Question 1

Although we know more about so-called Neanderthal men than about any other early population, their exact

relation to present-day human beings remains unclear. Long considered sub-human, Neanderthals are now

known to have been fully human. They walked erect, used fire, and made a variety of tools. They lived partly in

the open and partly in caves. The Neanderthals are even thought to have been the first humans to bury their

dead, a practice which has been interpreted as demonstrating the capacity for religious and abstract thought.

The first monograph on Neanderthal anatomy, published by Marcelling Boule in 1913, presented a somewhat

misleading picture. Boule took the Neanderthals’ lowvaulted cranium and prominent brow ridges, their heavy

musculature, and the apparent overdevelopment of certain joints as evidence of a prehuman physical

appearance. In postulating for the Neanderthal such “primitive” characteristics as a stooping, bent-kneed

posture, a rolling gait, and a forward-hanging head, Boule was a victim of the rudimentary state of anatomical

science. Modern anthropologists recognize the Neanderthal bone structure as that of a creature whose bodily

orientation and capacities were very similar to those of present-day human beings. The differences in the size

and shape of the limbs, shoulder blades, and other body parts are simply adaptations which were necessary to

handle the Neanderthal’s far more massive musculature. Current taxonomy considers the Neanderthals to have

been fully human and thus designates them not as a separate species, Homo neanderthalensis, but as a

subspecies of Homo sapiens: Homo sapiens neanderthalensis.

The rise of the Neanderthals occurred over some 100,000 years – a sufficient period to account for evolution of

the specifically Neanderthal characteristics through free interbreeding over a broad geographical range. Fossil

evidence suggests that the Neanderthals inhabited a vast area from Europe through the Middle East and into

Central Asia from approximately 100,000 years ago until 35,000 years ago. Then, within a brief period of five to

ten thousand years, they disappeared. Modern human, not found in Europe prior to about 33,000 years ago,

thenceforth became the sole inhabitants of the region. Anthropologists do not believe that the Neanderthals

evolved into modern human beings. Despite the similarities between Neanderthal and modern human anatomy,

the differences are great enough that, among a population as broad-ranging as the Neanderthals, such an

evolution could not have taken place in a period of only ten thousand years. Furthermore, no fossils of types

intermediate between Neanderthals and moderns have been found.

A major alternative hypothesis, advanced by E. Trinkaus and W.W. Howells, is that of localized evolution.

Within a geographically concentrated population, free interbreeding could have produced far more pronounced

genetic effects within a shorter time. Thus modern human could have evolved relatively quickly, either from

Neanderthals or from some other ancestral type, in isolation from the main Neanderthal population. These

humans may have migrated throughout the Neanderthal areas, where they displaced or absorbed the original

inhabitants. One hypothesis suggests that these “modern” humans immigrated to Europe from the Middle East.

No satisfactory explanation of why modern human beings replaced the Neanderthals has yet been found. Some

have speculated that the modern humans wiped out the Neanderthals in warfare; however, there exists no

archeological evidence of a hostile encounter. It has also been suggested that the Neanderthals failed to adapt

to the onset of the last Ice Age; yet their thick bodies should have been heat-conserving and thus well-adapted

to extreme cold. Finally, it is possible that the improved tools and hunting implements of the late Neanderthal

period made the powerful Neanderthal physique less of an advantage than it had been previously. At the same

time, the Neanderthals’ need for a heavy diet to sustain this physique put them at a disadvantage compared to

the less massive moderns. If this was the case, then it was improvements in human culture – including some

introduced by the Neanderthals themselves – that made the Neanderthal obsolete.

All of the following are hypotheses about the disappearance of the Neanderthals EXCEPT:

Section: Verbal Reasoning

Options :

A : the Neanderthal physique became a handicap instead of an advantage.

B :

the Neanderthals failed to adapt to climatic changes.

C :

the Neanderthals evolved into modern humans.

D : modern humans exterminated the Neanderthals.

Answer: C

Question 2

The nuclei of certain unstable isotopes will spontaneously decay, producing a more stable nucleus and

releasing a particle or quantity of energy. Alpha decay releases a helium nucleus, beta decay emits an electron,

while gamma decay is the emission of a high energy photon. Each type of radioactive decay is characterized, in

part, by the half-life of the radioactive material – the time required for half of the nuclei in a sample to undergo

decay. Examples of such decays are shown in Figure 1.

Figure 1

A Geiger counter can be used to detect the decay of radioactive materials. A simple Geiger counter consists of

a hollow metal cylinder with a wire along its axis. The cylinder is filled with low pressure argon gas and a high

voltage difference is applied between the wire and the cylinder. When alpha, beta, or gamma radiation passes

through the cylinder, it interacts with the gas particles and leads to the formation of ions which cause a

discharge between the wire and the cylinder. The consequent current may be used to drive a speaker,

producing the characteristic clicking sound of the Geiger counter each time a pulse of current occurs. The

Geiger counter circuitry is shown in Figure 2.

Figure 2

A Geiger counter is best suited for which of the following applications:

Section: Physical Sciences

Options :

A :

comparing the relative magnitudes of radioactivities of two nuclear waste depositories.

B : spatially locating a radioactive isotope injected into a patient.

C :

calculating the total energy of a radioactive particle.

D : determining the identity of various types of radioactivity.

Answer: A

Question 3

Four major blood types exist in the human ABO blood system: types A, B, AB, and O; and there are three

alleles that code for them. The A and B alleles are codominant, and the O allele is recessive. Blood types are

derived from the presence of specific polysaccharide antigens that lie on the outer surface of the red blood cell

membrane. The A allele codes for the production of the A antigen; the B allele codes for the production of the B

antigen; the O allele does not code for any antigen.

While there are many other antigens found on red blood cell membranes, the second most important antigen is

the Rh antigen. Rh is an autosomally dominant trait coded for by 2 alleles. If this antigen is present, an

individual is Rh+; if it is absent, an individual is Rh−. For example, a person with type AB blood with the Rh

antigen is said to be AB+.

These antigens become most important when an individual comes into contact with foreign blood. Because of

the presence of naturally occurring substances that closely mimic the A and B antigens, individuals who do not

have these antigens on their red blood cells will form antibodies against them. This is inconsequential until

situations such as blood transfusion, organ transplant, or pregnancy occur.

Erythroblastosis fetalis is a condition in which the red blood cells of an Rh+ fetus are attached by antibodies

produced by its Rh− mother. Unlike ABO incompatibility, in which there are naturally occurring antibodies to

foreign antigens, the Rh system requires prior sensitization to the Rh antigen before antibodies are produced.

This sensitization usually occurs during the delivery of an Rh+ baby. So while the first baby will not be harmed,

any further Rh+ fetuses are at risk.

The Coombs tests provide a method for determining whether a mother has mounted an immune response

again her baby’s blood. The tests are based on whether or not agglutination occurs when Coombs reagent is

added to a sample. Coombs reagent contains antibodies against the anti-Rh antibodies produced by the

mother. The indirect Coombs test takes the mother’s serum, which contains her antibodies but no red blood

cells, and mixes it with Rh+ red blood cells. Coombs reagent is then added. If agglutination occurs, the test is

positive, and the mother must be producing anti-Rh antibodies. The direct Coombs test mixes the baby’s red

blood cells with Coombs reagent. If agglutination occurs, the test is positive, and the baby’s red blood cells

must have been attacked by its mother’s anti-Rh antibodies.

How might one most practically assess the risk of erythroblastosis fetalis in a pregnant woman?

Section: Biological Sciences

Options :

A :

Test all women for the presence of anti-Rh antibodies.

B :

Test all fetuses for the presence of the Rh antigen within the first trimester of pregnancy.

C :

Test only Rh– mothers for the presence of anti- Rh antibodies.

D :

Test all mothers of Rh+ children for the presence of anti-Rh antibodies.

Answer: C

Question 4

TMS (tetramethylsilane) is commonly added to nuclear magnetic resonance (NMR) samples. It has a chemical

shift which is upfield of most organic signals, and it gives a strong, sharp singlet peak and can be easily

removed. Why is TMS added to NMR samples?

Section: Physical Sciences

Options :

A : to reduce noise in the spectrum

B : to calibrate the NMR spectrum

C :

to react with the sample

D : to provide a lock signal

Answer: B

Question 5

All of the following are true regarding the function of neurons EXCEPT:

Section: Biological Sciences

Options :

A :

Hyperpolarization at the end of an action potential is one mechanism by which neurons limit the rate at

which action potentials may fire.

B :

The flow of sodium into the neuron depolarizes the membrane in the first phase of an action potential.

C : The transmitting neuron secretes neurotransmitters into the synaptic cleft from its dendrites.

D :

An action potential is initiated when the axon hillock reaches the threshold potential.

Answer: C