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Intro To Biology: Evolution And The Diversity Of Life > Fossils And The History Of Life > Flashcards

Fossils And The History Of Life Flashcards

1
Q

What is the most common method of fossil formation?

A

Permineralization is the most common method of fossil formation. Dissolved minerals in groundwater permeate soft tissues, then crystalize, forming rock shaped like the organism.

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2
Q

What occurs during the replacement method of fossil formation?

A

In replacement, hard tissues are dissolved and replaced by minerals.

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3
Q

What is compression in fossil formation?

A

Compression most commonly occurs through carbonization, where heat and pressure release hydrogen and oxygen, leaving a thin layer of carbon residue. This occurs more often in plants than animals.

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4
Q

What is encasement in fossil formation?

A

Encasement preserves the entire body of an organism if it is frozen, dried, or trapped in tar or resin that hardens into amber.

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5
Q

What are impression fossils?

A

Impression fossils are formed when the rigid outer surface of an organism leaves an imprint in sediment as it decomposes. Internal molds can form if the specimen is hollow.

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6
Q

What are trace fossils?

A

Trace fossils are created when an organism leaves tracks or trails in soft sediment, which are preserved if the sediment hardens or is covered by another layer.

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7
Q

What are molecular fossils?

A

Molecular fossils are the organic molecules left behind by an organism.

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8
Q

Why are many organic molecules difficult to study?

A

Many organic molecules are susceptible to decay and are soluble in water.

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9
Q

What provides the most detailed information about an organism?

A

Nucleic acids, which form DNA and RNA, provide the most detailed information about an organism.

Nucleic acids break down quickly after cells die.

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10
Q

What other organic materials degrade easily?

A

Proteins and carbohydrates also degrade easily.

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11
Q

What happens to carbohydrates during decomposition?

A

Microorganisms often consume carbohydrates during decomposition.

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12
Q

Which organic molecules are moderately resistant to decay?

A

Lipids are moderately resistant to decay.

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13
Q

What is key to studying molecular remains?

A

The key is in isolating these delicate structures from air, extreme temperatures, and microorganisms.

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14
Q

Where can most molecular fossils be found?

A

Most molecular fossils can be found in kerogen, which is solid, water-insoluble organic matter embedded in rock.

Kerogen is found along with coal and shale.

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15
Q

What do fossils help researchers understand?

A

Fossils help researchers understand how species have evolved over time.

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16
Q

What are the earliest fossils?

A

The earliest fossils are cyanobacteria that date back about 3.5 to 3.7 billion years.

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17
Q

Why are cyanobacteria easy to recognize?

A

Cyanobacteria have had similar morphologies for billions of years.

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18
Q

What are chemical fossils?

A

Chemical fossils are traces of organic chemicals that indicate former life.

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19
Q

What do cyanobacteria sometimes leave behind?

A

Cyanobacteria sometimes leave chemical fossils in the form of pigment fragments.

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20
Q

Why is the fossil record for prokaryotes sparse?

A

The fossil record for prokaryotes is sparse because most prokaryotes don’t have distinctive morphologies.

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21
Q

When did eukaryotes appear in the fossil record?

A

Eukaryotes appeared later in the fossil record, about 2.1 billion years ago.

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22
Q

What information do fossils provide?

A

Fossils provide important information about the appearance, speciation, and extinction of different lineages over time.

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23
Q

Why are fossils essential in reconstructing evolutionary history?

A

Fossils are essential in reconstructing the evolutionary history of the earth because about 99 percent of all species that have existed are now extinct.

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24
Q

What can cause large numbers of species to go extinct?

A

A mass extinction event can cause large numbers of species or entire lineages to disappear from rock layers.

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25
What is relative dating?
Relative dating estimates the age of a feature based on the other layers around it.
26
What is absolute dating?
Absolute dating uses quantitative, laboratory-based techniques to determine the age of an object or feature.
27
What do studies using absolute dating techniques typically focus on?
Studies using absolute dating techniques typically focus on radioactive elements or changes in the Earth's magnetic field.
28
What do relative dating methods do?
Relative dating methods arrange evidence in a linear sequence, depending on whether a sample is younger or older than others surrounding it.
29
What is a stratum?
A stratum is a layer of rock, and multiple layers are referred to as strata.
30
What does the law of superposition state?
The law of superposition states that lower strata are older than the layers deposited on top of them.
31
Where are the oldest rocks found?
The oldest rocks are found at the bottom of the strata.
32
What are cross-cutting relationships?
Cross-cutting relationships are a geological principle stating that the geological feature that intrudes into another is younger than the feature it intrudes into.
33
What usually creates cross-cutting features?
Cross-cutting features are usually created by fault movements and span multiple strata.
34
What is absolute dating?
Laboratory techniques that quantitatively estimate the age of organic materials, fossils, minerals, or rocks.
35
What are common techniques used in absolute dating?
Radiometric dating and paleomagnetism.
36
What is radiometric dating based on?
The decay of radioactive isotopes of elements.
37
What does paleomagnetism measure?
Changes in the magnetic field of the Earth.
38
What are isotopes?
Different forms of the same elements that have different numbers of neutrons.
39
What happens to unstable isotopes?
They undergo radioactive decay, ejecting matter and energy from their nuclei.
40
What is the process of radioactive decay used for?
To determine the age of materials through radiometric dating.
41
What is half-life?
The length of time it takes for half of the radioactive elements in a sample to decay.
42
What is the age range for dating using radiocarbon?
Up to 70,000 years
43
What type of sample is used for radiocarbon dating?
Organic material (bone, wood, shells, some soils)
44
What is the age range for dating using potassium-argon?
1,000 to billions of years
45
What type of sample is used for potassium-argon dating?
Rocks and minerals
46
What is the age range for dating using uranium series?
1,000 to 500,000 years
47
What type of sample is used for uranium series dating?
Minerals, especially those containing calcium carbonate
48
What does microevolution address?
Microevolution addresses short-term evolutionary changes within a species or a population over relatively few generations, referred to as ecological time.
49
What is ecological time?
Ecological time is used to discuss how an environment changes over time and how that influences the species in that environment.
50
What does macroevolution focus on?
Macroevolution focuses on long-term changes in speciation and extinction over vast amounts of geologic time.
51
What is geologic time?
Geologic time considers the entire history of the Earth, beginning with the formation of the Earth about four to five billion years ago.
52
How is geologic time divided?
Geologic time is divided into eons, eras, periods, and epochs based on geologic events, such as changes in climate.
53
What is characteristic of different geologic ages?
The presence of certain fossils is also characteristic of different geologic ages.
54
What are the largest units of geologic time?
The largest units of geologic time are eons.
55
What do eons contain?
Eons contain eras.
56
How are eras broken down?
Eras are broken down into periods.
57
How are periods further divided?
Periods are broken down further into epochs.
58
How many eons are there in Earth's history?
There are four eons throughout the history of the Earth.
59
What are the four eons?
The four eons are the Hadean, Archean, Proterozoic, and Phanerozoic.
60
How long has Earth been in the Phanerozoic eon?
For the past 542 million years.
61
What is the Precambrian supereon?
The Hadean, Archean, and Proterozoic eons are sometimes referred to as the Precambrian supereon.
62
What characterized the Hadean eon?
There was no life on Earth during the Hadean eon.
63
When did the Hadean eon begin and end?
The Hadean eon began about 4.6 billion years ago and ended about 4.0 billion years ago.
64
What was happening to Earth during the Hadean eon?
The Earth was still forming and didn't have a solid crust until about 4.3 or 4.4 billion years ago.
65
What evidence supports the formation of the Earth's crust?
The presence of zirconium crystals in Western Australia.
66
What was the state of Earth's oceans during the Hadean eon?
The Earth's oceans didn't exist because the water was vaporized into steam.
67
Why isn't the Hadean eon divided into smaller units?
Scientists know so little about the Hadean eon.
68
What marked the start of the Archean eon?
The formation of the earliest rocks, granite.
69
When did the Archean eon occur?
The Archean eon occurred 4.0-2.5 billion years ago.
70
What happened to the Earth's crust during the Archean eon?
The Earth's crust cooled enough to form continents.
71
What is the earliest evidence of life?
The earliest evidence of life is from 3.7 billion-year-old rocks in Greenland that contain graphite created through a biological process.
72
What are the earliest fossils?
The earliest fossils, dating about 3.5 billion years old, are of microbial mats formed by cyanobacteria.
73
What types of organisms were present during the Archean eon?
Prokaryotes, both bacteria and archaea.
74
What is the final era of the Archean eon?
The final era of the Archean eon is the Nearchean.
75
What significant event occurred during the Nearchean era?
Microorganisms started releasing oxygen molecules into the air as a byproduct of photosynthesis.
76
Why was the release of oxygen significant?
It made the evolution of aerobic life possible.
77
What is an era in geologic time?
An era is a unit of geologic time spanning about one hundred million to a few hundred million years.
78
What are the three distinct eras of the Phanerozoic eon?
The three distinct eras are the Paleozoic, Mesozoic, and Cenozoic.
79
When did the Paleozoic era occur?
The Paleozoic era occurred 541-251 million years ago.
80
What types of organisms diversified during the Paleozoic era?
Aquatic invertebrates, mollusks, arthropods, fish, amphibians, and reptiles diversified.
81
What major event ended the Paleozoic era?
The era ended with the catastrophic Permian extinction.
82
What caused the Permian extinction?
Volcanic activity in Siberia wiped out around 90 percent of all species.
83
What is the Mesozoic era also known as?
The Mesozoic era is also known as the 'Age of the reptiles'.
84
What significant organisms arose during the Mesozoic era?
Dinosaurs, small mammals, birds, and flowering plants arose during the Mesozoic era.
85
What geological event was occurring during the Mesozoic era?
Pangea was slowly beginning to split apart.
86
What characterized the climate during the Mesozoic era?
The climate was hot and humid, with forests at the poles and higher sea levels than today.
87
When did the Cenozoic era begin?
The Cenozoic era began 66 million years ago.
88
What major changes occurred during the Cenozoic era?
Mammals diversified and the continents moved to their current positions.
89
What climatic changes occurred during the Cenozoic era?
The climate began to dry and cool, leading to glacial and interglacial periods.
90
What was the duration of the most recent ice age?
The most recent ice age lasted from 115,000-11,700 years ago.
91
What are the three eras of the Phanerozoic subdivided into?
Each of the three eras can be further subdivided into periods that span tens of millions of years.
92
What are the periods of the Cenozoic era?
The periods of the Cenozoic era are the Paleogene and Neogene periods.
93
What was the collective term for the Paleogene and Neogene periods?
The Paleogene and Neogene periods used to be collectively referred to as the Tertiary period.
94
What is phyletic gradualism?
Phyletic gradualism is the concept that speciation occurs at a constant rate, slowly and gradually over time. ## Footnote There is no clear differentiation between an ancestor and its descendants unless two different species evolve from one.
95
What is punctuated equilibrium?
Punctuated equilibrium is the concept that several descendant species quickly arise from a single ancestor at roughly the same point in geologic time. ## Footnote This can occur through sudden break-up of populations, destruction of different niches, or mass extinctions.

Intro To Biology: Evolution And The Diversity Of Life (4 decks)

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