Entrance Examination
For October 2021 and April 2022 students

Master’s Course(Specialized subjects)

Notes
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Select and answer 3 QUESTIONS from the total 12 QUESTIONS. The 3
QUESTIONS can be selected from any subjects.

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

l

Examinee’s number, Name, Subject and Question No. should be written oneach answer sheet.

Division of Biosphere Science
Graduate School of Environmental Science

Hokkaido University2021.08.M.S-E.1-1

QUESTION 1 (Subject: Field Science)

Answer the following questions.
Question 1-1. Explain each pair of terms in (1) to (4) in thefollowing to make clear the difference between the two terms. The
answer should be no longer than 4 lines (two terms combined) for
each of (1) to (4).
(1)Primary succession and secondary succession(2)a diversity and b diversity(3)Self-thinning and -3/2 power law(4)Net primary productivity and gross primary productivity
Question 1-2. Explain the equilibrium theory of island biogeography

proposed by R.H. MacArthur and E.O. Wilson, using all of thefollowing terms. Write in about 2 lines.
colonization, extinction
Question 1-3. Explain the biomes of the Earth, using all of thefollowing terms. Write in about 5 lines. If necessary, a figure may
be used for explanation.
annual precipitation, mean annual temperature, tundra, desert,
forest
Question 1-4. Explain the vegetation classification of the JapaneseArchipelago, using all of the following terms. Write in about 5lines. If necessary, a figure may be used for explanation.
subtropical forest, evergreen broad-leaved forest, deciduous
broad-leaved forest, coniferous forest, alpine vegetation2

2021.08.M.S-E.2-1

QUESTION 2 (Subject: Field Science)

Read the text below and answer the following questions.
To discuss the mechanisms of speciation, we first need todefine species. Among various definitions of species, (a) the
biological species concept coined by the evolutionary biologist E.
Mayr is widely known. The geneticist T. Dobzhansky defined species
as a group of individuals which share a common gene pool. Thismeans that there exist (b) mechanisms to prevent gene flow between
different species.
Speciation occurs via divergence of initially identical
populations and maintenance of differences that arise by (c)genetic drift and/or natural selection. Gene flow has thehomogenizing effect but when gene flow only occurs between
populations that are in contact, (d) allopatric speciation is
likely in geographically isolated populations. (e) On a geologicaltime scale, periodic geographic isolation promoted species
formation. For example, in New Zealand, multiple species of alpine
buttercup Ranunculus spp., that grow sometimes sympatrically inrocky crevices among outcrops within glacial areas, are considered
to have evolved from a common ancestor as caused by repeatedfragmentation of the distribution ranges in the Pleistocene.
Question 2-1. Explain the idea of the underlined term (a). Writein no more than 30 words.
Question 2-2. Regarding the underlined phrase (b), explain two
types of prezygotic isolation mechanisms. Write in about
20 words for each mechanism.
Question 2-3. Explain the underlined term (c), using the words,
Hardy-Weinberg equilibrium, founder effects, and thebottleneck effect. Write in about 100 words.
Question 2-4. The opposing concept of the underlined term (d) is
sympatric speciation. Explain the process of sympatricspeciation with chromosome polyploidization. Write inabout 70 words.
Question 2-5. This is a question regarding the underlined
sentences (e). Provide an explanatory hypothesis for theprocess of speciation from a common ancestor and3

2021.08.M.S-E.2-2

development of sympatric distribution of multiples species
growing within glacial areas, based on the Pleistocene
glacier expansion and retreat and the development ofreproductive isolation. Write in about 80 words.

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2021.08.M.S-E.3-3

QUESTION 3 (Subject: Field Science)

The following sentences state an ecological explanation of the
population of an organism. Read the explanation, and answer Question
3-1 to Question 3-3 below.
A group of individuals of the same species inhabiting a certain
space at a particular time is called a population. Various kinds ofinteractions are involved in population dynamics, including(a)biological interactions with other individuals of the same species
and with different species. One of major examples of interspecificinteractions is (b)competition. The resources that a species requires
and the environmental conditions in which it can survive are called( ① ). In the case of competition for the same ( ① ), local
extinction of one species can often be observed. Based on thisobservation, ( ② ) was proposed by G. F. Gauze.
In addition, habitats in nature are neither homogeneous nor
continuous. These have spatial structures (e.g., patch structures).
In this case, there are sub-populations within the population, anda structure is formed in which the sub-populations interact witheach other through limited individual migration. Such a population
is called ( ③ ). The following mathematical model describes thepatch occupancy dynamics of ( ③ ).
𝑑𝑝
= 𝑚𝑝(1 − 𝑝) − 𝑒𝑝𝑑𝑡p : A percentage of habitat patches occupied by sub-populations.
m: A probability that a vacant patch will be newly colonized byimmigrating individuals
e: A probability that the sub-population occupying the patch willgo extinct.
In order to find the condition for the persistence of ( ③ ), we
can calculate the equilibrium condition of the model, that is, dp/dt= 0. If we replace the left-hand side of the above equation with 0,
we can get the solution p = ( ④ ). p must be positive, so based on( ④ ), we can express the persistence condition in terms of m ande as ( ⑤ ). In other words, when the probability that a new subpopulation emerges (the probability that a vacant patch will be
newly colonized) exceeds the probability that sub-populations willgo extinct, the population should persist.

52021.08.M.S-E.3-2

Question 3-1. For the underlined part (a), answer the name of theinteraction between different species, which provides benefits
each other while paying costs. Moreover, shortly explain suchan interaction in terms of costs and benefits, raising a
specific example in nature in 300 words or less.
Question 3-2. Answer the appropriate words, phrases, and expressions
that fit in the blanks ( ① ) to ( ⑤ ).
Question 3-3. To examine the effects of the underlined interaction(b), a graduate student proposed a following experimental plan.
However, there are problems with his/her plan to test theeffect of interspecific competition. Choose all appropriate
criticisms from (A) to (G) below.

--- Graduate student's experimental design --Based on grassland observation, interspecific competition between
species A and species B may have an important role for the spatial
distribution and abundance of them. Therefore, I will conduct afield manipulative experiment to examine the effects ofinterspecific competition on the growth of these two species. The
field manipulation experiment is conducted by planting different
number of both species in pots. The total number of plants of two
species in one pot is constantly 12 individuals in total. But the
number of species A and B individuals varies as (i) 12:0, (ii) 9:3,
(iii) 6:6, (iv) 3:9, and (v) 0:12, respectively. In each of (i) to(v), 10 pots will be used as replicates. Two months after planting,
I will measure plant height, and then compare that among treatments(i) to (v). This will allow us to determine the strength ofinterspecific competition between the two species.
-- (END of the design explanation)-(A) The experimental treatments of 9:3 and 3:9 are unnecessary andsuch unnecessary experimental treatments should not be added tothe design.
(B) The data obtained from this experiment cannot correctly detect
the effect of interspecific competition because it is notpossible to distinguish whether it is due to density effect of
the same species or the different species.

62021.08.M.S-E.3-3(C) The effect cannot be fairly compared without measuring theheight and stem diameter at the beginning of planting as wellas two months later.
(D) In order to achieve the purpose of this research, it is necessary
to combine the experimental treatments in which both the total
number of individuals and the mix ratio of the two species are
independently changed.
(E) Because it is impossible to distinguish whether the effect isdue to intraspecific competition or interspecific competition,
the strength of the effect of interspecific competition cannot
be examined from the experimental data.
(F) Differences among treatments may not result from resourcecompetition but from herbivory. Hence, toward detecting effects
of resource competition exactly, it is critical to provide amesh net to prevent herbivory or measure the amount of herbivory.
(G) It is sufficient to examine whether the field distributions of
the two species are mutually exclusive. Manipulative experiments
are not necessary for the purpose.

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2021.08.M.S-E.4-1

QUESTION 4 (Subject: Field Science)
Question 4-1. Read the text and answer each question.

In understanding the morphology, behavior, or life history of anorganism, we should consider “why” and “how” the species has
acquired such a trait. For example, the red body of flamingos canbe explained as follows. Why: flamingos are reddish because
individuals with red body are preferred by the opposite sex, thereby
increasing the number of offspring. How: flamingos are reddish
because their foods, such as seaweeds and crustacean, containchemical compounds that produce red color. Why explanation is calledas ( 1 ) factor, whereas how explanation is called as ( 2 )factor.
Niko Tinbergen, who won the Nobel Prize in Physiology or
Medicine, proposed that there are four answers to the question "Whyis a certain behavior (or phenomenon) observed?" This can beconsidered as the further divisions of ( 1 ) and ( 2 ) factors.
The "Tinbergen's Four Questions" is now widely recognized in various
fields of life science, especially in animal behavior.
(1) Fill in the most appropriate word in blanks (( 2 ), respectively.

1

) and

(2) Explain "Tinbergen's Four Questions" in 2-3 sentences each.
Question 4-2. Read the text and answer each question.

Many ecologists used to consider that biological communities are
hardly to change and can quickly return to the ( 1 ) states even
if they are influenced by human activities or natural disturbances.
In addition, such stability was usually considered to be brought
about as a result of ( 2 ).
Recently, this way of thinking has been reexamined. It has

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2021.08.M.S-E.4-2

been recognized that biological communities are constantly
changing as a result of climate change, the invasion of new species,and disturbances. As a result, many ecologists are now advocating(
3) models that emphasize change rather than stability.
Ecological studies have particularly focused on (a) the role ofdisturbance in community structure and species diversity.
Source: The Raven & Johnson’s Biology textbook (partly modified)(1) Choose the most appropriate word from the following for blanks( 1 ) to ( 3 ), respectively.
"succession, neutral, climate change, equilibrium, non-equilibrium,
conflict, inter-specific competition, speciation”(2) For the underline (a), how species diversity changes withincreasing the level of disturbance? Explain the relationshipwith underlying mechanisms in 3-5 sentences.
Question 4-3. Over 90% of bird species are socially monogamous. It

is also known that more than 90% of monogamous birds haveoffspring with other than their mating partners (called“extra-pair paternity”). For males, extra-pair paternity
directly increases reproductive success. However, since thenumber of eggs that females can lay or the number of offspringthat they can raise is limited, mating with extra-pair males
may not necessarily increase the number of her fledgling.
Then, what are the possible reasons for females to mate withextra-pair males? Explain three reasons in 2-3 sentences each.

92021.08.M.S-E.5-1

QUESTION

5(Subject: Life Science)

Question 5-1. Eukaryotic cell division consists of mitosis andcytokinesis. Answer the following questions.
(1) Explain the following terms in about 50 words each.
“chromosome”, “chromatin”, “chromatid”(2) Explain the similarities and differences in cytokinesis between
animal and plant cells.
Question 5-2. Answer the following questions about bacterial

chromosome replication.
(1) The following table shows the bacterial DNA replication proteins
and their function. Fill in the blanks ① ~ ⑤ with theappropriate sentences.
Protein

Function

Helicase

Unwinds parent double helix at replication forks

Single-strand
binding protein

Binds to and stabilizes single-stranded DNA unit
it is used as a template

Primase①

DNA ligase②

DNA polymerase I③

DNA polymerase III④

Topoisomerase⑤(2) Which is the correct description of the elongation of theleading strand during DNA synthesis? Choose the correct one
from the following options.
(A) occurs in the 3′→ 5′direction.
(B) produces Okazaki fragments.
(C) depends on the action of DNA polymerase.
(D) progresses away from the replication fork.

102021.08.M.S-E.5-2(3) Choose one reason why the leading and lagging strands of DNA
molecules replicate in different ways.
(A) The origins of replication occur only at the 5′end.
(B) DNA polymerase can add new nucleotides only to the 3′
end of a pre-existing strand, and the strands are
antiparallel.
(C) Helicases and single-strand binding proteins work at
the 5′end.
(D) DNA ligase works only in the 3′→ 5′ direction.
Question 5-3. Bacteriophages are well-understood of all viruses.

Some phages have two replication mechanisms, the lytic
cycle and the lysogenic cycle. Explain their difference inabout 100 words.
Question 5-4. SARS-CoV-2 is an RNA virus responsible for thecoronavirus disease 2019 (COVID-19) pandemic. Explain themethod and principle of detecting RNA viruses using PCR in
about 100 words.

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2021.08.M.S-E.6-1

QUESTION 6 (Subject: Life Science)
Question 6-1. Read the text and answer the following questions.

Certain globular proteins are reversibly denatured by treatments
such as heat, extremes of pH, or denaturing agents. If the protein
is then gradually returned to its pre-treatment conditions, its
original activity is restored. This process is called ( ① ), whichis exemplified in the following experiment.
First, purified ribonuclease A is completely denatured in a highconcentration urea solution in the presence of a reducing agent. At
this step, the reducing agent cleaves the four ( ② ) bonds to yieldeight thiol groups, and the urea breaks the ( ③ ) bonds that
contribute to stabilization. As a result, it is released from its
folded state and the activity of ribonuclease is completely lost.
Then, the urea and the reducing agent are gradually removed, andthe randomly coiled ribonuclease spontaneously refolds into its
correct ( ④ ) structure and its activity is restored.
(1) Fill the blanks ( ① ) to ( ④ ) with the appropriate words.
(2) Explain the process by which proteins are folded into thecorrect structure during synthesis in the cell, considering
auxiliary proteins, in about 100 words.

Question 6-2. Describe the similarities and differences in the
structural features of each of the following combinations.
(1) cellulose and glycogen(2) D-glucose and D-fructose(3) maltose and sucrose

122021.08.M.S-E.6-2

Question 6-3. Read the sentences and answer the following questions.

Fatty acids generally have a long carbon skeleton consisting of
12 to 24 carbon atoms. The carbon at one end of the skeleton ispart of a carboxyl group and the rest of the skeleton consists ofa ( ① ) chain. ( ② ) have one or more double bonds between
carbons, which reduces the number of hydrogens attached to thecarbon. Nearly every double bond in naturally occurring fatty
acids exist in ( ③ )-form, which creates a kink in the ( ① )chain wherever it occurs. Therefore, the melting point of ( ② )is significantly lower than that of ( ④ ) with the same chain
length. Fatty acids are present in ( ⑤ ) of phospholipids thatare components of biological membranes.
(1) Choose the most appropriate word(s) to fill in the blanks ( ① )to ( ⑤ ) from the following terms.
steroid, hydrophobic region, hydrocarbon, trans, saturated
fatty acids, polycarbonate, unsaturated fatty acids,
carbohydrate, cis, lipids, hydrophilic region, geometricisomer(2) In many plants that tolerate extreme cold, such as winter wheat,
the fatty acid composition of phospholipids changes in the fall.
In addition, the composition of phospholipid fatty acids in
insects adapted to cold regions is different from that in otherspecies. Consider the cold adaptation of living organisms fromthe perspective of fatty acids, and describe it in about 100
words.
Question 6-4. For each the underlined part of the following
sentences, replace it with the appropriate word(s), if it
is not correct. Write “○” if it is correct.

(1) In bacteria, part of the RNA polymerase itself specifically132021.08.M.S-E.6-3

recognizes and binds to a promoter. In eukaryotes, repressor
proteins form a transcription pre-initiation complex and mediate
the initiation of transcription by RNA polymerase.
(2) Eukaryotic mRNA maturation generally needs RNA processing, which
includes the addition of a modified 5’cap to the 5’ end, theaddition of a poly-T tail to the 3’ end, and RNA splicing.
(3) Many eukaryotic genes consist of multiple exons which areinterrupted by introns. In RNA splicing, introns are removed,and exons joined to form a mature mRNA molecule. RNA splicing
is usually carried out by ribosomes(4) In some cases of RNA splicing, RNA alone catalyzes its own
splicing. RNA molecules with an RNA splicing ability are called
protease, and were first found in a protozoa called Tetrahymena.
(5) A tRNA molecule folds into a compact three-dimensional structurethat is roughly L-shaped. The protruding 3’ end acts as theattachment site for an amino acid. The loop extending from theother end of the L-shape includes an anticodon.

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QUESTION 7 (Subject: Life Science)

The following sentences describe the transfer of substances throughplasma membranes. Read the text carefully and answer each question.
(a)Phospholipid bilayers constituting plasma membranes are hardly
permeable to most polar molecules and ions. Instead, (b)ion andwater (H2O) channels, and various (c)membrane transporters areembedded in plasma membranes, and these proteins transfer ions,sugars, amino acids etc. to create (proper) concentration gradients
between the intracellular and extracellular space. For instance,
the Na+-K+ pump in animal cells and the H+-K+ pump in bacteria
generate concentration gradients of these monovalent cations andcontribute to establishing (d)membrane potential. On the other hand,(e)cholesterol, which is highly hydrophobic, is transported throughthe blood flow in a form that is encapsulated in lipoprotein
particles. When the lipoprotein particles bind to specific receptors
on the plasma membrane, the membrane becomes internalized, and as
a result, the cholesterol is taken into the cell with the
lipoprotein particles.
Question 7-1. Regarding the underlined part (a), write the following

substances in the order of “easily permeable”, “moderately
permeable”, and “almost impermeable” when they permeate the lipid
bilayer by simple diffusion without the aid of membrane proteins,
including channel proteins and membrane transporters.
H2O, O2, Na+

Question 7-2. Regarding the underlined part (b), the channels inplasma membranes are different from simple pores in two ways.
Explain them in about 10 words each.

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2021.08.M.S-E.7-2

Question 7-3. Regarding the underlined part (c), explain the threemodes of membrane transport using all of the following terms inabout 60 words in total.
facilitated diffusion, ATP hydrolysis, coupled transport

Question 7-4. Regarding the underlined part (d), the following two

processes are well known to illustrate an importance of membranepotentials in living organisms. ① neural transmission and ② ATPsynthesis in mitochondria. Choose either ① or ②, and explain how
the membrane potential is used in the process you choose in about
60 words.

Question 7-5. Regarding the underlined part (e), answer thefollowing questions.
(1)Answer the name of the biological process in which cells importextracellular substances by the plasma membrane internalization.
(2)The low-density lipoprotein receptor (LDLR) is a receptor for
lipoprotein particles. The gene expression of LDLR is positively
regulated by sterol regulatory element binding protein (SREBP).
On the other hand, the activity of SREBP is repressed when theintracellular cholesterol concentration is high. Answer the nameof the latter gene regulatory mechanism, and briefly explain the
biological merit of the gene regulatory mechanism.

162021.08.M.S-E.8-1

QUESTION 8 (Subject: Life Science)

Read the following sentences on cell metabolism and answer thequestions.
To maintain cellular functions, cells possess mechanisms to harvest
energy by stepwise oxidation of carbohydrates. As a part of theprocess, glycolysis and the （A） cycle are shown in the figure.
In glycolysis, glucose is converted into pyruvate, yielding （B）
and ATP. Under aerobic conditions, pyruvate is decarboxylated toform （B） and （C）. Transferring the acetyl group of （C） to （D）
produces （A）, starting the （A） cycle. （B） and （E） function
as electron donors that carry high-energy electrons.

Question 8-1. When ATP (molecular weight: 507) was measured in theextract of animal cells, ATP concentration was found to be
1.521 g/L. Calculate the molar concentration (mol/L) of ATP
in this cell extract. Answer the molar concentration withthe unit.

172021.08.M.S-E.8-2

Question 8-2. Fill the blankets （A） to （E） with appropriatecompounds.
Question 8-3. In yeast under anaerobic conditions, pyruvate produced
by glycolysis is converted into ethanol.
(1) Answer the name of the process.
(2) Ethanol cannot be used as energy for yeast. Explain why yeast
produces ethanol under anaerobic conditions.
Question 8-4. Which organisms perform glycolysis? Describe thepresence or absence of glycolysis in bacteria, archaea,
animals and plants, respectively.
Question 8-5. Explain the roles of the （A） cycle in metabolism
other than harvesting energy.
Question 8-6. Most of biological reactions are catalyzed by enzymes.
In the reaction ⑥ in the （A） cycle, succinate is converted
into fumarate, which is catalyzed by succinate
dehydrogenase.

(1) When it is assumed that this enzymatic reaction follows the
Michaelis-Menten equation, explain an experiment to estimate Km
and Vmax. You can include a figure to explain.
The Michaelis-Menten equation is presented as follows (v0:
initial velocity of the reaction, Vmax: maximum velocity of thereaction, [S]: substrate concentration, Km: Michaelis constant).

(2) Enzymatic activity of succinate dehydrogenase is inhibited byaddition of malonate, which is structurally similar to
succinate. Write the name of this type of enzyme inhibition,and explain how Km and Vmax will be changed when malonate isadded to the reaction system described in (1) above. You can
include a figure to explain.

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QUESTION 9 (Subject: Aquatic and Marine Science)
Question 9-1. The three fundamental strategies for the sustainable
use of fisheries resources are as follows: a) constantescapement strategy (CES), b) constant harvest rate
strategy (CHR), and c) constant catch strategy (CCS).
Select two the above three strategies and briefly explain
each strategy along with its advantages/disadvantages(about 100 words per strategy).

Question 9-2. Explain the methods for conducting the basic measuresof fishery resource management using all of the following
terms (about 150 words in total).

Input control, Output control, Technical control, TAC(Total Allowable Catch), MPA (Marine Protected Area)

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QUESTION 10 (Subject: Aquatic and Marine Science)

Read the following sentences, and answer the questions.
In

recentyears,

thedeclineanddisappearanceofseaweedcommunities due to a lack of nutrients is becoming more serious. On
the other hand, eutrophication of coastal areas is also seen due tolandfill, construction of shore protection-works, living drainage
and industrial drainage, and (a) the large-scale propagation of algaethat absorb excess nutrients has been reported in various regions.
Therefore, it is considered (b) to restore the environment by growing
seaweeds that are resistant to eutrophication against environmental
deterioration such as the load of nutrients in the sea. In addition,in fish and shellfish aquaculture grounds, attempts are being madeto improve the marine environment by combined aquaculture in whichuseful seaweeds are also grown.
Question 10-1. List one of the visible changes that occur in the

body of seaweeds due to a lack of nutrients.
Question 10-2. Explain the underlined part (a) in about 8 lines bygiving examples that include both micro-algae and macroalgae.
Question 10-3. Regarding the underlined part (b), seaweeds such as

Ulva, Gracilaria and coralline algae are said to be useful
bio-filters for seawater purification. Explain one of thesethree seaweeds (Ulva, Gracilaria, coralline algae) in about
6 lines.

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Question 10-4. Explain the merits of “combined aquaculture” inabout 6 lines.

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2021.08.M.S-E.11-1

QUESTION 11 (Subject: Aquatic and Marine Science)

Read the following text and answer each question below.
Marineorganisms

areclassified

according

to

their

lifestyle into the following three groups; plankton (organisms
drifting in the water column), nekton (organisms swimming in thewater column) and benthos (organisms living on the sea floor).
Benthos consists of various types of organisms, such as marine
plants, invertebrates, fishes and many microbial species. Amongthese, (a) many invertebrate and fish species have characteristicsof plankton or nekton during a part of their life cycles.
Benthic ecosystems are diverse, affected by various factors
such as depth, bottom type, geography and the input from terrestrial
ecosystems such as rivers. Among these, several conspicuous habitats
in the near shore, such as tidal flats, seagrass/seaweed beds,
mangroves and coral reefs are known to have high productivity andbiodiversity. Generally, the productivity of benthic ecosystems
decreases with depth, but some deep-sea ecosystems are known tohave higher biomass and biodiversity than their surrounding habitats.
Question 11-1. List up two invertebrate taxa belonging to benthos,and describe the characteristics of each taxon in about
30-50 words.
Question

11-2.

List

up

an

animal species

which

has

the

characteristics written in the underlined part (a), andexplain its life history in about 80-100 words.

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Question 11-3. Explain why coral reefs, seagrass beds and mangrovesin the tropics have high productivity and biodiversity inabout 80-100 words.
Question 11-4. Name a deep sea habitat which has high biomass andbiodiversity and explain the reason in about 40-60 words.

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QUESTION 12 (Subject: Aquatic and Marine Science)

Answer the following two questions.
Question 12-1. Explain the mechanisms of Ocean Acidification andthe specific issues on marine organisms and ecosystems
caused by Ocean Acidification in total ca. 200 words.
Question 12-2. Phytoplankton absorb carbon and nutrients during

photosynthesis in the sea, but carbon is not a limiting
factor for photosynthesis even in phytoplankton blooms.
Considering the chemical equilibrium of carbon, explain
why carbon is not a limiting factor for photosynthesis in
ca. 200 words.

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