacteria

Mitochondria is surrounded by two membranes (as if drawn in through vacuole)

New mitochondria produced through process similar to binary fission

Eukaryotic cells cannot make their own mitochondria from scratch

Not clear whether the endosymbiotic event that led to mitochondria happened before or after proto-eukaryotic cells developed nuclei

91
Q

Endosymbiosis

A

One cell lives inside another cell and both cells benefit from the relationship

92
Q

Origin of plastids

A

Endosymbiosis between a eukaryotic cell and cyanobacterium

93
Q

LECA

A

Last eukaryotic common ancestor

Contains mitochondria, cytoskeleton, made of microtubules and filaments, and a nucleus surrounded by a nuclear envelope with nuclear pores

May have lacked cell walls

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