Reading Quiz #5

To which phylum does this organism belong? (looks like a ball with craters)

...

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 mya

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

All of these (multiple causation) (Biomineralization, ecologic changes resulting from the reorganization of biogeochemical cycles, increasing oxygen, HOX gene mutations)

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

Ashfalls are deposited very rapidly (geologically speaking).

Describe the position of sea level at the location of Niagara over the timeframe from the Ordovician Period to the Silurian Period.

Sea level rose over time and was highest in the Middle Silurian.

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)

All cniderians have:

Stinging cells (cnidae)

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.

Which is the proper sequence in the fossil record?

Burrows—Ediacara Fauna—Burgess Shale

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

Europe

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 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 dominant phytoplankton of the Proterozoic belonged to a group called

acritarchs

To which phylum does this organism (Anomalocaris) belong?

arthropoda

Trilobites belong to which phylum?

arthropoda

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

banded iron formations

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

both have segmented representatives

To which fauna does this organism belong? (looks kinda like a shell and a butterfly)

brachiopoda

Which of these does not belong to the phylum Mollusca?

brachiopods

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

To which fauna does this organism belong? (looks like a spiral of rocks in a rock bed)

ediacara fauna

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

epoch

Swimming and deep burrowing are energetically inexpensive.

false

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

false

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)

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

mutation is constant

Niagara Falls rocks are known to contain fossils. Also, dinosaur fossils are known to occur in sandstones or shales. Would you expect to find fossils of dinosaurs at Niagara Falls?

no

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

predator

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

principle of superposition

Which layer in this diagram is the oldest? (Niagara Falls image)

queenston

Fossils yield which kind of ages?

relative

The Principle of Superposition yields which kind of ages?

relative

The Lockport and other layers indicated by the slanty-brick symbol are formed from dolomite, which is very much like limestone and is a major source of concrete. These rocks are formed in a calm, warm marine environment where plankton with microscopic calcite shells die and fall to the sea floor, and then lithify into rock. What type of rock is dolomite?

sedimentary

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 milliion 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.

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

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

Sponges do not possess true tissues.

true

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

walking the outcrop