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CHAPTER 3 ANSWERS
CYU 3.1 p. 67
1. Animals obtain the oxygen needed by their cells by diffusion. Diffusion is the movement of molecules from an area of
high concentration to an area of lower concentration. In unicellular animals, oxygen and carbon dioxide diffuse across or
through the cell membrane. In multicellular organisms, a special system is required to absorb oxygen from the air and
remove carbon dioxide from theblood.
2. Even though we can control our breathing to some extent, breathing is considered to be an automatic body function
because we breathe without having to think about it—it happens automatically. Even if we consciously stop breathing for a
short period of time, the body eventually takes over and we begin to breathe again.
3. Breathing is the regular contraction and relaxation of the diaphragm and rib muscles, which cause the chest cavity to
expand and contract. This causes air toflow into (inhalation) and out of (exhalation) the lungs. Respiration is the
absorption of oxygen from the air into the capillaries that surround the air sacs of the lungs, and the removal of carbon
dioxide from the capillaries into the air sacs.
4. Diffusion takes place in the air sacs (alveoli) of the lungs. Oxygen diffuses from the air in the air sacs into the capillaries
that surround the air sacs. Carbon dioxide diffuses from the capillaries that surround the air sacs into the air in the air
sacs.
CYU 3.2 p. 70
1. Sponges are only two layers thick. Nutrients can move from seawater to cell, and waste can move from cell to seawater
easily by diffusion.
2. In an open circulatory system, the blood is pumped from the heart into the body cavities. The blood is then returned
from the body cavities to the heart. In a closed circulatory system, the walls of the heart and blood vessels are
continuously connected. The blood is always contained within the heart and blood vessels.
3. Students’ diagrams should be similar to those in Figure 4 in the student book.
Deoxygenated blood from around the body returns through the veins to the right atrium. At the same time, oxygenated
blood from the lungs travels to the right atrium. From there, it is pumped to the right and left ventricles. The right ventricle
pumps the deoxygenated blood to the lungs, where it picks up oxygen.
The left ventricle contracts and pumps the oxygenated blood out to the body.
4. The valves in the heart keep the blood flowing in one direction. They prevent the blood from flowing backward when the
pressure decreases.
CYU 3.3 p. 74
1. The main parts of the excretory system are the kidneys, ureters, bladder, and urethra.
2. The lungs (part of the respiratory system) also play an important role in excretion. The lungs are responsible for getting
rid of the carbon dioxide that is produced in cells as a waste product.
3. In the nephrons, waste materials are collected from the bloodstream. Thewastes are dissolved in a small amount of
water in the tubules and are carried to the ureter, where they flow to the bladder.
4. Diffusion takes place in the nephrons in the kidneys. Waste materials diffuse from small blood vessels into the tubules
of the nephrons.
5. The team that is responsible for getting rid of wastes includes the excretory system, the circulatory system, the
respiratory system, and the digestive system. The excretory system eliminates wastes that are brought to it from the cells
of the body by the circulatory system. The respiratory system gets rid of carbon dioxide produced as a waste product in
the cells. The circulatory system delivers the carbon dioxide to the respiratory system. The digestive system gets rid of the
solid waste that remains after food is digested.
CYU 3.4 p. 76
1. Digestion is the breakdown of solid food into molecules that can be used by the cells of the body. Digestion starts with
the physical breakdown of food into smaller and smaller particles. Chemical digestion then breaks down the very small
particles into molecules that can be absorbed into the bloodstream and carried around the body.
2.
Digestion in the • The physical breakdown of food by chewing starts the process of digestion.
mouth
• An enzyme in saliva begins to digest starch.
Digestion in the • Very acidic gastric juices break down proteins in the food.
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stomach
Digestion in the
small intestine
• Pancreatic juices neutralize the acidic material that arrives from the stomach.
• Enzymes in the pancreatic juices break down proteins, carbohydrates, and fats.
• Bile, produced in the liver and stored in the gall bladder, is released when food enters the small
intestine. Bile breaks down fats.
• Nutrients are absorbed through the walls of the small intestine into the bloodstream as the
digested food passes through.
3. The mucous coating that lines the stomach protects the cells of the stomach wall from the very acidic gastric juices.
Removing the mucous coating allows the acidic contents of the stomach to irritate the lining and rupture the tiny blood
vessels, causing bleeding in the stomach.
CYU 3.5 p. 80
1. Other organ systems include the muscular system, nervous system, endocrine system, skeletal system, integumentary
system, lymphatic system, and reproductive system.
2. The circulatory system carries oxygen to the cells of the body and removes carbon dioxide. The respiratory system
supplies oxygen and removes carbon dioxide from the body. The respiratory system depends on the circulatory system to
deliver oxygen to the body, and to collect carbon dioxide from the body and deliver it to the respiratory system. The
circulatory system relies on the respiratory system to exchange oxygen and carbon dioxide with the outside air.
3. The nervous system is better suited to detect danger. The senses (e.g., vision, hearing, taste, touch) used to detect a
dangerous situation all produce electrical signals that are sent along the nerves of the nervous system.
4. The nervous system enables the body to adjust quickly to changes in the environment. The endocrine system is
designed to maintain control over a longer duration.
5. If you stepped on a tack, the receptors in your foot would send a signal to your central nervous system. A signal would
then be relayed to the muscles of your leg, and the muscles would respond by moving your foot.
6.
Organs that supply nutrients and remove wastes
Organs that regulate the body
Heart, intestines, artery, liver, kidney, stomach, lungs
Eyes, brain
7. Nerves carry signals to muscles. These signals cause the muscles to contract.
8. Skin cells would die if the circulatory system failed. Skin cells require oxygen and nutrients to function. Also,
accumulated wastes that were not removed by the circulatory system would eventually kill the skin cells.
9. The organ systems of the body are interdependent. They all exist close together in a common environment. A
malfunction of one system affects all the other systems. Therefore, it is important to have organ systems that regulate all
the other systems.
CYU 3.6 p.84
1. Pathogens are a threat to the body because they interfere with the normal functioning of body cells or they produce
toxins that prevent the normal functioning of body systems.
2. The first line of defence involves physical barriers (e.g., hairs, ear wax, mucus, acidic secretions) that prevent
pathogens from entering the body. The second line of defence consists of specialized white blood cells, which seek out,
attack, and destroy pathogens that have entered the body. The third line of defence is the immune system. Special white
blood cells produce antibodies that protect the body by locking onto markers or antigens on the surface of pathogens and
prevent the pathogens from attacking the body cells.
3. The white blood cell is attacking the bacteria with its pseudopods. The bacteria will eventually be engulfed when the
white blood cell’s cytoplasm wraps completely around them. The second line of defence is in action here.
4. Both amoeba and specialized white blood cells in the human defence system use projections of their cytoplasm (called
pseudopods) to capture, engulf, and destroy micro-organisms.
5. Antibodies protect the body from attack by locking onto markers or antigens on the surface of bacteria, viruses, and
toxins. This prevents the bacteria or virus from attacking the cells of the body, or prevents the toxin from interfering with
the normal functioning of cells.
6. We can become immune to a disease by being exposed to the pathogen that causes the disease and developing
antibodies, or by being vaccinated so that our body can produce the antibodies before we are exposed to the disease.
Chapter 3 Review p.88
1. (c)
2. (a)
3. (d)
4. (e)
5. (d)
6. Mouth, esophagus, stomach, small intestine, large intestine, anus
7. More advanced animals digest food along a tube or canal that provides a separate mouth and anus. Because food
moves along the tube in one direction, different areas can be organized for specific functions. Animals that have only one
opening must stop eating to move waste from the cavity. Animals with a one-way tube can eat and remove waste at the
same time.
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8. The liver has a role in both the digestive system and the excretory system. In the digestive system, the liver produces
bile, a chemical that breaks down the fat in food. In the excretory system, the liver breaks down proteins that are not
needed by the body. This breakdown produces a poisonous substance called ammonia. The liver then converts ammonia
into urea, which is carried to the kidneys and excreted.
9. An antigen is a chemical that is produced by a foreign invader. The antigen signals the body to produce antibodies that
attach to the antigen and disable the invader.
10. Despite the body’s first two lines of defence, pathogens are still able to gain access to the body’s internal environment
through food or water, or from insects that bite or feed on human blood.
11. There is a control centre in your brain with the standing order “Stop any puck that is heading for your goal!” You hear
the slap of the stick on the puck, and you see the puck coming toward you. Sensory neurons from your ears and eyes
send messages to your brain. The control centre in your brain interprets these messages in light of the standing order and
sends signals through motor neurons to the muscles in your shoulder and arm. Your muscles react, and you catch the
puck.
12. “Fluid movement is the most important function of the human body systems.” The fluids involved are air and blood.
The body systems involved are the respiratory system and the circulatory system. The respiratory system moves air into
and out of the lungs. During inhalation, air is pulled into the lungs. Oxygen diffuses into the bloodstream and is carried to
all the cells in the body. Oxygen is essential for the operation and survival of all cells, and therefore essential for the
survival of an organism. The cells produce carbon dioxide as a waste product of cellular respiration. The carbon dioxide
must be removed from the body. It diffuses into the bloodstream, which carries it back to the lungs where it is removed
during exhalation.
13. (a) Multicellular animals need a respiratory system to ensure that oxygen can be absorbed from the air and carbon
dioxide can be returned to the air.
(b) The excretory system is essential to help the body get rid of all the other waste materials that are produced in the cells
during cellular respiration.
(c) The circulatory system is necessary for the distribution of oxygen from the respiratory system to all the cells in the body
and for the removal of carbon dioxide from all the cells.
14. If the heart valves failed, some blood would flow backward after the contraction of the ventricles. Less blood would be
available to be pumped through the system. Less blood through the system would result in less oxygen being delivered to
the cells and carbon dioxide not being removed as efficiently.
15. Your body does not swell after drinking four glasses of pop because the kidneys remove excess fluids and produce
more urine. The urine is temporarily stored in the bladder until it is excreted from the body. Drinking four glasses of pop
will mean a trip to the washroom to get rid of the excess water.
16. “Organ systems interact and are interdependent.” Their functions overlap, and they cannot complete their functions
without assistance from other systems. For example, the circulatory system carries oxygen to the cells of the body and
removes carbon dioxide. The respiratory system supplies oxygen and removes carbon dioxide from the body. The
respiratory system depends on the circulatory system to deliver oxygen throughout the body and collect carbon dioxide
from the body and deliver it to the respiratory system. The circulatory system relies on the respiratory system to exchange
oxygen and carbon dioxide with the outside air. The digestive system relies on the circulatory system to deliver the
nutrients from digested food to the cells. The excretory system depends on the circulatory system to bring waste materials
from the cells to the kidneys, where they are dissolved in water and excreted as urine.
17. Pus around a cut or sore may look dangerous, but it is actually a good sign because it indicates that the body’s second
line of defence is functioning properly and actively working to stop an infection.
18. If disease affected an organ that delivered nutrients, an organ that removed waste, an organ that informed the animal
about environmental change, or an organ that controlled other organ systems, the animal’s health would suffer and the
animal could die. If cells cannot obtain nutrients or get rid of waste, they will die. If enough cells die, the animal will also
die. If an animal is unaware of its environment, it could possibly encounter a dangerous situation without realizing that the
situation is dangerous. For example, it could become prey for another animal. If an animal’s organ systems are not
working together, the animal’s internal environment will not be in balance and it will likely develop a disease or disorder
that could lead to its death.
19. Two different types of blood cells could be used—one to carry oxygen and one to carry carbon dioxide. Other cells
could be specialized for carrying nutrients. Ciliated cells along the lining of the blood vessels could help move the blood in
one direction.
20. In an open circulatory system, blood is pumped from the heart into body cavities. The blood is then returned from the
body cavities to the heart. In a closed circulatory system, the walls of the heart and blood vessels are continuously
connected so the blood is contained within the system. A closed system is more efficient because a higher pressure can
be built up, allowing blood to circulate more rapidly and therefore deliver oxygen and nutrients more efficiently.
21. Obesity is considered to be a serious problem among young people in Canada. Obesity is the accumulation of an
excessive amount of fatty tissue. Obesity results from unbalanced energy. An overweight person consumes more food
energy than is used and stores the surplus in body fat. For adult males, the recommended body fat content is 15 to 18 %
of total body weight. Obesity is defined as having a body fat content of 25 % or greater. For adult females, the
recommended body fat content 20 to 25 % of total body weight. Obesity is defined as having a body fat content of 30 % or
greater. A 2002 report indicated that, in 1996, just over 10 % of boys and about 9 % of girls were obese. This represented
a greater than 400 % increase from 1981. The two main causes of obesity are inappropriate diet and physical inactivity.
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27.7 % of Canadian youth (aged 12 to 19) are considered to be physically inactive, 21.1 % are considered to be
moderately active, and only 38.4 % are considered to be physically active. The reduction of the obesity rate can be
achieved by changing the two factors that cause obesity—diet and physical activity. Approaches such as mandatory daily
physical activity in schools and the promotion of healthy food choices in schools are being used in some areas, but not all.
Changes in lifestyle at home (e.g., fewer meals at fast-food restaurants, healthier meals, more physical activity) are also
important for fighting obesity. The Public Health Agency of Canada has published a Physical Activity Guide for Children
and a Physical Activity Guide for Youth.
22. The body needs to have three lines of defence against invasion because one system cannot deal with all the possible
ways that pathogens can invade the body. The lines of defence are also specialized to deal with different kinds of
invasions.
23. Lyme disease
Lyme disease is caused by a bacterium (Borrelia burgdorferi) that is carried by ticks. Ticks are tiny bugs, about the size of
a sesame seed, which feed on blood. Different ticks bite different animals. Some ticks bite humans, but not all tick bites
result in the disease. The organism that causes Lyme disease has been found in ticks collected from many areas of British
Columbia, and health authorities now believe that it may be present throughout the province. Many of the people in British
Columbia who have contracted Lyme disease have not travelled outside the province, so they have likely contracted the
disease within British Columbia. The symptoms include fever, headache, muscle and joint pains, and tiredness or
weakness of the face muscles. There may also be a rash, especially one that looks like a “bull’s eye,” which may or may
not be at the site of the bite. In some cases, paralysis may begin within a few hours or up to several days later. The
paralysis begins in the feet and legs, and works its way up the body to the arms and head. Lyme disease is treated with
antibiotics to prevent further complications.
To protect yourself against tick bites,
• walk on cleared trails where possible
• wear light-colored clothing and tuck in shirts and pants legs
• use insect repellent that contains DEET
• check clothing and skin often (with help from someone else)
• check household pets regularly
If you discover a tick, you may remove it yourself (gently, using tweezers) if it is accessible and not buried into the skin.
Otherwise, have someone else remove it (a doctor if the tick is buried deep in the skin). Once the tick is removed, wash
the area with soap and water, and disinfect the area with an antiseptic.
West Nile Virus
West Nile virus (WNV) is an arbovirus (derived from arthropod-born virus). It was first isolated in 1937 from a woman in
the West Nile province of Uganda. (It was expected that the WNV would reach BC some time in the summer of 2005.)
WNV is transmitted by bloodfeeding insects. The primary host for WNV is wild birds. It is picked up by mosquitoes when
they feed on infected birds, and is transmitted when the mosquitoes bite humans, animals, and birds. WNV is not known
to spread from personal contact. The incubationperiod ranges from 5 to 15 days. The symptoms include fever, headache,
body aches, mild rash, and swollen lymph glands. The majority of people infected with WNV have no symptoms. One in
five people has a mild illness that lasts three to six days. One in 50 people infected develops meningitis or encephalitis.
When the virus crosses the blood-brain barrier, it causes inflammation in brain tissue and interferes with the normal
functioning of the central nervous system. Fatality rates range from 3 to 15 %, with the elderly being most susceptible.
There is no specific treatment for WNV. Patients who develop severe cases are hospitalized and given intravenous fluids,
respiratory support (a ventilator), and treatment of secondary infections such as pneumonia. A vaccine is being
developed. In March 2005, phase I human clinical trials of the vaccine were approved by the FDA in the United States.
There are many simple things that you can do to protect yourself. For example,
• use mosquito repellent
• wear protective clothing
• install mosquito screens on windows
• prevent mosquitoes breeding around your home
• do not touch wild birds, dead or alive, with your bare hands
24. Reaction time is an important factor for athletes. In most sports, success is often determined by skill and strategy. A
significant part of an individual’s skill is how fast she or he reacts to the game situation and, more importantly, whether she
or he reacts faster than the competitor.
25. Factors that affect one body system may also directly or indirectly affect other body systems. For example, smoking
affects the respiratory system directly. If the respiratory system is negatively affected, then the circulatory system will also
be affected. If less oxygen is absorbed in the alveoli, then the heart will pump faster in order to deliver the required amount
of oxygen to the cells. This increased heart rate may negatively affect a person’s health in the long term. Diets that lead to
excess body fat also have an effect on the circulatory system. It has been estimated that each kilogram of fat requires an
additional 3.5 km of blood vessels. The heart therefore has to work harder to circulate the blood through the additional
blood vessels.
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26. Students will likely be aware of lifestyle choices that negatively affect their health. They will likely identify smoking,
high-fat diets, and lack of exercise as sources of potential health problems. Even students who smoke, consume high-fat
foods, and/or do not exercise will recognize the negative impacts of these choices on their health.
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