Biology Chapter 14 - The History of Life

Questions and Answers

What is the early history of Earth?

Earth formed ~4.6 billion years ago; molten for around 500 million years, then solid crust formed.

What did the early atmosphere contain?

Both B and C (correct)

Free oxygen

Greenhouse gases

Poisonous gases

Where are clues of life on Earth found?

Rocks

When do the earliest clues about life on Earth date to?

3.5 billion years ago Signup and view all the answers

What are fossils?

Any preserved evidence of an organism Signup and view all the answers

What are trace fossils?

Any indirect evidence of an organism Signup and view all the answers

What are molds in paleontology?

Impressions of organisms left in sediment Signup and view all the answers

What are replacement fossils?

Fossils formed when minerals replace the original material of an organism Signup and view all the answers

What are petrified specimens?

Have mineral deposition in empty pore spaces Signup and view all the answers

What is amber?

Hardened tree sap that can trap and preserve an organism Signup and view all the answers

How can original material be preserved?

By freezing or mummification Signup and view all the answers

Who are paleontologists?

Scientists who study ancient life through fossils Signup and view all the answers

In what type of rock do fossils form?

Sedimentary rock Signup and view all the answers

Typically, a fossil forms when: An organism dies and is buried in ______

sediment Signup and view all the answers

Why must fossils be dated?

To understand patterns in ancient environments Signup and view all the answers

What is relative dating?

Used to determine if certain rock layers are older or younger than others Signup and view all the answers

What does the law of superposition state?

Younger layers of rock are deposited on top of older layers Signup and view all the answers

What is radiometric dating?

(A form of absolute dating) uses the decay of radioisotopes to get a more exact age for the rock Signup and view all the answers

What is the half-life of an isotope?

The amount of time it takes for half of a sample of that isotope to decay Signup and view all the answers

What are radioisotopes with long half-lives used for?

To date minerals in igneous or metamorphic rocks Signup and view all the answers

What is radiocarbon dating used for?

To date relatively recent organic material Signup and view all the answers

What is the geologic time scale?

The Earth's history is recorded as the geologic time scale Signup and view all the answers

What are the units of the geologic time scale?

Eons, eras, periods, and epochs Signup and view all the answers

What does Precambrian Time include?

The first 4 billion years of Earth's history (the Hadean, Archean, and Proterozoic Eons) Signup and view all the answers

What happened during Precambrian time?

The Earth formed and the first life developed. Signup and view all the answers

What characterizes the Phanerozoic Eon?

Encompasses the major diversification of life Signup and view all the answers

What major events occurred during the Cambrian explosion?

Life experienced major diversification; all body plans appeared. Signup and view all the answers

What occurred at the end of the Permian Period?

The largest mass extinction event Signup and view all the answers

What does the Mesozoic Era include?

The Triassic, Jurassic, and Cretaceous Periods Signup and view all the answers

What happened during the Mesozoic Era?

Pangaea breaks up and begins drifting apart; dinosaurs dominate land. Signup and view all the answers

How did the Mesozoic Era end?

With a bolide impact that caused another mass extinction event Signup and view all the answers

What does the Cenozoic Era include?

The Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene Epochs Signup and view all the answers

What happened during the Cenozoic Era?

Mammals and birds diversify; modern humans appear. Signup and view all the answers

In what Era do modern humans appear?

Pleistocene Signup and view all the answers

In what Era do modern humans form civilizations?

The Holocene Signup and view all the answers

What is spontaneous generation?

An early idea about the origin of life in which nonliving material produces life Signup and view all the answers

What did Francesco Redi's 1668 experiment demonstrate?

Spontaneous generation was disproved by Redi's experiment with meat in flasks Signup and view all the answers

What does the theory of biogenesis state?

Only living organisms can produce other living organisms Signup and view all the answers

What did Pasteur's experiment prove?

Theory of biogenesis was proven by Pasteur's experiment Signup and view all the answers

How did simple organic molecules like amino acids form?

From base compounds like water, methane, ammonia, and hydrogen; with energy from lightning and UV radiation. Signup and view all the answers

What may have helped to form proteins?

Clay particles served to hold amino acids together Signup and view all the answers

How did cells form?

By enclosing protein metabolic machinery in a lipid membrane Signup and view all the answers

When were early photosynthetic bacteria (cyanobacteria) present?

At least 3.5 billion years ago Signup and view all the answers

When did eukaryotic cells form?

1.8 billion years ago Signup and view all the answers

What does the endosymbiont hypothesis suggest?

Mitochondria and chloroplasts formed from prokaryotes living inside larger eukaryotic cells Signup and view all the answers

What is evidence for the endosymbiont hypothesis?

Mitochondria and chloroplasts have their own DNA and double membrane. Signup and view all the answers

Study Notes

Early Earth and Atmosphere

Earth formed approximately 4.6 billion years ago and was molten for around 500 million years before solidifying into a crust.
The early atmosphere contained many greenhouse and poisonous gases, with little to no free oxygen.

Evidence of Early Life

Clues indicating early life on Earth are preserved in rock formations.
The earliest evidence of life dates back to about 3.5 billion years ago.

Fossils and Their Types

Fossils are any preserved evidence of ancient organisms, while trace fossils serve as indirect evidence.
Molds are impressions left by organisms, and casts form when these molds are filled with sediment.
Replacement fossils arise when minerals replace the original organic material.
Petrified specimens showcase mineral deposits within empty pores.
Amber is hardened tree sap that can trap and preserve organisms.
Original material preservation occurs through processes like freezing or mummification.

Paleontology and Fossil Formation

Paleontologists are scientists who specialize in studying fossils and ancient life.
Fossils are typically formed in sedimentary rock, not in igneous or metamorphic types.
The fossilization process involves an organism's burial in sediment, layer building, mineral replacement, and eventual erosion revealing the fossil.

Dating Fossils

Fossils must be dated to interpret ancient environmental patterns.
Relative dating assesses age relations between rock layers, adhering to the law of superposition—where younger layers lie atop older layers.
Radiometric dating, an absolute dating method, utilizes radioisotope decay to determine precise ages.
The half-life of an isotope is the time required for half of its sample to decay.

Geologic Time Scale

Earth's history is charted on the geologic time scale, divided into eons, eras, periods, and epochs, with Precambrian Time covering the first 4 billion years.
During Precambrian Time, Earth formed, prokaryotic life emerged, and oxygen-producing bacteria contributed to the atmosphere.

Major Eons and Eras

The Phanerozoic Eon marks significant life diversification.
The Paleozoic Era includes diverse periods such as the Cambrian, characterized by a major life diversification known as the Cambrian explosion.
The end of the Permian Period is noted for the largest mass extinction event.
The Mesozoic Era is distinguished by dinosaur dominance and the breakup of Pangaea, concluding with a mass extinction caused by a bolide impact.
The Cenozoic Era features diversification of mammals, birds, and flowering plants, with modern humans appearing in the Pleistocene and forming civilizations in the Holocene.

Theories of Life's Origin

Spontaneous generation proposed that nonliving materials could produce life, later disproven by Francesco Redi's meat experiment.
The theory of biogenesis states that living organisms produce other living organisms, validated by Pasteur's broth experiment.

Formation of Organic Molecules and Cells

Simple organic molecules, such as amino acids, are believed to form from water, methane, ammonia, and hydrogen, energized by lightning and UV radiation.
Proteins potentially formed with the assistance of clay particles, which helped bind amino acids together.
Early cells enclosed their metabolic machinery in lipid membranes, with the first cells being prokaryotes.

Development of Eukaryotic Cells

Eukaryotic cells are thought to have emerged around 1.8 billion years ago.
The endosymbiont hypothesis suggests that mitochondria and chloroplasts originated from prokaryotes that lived within larger eukaryotic cells.
Evidence supporting this hypothesis includes the presence of independent DNA in mitochondria and chloroplasts, their double membranes, similar sizes to prokaryotes, and reproductive methods resembling prokaryotes.

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Test your knowledge on Chapter 14 of Biology, focusing on the history of life on Earth. This quiz covers the formation of the Earth, the early atmosphere, and the clues that suggest the presence of life in ancient times. Perfect for students looking to reinforce their understanding of Earth's early history!