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Biology 182 Answers

Question 1
Part A
Miller and Urey’s experiments that attempted to recreate conditions on early Earth were significant because _____.

Hint 1.
They gave credence to the idea of abiotic synthesis.

ANSWER:

they showed how polymers could form spontaneously on a clay substrate

they produced the first protocells

they showed how radiometric dating could be used to give the absolute ages of rocks and fossils

proved the endosymbiotic theory

they showed that organic molecules such as amino acids could be produced from inorganic molecules

Correct
Miller and Urey showed that under conditions postulated to have existed on early Earth, it was possible to spontaneously form essential organic molecules.

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Question 2
Part A
Why do some scientists believe that RNA, rather than DNA, was the first genetic material?

Hint 1.
Which is structurally simpler?

ANSWER:

RNA can replicate more accurately than DNA.

RNA could have evolved into DNA.

All the proto-cells on early Earth contained RNA.

RNA has both information storage and catalytic properties.

RNA contains uracil in place of thymine

Correct
RNA has been shown to catalyze certain reactions (as part of ribosomes, rRNA participates in the catalysis of the peptide bonds that form proteins). It can also store information and perform some self-replication.

Question 5
Part A
Earth probably formed _____ years ago, and the first life evolved as early as _____ years ago.

Hint 1.
How long has life had to evolve?

ANSWER:

4.5 billion years ago … 3.9 billion years ago

10 billion years ago … 4.5 billion years ago

Humans observed neither event, so there is no way to tell.

3.9 million years ago … 2.0 billion years ago

6,000 years ago … 6,000 years ago

Correct
Because fossils of bacterial communities have been discovered that are 3.5 billion years old, it is reasonable to assume life originated around 3.9 billion years ago.

Question 3
Part A
The oldest fossils usually _____.

Hint 1.

Think about messy desktops with papers piled on them.

ANSWER:

contain more radioactive isotopes than younger fossils

are found in the deepest strata

are found in sediments formed during the Cenozoic era

are found above younger fossils

have the longest half-lives

Correct
Younger sediments are deposited over older sediments; thus, relatively older fossils are found in deeper strata than relatively younger fossils.

Question 4
Part A
Radiometric dating _____.

Hint 1.
How can absolute ages be determined, and what are the limits of different radiometric techniques?

ANSWER:

relies on the fact that the daughter isotope decays to the parent isotope at a constant rate

allows us to determine an absolute, errorless date

only works on rocks younger than 75,000 years

allows us to indirectly date fossils up to billions of years old based on minerals in surrounding volcanic strata

can be used to directly date fossils in sedimentary rock

Correct
By dating minerals in volcanic strata above and below the fossils, we can determine a reasonable age range for the fossils.

Question 11
Part A
Approximately how far back in time does the fossil record extend?

ANSWER:

5.0 million years

5.0 billion years

3.5 billion years

3.5 million years
Correct

Question 46

Part A
The following question refers to the paragraph below.

A sediment core is removed from the floor of an inland sea. The sea has been in existence, off and on, throughout the entire time that terrestrial life has existed. Researchers wish to locate and study the terrestrial organisms fossilized in this core. The core is illustrated as a vertical column, with the top of the column representing the most recent strata and the bottom representing the time when land was first colonized by life.

Assuming the existence of fossilized markers for each of the following chemicals, what is the sequence in which they should be found in this sediment core, working from ancient sediments to recent sediments?
1. chitin coupled with protein
2. chlorophyll
3. bone
4. cellulose

ANSWER:

4, 2, 1, 3

2, 4, 3, 1

4, 2, 3, 1

2, 4, 1, 3
All attempts used; correct answer displayed

Question 6
Part A
The earliest organisms were most likely _____.

Hint 1.
Simpler forms arose first.

ANSWER:

eukaryotic

plants and fungi

multicellular

prokaryotic

proto-cells

Correct
Prokaryotes originated a few hundred million years after Earth’s crust cooled and solidified.

Question 7
Part A
The atmosphere of early Earth probably contained no O2 until the emergence of organisms that _____.

Hint 1.
Consider the name of the process that releases oxygen into the atmosphere.

ANSWER:

were oxygen respiring

used water as an electron source for photosynthesis

were chemoautotrophic

had chloroplasts

used hydrogen sulfide as an energy source

Correct
Oxygen began to accumulate in the atmosphere due to the action of photosynthetic cyanobacteria.

Question 14
Part A
An early consequence of the release of oxygen gas by plant and bacterial photosynthesis was to

ANSWER:

make it easier to maintain reduced molecules.

prevent the formation of an ozone layer.

generate intense lightning storms.

change the atmosphere from oxidizing to reducing.

cause iron in ocean water and terrestrial rocks to rust (oxidize).

Correct

Question 15
Part A
Which of the following statements provides the strongest evidence that prokaryotes evolved before eukaryotes?

ANSWER:

Prokaryotic cells lack nuclei.

Laboratory experiments have produced liposomes abiotically.

Liposomes closely resemble prokaryotic cells.

The meteorites that have struck Earth contain fossils only of prokaryotes.

The oldest fossilized cells resemble prokaryotes.

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