Transcript chapter_3_presentation

CHAPTER 3
HOW RAPIDLY DO CELLS DIVIDE?
All healthy cells have regular rates of
dividing. For example, certain bacterial
cells divide once every 20 minutes. Frog
embryo cells divide in about an hour,
cells lining your intestine take about 48
hours to divide, and liver cells divide
once every 200 days.
CELLS AND CANCER
Cell division is essential for body growth and
repair. What happens if cells begin to multiply
and spread in an uncontrolled way? That is
what happens in the bodies of people with
cancer.
Cancer cells divide at a far greater rate than
normal cells and they spread to other parts of
the body.
CELLS AND CANCER
Cancer has been referred to as “mitosis gone
wild”. As the abnormal cancer cells continue
to multiply, they spread to other parts of the
body and damage them.
Cancer is one of the leading causes of death
in Canada today .
CELLS AND CANCER
Cancer can affect many parts of the body and
may be caused by many different factors.
Factors that can produce cancer are called
carcinogens. They include some types of
chemicals, radiation, inherited (genetic)
factors, certain viruses, and repeated damage
to the body.
STOP AND THINK:
Name 3 things you already knew about cancer
before you came to class today.
List 2 questions you’ve had about cancer.
What is one thing you’ve learned already in
this class about cancer?
CELLS AND CANCER
• People working in some jobs may be exposed
to particular types of carcinogens.
• For example, people working in industries
using asbestos have had high rates of lung
cancer because they inhaled find particles of
this substance over long periods of time.
• Some farmworkers have had high rates of
cancer after improperly using certain
pesticides.
CELLS AND CANCER
• Some cancers can be prevented by changing
lifestyle habits to reduce exposure to
carcinogens.
• One example is the link between smoking and
lung cancer. Smokers are far more likely to
die of lung cancer than non smokers and they
can reduce this risk by not smoking.
CELLS AND CANCER
Another example is the connection between
sun exposure and skin cancer. People who
spend many hours in the sun without
protective clothing or sunblock have a high
risk of developing skin cancer, which is
caused by ultraviolet radiation from the sun.
CELLS AND CANCER
• Although prevention is better than cure, there
are some treatments that can slow or stop the
spread of cancer in patients who already have
the disease.
• The techniques consist of destroying the
cancerous cells while leaving normal cells
intact.
CELLS AND CANCER
This can be done by chemicals
(chemotherapy) or by radiation treatmentusing high-energy particles to kill cells.
These treatments are most successful if the
cancer is diagnosed in an early stage, before
the abnormal cells have spread widely through
the body.
CELLS AND CANCER
New techniques may give better methods of
curing cancer in the future.
One method is gene therapy, which alters
genes that case cells to divide and produce
cancer.
Alternative therapies focus on ways to boost
the body’s own natural immune system.
SPECIALIZED CELLS
Although multicellular organisms grow from
single cells that repeatedly divide, not all cells
are the same.
Like instruments in a band, different cells
have different appearances and perform
different jobs. They are said to be specialized
for particular tasks.
STOP AND THINK:
Write down at least 5 types of specialized
cells found in the human body.
Pair up with a classmate, and see which cells
you thought of.
Be ready to share your answers!
SPECIALIZED CELLS
For example, your muscle cells are shaped to
move parts of your body, and your skin cells
are built to protect your body from the sun’s
rays.
Humans have about a hundred different types
of cells, each with their own special structure
and function.
SPECIALIZED CELLS
• In the previous slide, you saw nerve cells,
muscle cells, red blood cells, and onion skin
cells. Each has a different shape relating to its
function.
• For example, red blood cells are disk-shaped
because they carry oxygen in the bloodstream.
Their shape gives them a large surface area to
pick up large amounts of oxygen and carry it
to its destination.
THE ADVANTAGES OF BEING MULTICELLULAR
Imagine you are a microscopic, unicellular
organism. Your whole body is one cell. This
one cell must carry out all the functions
needed to keep you alive.
It must be able to move, obtain food,
reproduce, and respond to the environment.
THE ADVANTAGES OF BEING MULTICELLULAR
There are many living organisms that are only
one cell.
What disadvantages do you think they have,
compared with multicellular organisms?
THE ADVANTAGES OF BEING MULTICELLULAR
We already know one disadvantage:
unicellular organisms can’t grow very big.
Also, because they need to take in all the
materials they need through their cell
membranes, most unicellular organisms can
only live in watery, food-rich surroundings.
THE ADVANTAGES OF BEING MULTICELLULAR
Multicellular organisms have several
advantages compared to unicellular living
things.
They can live in a wide variety of
environments.
They are able to grow very large, like a whale
or a Douglas fir tree.
THE ADVANTAGES OF BEING MULTICELLULAR
Multicellular animals can obtain their energy
from a wide variety of foods.
Their bodies are more complex.
By specializing in particular functions, each
cell in a multicellular organism can work
much more efficiently than the cell of a
unicellular organism, which must do all the
jobs.
THE ADVANTAGES OF BEING MULTICELLULAR
In multicellular organisms, specialized cells of
a similar kind work closely together, and are
usually found grouped closely together in the
body.
Groups of specialized cells, in turn, work in
harmony with other groups.
STOP AND THINK
Would you rather be a unicellular organism, or
a multicellular organism?
Do you think there are advantages to being
unicellular?
CELLS WORKING TOGETHER
Most cells of a multicellular organism such as
a horse or a tree (or yourself!) are not in direct
contact with the outside environment.
How do these cells get the things they need?
CELLS WORKING TOGETHER
• To think about this problem imagine that all
the cells of an animal or plant are organized
into different systems.
• Each system has a particular function to
perform.
• For example, one system carries oxygen
throughout the body to every cell. Other
systems make sure that each cell receives
food, and so on.
HOW CELLS ARE ORGANIZED
We already know that many animals and
plants are made up of trillions of cells.
How are all of these cells organized so
that our bodies can function properly?
HOW CELLS ARE ORGANIZED
First, cells with the same structure and
function are grouped into tissues (like
muscles, nerves, and skin), in the same way
that students are grouped into grades and
classes at school.
HOW CELLS ARE ORGANIZED
Groups of tissues form organs (like the heart,
stomach, and liver), just like different classes
of students form a school.
HOW CELLS ARE ORGANIZED
The organs work together in organ systems
(like the digestive system, for example), just
like schools are grouped together in a school
district.
This arrangement of cells, tissues, organs and
systems form levels of organization in living
things.
Each level can be studied on its own, or in
relation to the levels above or below it.
TISSUES
Tissues are a group of similar cells. Onion skin
is a tissue made of sheets of similar, thin,
tightly-packed cells. These specialized skin
cells form a layer that covers and protects the
onion.
Muscle Tissue
Nerve Tissue
Epithelial tissue
Connective Tissue
ORGANS
Eating a juicy apple or a plate of french fries
wouldn’t be possible without your organs.
Organs are distinct structures in the body that
perform particular functions.
Eating involves many organs: your eyes (to see
the food), your brain (to co-ordinate your
actions), and your mouth and stomach (to
digest the food).
ORGANS
Each one of your organs is made of several
tissues working together. For example, your
stomach is made up of 4 types of tissue
(muscle, epithelial, connective, and nerve).
Other examples of organs in your body are the
lungs, the heart, and the kidneys.
Plants have organs, too. Plant organs include
roots, stems, leaves and flowers.
STOP AND THINK:
List the 4 levels of organization.
Can you think of another analogy to
explain the organizational system,
instead of comparing it to a school
system?
ORGAN SYSTEMS
So far, we’ve learned that organs work
together just as cells and tissues do. Organs
form organ systems to perform activities that
help the body function as a whole.
For example, your stomach is part of a group
of organs that form your digestive system.
Other organs in their system include your
tongue, pancreas, and small intestine.
ORGAN SYSTEMS IN PLANTS
Why don’t plants have muscles?
The function of muscles is movement, which is
essential to animals because we need to find
food. Plants don’t need to move, because they
can produce food through photosynthesis.
ORGAN SYSTEMS IN PLANTS
Because of the differences in how plants and
animals survive, plants have fewer types of
tissues and organ systems than animals have.
For example, plants don’t need “sense organs”
(like eyes and ears) to find their food. They
also don’t need a digestive system to break
down large pieces of food, nor do they need a
nervous system to co-ordinate movement.
ORGAN SYSTEMS IN PLANTS
 You might be wondering what plants do need.
Plants have two main organ systems: a root
system below ground, and a shoot system (the
stems and leaves) above the ground.
 The root system exists to obtain water and
minerals from the soil and to anchor the plant in
the ground. The shoot system makes food for the
plant.
 Sometimes, flowering plants produce a third
system for reproduction. The main organs of the
reproductive system are the flowers.
CONNECTING THE SYSTEMS
 The plant’s tissues are responsible for transporting the
nutrients.
 Inside the plant, two types of tissues, called vascular tissues,
connect the root system and the shoot system.
 Phloem tissue transports sugar manufactured in the leaf to
the rest of the plant.
 Xylem tissue conducts water and minerals absorbed by the
root cells to every cell in the plant.
 Don’t forget that all cells need food and water, plus oxygen to
carry out their functions.
 Phloem and xylem tissues are found together along the length
of the plant stems and roots.
FROM ROOT TO LEAF
 One way to understand how the dif ferent levels or
organization (cells, tissues, organs, and systems) work
together is to follow the path of water through a plant.
 Most plants need a large supply of water, to make sugars in
the process of photosynthesis.
 If you examine the structure of a root system, you will see
that its growing tips are covered with fine root hairs.
 These “hairs” are in fact, extensions of single epidermal cells.
When the concentration of water in the soil is greater than the
concentration of water in the root cells, water enters the root
hairs by osmosis.
 Getting water for the plant is a process of the first level of
organization-the cells.
FROM ROOT TO LEAF
 From the root hairs, water passes from cell to cell by osmosis
until it reaches the xylem tissue. The tube -shaped cells
making up xylem tissue have thick walls with hole in their
ends.
 Stacked end to end, they form bundles of hollow vessels
similar to drinking straws. Water can flow easily through these
vessels.
 As more water enters the root hairs, it creates pressure that
pushes water up the plant through the xylem tissue- the
second level of organization.
FROM ROOT TO LEAF
 Water is transported by xylem tissue into the stems and the
leaves. Leaves are the plant’s food producing organs - the third
level of organization.
 Don’t forget that photosynthesis makes sugars from water,
carbon dioxide, and sunlight. Most photosynthesis takes place
in a layer of cells in the leaf that are filled with chloroplasts.
 These cells are called palisade cells.
 You may have wondered why leaves are flat and thin. This
shape provides a large surface area to absorb sunlight and it
makes it easy for gases to dif fuse into the leaf cells.
FROM ROOT TO LEAF
 Did you notice the tiny openings on the underside of the leaf?
These openings are called stomata, and they allow air to enter
the leaf, supplying the oxygen the cells need for respiration
and the carbon dioxide they need for photosynthesis.
 Spaces between leaf cells allow the air to flow around each
cell. Surrounding each stoma are guard cells, which can
expand to close of f the stoma.
FROM ROOT TO LEAF
 Unlike our blood, water doesn’t continually circulate through
the plant. Instead, water leaves the plant through the open
stomata.
 The loss of water from a plant is called transpiration. The loss
of water is not a problem as long as it is replaced by more
water that enters the plant through the roots.
PUSHING AND PULLING
 If all of the tissues of a plant were to magically disappear,
leaving only the water in them behind, you would see an
outline of the plant in a web -like network of water.
 There is no break in the water system. Fine columns of water
connect every cell, from the leaves to the roots. The network
extends even beyond the root hairs - it connects root hairs to
channels of water in the soil.
PUSHING AND PULLING
 According to particle theory, individual water particles are
held together by bonds of attraction, which make the plant’s
water network behave as a single unit.
 Water drawn in to the root hairs by osmosis pushes slender
water columns up the plant. At the same time, water lost from
the leaves by transpiration pulls water up the xylem tissues all
the way from the roots.
 Both of these actions - pushing and pulling- are necessary to
raise the water up to the top of very tall trees. In this way,
trees can transport water without having a pumping organ
similar to the human heart.
ORGAN ADAPTATIONS IN PLANTS
 Like animals, plants have adaptations that help them grow
and survive in dif ferent environments. You can see some of
these adaptations in the structure of roots, stems, and leaves.
 For example, many plants growing in deserts have small,
fleshy leaves with a heavy wax coating that helps reduce
water loss.
 Cactus spines are, in fact, narrow, waxy leaves. To
compensate for their reduced leaf area, cacti carry out
photosynthesis in their stems.
 The leaves of coniferous (cone -bearing) trees such as pines
and other evergreens are also adapted to dry conditions. The
needle like shape of the leaf reduces evaporation from the
surface of the leaf.
ORGAN ADAPTATIONS IN PLANTS
 Plants that grow in water, such as water lilies, could have a
problem obtaining the air they need to survive.
 To ensure their underwater roots obtain the oxygen they need
for cell respiration, the root tissues of these plants have large
air spaces in them.
 Still other plants have roots in the air. Orchids grow high
above the ground on the branches of trees in tropical forests.
Their root tissues are specially adapted to absorb moisture
from the warm air.
ORGAN SYSTEMS IN HUMANS
 Every cell in the body needs a steady supply of food and
oxygen to give it energy.
 Three dif ferent organ systems must work together to make
this possible.
 Do you know what they are?
ORGAN SYSTEMS IN HUMANS
DIGESTIVE SYSTEM
 Food first enters the body through the mouth, then passes in
to the stomach and the intestine.
 It is broken down along the way into small, soluble particles
that can be used by cells. Unused food is expelled from the
body as waste.
ORGAN SYSTEMS IN HUMANSRESPIRATORY SYSTEM
 The person in this photo is
doing yoga, which requires
long, deep breaths.
 Breathing in (inhalation) fills
her lungs with oxygen
containing air.
 Breathing out (exhalation)
rids her body of waste carbon
dioxide.
 The organs involved in this
gas exchange form the
respiratory system.
ORGAN SYSTEMS IN HUMANSCIRCULATORY SYSTEM
 The digestive system puts food into the intestine and the
respiratory system puts oxygen into the lungs. How do
particles of food and oxygen eventually get from these
systems to cells in the toes, the brain, and other parts of the
body?
 A third system transports particles of food and oxygen. The
circulatory system consists of the heart, blood, and blood
vessels.
 This system circulates blood around the body, delivering food
particles, dissolved gasses, and other materials to every cell
and carrying away cell wastes.
A TALE OF TWO SYSTEMS
 To connect all the individual cells throughout your body with
the air around you, the respiratory system and the circulatory
system work together.
 The function of the respiratory system is to exchange oxygen
and carbon dioxide, while the circulatory system transports
those gases throughout the body. How do the gases pass from
one system to the other? Look for an answer where the two
systems come into closest contact - among the tissues of the
lungs.
A TALE OF TWO SYSTEMSRESPIRATORY SYSTEM
 After air enters the nose, it passes to
the lungs through a series of smaller
and smaller tubes. The trachea
(windpipe) is about 20 mm in
diameter.
 It divides into a right and left
bronchus, which are each about 12mm
in diameter. Each bronchus tube
branches into thousands of small,
narrow bronchioles, which diameters
of 0.5mm.
 Finally, the bronchioles divide and end
in millions of tiny air sacs called
alveoli, which are only 0.2mm in
diameter.
A TALE OF TWO SYSTEMSCIRCULATORY SYSTEM
 The circulatory system also involves a series of tubes - the
blood vessels. Like the air tubes of the respiratory system,
blood vessels branch and divide into smaller and smaller
channels.
 The three main types of blood vessels are:
 Arteries, which have thick, muscular walls for carrying blood under
pressure.
 Veins, which have thinner walls compared to arteries, and valves to
prevent the blood from flowing backward.
 Capillaries are hair-thin vessels. Their walls are made of epithelial
tissue only one cell layer thick.
A TALE OF TWO SYSTEMS
 Each alveolus in your lungs is surrounded by a web of
capillaries. It is here that gases are exchanged.
 Oxygen and carbon dioxide pass back and forth between the
air in the alveoli (respiratory system) and the blood in the
capillaries (circulatory system).
 Oxygen passes from the alveoli into the capillaries by
dif fusion. The air in your alveoli has the same composition as
the air in the atmosphere (20%). This is much higher than the
concentration of oxygen found in your blood.
 The oxygen first dissolves in a thin film of moisture covering
the walls of the alveoli, then it dif fuses from the alveoli
through the thin capillary walls into the bloodstream.
A TALE OF TWO SYSTEMS
 Carbon dioxide dif fuses in the opposite direction. Air normally
contains only a very low concentration of carbon dioxide
(about 00.3 percent). Blood in the capillaries carries all the
dissolved carbon dioxide collected from cells throughout the
body.
 Don’t forget that carbon dioxide is a waste product of cellular
respiration.
 This gas therefore moves from the capillaries into the alveoli.
When you exhale, you release the carbon dioxide and water
vapour into the air.
DID YOU KNOW?
 Many seals, with lungs no bigger than a human adult’s, can
easily stay underwater without breathing for 20 minutes or
more.
 Before they dive underwater, they exhale.
 How is this possible?
DID YOU KNOW?
 The answer to this problem lies in how the seal’s blood and
circulatory system function. All the oxygen a seal needs while
underwater is stored in its blood and muscle tissue, rather
than in its lungs.
 To be able to store this large amount of oxygen, a seal has
about one and a half times to twice as much blood in its body
as other mammals of similar size.
 When seals dive underwater, their heartbeats slow down
immediately from about 100 beats per minute to as little as
10 beats a minute. Blood flow to some parts of their bodies,
like the kidneys and the muscles, stops completely. Seals are
also able to tolerate large amounts of carbon dioxide in their
blood.
GETTING FOOD TO BODY CELLS
 We’ve already learned that your bloodstream takes oxygen
from your lungs, and that it carries food particles from your
digestive system.
 The transfer of food from the digestive system to the
circulatory system takes place in the inner lining of the small
intestine.
 Covering the surface of this lining are millions of tiny,
fingerlike projections called villi (singular villus).
 Each villus contains a network of capillaries. Dissolved food
particles pass from the intestine into the capillaries by a
process called absorption. The food particles are now small
enough to enter your body’s cells to supply them with the food
they need.
GETTING FOOD TO BODY CELLS
 Do you see any similarities between the villi in the intestine
and alveoli in the lungs?
 Like alveoli, villi have thin walls through which particles can
pass into the circulatory system. Both alveoli and villi consist
of tiny particles, and both occur in huge numbers.
 The arrangement greatly increases the surface area that is in
contact with capillaries, without taking up a large amount of
space in the body.
IT’S ALL UNDER CONTROL
 When you feel tired, you know you need to sleep. When you
are cold, you know to turn up the heat or put on warmer
clothing. When you are feeling hungry, you know it’s time for
a snack.
 In these and other ways, you respond to changing external
conditions and make appropriate adjustments. Your body
systems also make constant adjustments to maintain a stable
internal environment for your cells. This process is known as
homeostasis.
 It occurs automatically, usually without you even being aware
of it.
IT’S ALL UNDER CONTROL
 For example, no matter whether it is hot or cold outside, the
inside of our bodies remains at an amazingly constant
temperature of 37 degrees Celsius all year.
 A change in body temperature of as little as 0.5 degrees
Celsius can make us feel either feverish or chilled. How is this
steady body temperature maintained?
IT’S ALL UNDER CONTROL
 Nearly 90% of your body heat is lost through the skin. Most of
the rest of your body heat is lost through your lungs.
 When you get cold, you may shiver. Your shaking muscles
generate heat. You may also get goosebumps, which are
produced by the contraction of small muscles in the skin that
make your hairs stand on end. In animals with a thick coat of
hair, and in our hairier prehistoric ancestors, fluf fing up the
body hair helps reduce heat loss by improving insulation.
IT’S ALL UNDER CONTROL
 Do you get flushed and red after exercise? This happens
because tiny blood vessels in your skin expand. This increases
blood flow near the body surface where heat can be lost to
the outside.
 Sweating helps cool your body as the moisture evaporates
from your skin surface.
 Your body’s responses to stimuli are co -ordinated by the
nervous system (the brain, the spinal cord, and nerves), and
the endocrine system (a set of glands that produce
hormones).
 Diet, exercise, drugs, injury, and disease can af fect body
systems and disrupt homeostasis.
IT’S ALL UNDER CONTROL
 Information from temperature receptors in your skin goes to
the heat-regulating center of your brain, called the
hypothalamus. Responding to this information, the brain
sends nerve signals to your muscles, skin, and blood vessels.
 Working together, your muscles, skin, and blood vessels
adjust your blood flow and muscle activity, causing your body
to increase its heat production or reduce its heat loss.
BODY SYSTEMS AND YOUR HEALTH
 A healthy heart and blood vessels are essential to good
health. Without this, your blood would not circulate, and your
cells would not get the supplies of food and oxygen they need.
 Moving substances around the body is a necessary job in all
multicellular organisms. In a unicellular organism, materials
are exchanged between the cell and the environment.
 In humans, our blood transports substances. About 8 percent
of an adult’s body weight is blood.
 The main components of blood are plasma, red blood cells,
white blood cells, and platelets.
BODY SYSTEMS AND YOUR HEALTH
 Plasma makes up 55% of your blood. It is the liquid portion of
the blood, and it transports most of the carbon dioxide
produced during cellular respiration.
 Red blood cells make up 44% of your blood. They are
specialized to carry oxygen. Red blood cells contain an iron rich chemical called hemoglobin, which attracts oxygen. This
allows the blood to carry much more oxygen than it would
normally.
 White blood cells make up less than 1% of your blood. They
defend your body against disease and infection.
 Platelets make up less than 1% of your blood. They cause the
blood to clot at the site of wounds to prevent blood loss.
BLOOD PRESSURE
 Doctors measure a patient’s blood pressure because it
indicates several things about the health of the circulatory
system.
 For example, if someone has lost a lot of blood due to injury,
the pressure of blood will be lower. If someone has a higher
than usual heart rate, their blood pressure will be higher
because the blood is being pushed quickly through the
arteries. If someone has partially clogged arteries, their blood
pressure will be higher than someone with open arteries.
YOU ARE WHAT YOU EAT
 Dif ferent foods contain dif ferent combinations of substances
that your body needs. Substances that provide energy and
materials for cell development are referred to as nutrients.
 Carbohydrates are the cells’ main source of quick energy. Fats
are another source of energy, but unlike carbohydrates, they
can be stored by the body. When you eat more food than the
body needs for an activity, the extra is stored in your tissue as
fat.
 Proteins are essential for growth and repair of the body’s
tissues.
YOU AND YOUR BODY
 Like any complex structure, your body needs proper care to
function properly.
 To maintain healthy organs and systems, everyone has the
same essential needs: clean air and water, nutritious foods,
exercise, and sleep.
 Clean air means oxygen for your cells, which use the oxygen to
produce energy.
 A balanced diet provides your cells with the food materials
they need for growth and activities. Lack of essential
materials makes the body grow weaker, while too much of
some substances such as fats, sugars, and salt can make
more work for some systems.
YOU AND YOUR BODY
 Exercise is important because it helps the body process food
and oxygen more ef ficiently. A healthy heart and lungs help
carry materials to the cells and get rid of wastes. Strong
muscles help protect the body from injury.
 Not only do healthy lifestyle habits make you feel better, they
help your body resist diseases. Your immune system attacks
and destroys invading germs and helps break down harmful
materials in your body. If you do get a cold, a disease, or an
injury, you are likely to recover faster if you are healthy to
begin with.