Reading Quiz 5: Geologic Time, Evolution, and Fossils (Ch. 5, 6 & 10) Week 6 & 7

What dating principle is most useful in determining the relative ages of the Niagara Falls rock sequence

Principle of Superposition

The Principle of Superposition yields which kind of ages?

Relative

Major animal taxa may have appeared during the Proterozoic-Phanerozoic transition in part because of:

(multiple causation) HOX gene mutations; increasing oxygen; ecologic changes resulting from the reorganization of biochemical cycles; biomineralization

A feldspar crystal in a sample of granite is subjected to potassium-40:argon-40 radioisotope analysis. 25% of the parent potassium-40 remains; 75% of the original sample has been converted over time to argon-40. How many half-lives have passed?

2

A feldspar crystal in a sample of granite is subjected to potassium-40:argon-40 radioisotope analysis. 25% of the parent potassium-40 remains; 75% of the original sample has been converted over time to argon-40. If the radioactive isotope has a half-life of 1.25 billion years. How old is the sample?

2.5 billion years

Two magnetic reversals are dated: the lower one at 50 MYA and the upper one at 45 MYA. The section between them is 10 meters thick. A biostratigraphic datum is found 5 meters above the lower paleomagnetic datum (i.e., halfway between the two absolute ages). Assuming a uniform rate of sedimentation, what is the age of the biostratigraphic datum?

47.5

Trilobites belong to which phylum?

Arthropoda

Why are beds of volcanic ash exceptionally useful for lithocorrelation in the field?

Ashfalls are deposited very rapidly (geologically speaking)

Phosphorus weathered from land earlier during the Proterozoic may have been sequestered (trapped) primarily in which type of rock?

Banded iron formations

What type of rock is dolomite?

Sedimentary (like limestone)

Which statement best describes the concept of facies?

Similar environments exist at different times and different environments exist at the same time.

The simplest multicellular animals without true tissues belong to the:

Sponges (Porifera)

Aerobic respiration produces more ATP than anaerobic respiration`

True

Most of the major phyla known today were present by the beginning or shortly after the beginning of the Phanerozoic.

True

What belongs to the phylum Mollusca?

Cephlapods, Gastropods, Bivalves, Chintons

Index fossils can sometimes provide time resolution down to about which level?

Epoch

Sponges do not possess true tissues

True

Most of the periods of the geologic time scale were originally recognized and named by researchers studying which area?

Europe

Swimming and deep burrowing are energetically inexpensive

False

True or false: Based on the geologic record, magnetic reversals are predictable

False

The periods of the modern geologic time scale (the one you will have memorized by the end of the class) are based mainly on the Principle of:

Faunal Succession

What would probably be the most reliable for detecting that a limestone formation is actually two separate limestone formations, separated by a paraconformity?

Fragments from the lower formation reworked into the lower beds of the formation that have been incorporated into the top formation

What is the primary reason to use igneous rocks for radiometric dating, rather than metamorphic rocks?

Metamorphism "resets" the radioactive clock, so it can be impossible to tell if the radiometric date refers to the original rock or to the date of metamorphism

The main assumption of dating species divergence using molecular clocks is that:

Mutation is constant

The dominant phytoplankton of the Proterozoic belonged to a group called:

acritarchs

Molluscs and annelid worms are thought to have been derived from a common ancestor because:

both phyla have segmented representatives

Halkieria may have been a primitive:

chiton (Mollusca)

The eye of cephalopods and vertebrates is quite similar. Why?

convergent evolution

If you identified an unconformity at the boundary between two depositional sequences of sedimentary rocks, which type of unconformity would it most likely be?

disconformity

All mollusks possess (a) muscular:

foot

Cnidarians and flatworms both have:

incomplete guts

Brachiopods are characterized by their distinctive:

lopophore (horseshoe-shaped, cilia-lined feeding structure)

Anomalocaris may have been the first known ___________ to be preserved in the fossil record

predator

Fossils yield which kind of ages?

relative

Increasing fecal pellet formation would have oxygenated the oceans by:

sending more organic matter to the ocean bottom rather than having it suspended in the water column

Complete cycles of sea-level change (high to low and back to high again) associated with the tectonic cycle occur on approximately which durations?

several hundred million years

Which stable isotope (discussed in the text) is used as a marker for increased nutrient runoff (erosion) of the continents?

strontium

Scientists' very earliest efforts at geologic time scales were based on:

superposition and lithology

Complete cycles of sea-level change (high to low and back to high again) associated with Milankovitch cyclicity occur on approximately which durations?

tens-of-thousands to about a hundred thousand years

Which type of gut provides for more efficient digestion?

that of an organism of the phylum Annelida

In order to use a fossil species as an index fossil, one must know:

the fossil's total range zone wherever it existed

A relative sea-level rise - where sea level appears to move landward - is called a:

transgression

What is best suited to provide a unique marker bed for lithocorrelation while conducting field work?

volcanic ash

During field work, lithocorrelation would be done by which of the following methods?

walking the outcrop