Fossils and Earth History Review

Flashcards covering key concepts from lecture notes on Fossils and Earth History, including paleobiology, fossil formation, relative and absolute dating methods, continental drift, and radiocarbon dating.

What is the study of ancient organisms, macroevolution, and the discovery of new fossil species called?

Paleobiology

What do fossil records provide regarding life in the past?

Physical evidence

What is the fossil record considered to be for data about evolutionary history?

The primary and most direct source of evidence

What are fossils?

Preserved remains of once-living organisms

Besides amber, Siberian permafrost, and dry caves, where can fossils be found?

Rocks

How do fossils form?

Organisms are buried by sediments and preserved in oxygen-poor environments

What types of organic structures are most commonly preserved due to their durability?

Hard structures like bones, teeth, shells, wood, leaves, and pollen

What typically happens to soft remains of organisms after death?

They are quickly consumed by scavengers or decomposed by microorganisms

What condition is essential during fossilization to prevent decomposition?

Absence of oxygen

What is the process where dissolved minerals replace parts of an organism molecule by molecule, leaving a solid fossil?

Fossilization

Approximately how many fossil species have been described, representing a small percentage of all species that have ever lived?

300,000

What types of organisms are most commonly found as fossils?

Hard-bodied, widespread, and abundant organisms that lived near swamps or shallow seas where sedimentation is ongoing

What are some reasons why the fossil record provides an incomplete portrait of past life?

Fossils can be deformed by pressure, destroyed in geological disturbances, or eroded by rain and wind.

According to the principle of superposition in relative dating, which strata contain the most recent fossils?

Highest strata

What is a major drawback of relative dating?

It does not provide specific numerical ages in years and layers are not always deposited in a horizontal fashion.

What process do some isotopes undergo that is fundamental to absolute dating?

Radioactive decay

In absolute dating, what breaks down at steady rates and is unaffected by chemical reactions or environmental conditions?

Radioisotopes

What two quantities are measured to estimate the age of a rock or fossil using absolute dating?

The relative amounts of a radioisotope ('parent') and its half-life

What information can be reconstructed from fossilized skeletons, shells, leaves, and flowers?

The size and appearance of ancient plants and animals, vegetation and climate of ancient sites, how structures modified, and extinction of evolutionary lineages

What geological process facilitated the diversification of distinct evolutionary lineages in different regions of the world?

Continental drift

How many protons do all carbon atoms consistently have in their nucleus?

Six

Which carbon isotope is stable, has 6 protons and 6 neutrons, and makes up 99% of all natural carbon?

Carbon-12 (¹²C)

Which carbon isotope is unstable and radioactive, with 6 protons and 8 neutrons, found in about 1 in 10¹² carbon atoms in the atmosphere?

Carbon-14 (¹⁴C)

How is radioactive Carbon-14 generated in Earth's atmosphere?

Cosmic rays from the sun enter the atmosphere, energetic neutrons collide with nitrogen gas, causing nitrogen (¹⁴N) to lose a proton and become ¹⁴C.

How do living organisms acquire Carbon-14?

Plants take in ¹⁴C through photosynthesis, and animals eat plants, thereby absorbing ¹⁴C.

What happens to the amount of Carbon-14 in an organism once it dies?

It stops absorbing ¹⁴C, and the amount of ¹⁴C decreases through radioactive decay, becoming stable, nonreactive ¹⁴N.

What is the half-life of Carbon-14?

5,730 years

What is the approximate dating limit for Carbon-14?

60,000 years

What ratio is measured to estimate how long ago something died using radiocarbon dating?

The ratio of ¹⁴C to ¹⁴N