Entrance Examination
For October 2022 and April 2023 students

Master’s Course(Specialized subjects)
NotesSelect and answer 3 QUESTIONS from the total 12 QUESTIONS. The 3
QUESTIONS can be selected from any subjects.

One sheet should be used for each selected QUESTION. The reverse side
could be used, if necessary.

Name, examinee’s number and subject name should be written on eachanswer sheet.



QUESTION number should also be written on each answer sheet.

Division of Biosphere Science
Graduate School of Environmental Science

Hokkaido University

QUESTION No. 1(Subject on Field Science)

Read the following sentences and answer the questions.
Almost all animals don’t have (a) enzymes that digest (A). (A) is a structural (B) which is
the main component of plants as structural material. (C) inhabit the digestive tract of (b)certain kind of animals and convert (A) to a substance that the host can digest. Anotherexample of the function for host metabolism by intestinal (C) is the synthesis of (D). (D)is necessary for blood coagulation and (c) Aves (d) must take (D) from food because of theirlack of intestinal (C).
Question 1-1. Fill in the correct words from (A) to (D).
Question 1-2. For the underlined sentence (a), describe the functions of digestive
enzymes and hormones secreted by the stomach of mammals in about 100 words.
Question 1-3. For the underlined sentence (b), ruminant is one of such kind of animals.
Describe the characteristics of the gastrointestinal tract of ruminants in about 100 words.
Question 1-4. Describe the functions of crops and characteristics of stomach ofunderlined Aves (c) comparing with mammals in about 100 words.
Question 1-5. For the underlined sentence (d), write down the term of such substances
which is necessary for animal health, but they cannot make themselves. And give 2
examples of the substance and each deficiency disease.

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QUESTION No. 2(Subject on Field Science)

Read the following text related to nitrogen and answer each question below.
A) Environmental load in agriculture
Nitrogen is one of (a) the three most important elements for fertilizer. In nature, N2
circulates in the ecosystem; N2 in the air is fixed by rhizobium and other bacteria. In
addition, nitrogen has been used in various applications such as nitrogen fertilizer becauseof artificial ammonia synthesis by the Haber-Bosch process.
Excessive synthesized nitrogen compounds are released into the atmosphere as air
pollutants and greenhouse gases; (1) and ammonia. They have a significant impact on thenatural world. As a global warming countermeasure in agricultural production, (b)it isimportant to reduce emissions of (1) and (2) from paddy fields and livestock, as well ascarbon dioxide.
Question 2-1. Regarding underlined words (a), answer the two major elements except
nitrogen.
Question 2-2. Fill in the most appropriate word(s) in blanks (1) and (2).
Question 2-3. Regarding underlined sentence (b), consider for reduction of greenhousegas on crop production and summarize them in about 150 words.
B) Amino acids and proteins
Nitrogen is a major constituent of proteins. Proteins in living organisms have diverse
structures and many functions. However, (c) proteins are merely assemblies of only twenty
sorts of amino acids.
Question 2-4. Regarding the underlined sentence (c), answer one for each of the threegroups of amino acids that make up living organisms: polar amino acids, nonpolar aminoacids, and aromatic amino acids.

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Question 2-5. Regarding the underlined sentence (c), answer how amino acids arebound using the keywords below about 150 words.
Keywords; dehydration reaction, disulfide bond, polarity, electric charge

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QUESTION No. 3(Subject on Field Science)

Read the text below and answer the questions 1-5.
The three elements of biodiversity are referred to as (a) species diversity, (b) genetic
diversity, and (c) ecosystem diversity. Threats to the diversity of wild plants are increasing,and about 25 % of wild vascular plant taxa in Japan are listed in the Red List (the Ministryof the Environment, Japan, 2020). Major threats that increase the risk of extinction
include (d) habitat fragmentation and loss by land-use change, excess collection or
harvesting, overgrazing by herbivorous animals, and so on. To evaluate the population
dynamics of an endangered plant species, i.e., whether specific population is increasing,decreasing or keeping stable, under the condition without drastic environmental change,
construction of (e) life table based on the age constitution of the population is a useful
method in population ecology.

Question 3-1. This is a question regarding the underlined term (a). Assuming that alarge geographic area is subdivided into small unit (site), how “alpha diversity”, “betadiversity”, and “gamma diversity” are calculated on the basis of the number of species?
Explain in about 60 words.
Question 3-2. This is a question regarding the underlined term (b). Gene diversity is ameasure of the extent of allelic diversity at each locus, and it is quantified using thefrequency of heterozygotes. First, write the general formula for expected heterozygosity(He) under the assumption of random mating, using pi that is the frequency of the i-thallele within a population. Second, explain two phenomena that cause the deviation ofobserved heterozygosity from expected heterozygosity in about 40 words.
Question 3-3. Regarding the underlined term (c), ecosystem diversity is evaluatedbased on two different aspects of ecosystem. Explain these in about 60 words.

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Question 3-4. Regarding the underlined term (d), explain how habitat fragmentation
causes genetic degradation of the population, using the following two terms: “recessive
harmful allele” and “weakly harmful mutation” in about 40 words.
Question 3-5. Regarding the underlined term (e), explain how net reproductive rate R0
is calculated using the following two terms, where x indicates age, in about 60 words.
• survivorship lx• age-specific fecundity mx

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QUESTION No. 4(Subject on Field Science)

Answer each question about cross-pollination and ploidy levels in plants.

Question 4-1. When cross-pollination was conducted between a diploid plant and atetraploid plant in same species, answer the ploidy level of the hybrid plants.

Question 4-2. In the case of cross-pollination between diploid and tetraploid plants (asstated in Question 4-1), explain the differences in the genetical properties between the
hybrid offspring produced by diploid plant (i.e., their father is tetraploid) and the hybrid
offspring produced by tetraploid plant (i.e., their father is diploid).

Question 4-3. When pollen fertility of the hybrid plants between diploid and tetraploid
plants (as stated in Question 4-1) was tested, it was proved that the pollen did not havegermination ability. Explain the possible reason of this phenomenon.

Question 4-4. Explain a method producing tetraploid plants from diploid plants.

Question 4-5. Explain a method producing haploid plants from diploid plants.

Question 4-6. Explain the following terms:(1) Aneuploid(2) Alloploidy / Autoploidy(3) Double fertilization(4) Horizontal gene transfer

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QUESTION No. 5(Subject on Life Science)

Read the following sentences and answer the questions.
The endomembrane system (ES) is a complex membrane network that structurally divides
the functions of eukaryotic cells. ES includes nuclear membrane, endoplasmic reticulum(ER), Golgi bodies, lysosomes, vesicles, endosomes, and ( ① ) membrane. Eachmembrane system does not exist independently but is interacted with each other. Most of
ES are occupied by ER. In addition to the biosynthesis of cellular compounds as well as
the processing and transport of membrane or secretory proteins, ER plays a central rolein the storage and release of the signaling molecule, (②) ion. ⓐThere are two structurally
different regions in ER: those with ribosomes scattered on the surface are called (③)surfaced ER, and those with almost no attachment are called (④)-surfaced ER. They act
differently in the production of cellular compounds.
ⓑCompounds made from ER are transported to the Golgi bodies by transport
vesicles and undergo chemical modifications such as glycosylation, while some of themremain inside ER. The Golgi bodies exist as a multilayer of separate sacs. The receivingside from ER is called the (⑤) plane, and the side sending out secretory vesicles is called
the (⑥) plane. Compounds completed in the Golgi bodies are stored in secretory vesicles
and finally transported outside the cell or to the target site. The normal functions of ES
are essential for maintaining homeostasis of cells. When exposed to cellular stresses, it
falls into a disfunction specific for ES. In particular, when severe stresses are applied toER, accumulations of unfolded proteins are observed, which may eventually lead to cell
death. Thus, ER stress has been postulated to be involved in various diseases. ⒸThe cellthat senses ER stress tries to recover to a steady state by inducing 1) translational
suppression of nascent proteins, 2) recruitment of the molecular chaperone, and 3)
activation of the proteasome pathway.
Question 5-1. Answer the most appropriate words in the blanks from (①) to (⑥).
Question 5-2. Even in the same organelle, mitochondria and chloroplasts are often
distinguished from other endomembrane systems. Answer the reason in about 100 words.
Question 5-3. Regarding the underlined part ⓐ , explain the differences in thefunctions of the endoplasmic reticulum with two distinct structures in about 100 words.

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Question 5-4. Regarding the underlined part ⓑ , the text below explains thecharacteristics of the primary structure of a protein. Select the most appropriate proteinwith characteristics that is likely to remain inside ER.
a) It has a signal peptide centered on 5-10 hydrophobic amino acids at the N-terminus.
b) It has hydrophobic helix structures that span the biomembrane 7 times in the molecule.
c) It has a signal sequence K-D-E-L at the C-terminus.
d) It has a signal sequence rich in basic amino acids of P-P-K-K-K-R-K-V in the molecule.
e) It has an N-X-S/T glycosylation site of sugar chain in the molecule.
Question 5-5. Regarding the underlined part ⓒ, explain the mechanism of recovery
from ER stress, in which unfolded proteins have accumulated, in about 200 words,
including the specific functions of the three response reactions shown in the text.

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QUESTION No.6

(Subject on Life Science)

Question 6-1. The figure depicts the structure of deoxyguanosine triphosphate. Choose
the most appropriate answers that apply to R1-R4 from the choices given (a, b, c, d, e, f).
The same choice may be used more than once.
H
R1
H

H
H

H
R4

H

H

R2

R3

H

(a) ̶ H(d) ̶ NH2(b) ̶ OH(e) ̶ SH(c) ̶ CH 3(f) ̶ P 3O10H4

Question 6-2. Select all correct answers from the following sentences.
(1) DNA primers are indispensable for the elongation of the lagging strand during DNA
replication.
(2) RNA editing does not occur in eukaryotes.
(3) Methylated GTP is added to the 5 end of eukaryotic mRNA.
(4) Both the large and small subunits of the ribosome contain RNA.
(5) No tRNA recognizes nonsense codons.
Question 6-3. Nierenberg and his colleagues found that when artificially synthesized
RNA in addition to ATP and amino acids was added to a crude extract of E. coli, thesuspension functioned as a cell-free translation system and synthesized polypeptides.
Khorana and his colleagues further proceeded to decipher the codons by adding
artificially synthesized RNA with two- or three-base repeats to the above cell-freetranslation system. Assuming that a codon is specified by three bases, answer thefollowing questions based on the results of Experiments 1, 2, and 3 below.
[Experiment 1]
When a repeat sequence of GU (GUGUGU...) was synthesized as RNA and added tothe cell-free translation system described above, a polypeptide with alternating
cysteine (Cys) and valine (Val) repeats was synthesized.

9[Experiment 2]
When a repeat sequence of GGU (GGUGGUGGU...) was synthesized as RNA andadded to the cell-free translation system described above, three polypeptides weresynthesized: a polypeptide consisting only of glycine (Gly), another consisting only ofvaline (Val), and another consisting only of tryptophan (Trp).
[Experiment 3]
When a repeated sequence of AUG (AUGAUGAUG...) was synthesized as RNA andadded to the cell-free translation system described above, only two polypeptides weresynthesized, one consisting only of methionine (Met) and the other consisting only of
aspartic acid (Asp).
(1) Briefly explain, using the term "tRNA", why not only amino acids but also ATP wererequired in the experimental system for synthesizing polypeptides.
(2) From the results of Experiments 1 and 2, answer one codon each encoding cysteineand valine.
(3) The results of Experiments 1 and 2 suggest that two codons possibly specify
tryptophan. Answer these two codons.
(4) Describe two possible reasons why only two polypeptides were synthesized inExperiment 3 while three polypeptides were synthesized in Experiment 2 in 40 words
or less.

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QUESTION No. 7(Subject on Life Science)

Question 7-1. The following sentences mention the intercellular adhesion. Read thetext and fill the blankets from（ a ）to（ j ）with the most appropriate term. Select theterm from ① 〜 ⑩ showing below. Describe the answer as ‘a : term’.

Of all the social interactions between cells in a multicellular organism, the mostfundamental are those that hold the cells together. Cell junctions are largely divided into
three categories, based upon their functions:（ a ）junctions,（ b ）junctions, and（ c ）junctions.
（ a ） junctions connect the plasma membranes of adjacent cells in a sheet,preventing small molecules from leaking between the cells. This allows the sheet of cells
to act as a wall within the organ, keeping molecules on one side or the order.
In（ b ）junctions, there are several types.（ b ）junctions called ‘desmosome’connect the（ d ）of adjacent cells, which hemidesmosomes anchor epithelia cells to a
（ e ） . Proteins called （ f ） , most of which are single-pass transmembrane
glycoproteins, create the critical link. And,（ b ）junctions called ‘adherens junctions’connect the actin filaments of once cell with those of neighboring cells or with theextracellular matrix. The linking proteins in these junctions are members of a large
superfamily of cell surface receptors called（ g ）that bind to a protein component of
the extracellular matrix.
（ c ）junctions establish direct physical connections that link the cytoplasms of two
cells together, permitting small molecules or ions to pass from one to the other. In animals,
these direct communication channels between cells are called gap junctions, and in plants,
these channels are called（ h ）.
（ h ）in plants are organized on different principles from those of animals. This isbecause plant cells are imprisoned with tough（ i ）composed of rich in（ j ）and otherpolysaccharides.
①：cadherin②：cell walls④：cytoskeletons ⑤：basement membrane⑦：intergrin⑧：tight⑩：communicating

11③：plasmodesmata⑥：anchoring (occluding)⑨：cellulose

Question 7-2.
Explain ‘gap junctions’ in animal cells using all the following four terms in about 150
words. You can use the same term several times. Underline the terms that you used in the
text.
1) connexin2) connexon
3) hemichannel
4) opening and shutting function of the channel

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QUESTION No.8

(Subject on Life Science)

Question 8-1. The following text mentions energy conservation in cells. Read the text
and answer to questions.
An oxidation is the removal of electrons from a substance and a reduction is the
addition of electrons to a substance. The ( ① ) reaction, which is also the reduction, adds
electrons and ( ② ) to a substance, and the reverse reaction is the dehydrogenation
reaction. Part of the energy from the redox reaction is conserved in activated carriers as
high-energy chemical bonds and/or electrons at high energy levels. ATP, NADH and
NADPH are representative activated carriers. ATP is formed by the phosphorylation of
ADP. Addition of two electrons and ( ② ) to NAD+ and NADP+ generates NADH and
NADPH, respectively. The activated carriers are formed by the ( ③ ) reactions in which
an energetically unfavorable reaction is driven by an energetically favorable reaction.
These reactions are catalyzed by enzymes, which accelerate the reaction rates by lowering( ④ ). These energy-rich compounds fuel energy-requiring cell functions.
(1) Describe the most appropriate term on the answer sheet to fill the blankets ( ① ) to (④ ).

(2) Answer the full names of the underlined compounds.

Question 8-2.
Choose one correct sentence and describe the selected number on the answer sheet.
① Organisms live by creating energy.
② The reaction that desaturates fatty acids is oxidation.
③ Acetyl-coenzyme A contains a high-energy phosphate bond.
④ Cells are primarily composed of four elements, C, H, P, S.
Question 8-3.
The substrate-level phosphorylation and chemiosmosis are representative reactions incellular energy metabolism. Explain these reactions in 80 words or less.

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QUESTION No. 9(Subject on Aquatic and Marine Science)

Question 9-1. Fisher’s sex ratio, one of the adaptation strategy models, is anevolutionary stable strategy of frequency-dependent selection type. Fill () in thenext sentence.
Consider a group with two tactics. The evolutionary stability is a state in which
the average adaptation of the two tactics that changes depending on the frequency in thegroup is equal. Taking the two tactics of "male" and "female" as an example, individuals
in low frequency sex has more opportunities to meet the opposite sex, but when
individuals in the same sex increases, the advantage disappears. Let's consider this in aformula. First, if the female male is “1: x”, and the total number of individuals in thegroup is “n”, the number of females is “(①)” and the number of males is “(②)”.
If “f” is the average number of offspring that one female produce is, the total number ofoffspring in the group is “(③)”, and the average number of offspring sired by one
male is (total number of offspring)/(total number of male) = “(④)”. The average
number of offspring produced by one female and sired by one male is the ratio of“(⑤ :)”, which is (⑥) to the sex ratio. Therefore, less either of sex individual
can leave many offspring and gradually increases individuals in the same sex. However,as the number of the same sex individuals increases, their chances to meet opposite sex
individuals decreases, so the gender ratio is eventually stable at “(⑦ ： )”.
Question 9-2. Following text asks about the principles of mating system. Fill (the next sentence.

) in

There is a group with the Fisher’s sex ratio, that is, the 0 -year -old sex ratio isstable at “(⑧:)”. After mature, experimentally examining the breeding interval,
it was found that male could breed five times a day and female once every two days. In
other words, the potential breeding speed is different for male and female, and(⑨) is expected to be male: female =“(⑩:)”. However, in the wild
population, the male was the maximum four times a day, the female breed only once
every three days, and the ratio of mature individuals was “N” times of females. Therefore,
the (⑨) is considered to be “(⑪:)”. In this way the reason why many
mature males inhabit may be that males have lower (⑫) or (⑬)
than females.

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QUESTION No. 10(Subject on Aquatic and Marine Science)

Question 10-1. Read the following text about the fundamental properties of water andanswer each question below.
Water consists of two atoms of hydrogen that are chemically bounded to one atomof oxygen. It is well known that the (a) and boiling temperatures of water are much higher
than expected when compared with chemically related (b) compounds((c), H2Se, H2Te).
In fact, water is the only substance that can coexist naturally as a gas, a liquid, and a solidon the earth’s surface. Therefore, it is not surprising to discover how fundamental it is to
all forms of life.
The higher-than-expected (a) and boiling temperatures of water depend directly onthe (d) structure of the water molecule. More energy is required than expected to vaporize
liquid water and to melt ice because (b) bonds that join water molecules together mustfirst be broken before the solid can melt and the liquid can vaporize. The unusually high(e) of water prevents extreme variation in the temperature of the oceans.
Because of the open-crystal structure of solid water, the (f) of ice is less than that ofliquid water. That is, ice floats on water. ○1 When ice is warmed to 0℃, it begins to melt
as thermal vibrations of the molecules cause the crystalline structure to break apart.
Pure water freezes at 0℃, but ○2 the addition of salt to the water lowers its freezing
point. For example, seawater with salinity of 35‰ freezes at a temperature of (g) ℃.
Also, ○
3 the (f) of water increases with salinity because solutes have a greater atomic
mass than water molecules have.
(1) Fill the blanks (a) to (g) with the appropriate words.
(2) In the underlined part ○1 , how is the (f) of water changed as temperature
continues to increase after melting. Explain it in about 20 words.
(3) In the underlined part ○2 , why is the freezing temperature depressed relative tothat of pure water? Explain it in about 20 words.
(4) In the underlined part ○3 , if there is contact between fresh water and sea water
without their turbulence, how phenomenon would occur? Explain it in about 10
words.

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Question 10-2. Explain each pair of terms in limnology to make the difference clear.
Explain it in about 60 - 100 words.
(1) Biochemical oxygen demand (BOD) and chemical oxygen demand (COD)(2) Epilimnion and hypolimnion(3) Dimictic lake and monomictic lake
(4) Surface seiche and internal seiche

Question 10-3. Read the following text about lacustrine food web and fill the blanks(a) to (e) with the appropriate words.
In pelagic food webs, it was recently elucidated that the carbon produced byphytoplankton was not enough to explain the growth capacity of animals higher up thefood web in many lakes. One of the major missing links in many attempts to quantify
energy flow was the (a) community, consisting of (b), heterotrophic flagellates, and (c).
(b) retrieve part of their carbon from phytoplankton, zooplankton, and fish excreta in theform of (d) carbon, and then they are eaten by heterotrophic flagellates and (c), which inturn are eaten by rotifers, crustaceous zooplankton, and even small fish. Thus, part of the
carbon lost from the pelagic system is returned to the traditional food web by (a)components. This recycling of carbon is termed the (a) (e).

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QUESTION No.11(Subject on Aquatic and Marine Science)

Question 11-1. Primary factors limiting primary production in the ocean include solar
radiation and nutrient concentrations. In about 250 words, explain how each factor
regulates primary production. You may use diagrams in your explanation.
Question 11-2. As shown in the table below, total annual primary production in theoceanic area accounts for more than 80% of the total primary production, but fish
production accounts for less than 1%. On the other hand, total annual primary productionin the upwelling area is only 0.5% of the total primary production, but fish production
accounts for 50% of the total production. Explain in about 250 words why the percentagesof total primary production and fish production are reversed in the oceanic and upwellingareas, using the all following words. Underline the words when they are used in a sentence.
Words: transfer efficiency, ocean area, average number of trophic steps, size of primary
producer, nutrients, number of transfers, diatom
Table. Primary production and fish production in each area.
(Invitation to Oceanography, Pinet, 4th ed. partly modified)Area

Primary
production(gC /m2/ yr)

Ocean
(km2)

area Total primary（%） production(t C/yr)(%)

Averagenumberoftrophic
steps

Transfer
efficiency
per trophic
level (%)

Fish production(t C/yr) (%)

Oceanic50

325x106

90.0

16.3x109 81.5

6

10

0.16x106 <0.7

Coastal100

36x1069.9

3.6x109

18.0

4

15

12x10650

Upwelling300

0.36x1060.1

0.1x109

0.5

2.5

20

12x10650

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QUESTION No.12(Subject on Aquatic and Marine Science)

As shown in the figure, a spherical float is moored by a thin metal wire in water withuniform flow. When trying to estimate the magnitude of the velocity of this uniform flowfrom the angle of inclination θ of the wire, answer the following questions. Assume thatthe wire is sufficiently thin that its mass and the fluid force acting on it are negligible, andthat the floats are in equilibrium without oscillation.
water surfaceyx

Question 12-1.

Buoyancy, gravity, drag, and other forces act on the float. Draw theabove figure on your answer sheet and use arrows to indicate all the vectors of forces thatare considered to act on the float. The arrows, however, should clearly indicate what theforces are.
Question 12-2.

Assuming that the magnitude of the buoyancy force acting on the float

is B, the magnitude of the gravitational force is G, and the magnitude of the drag force isD, express the inclination angle θ of the wire using B, G, and D.
Question 12-3.

Assuming that the velocity of uniform flow is U (m·s-1), the densityof water is ρw (kg·m-3), and the volume, projected area (area of the object viewed fromthe front), and drag coefficient of the floats are V (m3), S (m2), and Cd, respectively,
express the magnitude of the buoyancy force B and drag force D acting on the float using
these parameters. Let the gravitational acceleration be g (m·s-2).
Question 12-4.

Assuming that the object density of the float is ρM (kg·m-3) (where ρw>ρM), express the inclination angle θ of the wire using the parameters given in Question
12-3.

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Question 12-5.

If θ represents an angle of 45 degrees, what is the approximate

velocity U? Indicate the value using one significant digit. Let g=9.8 (m·s-2), ρw=1000(kg·m-3), ρM=998 (kg·m-3), Cd=0.5, and the diameter of the float is 1.0 (m).

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