10 - History of Earth and Its Life Forms

Question 1

Define:

principle of uniformitarianism

Answer 1

The idea that geological processes today also operated in the past.

The same geological processes we observe today, such as erosion and sedimentation, have been occurring in the same manner throughout Earth’s history.

Question 2

Identify:

Who developed the principle of uniformitarianism?

Answer 2

James Hutton

James Hutton was a Scottish geologist, often referred to as the Father of Modern Geology. His observations and theories laid the groundwork for understanding Earth’s geological processes and history.

Question 3

Explain:

Why do rocks provide a record of Earth’s history?

Answer 3

They preserve evidence of past environments, events, and life forms.

Rocks hold fossils, mineral deposits, and layers that document Earth’s changes over millions of years.

Question 4

Explain:

What is the role of fossils in understanding Earth’s history?

Answer 4

They reveal past life and environmental conditions.

Fossils provide insights into evolutionary changes, serve as a timeline of biodiversity, and help reconstruct ancient ecosystems.

Question 5

Define:

relative age dating

Answer 5

The method of determining the sequence of events without exact ages.

Relative age dating helps determine the sequence of events in Earth’s history by examining how layers and features are positioned relative to each other.

Question 6

Explain:

What are the 3 main principles used in relative age dating?

Answer 6

1. Superposition
2. Original Horizontality
3. Cross-Cutting Relationships

Superposition: In undisturbed layers, the oldest rocks are at the bottom, and the youngest are at the top.

Original Horizontality: Sedimentary layers are originally deposited flat, with any tilting or folding occurring later.

Cross-Cutting Relationships: A feature (e.g., fault or intrusion) that cuts through layers is younger than the layers it affects.

Question 7

Identify:

What principle states that in undisturbed layers, oldest rocks are at the bottom, youngest at the top?

Answer 7

The principle of superposition

The principle of superposition is fundamental in geology, helping to determine the relative order of sedimentary layers by their position.

Question 8

Define:

absolute age dating

Answer 8

The process of determining the exact age of rocks or fossils.

Radiometric methods, such as measuring isotopes like carbon-14 or uranium-238, are used to calculate precise ages.

Question 9

Explain:

Why does absolute age dating use radioactive isotopes to determine the age of rocks?

Answer 9

Radioactive isotopes decay at predictable rates, providing reliable age estimates.

Question 10

Identify:

List 3 isotopes used in radiometric dating.

Answer 10

1. Carbon-14
2. Uranium-238
3. Potassium-40

Carbon-14: Used to date organic materials up to about 50,000 years old.

Uranium-238: Effective for dating rocks and minerals millions to billions of years old.

Potassium-40: Commonly used to date volcanic rocks and minerals over a wide range of ages.

Question 11

True or False:

Radiometric dating is the most accurate method for determining rock ages.

Answer 11

True

Radiometric dating provides precise numerical ages, essential for absolute age determination.

Question 12

Define:

What is half-life in radiometric dating?

Answer 12

The time it takes for half of a radioactive isotope to decay.

Half-life helps calculate the age of rocks and fossils using predictable decay rates.

Question 13

Explain:

What are some limitations of radiometric dating?

Answer 13

• Contamination
• Initial Conditions
• Closed System Requirement
• Age Range Limits
• Material Suitability

Contamination: Foreign materials can alter isotope ratios, leading to inaccurate results.

Initial Conditions: Assumptions about the starting amount of isotopes may not always be accurate.

Closed System Requirement: Isotope leakage or alteration makes dating results unreliable.

Age Range Limits: Methods are effective only within specific time ranges (e.g., carbon-14 works up to ~50,000 years).

Material Suitability: Not all materials can be dated; only certain types of rocks or organic materials are usable.

Question 14

Define:

radioactive decay

Answer 14

The process by which unstable isotopes break down into stable forms.

Radioactive decay releases energy and forms the basis of radiometric dating.

Question 15

Identify:

What is the study of rock layers and their sequence?

Answer 15

Stratigraphy

Stratigraphy analyzes layers to reconstruct Earth’s history and correlate events across locations.

Question 16

Identify:

What is a gap in the geologic record caused by erosion or non-deposition?

Answer 16

Unconformity

An unconformity represents missing time in the geologic record, often caused by erosion or non-deposition, and reveals past geological events.

Question 17

Define:

geologic time

Answer 17

The vast span of time covering Earth’s history.

Geologic time divides Earth’s history into eons, eras, periods, and epochs to organize and study major events.

Question 18

Identify:

What does the geologic time scale represent?

Answer 18

Earth’s 4.6 billion-year history.

It helps scientists study Earth’s development by grouping time based on significant changes in geology and life.

Question 19

Explain:

What are the four major eons of Earth’s history?

Answer 19

1. Hadean
2. Archean
3. Proterozoic
4. Phanerozoic

Hadean: Formation of Earth and initial development, approximately 4.6 billion to 4 billion years ago.

Archean: Formation of the first stable continental crust and early life, approximately 4 billion to 2.5 billion years ago.

Proterozoic: Geological, atmospheric, and biological changes, including oxygen buildup, approximately 2.5 billion to 541 million years ago.

Phanerozoic: Development of diverse life forms, from the Cambrian explosion to the present, approximately 541 million years ago to now.

Question 20

Identify:

What is the Phanerozoic eon known for?

Answer 20

The presence of abundant fossil evidence.

The Phanerozoic eon is marked by a rich fossil record, providing detailed evidence of the evolution and diversification of life on Earth.

Question 21

Explain:

List the three eras of the Phanerozoic eon.

Answer 21

1. Paleozoic
2. Mesozoic
3. Cenozoic

Paleozoic: Known for the emergence of early life forms, including fish, amphibians, and the first land plants.

Mesozoic: The age of reptiles, marked by the dominance of dinosaurs and the first birds.

Cenozoic: The age of mammals, characterized by their rise and diversification.

Question 22

Define:

Mesozoic era

Answer 22

The era known as the Age of Reptiles.

It lasted from about 252 to 66 million years ago and saw the dominance of dinosaurs.

Question 23

Define:

What is the Great Oxidation Event?

Answer 23

A period when Earth’s atmosphere and oceans gained more oxygen.

The Great Oxidation Event, around 2.4 billion years ago, marked a significant increase in atmospheric and oceanic oxygen, enabling the evolution of aerobic organisms and reshaping Earth’s environment.

Question 24

True or False:

The last ice age ended about 11,700 years ago.

Answer 24

True

The end of the last ice age, around 11,700 years ago, marked a shift to the warmer and more stable climate of the Holocene epoch, which is the current geological epoch.

Question 25

# Identify: Which era is **known** for the **dominance** of dinosaurs?

Answer 25

Mesozoic ## Footnote This era includes the **Triassic**, **Jurassic**, and **Cretaceous** periods.

Question 26

# Explain: List the **periods** of the **Paleozoic era**.

Answer 26

* Cambrian * Ordovician * Silurian * Devonian * Carboniferous * Permian ## Footnote **Cambrian**: Known for the "Cambrian Explosion," a rapid diversification of life forms. **Ordovician**: Marked by the development of marine life and the first vertebrates. **Silurian**: Characterized by the stabilization of Earth's climate and the spread of jawed fish. **Devonian**: Known as the "Age of Fishes," with significant evolution of fish and the first land plants. **Carboniferous**: Noted for extensive forests and the formation of vast coal deposits. **Permian**: Ended with the largest mass extinction in Earth's history, paving the way for the Mesozoic era.

Question 27

# Explain: Why is the **Precambrian time** important?

Answer 27

It covers the **formation** of Earth and the **earliest development** of life. ## Footnote This time period saw the formation of the *first continents*, *oceans*, and *atmosphere*.

Question 28

# Identify: What marks the **beginning** of the **Holocene epoch**?

Answer 28

The **end** of the last ice age. ## Footnote The **Holocene** began approximately 11,700 years ago and is characterized by the development of human civilizations.

Question 29

# Define: mass extinction event

Answer 29

A widespread and **rapid decrease** in the **biodiversity** on Earth. ## Footnote These events are characterized by the extinction of a *large number* of species in a relatively *short period* of time.

Question 30

# Explain: What are the **five major mass extinction events**?

Answer 30

1. Ordovician-Silurian (443 MYA) 2. Late Devonian (372-359 MYA) 3. Permian-Triassic (252 MYA) 4. Triassic-Jurassic (201 MYA) 5. Cretaceous-Paleogene (66 MYA) | **MYA=Million Years Ago** ## Footnote **Ordovician-Silurian (443 MYA)**: Major marine species loss due to climate change and sea level shifts. **Late Devonian (372-359 MYA)**: Many marine species went extinct, likely from sea level changes and anoxic events. **Permian-Triassic (252 MYA)**: Largest extinction, with 96% of marine and 70% of terrestrial species wiped out. **Triassic-Jurassic (201 MYA)**: Many species extinct, enabling dinosaur dominance. **Cretaceous-Paleogene (66 MYA)**: Dinosaur extinction from asteroid impact and volcanic activity.

Question 31

# Identify: What **major event** marks the end of the **Paleozoic era**?

Answer 31

The **Permian-Triassic** extinction event. ## Footnote This was the **largest** mass extinction in Earth's history, wiping out approximately 90% of marine species.

Question 32

# Explain: Why are **mass extinction events** important in **geological history**?

Answer 32

They **reshape** evolution and **create** new opportunities for species. ## Footnote These events eliminate dominant species, allowing *new species* to diversify and fill ecological niches, leading to rapid evolutionary changes and the emergence of new dominant species.

Question 33

# Define: fossil

Answer 33

The **preserved** remains or traces of ancient organisms. ## Footnote Fossils can include *bones*, *shells*, *imprints*, or evidence of activity like *footprints*.

Question 34

# Explain: List **three types** of fossils.

Answer 34

1. Body Fossils 2. Trace Fossils 3. Mold/Cast Fossils ## Footnote **Body Fossils**: Physical remains of organisms, such as bones, teeth, or shells. **Trace Fossils**: Evidence of behavior, such as footprints, burrows, or tracks. **Mold/Cast Fossils**: Impressions or replicas of organisms created in rock.

Question 35

# Define: What is a **living fossil**?

Answer 35

A species that has **remained unchanged** for millions of years. ## Footnote Living fossils are species that have evolved *very slowly* or *not at all*, maintaining a similar appearance and behavior to their ancient ancestors.

Question 36

# Identify: What is an **example** of a **plant** considered a living fossil?

Answer 36

Ginkgo biloba ## Footnote Known as the *maidenhair tree*, **Ginkgo biloba** has existed for over 200 million years. It is the only surviving member of its genus, family, and order, making it a unique link to ancient plant life.

Question 37

# Define: index fossil

Answer 37

A fossil that is used to **define** and **identify** geologic periods. ## Footnote Index fossils are typically widespread, abundant, and limited to a short span of geologic time.

Question 38

# Define: fossilization

Answer 38

The process where remains of living organisms are **preserved** over time. ## Footnote Fossilization typically involves the replacement of organic materials with minerals over long periods.

Question 39

# Explain: What are the **steps** in the process of **fossilization**?

Answer 39

* Death * Decay * Burial * Mineralization ## Footnote **Death**: The organism dies, leaving behind remains. **Decay**: Soft tissues decompose, leaving hard parts like bones or shells. **Burial**: Remains are quickly covered by sediment, protecting them from further decay. **Mineralization**: Minerals fill the cellular spaces of the remains, preserving their structure.

Question 40

# Identify: What **type of rock** is most likely to **contain fossils**?

Answer 40

Sedimentary ## Footnote *Sedimentary rocks* form in layers, preserving remains that igneous or metamorphic processes would destroy.

Question 41

# Explain: What is the **role** of **sediment** in fossilization?

Answer 41

It **protects** and **preserves** remains by covering them. ## Footnote Over time, the sediment hardens into rock, encasing the remains and aiding in their preservation.

Question 42

# Define: permineralization

Answer 42

A **fossilization type** where **minerals** fill an organism's cellular spaces. ## Footnote This process preserves the *structure* of the organism by replacing organic material with minerals, often resulting in detailed and durable fossils.

Question 43

# Explain: How does the **fossil record** provide **evidence** for evolution?

Answer 43

It shows the **sequence** of life forms and their **changes** over time. ## Footnote The fossil record documents the *appearance*, *diversification*, and *extinction* of species, supporting the *theory of evolution*.

Question 44

# Explain: Why are **transitional fossils** important?

Answer 44

They show intermediate traits between **ancestors** and **descendants**. ## Footnote Transitional fossils provide evidence of evolutionary links, illustrating how species have changed and adapted over time.

Question 45

# Explain: What are **examples** of **transitional fossils**?

Answer 45

* Tiktaalik * Ichthyostega * Archaeopteryx * Basilosaurus ## Footnote **Tiktaalik**: A fish with fins that look like legs, connecting fish and amphibians. **Ichthyostega**: An early amphibian that lived both in water and on land. **Archaeopteryx**: A feathered dinosaur that shows how birds evolved. **Basilosaurus**: An early whale with small back legs, linking land mammals to whales.

Question 46

# Describe: The **relationship** between **geological history** and the evolution of life.

Answer 46

Geological events have **influenced** life's evolution and distribution. ## Footnote Events like volcanic eruptions, climate changes, and tectonic shifts *create* new environments and selective pressures that drive *evolutionary change*.