Life Science (Biology), Grades 3

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Life Science (Biology), Grades 3

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Title: Life Science (Biology), Grades 3

1
2009
2
Life Science (Biology), Grades 35

Characteristics of Plants and Animals
Structures and Functions
Adaptations of Living Things
Energy and Living Things

3
Characteristics of Plants and Animals

Classify plants and animals according to the
physical characteristics that they share.
Sort plant and animal pictures based on physical
characteristics.
Use a dichotomous key to identify plants and
animal.

4
Structures and Functions

2. Identify the structures in plants (leaves,
roots, flowers, stem, bark, wood) that are
responsible for
food production
support
water transport
nutrient transport
reproduction
growth
protection

Observe-- plant/pollinator interaction seed
dispersal methods. Study maple trees and go maple
sugaring. Identify the structures in the maple
tree and their functions.
5

3. Recognize that plants and animals go through
predictable life cycles that include
birth
growth
development
reproduction
death.

Grow plants from seed. Document the complete life
cycle of the plant. Describe emergence of
structures and the functions of these structures.
Record changes in height over time. Graph the
data.
6

4. Describe the major stages that characterize
the life cycle of the frog and butterfly as they
go through metamorphosis.
Using either live organisms or pictures/models,
observe the changes in form that occur during the
life cycle of a butterfly or frog.

7
Adaptations of Living Things

5. Differentiate between observed
characteristics of plants and animals that are
fully inherited
(e.g., color of flower, shape of leaves, color
of eyes, number of appendages)
characteristics that are affected by the climate
or environment
(e.g., browning of leaves due to too much sun,
language spoken).
Make frequency tables of the number of students
with certain inherited physical traits,
e.g., eye color, hair color, earlobe free or
attached.

6. Give examples of how inherited characteristics
may change over time as adaptations to changes in
the environment that enable organisms to survive
e.g., shape of beak or feet, placement of eyes
on head, length of neck, shape of teeth, color.
Compare and contrast the physical characteristics
of plants or animals from widely different
environments (e.g., desert vs. tropical plants
aquatic vs. terrestrial animals).
Explore how each is adapted to its environment.

7. Give examples of how changes in the
environment (drought, cold) have caused some
plants and animals to die or move to new
locations (migration).
Investigate how invasive species out-compete
native plants (e.g., phragmites and purple
loosestrife).
Discuss how some native plants die as a result.

8. Describe how organisms meet some of their
needs in an environment by using behaviors
(patterns of activities) in response to
information (stimuli) received from the
environment.
Recognize that some animal behaviors are
instinctive (e.g., turtles burying their eggs),
and others are learned (e.g., humans building
fires for warmth, chimpanzees learning how to use
tools).
Discuss how newly born sea turtles find their way
to the ocean.
Discuss how pets are trained to learn new tricks.
Discuss how migrating birds navigate.
Discuss the actions that coastal species take to
adjust to the changing levels of the tide.
Observe an earthworm placed on top of soil in a
container that is exposed to light.
Discuss how its ability to sense light helps it
survive (by burrowing) and how its structure
allows it to burrow through soil.

9. Recognize plant behaviors, such as the way
seedlings stems grow toward light and their
roots grow downward in response to gravity.
Recognize that many plants and animals can
survive harsh environments because of seasonal
behaviors, e.g., in winter, some trees shed
leaves, some animals hibernate, and other animals
migrate.
Set a germinating bean in a glass filled with
water next to an asymmetric source of light.
Allow the root and stem to grow a few inches.
Rotate the bean so that the roots are now
touching the water at an angle and the stem is
away from the light source. Observe how the root
system and stem respond to this change by
changing their direction of growth

10. Give examples of how organisms can cause
changes in their environment to ensure survival.
Explain how some of these changes may affect the
ecosystem.
Discuss the importance of wetlands to human
survival.
Investigate how an invasive species changes an
ecosystem.
Research local projects where humans are changing
the environment to ensure a species survival.

13
Energy and Living Things

11.Describe how energy derived from the sun is
used by plants to produce sugars (photosynthesis)
and is transferred within a food chain from
producers (plants) to consumers to decomposers.
Make a food chain. Begin with the sun as the
source of energy and end with decomposers. Create
links that show the relationships of plants and
animals in the chain.
Show the direction of the flow of energy.
Discuss results if various links in the chain are
broken.

The four pictures below show how a pond
environment changed from 1900 to 2000.Which of
the following processes was most directly
responsible for the changes that occurred in the
pond environment?
A. freezing
B. evaporation
C. sediment deposition
D. chemical weathering

Which of the following best describes a role of
mushrooms in ecosystems?
A. capturing energy from sunlight
B. consuming living plant material
C. service as food for human
D. breaking down dead plant material

Which of the following statement is not true for
H1N1 virus?
(A) It is composed of cells
(B) It is able to infect swine
(C) It is a new strain of Influenza virus
(D) It has been reported of sever pneumonia cases
on infected patient.

List three ways to reduce the spread of influenza
infection

Population growth pattern of bacteria is very
important in a fermentation industry. If an
Erlenmeyer flask containing nutrient broth was
inoculated by a certain amount of bacterial cells
(No) at To, after a certain period of time the
bacteria will show a specific growth curve.
In the beginning of growth (To T1) the cells
are under adaptation phase.
After adaptation phase, cells start to multiply
by binary fission process. Each cell will divide,
and become two cells.
In a closed system where the nutrient supply is
limited, the population of dividing cells will
become relatively the same amount with the dead
cells (T2 T3).
After T3 the amount of dead cells will be higher
than the living ones, then eventually all cells
will die.

19
The growth curve (N in logarithmic scale) from
the above description is
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The plant structures (the sketch is not the real
size).
Fill in a box for appropriate plants organs of
1. Monocots
2.Dicots

23
The picture below shows a terrarium ecosystem,
with four (4) processes occurring in it which are
symbolized by I to IV. From the picture, process
II involves
II
I
III
IV
A. Heat Energy B. Light Energy C. Chemical
Energy D. Chemical cycling
24

Every organism consists of cells.
1. Select correct group of organisms listed in
the Table 2 below and match it with Figure 2a and
2b

Avian Influenza or bird flu is a contagious
disease of animal caused by viruses that normally
infect only bird and less commonly pigs. Avian
Influenza viruses are highly species-specific,
but have, on rare occasion, crossed the species
barrier to infect humans.
Avian Influenza viruses have 16 H (H1 H16)
subtypes x 9 N (N1 N9) subtypes. Among them are
known to cause highly pathogenic form of the
diseases. However, not all the subtypes of the
viruses are highly pathogenic and not all will
cause severe disease in poultry.

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1. Based on current understanding, viruses are
introduced to poultry flock in their low
pathogenic form. Allowing them to circulate in
poultry population within few months, usually the
viruses undergo mutation into a highly pathogenic
form. The virus subtype that we (human) are most
concerned about, are ., and ..
2 .Is the virus transmitted easily from birds to
humans ?
A. Yes, avian influenza virus is easily
transmitted to human, especially in chicken farms
area
B. Yes, avian influenza virus can be transmitted
from chickens/bird to human, because human and
chickens/bird posses the same virus receptor
C. No, because human does not have the particular
virus receptor
D. No, because only relatively small number of
people is infected compared to the significant
number of infected chickens and birds

15. In general, plants have a much larger surface
area/volume ratio. What is the main reason for
this?
(A) The advantages of having a larger body
surface in plants are correlated to the area of
light absorption.
(B) Plants, in general, are bigger than animals.
(C) Animals need a larger volume in order to
store water.
(D) Animals have more complex chemical substances
in their bodies.

16. The organic pesticides were developed in the
1940s. Their effectiveness against crop diseases
surprised everybody at the time. On the other
hand, their high persistence in the environment
resulted, after a period of time, in a large
incidence of mortality of birds, which didn't
come into direct contact with these products.
This fact is related to the ecological concept of
trophic magnification which means
(A) Degeneration of the food chain.
(B) Accumulation of toxic residues in the large
animals, because those consume larger quantities
of food.
(C) Gradual increase in the concentration of the
toxic products at every trophic stage in the food
chain.
(D) A larger resistance of the animals of lower
trophic levels to the toxicity of those products
in relation to animals in upper trophic levels.

17.Water plays an important role in biology.
Indicate the option that presents the correct
affirmative about this liquid.
(A) The metabolic activity of a cell is directly
related to its hydration condition.
(B) Water living beings obtain oxygen needed for
their respiration from water molecules.
(C) The terrestrial living beings do not depend
on water for their reproduction, respiration and
metabolism.
(D) Water dissolves only cellular molecules, but
does not participate in the cellular metabolic
activities.

18. The majority of the energy used in the planet
today is produced by burning fossil fuels. The
Kyoto protocol, an international agreement that
includes the decrease in the emission of CO2 and
other gases, demonstrate the present
preoccupation with the environment. The excess of
fossil fuel burning can have as consequences
(A) Increase in acid rains and increase in the
ozone layer.
(B) Increase in the greenhouse effect and the
level of the oceans.
(C) Global temperature decrease and increase in
the levels of oceans.
(D) Destruction of the ozone layer and decrease
of the greenhouse effect.

19. One of the problems in the use of solar
energy as an alternative energy source is the
difficulty in storing that energy. Some group of
living beings developed the capacity of storing
that energy in organic compounds to use in their
metabolic processes.
The process of storing this energy and example of
groups that can perform it are, respectively

The figure shown below is the food-network of a
community. Which one of the following consumers,
if it becomes extinct, will make the most
significant impact on this ecosystem?

(A) Lizards (B) Snakes (C) Eagles (D) Rats
34

For several years, Mr. Tu had continuously been
applying a certain amount of X-pesticide on the
field for reducing the damage of pests on rice
production. For each year, he counted pests found
in the rice field by numbers/m2 and plotted the
results shown in Figure

According to the above observation, Mr. Tu
concluded that the X-pesticide was very effective
in the earlier years, but, it gradually became
ineffective in later years. Based on the above
information, please answer the following
questions.
III-3-A
By examining the data shown in Fig., which year
was the first year for applying X-pesticide?

III-3-B
Which one of the following statements matches Mr.
Tus conclusion?
(a) Mutations happened in Mr. Tus rice plants
and the mutated rice plants attracted a large
quantity of various other pests to come.
(b) A pesticide-resistant line was developed in
the pest population, after which the number of
the pesticide-resistant insects increased.
(c) Bad quality control in the production of the
pesticide resulted in the ineffectiveness of the
pesticide.
(d) After Mr. Wang applied X-pesticide in the
field, heavy rains reduced the efficiency of the
pesticide.

III-3-C
Based on the study of Mr. Tu, to prolong the
effectiveness of X-pesticide, which one of the
following suggestions is the best?
(a) Lowering the applied dosage of X-pesticide
every year
(b) Doubling the applied dosage of X-pesticide
every year
(c) Alternation of high and low X-pesticide
dosages on a yearly basis
(d) Alternating application of X-pesticide with
another effective pesticide each year.

38
ANS

III-3 Pests in the rice field
III-3-A (0.4 point)
By examining the data shown in Fig.III-3, which
year was the first year for applying X-pesticide?
Answer 2003. The number of pests in 2003 was
smallest.
III-3-B (0.3 point)
Which one of the following statements matches Ms.
Tus conclusion?
Answer (b).
III-3-C (0.3 point)
Based on the study of Ms. Tu, to prolong
effectiveness of X-pesticide, which of the
following suggestions is the best?
Answer (d)
Alternating application of X-pesticide with
another pesticide each year could decrease the
formation of pesticide-resistant lines.

A25. The diagram below shows a typical foodweb of
a rice paddy.
Regarding this foodweb, which of the following
statements are true?
(a) Biomass decreases as you go up the trophic
level in this foodweb.
(b) Heron has the most impact on this ecosystem.
(c) If the number of spiders decreases, the
number of brown planthoppers will increase.
(d) If the number of heron increases, the amount
of rice will increase.
(e) If the number of grasshoppers increases, the
amount of rice will decrease.
(A)a, e (B) b, d (C) a, c, d (D) b, c, e

26. The graph below shows experimental results
which regards hatching of fruitfly eggs. A
researcher hatched fertilized eggs at 10?, 15?,
20?, 30? after they were incubated at 2? (Exp. I)
or at 21? (Exp. II) for 3 days.

Select an option with the optimum incubation
temperature and optimum hatching temperature.

18. Biological species concept is stressed on the
organisms ability to interbreed and produce
viable and fertile offspring. Different species
are separated by barriers that prohibit
interbreeding it also called as reproductive
isolation.
Which of the following isolating mechanism is
responsible for the origin of the Darwin finches
on Galapagos island?
A. Geographical isolation
B. Mechanical isolation
C. Behavioral isolation
D. Temporal isolation

19. The information of the physical world outside
our body, as well as the processes inside, is
collected by sensory receptors. Most of these
receptors are specialized neurons or epithelial
cells, existing in single or groups with other
types of cells within the sensory organs. Choose
the correct match among organs, sensory cells and
receptor types from the table below.

A. I, 1, b B. II, 2, c C. III, 3, a D. IV, 4, d
44

A21. The foods that enter our digestive system
will undergo several processes, which are
function- and place-specifics. Choose the correct
statement.
A. While in the mouth, starch is broken down into
disaccharide by the action of salivary amylase
B. Stomach lining produces peptides
C. The function of large intestine is to produce
digestive enzymes
D. The function of small intestine is to absorb
water

C22. Global warming is considered as a big
environmental issue. This phenomenon creates
climate change, which causes several effects of
different magnitudes.
Minimum effect(s) of climate change can be
observed on
I. plant growth
II. plant flowering
III. deciduous trees losing leaves in the fall or
dry season
A. I only
B. II only
C. II and III
D. I and III

C23. AIDS (Acquired Immune Deficiency Syndrome)
is caused by HIV (Human Immunodeficiency Virus).
People with AIDS are susceptible to opportunistic
diseases, infections and cancers that take
advantage of the collapsed immune system. HIV
suppresses the immunes system by killing the
victims
A. B-cells
B. Macrophage
C. T-cells
D. Plasma cells

A24. Insects can provide important evidence in a
crime investigation. Size and age of particular
larvae found in corpse can be used to estimate
the time of death. Which insects with larvae
usually arrive earliest on human dead bodies?
A. Blowflies
B. Ants
C. Mites
D. Dung beetles

C23. The table shown below is the analytical data
of mitochondrial DNA of four different, but
related animal species.
If you made a phylogenic tree of these four
animals with the data above, which would be the
correct answer? (You should consider the fewest
change of sequence of bases in DNA)

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Episcia reproduces young plants by runners
From the picture above
a. How many runners shown in the picture?
Answer ___________________.
Which one is the oldest runner?
Answer ___________________.
A runner is a special kind of ___________________
_.
(choose one right answer Stem/root/leaf/flower/pl
ants)

51
Part of plant which absorb water and mineral is
__________. Part of plant which produces
carbohydrates is ___________. Where is the food
stored? ___________________________.
52
Which part of flower that function to attract the
insect? The flower indicates as A)perfect
flower B)imperfect flower C)complete
flower D)incomplete flower
53

What is the name of the process which is
responsible for the production of oxygen by green
plants?

Which statement about sexual reproduction in
flowering plants is correct?
A)It is conducted through bud formation.
B)It requires the presence of petals.
C)It can be accomplished by grafting.
D)It gives rise to genetically diverse offspring.
E)It cannot result from self-pollination.

Pollination in the flowering plants ________ .
A)never requires external water
B)never occurs within a single flower
C)always requires help by animal pollinators
D)is also called fertilization
E)make most angiosperms independent of external
water for reproduction

Stomata in the typical green leaves, _______ .
A)are covered by a waxy cuticle
B)control the opening of guard cells
C)close when water is being lost at too great a
rate
D)are usually most abundant on the upper
epidermis of a leaf
E)release less water to the environment than
other parts of the epidermis

Tuti conducted the experiment concerning the
relationship between transpiration and leaf area
in two different plants (plant A and plant B).
She wrote the result of the experiment in a form
of graph shown below.

From the graph above
A. Explain how leafs area influences the
transpiration of plant A and plant B.
B. Which plant respirates faster?

59
The figure above show plant ringed in part 3.
Do branch 1 and 2 will still alive? Give
reason to your answer! Does branch 4 still can
get photosynthesis product from leaves in branch
1, 2? Give explanation to your answer.
60

Donny conducts the experiment in the laboratory.
He grows corn plants in two different
environments. He sets up the plant A in an
environment with low CO2 and plant B in a high
CO2. He writes the result of his experiment as
shown in a table below.

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A. Change the table above into a graph. Time on
the horizontal axis and growth rates in the
vertical axis
B. How does carbon dioxide influence growth of
the corn plants?
C. Which plants has a higher growth rate?

Look at the drawings 1 to 5 of the larvae of
common freshwater insects (the drawing is not
drawn to scale)

Identify each one in turn by using the key. No
legs go to no. 2 Three pairs of
legs present . go to no. 3 Bristles on all
segments .. Culex Bristles not present on
all segment Simulium One tail fillament
Sialis Two tail fillament present
.. go to no 4 Long fillament on head
.. Perla Short fillament on head
... Dyctisus
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From the table above answer these following
questions
A)Which food is the richest protein?
B)Which food is a highest value in bone formation
C)Which food would you recommend for someone
suffering from aptha/mouth ulcer?
D)How many calories would you obtain if you ate a
cheese sandwich containing 100 g of bread, 50 g
of cheese and 2,5 g of butter?

66
Write down 2 plants parts that have function as
storage organs! If some of the leaves are
eaten by caterpillar, is the plant still produce
storage organs? Give the reasons!
67
Explain the stomatas behavior in plant A and B
based on the graph above! Give the reason why
some plants open the stomata during the night,
while it must be closed during the day?
68

Plants lose water through their leaves by
transpiration. The graph below is the result of
transpiration experiment using Hibiscus
rosa-sinensis. Answer the questions based on the
graph!

When did the plant lose the most water and how
much water evaporate from the plant?
Answer
How do the plant lose the water?
Answer
When did the plant lose the least water? Why?
Answer
How can you explain these results?
Answer

70
Part of the seed which stores food is
_____________________ Part of the seed which
grows into shoot is __________________
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According to the picture below, some plants trap
and digest insect to fulfill their needs that is
not available in soil. This ability is a kind of
plant adaptation to the terrestrial ecosystem,
which lacks .
A)oxygen
B)hydrogen
C)nitrogen
D)sulphur
E)carbon dioxide

73
Look at the picture below. Acid rain may occur in
this area due to the gases produced from human
activities. The gases may react with water and
form an acid. Which one of the following gases
causes acid rain? A)Nitric oxide B)oxygen C)carbo
n dioxide D)Nitrogen E)Hydrogen
74

Plant loses water through the leaves by
transpiration. An experiment was set up to
measure the loss of water from the leaves. Prior
to the experiment, pot and soil were covered
using the plastic bag, as shown in the picture.
Loss of water from plant could be regularly
measured by weighing the potted plant.

When does the plant lose the most amount of water
during the day?
A)At noon. It is due to the highest temperature
and maximum light intensity of the sun.
B)At noon. It is due to the highest temperature
and humidity at that time.
C)At noon. It is due to the highest humidity and
maximum light intensity of the sun.
D)In the morning. It is due to the lowest
temperature and humidity
E)In the morning. It is due to the sun and
temperature start to rise

Why must the plastic bag cover the pot and soil?

What will happen if all the leaf surfaces were
covered by clear plastic?
A)The plant will die due to the lack of oxygen
needed for their respiration.
B)The transpiration will be disturbed due to the
decline of pores needed for gas exchange.
C)The plant will die because less water enters
the plant.
D)The photosynthesis will be affected because the
clear plastic will prevent the sunlight from
reaching the leaves
E)The plant will die because the accumulation of
carbon dioxide in leaves is toxic for plant.

78
Which one of the following statements indicates
the correct food chain?
79

Which one of the following statements indicates
the correct food chain?
A)1,2,3,4,5,6,7,8,9,10,11,12
B)3,4,5,6,7,8,9,10
C)5,6,7,8,9,10,11,12
D)1,5,9,12
E)1,2,3,4

Overuse of pesticide can cause some of the
following events
1.The plants die
2.Most of the targeted pests die
3.Soil organisms die
4.Plants may grow rapidly
5.Pests become resistant to pesticide
6.Soil microorganisms grow rapidly
Which of the following sets of statements is
true?
A)1,2,3,4,5,6
B)1,2,3,4,5
C)1,3,5
D)2,4,5
E)3,6

Identify the part labeled i and state its
function.
Identify the part labeled f and state its
function.

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Some animals have strategies to escape from
predators or enemies, such as producing a bad
smell, changing color, etc. Which is the
following tactics that is used by squid?
A. By curling its body
B. By having an electric tail
C. By detaching its tail easily
D. By excreting ink
E. By changing body color

Snakes are different from worms because snakes
have .......
A. Slime
B. Eggs
C. Segments
D. Scales
E. Color

Which one of the activities described in the
table below does not match the characteristic of
all living things.

Elvira wants to prove that plants need some
nutrients in the soil. In order to test her idea
she uses two pots of plant. She sets up one pot
of plant as shown below.

Which one of the following should she use as a
control set-up?

Choose a hypothetical graph to show the
respiration of an animal in a closed chamber over
a period of time.

89
Based on your understanding in biology, identify
how many population in A and how many population
in B.
90

Desert is an area characterized by low rainfall,
high evaporation and low humidity. In such a
condition, desert plants survive by adapting
themselves structurally and physiologically.
Which of the following is the least possible
adaptation of desert plants?
A. shallow and spreading roots
B. fleshy leaves
C. thin wide leaves
D. green stems
E. thick-cuticle leaf
Explain your answer.

Two identical plants are grown in two different
places, dark (plant A) and light (plant B).After
some weeks, what is the appearance of both plants?

Tofu (soybean curd) contains high amount of
protein from soybean. Choose other examples
of food which contains high protein
A. Cheese
B. Bread
C. Potato chips
D. Chicken curry
E. Jelly

Plants use water for .
(1) cell growth (2) photosynthesis (3)
germination
A. (1) and (2)
B. (1) and (3)
C. (2) and (3)
D. (1), (2) and (3)
E. None of them

Animals in the house may indicate a potential
disease that may be spread in the family. If you
have a cat in the house, choose the following
disease that may be spread by the cat to human
A. Dengue
B. Avian influenza
C. AIDS
D. Polio
E. Tuberculosis

Why does the seed of the coffee have a very tough
seed coat? The seed can .
A. be dispersed by propulsion
B. extend the distance of its dispersal by
traveling breezes
C. adhere to passing animals
D. survive the mechanical forces and conditions
of the animals gut
E. attract the animals

Which of the following statements about an
animals size and shape is not true?
A. larger animals require more food than smaller
animals
B. larger animals produce more waste than smaller
animals
C. larger animals are more vulnerable to cold
than smaller animals
D. larger animals require more oxygen than
smaller animals
E. larger animals require larger area than
smaller animals

If you want to make your plant increase in
height, which part of the plant you have to cut?

Choose the correct picture showing the path of
light entering a normal eye?

Which of the following substances can be recycled
in an ecosystem?
(1) carbohydrate (2) water (3) nitrate
A. (1) and (2)
B. (1) and (3)
C. (2) and (3)
D. (1), (2) and (3)
E. None of them

100

In order to increase speed and agility, an animal
uses different kinds of strategy. Complete the
table by writing the body part used by the animal.

101

Which of the following type of reproduction
produces offspring with identical genotypes?
(1) buds from the same potato tuber (2) seeds
from the same tomato (3) spores from the same
fungus.
A. (1) and (2)
B. (1) and (3)
C. (2) and (3)
D. (1), (2) and (3)
E. None of them

102

The following picture is a diagrammatic figure of
various kinds of systems in animal.

103
..(4.1) pumps the blood to the lungs
through (4.2). Within the lungs, blood cells
discharge carbon dioxide and take in
oxygen. Oxygen-rich blood from the lungs goes
back to the heart through (4.3), then it is
pumped from the (4.4) to all over the body
through the (4.5).
104

The following is a list of substances which can
be found in blood. Match the substances with the
correct description on the left box by putting
only one letter in the blank box

105
What are the conditions of the heart valves when
the ventricles are all relaxed? A. Valves 1 and 2
are closed valves 3 and 4 are open. B. Valves 1
and 3 are closed valves 2 and 4 are open. C.
Valves 1 and 3 are open valves 2 and 4 are
closed. D. Valves 1 and 2 are open valves 3 and
4 are closed. E. All of the valves are open
106

Some people may have a hole in the septum that
separates chambers X and Y. What problem will
they have?
a. They may develop anemia.
b. They may have a lower blood pressure.
c. Their blood may not be able to clot normally.
d. Their arterial blood may not be fully
oxygenated
e. They may have a higher blood pressure

107
When there is a large defect between the atria, a
large amount of oxygen-rich (red) blood leaks
from the heart's left side back to the right
side. Then this blood is pumped back to the
lungs, despite already having been refreshed with
oxygen. This is inefficient, because
already-oxygenated blood displaces blood that
needs oxygen. Many people with this defect have
few, if any, symptoms.
108

An ecologist studied the number of organisms in
grassland area over a three year period

109

Pick from the following choices to answer
question (a), (b), and (c)
A. Mice population is increasing
B. Mice population does not depend on the area of
grassland
C. Insectivorous birds is migrating into the area
D. The grassland area is decreasing
E. Insectivorous bird depends on population of
grasshopper
F. The grassland area affects the population of
bird
(a) What is the best explanation for the decrease
in the population of grasshoppers
from year 1 to year 3? ..
(b) What is the best explanation for the change
in the mice population? ..
(c) What is the best explanation for the change
in the bird population?