Transcript Gas exchange in organisms Powerpoint

Ch 22
Gas Exchange in Organisms
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3.4.3 The Structure of an Exchange System in Flowering Plants
Examination of the structure of the leaf in relation to gaseous exchange. Reference to the
presence of lenticels in stem structures
3.4.4 The Breathing System in the Human
Objectives – What you will need to know from this section
Outline the macrostructure & function of the breathing tract in humans.
Outline the essential features of the alveoli & capillaries (as surface) for gas exchange.
Describe the mechanism of the breathing system in gas exchange .
Outline a breathing disorder: Know one example of a breathing disorder, from the
following: asthma and bronchitis; one possible cause, prevention, and treatment.
3.4.5 Plant Excretion
Objectives – What you will need to know from this section
Outline the role of leaves and lenticels as excretory organs of plants.
Students should appreciate however that excretion is an animal function and that
secretion or loss from plant would be more appropriate.
H.3.4.7 Carbon Dioxide: A Controlling Factor in Gaseous Exchange
Objectives – What you will need to know from this section
Explain how CO2 is a controlling factor in stomata opening and in the human breathing
(respiratory) system.
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1. All organisms have the ability to maintain
constant conditions in their cells and bodies
such as temperature, fluid balance and
chemistry. This is achieved by homeostasis
e.g. by diffusion, by developing exchange
systems which include the respiratory and
excretory systems.
2. In all organisms adequate amounts of gases,
nutrients and toxic wastes are exchanged by
diffusion between cells and their environment.
The efficiency of exchange is proportional to
the surface area over which diffusion can take
place.
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Your body and its individual cells need just the
right conditions to perform at their best.
Tissue Fluid
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GASEOUS EXCHANGE
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In simple unicellular organisms like Amoeba,
they obtain their food, water and oxygen directly
from the water that surrounds them via diffusion.
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• In large organisms, such as plants and
animals, the problem of size in relation to
diffusion and exchange have been overcome by
various means such as:
• the body may be flattened, reducing the
distance between the two surfaces e.g. the
leaves of plants.
• increasing the surface area e.g. alveoli in the
respiratory system.
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GASEOUS EXCHANGE IN THE FLOWERING
PLANT
Diffusion is the movement of molecules from a
region of high concentration to region of lower
concentration
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Plant Structure
Flower – contains the
reproductive organs
Stem – supports the plant and
provides transport for water
and nutrients
Leaves – provide a surface for
photosynthesis
Roots – anchor the plant
absorb water
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Four things are needed for photosynthesis
SUNLIGHT
Gives the plant energy
CHLOROPHYLL
WATER
The green
stuff where
the chemical
reactions
happen
Travels up from the
roots
CARBON DIOXIDE
Enters the leaf through small holes on the
underneath
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CO2 - a controlling factor in stomata
opening/closing.
• Transpiration is the evaporation of water from
leaves [and stems].
• The loss of water is reduced by a waxy cuticle
and by the opening and closing of pores in the
leaves called stomata.
• If a plant loses more water in transpiration
than it can absorb from the soil, it becomes
dehydrated and wilts.
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Structure of the Leaf
Lots of
chlorophyll
Large surface
area
Transparent
Thin structure
Packed with
chloroplasts
Network of veins
Lots of air
spaces
Holes
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Leaf structure
Ground Tissue -mesophyll cells have large
air spaces between them to allow rapid
diffusion of gases in and out.
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• The epidermis of stems and lower surface of
leaves have many stomata to allow for gas
exchange.
• CO2 and H2O are taken in during
photosynthesis to make food.
• O2 is excreted out during Photosynthesis as a
waste gas.
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Water loss
Gases move in and out through the pores on the
under surface of the leaf - stomata
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Diffusion of water from leaves
Low conc.
of water
Low conc.
of water
High conc.
of water
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• Each stoma is a gap between two specialised
cells, called guard cells.
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• When water enters the guard cell, it expands
into a curved shape and a gap (the stoma)
opens up between the two cells.
• Whether a stoma opens or closes depends
on how much CO2 is in the two guard cells.
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• The stomata stay open during the day so
that CO2 can enter, for photosynthesis.
• Stomata then close at night, when there is
no light for photosynthesis.
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Richard Attenborough video
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Controlling water loss
Carbon dioxide enters a leaf through the
________. These cells are also responsible for
controlling the ______ content of the leaf.
Water and carbon
dioxide pass through
here
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Controlling water loss
The ______ cells control how wide the stomata
opens (if at all). If too much water is being lost
through the stomata then the guard cells will
_____ to prevent further loss.
No more water and
carbon dioxide allowed
through
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What about trees and woody plants ?
• How do gases - oxygen and
carbon dioxide get through
the waterproof, corky
surface of bark?
• They do so through
lenticels, which are areas
where the packing of bark
cells is loosened up a bit.
• Lenticels often look like tiny
raised blisters on a branch
or twig.
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Winter twig – showing lenticels
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LEARNING CHECK
1.
2.
3.
4.
5.
6.
7.
Plants absorb water from where?
Plants can lose water from where?
What are stomata? Where are they found?
What gases diffuse in and out of the leaf?
What is diffusion?
What are lenticels?
How are lenticels different from stomata?
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3.4.4 The Breathing System in the Human
Objectives – What you will need to know from this section
Outline the macrostructure & function of the
breathing tract in humans.
Outline the essential features of the alveoli &
capillaries for gas exchange.
Describe the mechanism of the breathing system in
gas exchange .
Outline a breathing disorder: Know one example of
a breathing disorder, from the following: asthma
and bronchitis; one possible cause, prevention, and
treatment.
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3.4.4 The Breathing System in the Human
• We get our energy for
metabolism by
burning food in our
cells - respiration.
• We get fresh supplies
of oxygen by
breathing it in
through our lungs.
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LUNGS
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The pathway of Air in:
•The nose is lined with a moist layer of tissue
called a mucous membrane. This warms &
moistens the air before it goes to the lung.
•The mucous membrane makes mucus that
captures dust, germs, and other small particles
that could irritate your lungs.
•Small hairs – Cilia, trap large particles, like dirt
or pollen.
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• Your lungs are enclosed (along with the heart)
between the ribs and the diaphragm - the
thorax.
• The ribs form a protective cage of twelve
pairs of bones.
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• Intercostal muscles, attached between the
ribs, move the rib cage up or down.
• The diaphragm is a sheet of muscle at the
base of the rib cage.
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LEARNING CHECK
1. What is respiration?
2. How is the nose adapted to warming,
moistening & filtering incoming air?
3. Your lungs are enclosed by what parts of
the body?
4. What is the function of your ribs?
5. What is your diaphragm?
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Inhaling means breathing in.
1. The brain sends signals to the rib muscles
and diaphragm to contract.
2. The ribs are pulled up and out and
3. the diaphragm flattens downwards.
4. The volume of the chest increases, so air
pressure drops and
5. more air is drawn into the lungs and alveoli.
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Exhaling means breathing out
1. The brain sends signals to the rib muscles
and diaphragm to relax, they spring back to
their original positions,
2. The ribs move down and in,
3. the diaphragm relaxes and moves back up,
4. The volume of the chest decreases, so air
pressure increases and
5. air is pushed out of the lungs and alveoli.
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Role of the Brain in Breathing
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Role of the Brain in Breathing
• Mostly breathing rhythm is unconsciously set
by the brain.
• We breathe automatically by involuntary reflex
action.
• It is controlled by the medulla oblongata of the
brain.
• The rate of breathing is continually adjusted
to meet the body’s needs (an example of
homeostasis).
• We can voluntarily change the rate at which
we breath.
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Receptors (nerves) in the medulla are sensitive
to changes in the CO2 concentration of the
blood.
If we are exercising,
• a rise in the CO2 levels in the blood results
in the medulla sending impulses to the
diaphragm and intercostal muscles,
• causing an increased rate of contraction and
deeper inspiration.
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LEARNING CHECK
1. What part of the brain controls breathing rate?
2. What stimulus in the body causes our rate to
increase?
3. Inhaling means breathing in. Explain the
process.
4. What happens to your rate of breathing at high
altitudes? www.altitude.org/breathing.htm
5. How does exercise effect your breathing?
http://www.fi.edu/learn/brain/exercise.html
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The Alveolus
• Air enters the nose,
travels down the
windpipe, the bronchus
and the bronchioles, to
the alveoli.
• Each alveolus is covered
in a net of thin-walled
blood capillaries.
• The lining of an alveolus
is only one cell thick.
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• Oxygen diffuses
through the alveolus
and capillary linings,
and attaches to red
blood cells.
• At the same time,
carbon dioxide
diffuses from the
plasma into the
alveolus.
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Transport of Oxygen in blood
1. In our lungs, the concentration of oxygen is
high.
2. Oxygen enters the red blood cells and binds
to the iron within the hemoglobin molecules
= oxyhaemoglobin.
3. From our lungs, this oxygen rich blood goes
to our hearts via the pulmonary veins and
travels to the heart.
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4. It is then pumped through the biggest artery
in our body, the aorta out into our bodies.
5. Our aorta branches into many other arteries
that deliver this blood, which contains fresh
oxygen to our brain, muscles, organs and
other tissues.
6. Once it reaches these working tissues, it
drops off some if it's oxygen so these cells
can use it to make energy during respiration.
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Transport of Carbon Dioxide
1. Then because the oxygen concentration is
low at these places, it can come off of the
haemoglobin.
2. It will then pick up carbon dioxide - produced
as a waste product of respiration.
3. And return to our lungs where it will drop off
the carbon dioxide (which we will breath out)
and pick up some more oxygen
(which we breath in).
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LEARNING CHECK
1. Name the two sets of muscles involved in
inhalation.
2. List the steps involved in inhaling air.
3. How is oxygen transported in the blood?
4. What does oxygenated blood mean?
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Respiration
Glucose + oxygen --> carbon dioxide + water +
energy
C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy
The body depends on a steady supply of oxygen
to reach its billions of cells to help it make
energy by breaking down sugars and extracting
the energy from it.
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Carbon dioxide reacts with water forming
carbonic acid, which then breaks down into
Hydrogen and bicarbonate ions.
CO2 + H2O ===> H2CO3 + H+ + HCO3carbon dioxide + water ==> carbonic acid +
hydrogen ion + bicarbonate ion
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Adaptations of the Lungs for Gas Exchange
Alveoli have a large surface area [90m²]
Numerous in number [350 million]
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 Inhaled air contains Oxygen [21%], Carbon dioxide
[0.04%], Nitrogen [79%] and some Water vapour
 Exhaled air contains Oxygen [16%], Carbon dioxide [4%],
Nitrogen [79%] and extra Water vapour
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LEARNING CHECK
• List the pathway of air from our nose to
alveolus.
• How is the alveolus adapted to gas exchange?
• Explain the differences between inhaled and
exhaled air.
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Breathing Disorders
• Asthma – inflammation & constriction of
bronchi
• Bronchitis
• Emphysema – destruction of alveoli
• TB – elasticity reduced (bacteria)
• Pneumonia – fills with fluid
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ASTHMA
• Asthma is a narrowing
of the bronchioles due
to some irritant (dust
mite, pollen, cold virus)
and so the sufferer finds
it difficult to inhale
enough oxygen.
• Removing the offending
agent can prevent it
and treatment is by use
of inhalers that dilate
the tubes again.
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•
•
•
•
Asthma
symptoms
Asthma:
Causes
Coughing
Wheezing
Breathlessness
Chest tightness
•
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•
•
Pollen
Animals
Smoke
Dust mites
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Asthma -- Prevention and
Treatment
•Identify triggers
-avoid or remove
•Use specific drug
treatments
•Bronchodilator
•Steroids
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LEARNING CHECK
• What role does the brain play in breathing?
• What happens your breathing rate when you
exercise?
• What advantage is this for you?
• Name a disorder of the breathing system.
• What are its symptoms?
• What are its Causes?
• What are its Treatments?
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Mechanism of breathing
Bell Jar Model
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The Effect of Exercise
Heart rate/min
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Breathing
rate/min
Rest
Exercise
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Recovery
175
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125
50
75
25
5 mins
10 mins
15 mins
20 mins
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Photosynthesis starts when the sun rises in the morning.
CO2 starts to get used up in
photosynthesis and so there is a
drop in CO2 levels in the guard
cells.
This causes potassium ions to
enter them
By osmosis, water enters them
from neighbouring cells.
The extra water causes the stoma
to open.
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At night, the sun goes down and photosynthesis stops
Respiration continues as always
This raises the CO2 levels in the guard
cells.
This causes potassium ions to leave
By osmosis, water is drawn out of the
guard cells,
The loss of water causes each stoma to
close.
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LEARNING CHECK
• What is photosynthesis?
• When and where does it take place?
• What is the trigger for guard cells to take up
water in the morning?
• Why do stomata need to be open during
daylight hours?
• What happen at night to the guard cells?
• What happens aplant cell if it loses too
much water by osmosis?
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5. Following an understanding of the role of the breathing and excretory
systems, students should understand the structures and functioning of these
systems.
Higher Level Extension
6. Controlling factors in gaseous exchange and excretory functions.
MANDATORY ACTIVITY
LABORATORY INVESTIGATION
Investigate the effect of exercise on the breathing rate or pulse rate of a
human.
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3.4.3 The Exchange System in Plants
•
Examination of the structure of the leaf in relation to gaseous
exchange of oxygen and carbon dioxide through the stomata.
•
Reference to the presence and role of lenticels in stem
structures.
•
ACTIVITIES
* Examine microscopically a T.S. of a leaf blade. Note the
intercellular air spaces allowing free diffusion of carbon
dioxide and oxygen.
•
* Examine stomata distribution on a leaf blade.
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leaf
Nutrients
Oxygen
Carbon dioxide
Leaf fall
transpiration
photosynthesis
Cell sap
Toxins
Stomata,
lenticels
Water
HOMEOSTASIS in plants
heartwood
root
Distribution around the
body
Temperature
Xylem phloem
Invaders
bark
Adaptation
cuticle
leaf
Dormancy
As plant
Leaf fall
Bud protected
As seed
underground
Perennating organ
Thick cuticle
Thin, narrow
e.g. cactus
Sunken
stomata
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Syllabus & Teacher Guidelines
3.4.3 The Exchange System in Plants
•
Examination of the structure of the leaf in relation to gaseous
exchange of oxygen and carbon dioxide through the stomata.
•
Reference to the presence and role of lenticels in stem
structures.
•
ACTIVITIES
* Examine microscopically a T.S. of a leaf blade. Note the
intercellular air spaces allowing free diffusion of carbon
dioxide and oxygen.
•
* Examine stomata distribution on a leaf blade.
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Syllabus & Teacher Guidelines
PREAMBLE TO SUB-UNIT 3.4: BREATHING SYSTEM AND EXCRETION
1. All organisms have the ability to maintain constant conditions in their
cells and bodies such as temperature, fluid balance and chemistry. This is
achieved by homeostasis e.g. by diffusion, by developing exchange
systems which include the respiratory and excretory systems.
2. In all organisms adequate amounts of gases, nutrients and toxic wastes
are exchanged by diffusion between cells and their environment. The
efficiency of exchange is proportional to the surface area over which
diffusion can take place.
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Syllabus & Teacher
Guidelines
PREAMBLE TO SUB-UNIT 3.4:
BREATHING SYSTEM AND EXCRETION
3. In large organisms, such as plants and animals, the problem of size in
relation to diffusion and exchange have been overcome by various
means such as:
(a) the body may be flattened, thus reducing the distance between the
two surfaces e.g. the leaves of plants.
(b) increasing the surface area e.g. alveoli in the respiratory system.
(c) the body may develop systems where the material is brought to the
body surface e.g. by respiratory and excretory systems.
4. Because diffusion can only effectively distribute materials over a short
distance, about 0.5 mm, large active animals such as humans also
require a circulatory system to help in the transport of gaseous materials
and toxic waste.
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Syllabus & Teacher
Guidelines
PREAMBLE TO SUB-UNIT 3.4:
BREATHING SYSTEM AND EXCRETION
5. Following an understanding of the role of the breathing and excretory
systems, students should understand the structures and functioning of these
systems.
Higher Level Extension
6. Controlling factors in gaseous exchange and excretory functions.
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Syllabus & Teacher Guidelines
3.4.5 Plant Excretion
 Examine the role of leaves and lenticels as excretory organs of plants.
Students should appreciate however that excretion is an animal function
and that secretion or loss from plant would be more appropriate.
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Anemia is accompanied by a decrease in
the amount of hemoglobin & a lower-thannormal number of red cells in the blood.
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