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BiologyPreliminary CourseStage 6
Patterns in nature
Part 7: Transporting materials in animals
Incorporating October 2002
AMENDMENTS
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Part 7: Transporting materials in animals 1
Contents
Introduction................................................................................ 2
Transport systems in animals .................................................... 3
Respiratory system ..............................................................................3
Circulatory system................................................................................3
Excretory system..................................................................................4
Circulatory systems ................................................................... 5
Gas exchange in animals .......................................................... 8
Insects ..................................................................................................8
Fish .....................................................................................................10
Frogs...................................................................................................11
Mammals ............................................................................................12
Investigative technology .......................................................... 16
Exercises–Part 7 ..................................................................... 19
2 Patterns in nature
Introduction
In plants and animals transport systems and gaseous exchange move
chemicals through the internal environment as well as the external
environment.
In the previous parts you have identified the nutrients required by living
things and how they are obtained form the surroundings. In this part you
will be looking at how these nutrients are transported around animals.
In this part you will be given opportunities to learn to:
• compare the roles of the respiratory, circulatory and excretory
systems
• identify and compare the gas exchange surfaces in an insect, a frog, a
fish and a mammal
• explain the relationship between the requirements of cells and
transport system in multicellular organisms
• compare open and closed circulatory systems using one vertebrate
and one invertebrate as examples
In this part you will be given opportunities to:
• use available evidence to discuss, using examples, the role of
technologies, such as the use of radioisotopes in tracing the path of
elements through living plants and animals.
Extract from Biology Stage 6 Syllabus © Board of Studies NSW, originally
issued 1999. The most up-to-date version can be found on the Board's website
at http://www.boardofstudies.nsw.edu.au/syllabus_hsc/syllabus2000_lista.html
This version November 2002.
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Part 7: Transporting materials in animals 3
Transport systems inanimals
In animals there are three systems that move materials around the body
and between the body and the surrounding environment.
These systems are:
• respiratory system
• circulatory system
• excretory system.
Respiratory system
The respiratory system is responsible for the movement of gases
throughout the body. Oxygen is required for every cell in the body and
carbon dioxide must be removed from every cell in the body.
The respiratory system performs this function. Organs that are part of
the respiratory system of animals are lungs, gills and spiracles in insects.
Circulatory system
The circulatory system transports food, oxygen and wastes throughout
the body. Every cell has requirements for nutrients and must get rid of
poisonous waste materials. This is the role of the circulatory system.
Organs of circulatory systems are heart, veins, arteries, capillaries and
the haemocoel in insects. Circulatory systems may be open or closed.
4 Patterns in nature
Excretory system
All animals need to excrete wastes produced from metabolic processes in
their cells. A build–up of wastes can produce unwanted effects and
many substances such as urea can become toxic in excess qualities.
Wastes substances that have to be remove include water, carbon dioxide
and nitrogenous compounds. Organs of excretion include kidneys, lungs,
skin and malpighian tubules in insects.
Comparison of the systems
All three systems have different tasks but they share common features
and common roles. The circulatory system has a role in the other two
systems because the blood vessels move materials to the organs of
respiration and excretion. Organs of the respiratory system such as the
lungs have a function in excretion of carbon dioxide. All three systems
work together to transport nutrients and waste products from where they
enter the body to where they leave the body.
The table below summarises this information.
Respiratory system Circulatory system Excretory system
Organs Lungs, gills, skin,spiracles
Heart, blood vessels,lymph, haemocoel
Kidneys, lungs, skin,malpighian tubules
Function Movement of gasesthrough the body
Transport nutrients andwaste products around thebody
Rid the body ofwaste materials,water balance
Complete Exercise 7.1.
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Part 7: Transporting materials in animals 5
Circulatory systems
All multicellular plants and animals require a transport mechanism to
move nutrients, gases and wastes to and from cells. These materials need
to be moved around an organism’s body efficiently. This to ensure that
all cells obtain the appropriate materials to maintain function and any
products and wastes are removed.
Both plants and animals have methods of transporting materials within
the body. However, the transport of materials occurs in different ways.
In this section you will focus on transport in animals.
The circulatory system transports oxygen, food material and wastes to
and from cells. The movement of the blood through an organism
depends on the action of a heart.
All vertebrates and some invertebrates such as earthworms have a closed
circulatory system. This means that blood is transported around an
organism within muscular tubes or blood vessels.
The diagram following shows the movement of blood through the human
circulatory system.
Invertebrates such as arthropods have an open circulatory system.
A pool of blood is circulated by the action of a heart, there are no
specialised vessels for transporting blood.
An insect’s blood is in direct contact with its body cells–blood is not
contained in blood vessels as such. The internal space of an insect’s body
can be considered as a single blood vessel called the haemocoel.
This name comes from Greek words: haima (blood) and koilia (hollow).
An insect’s circulation system is in fact not entirely ‘open’ as they have
pumping vessels to promote the flow of blood.
6 Patterns in nature
capillariesin kidneys
capillariesin lungs
capillariesin liver
capillaries inlegs and
abdominal organs
capillaries instomach and
small intestine
anteriorvena cava
pulmonaryartery
capillariesin arms and
head
capillariesin lungs
mesentericartery
rightatrium
rightventricle
posteriorvena cava
pulmonaryvein
leftatrium
leftventriclehepatic
portal vein
renalvein
hepaticartery
renalartery
oxygenated blood de-oxygenated blood
mesentericvein
Human circulatory system – a closed system.
brain
gut
haemocoel
accesory pump
pumping vessel
Insect circulatory system – partially open system.
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Part 7: Transporting materials in animals 7
A closed circulatory system ensures that there is one pathway ensuring
tissues are supplied with blood. It relies on a central heart to pump the
blood around within the specialised blood vessels. These require large
amounts of energy. All vertebrates have a closed circulatory system.
Open circulatory systems do not require the large amounts of energy
required by closed circulatory systems. They suit smaller animals that do
not make rapid movements.
Complete Exercise 7.2.
8 Patterns in nature
Gas exchange in animals
All animal cells respire. Animal cells respire aerobically (most of the
time). They use oxygen gas in the process and release carbon dioxide
gas as a waste product. Animal cells do not photosynthesise.
In this section you will investigate and compare gas exchange surfaces of
an insect, a fish, a frog and a mammal. The gas exchange tissues and
organs of major groups of multicellular animals are often different.
In this section you will examine those differences.
Insects
Insects do not have lungs or gills. Insects exchange gases with the
atmosphere using trachea, tracheoles and spiracles.
longitudinaltrachea
spiracle
tracheoles
Structures used in gas exchange in an insect.
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Part 7: Transporting materials in animals 9
Insects carry out gas exchange through a series of internal tubes (trachea)
that connect to the outside through holes (spiracles) located at various
points on the insect body.
The trachea branch into smaller and smaller tubes (tracheoles).
Tracheoles are very tiny (about one micron in diameter). The branching
into many tiny tubes has two advantages for the insect.
• Because the tracheoles are extensively branched throughout the
insect, most cells are close to specialist gas exchange surfaces.
• The branching and the small size of the tracheoles greatly increases
the surface area to volume ratio of the gas exchange surfaces.
Fluid collects in the ends of the tracheoles and it is into this fluid that
gases dissolve before diffusing into the surrounding cells.
The tracheoles are close to body cells. When waste gases eg. carbon
dioxide concentrations are higher in the cell than the neighbouring
trachea, then the waste gases diffuse out of the cell. When oxygen levels
are higher in the trachea than the surrounding cells oxygen will diffuse
into the cells.
The spiracles connect the trachea to the atmosphere surrounding the
insect. When the insect uses its muscles the trachea are compressed
and this causes gases to be pushed out of the spiracles. When the
muscles relax the trachea are not compressed and gases flow back into
the trachea.
Spiracles are able to close to help reduce water loss. Because the internal
parts of the body are very humid it is possible for water be removed as a
vapour from the body.
Spiracles also have fine hair–like structures to prevent dust entering the
system. If dust were to enter, the tracheoles could become blocked and
this would reduce the efficiency of the gas exchange surfaces.
10 Patterns in nature
Fish
Most fish use gills for gas exchange. Gills are external structures–they
hang outside the main body cavity and often have a protective cover over
them. Gills have a large surface area because they are thin and
highly folded.
Gas exchange in fish
Water enters a fish’s mouth and passes over the gills. When most fish
are stationary they gulp water to maintain the flow over the gills.
This also explains why so many fish (sharks included) swim with their
mouth open–this allows the water to pass into the mouth and over the
gills without the need to gulp water.
Gases are exchanged between the surrounding water and the fish on the
gill surface. The gases enter the circulatory system where they are
transported to cells throughout the body. The main blood vessels
entering the gills branch into tiny tubes called capillaries.
The capillaries are very close to the gill surface. It is the colour of the
blood in the capillaries that makes gills appear red. Capillaries being tiny
and numerous make the surface area to volume ratio for diffusion of
gases very high in the gills.
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Part 7: Transporting materials in animals 11
Frogs
Frogs have two methods of gas exchange: gas exchange via the lungs and
gas exchange via the skin. The diagram below shows the structures
involved.
lungs
diffusion in moist skin
Frogs exchange gases through their lungs and moist skin.
Gas exchange via the lungs
Lungs are internal organs involved in gas exchange. The gas exchange
surfaces of terrestrial organisms are usually internal to prevent
desiccation (drying out). You will have noticed that the gas exchange
surfaces of insects (also terrestrial) are internal too.
Frogs ventilate their lungs by positive pressure breathing. This means
that they force air into the lungs. This method of breathing is very
different to the negative pressure breathing seen in mammals. You will
look at negative pressure breathing later.
Unlike human nostrils, which stay open all the time, frogs are able to
open and close their nares (nostrils). To breathe, a frog
• closes its mouth and opens its nares
• lowers the floor of the mouth causing air to be ‘sucked’ into the
mouth cavity
• closes the nares (nostrils)
• raises the floor of the mouth.
This forces the air in the mouth into the lungs.
12 Patterns in nature
Lung structure of a frog
The internal structure of a frog lung is not too dissimilar to a human lung.
Air enters the lungs and then moves through a series of branching tubes.
The tubes become smaller and smaller as they branch (this is becoming a
familiar theme for gas exchange). The finest tubes are in close
association with capillaries (small blood vessels). Gases diffuse into and
out of the blood at these sites.
Like the fish, the circulatory system delivers gases to the cells.
The circulatory system also receives the waste gases from cells and
delivers them to the lungs. You will take a much closer look at the
structure of lungs in the next section.
Gas exchange via the skin
The skin of a frog is thin and kept moist by the habitats in which the frog
lives. The skin is permeable to water (unlike human skin).
Frogs dehydrate rapidly if they are not kept in a moist environment.
This is why you find frogs in moist locations.
Gases from the atmosphere dissolve into the moisture on the skin.
From there the gases can diffuse into the capillaries beneath the skin.
The skin does not exchange sufficient gases for all of a frog’s needs.
However, the gas exchange is important and allows the frog to remain
submerged for longer than if it had to depend on lungs alone.
While submerged, gaseous exchange occurs on the frog’s skin.
Mammals
Mammalian lungs are internal. This helps to reduce the loss of water
and heat through these structures that have a high surface area to
volume ratio.
To get air into the lungs the mammal lowers the air pressure in the lungs.
When the air pressure in the lungs is lower than the surrounding
atmosphere, air enters via the nose.
To remove air from the lungs, mammals increase the pressure of the air
in the lungs. When air pressure in the lungs is higher than the
surrounding atmosphere air moves out of the lungs.
The structure of the human respiratory system is shown on the diagram
on the following page.
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Part 7: Transporting materials in animals 13
epiglottis
to the stomach
rib
right lungshowinglobes
diaphragm
air
nosetrachea wallmagnified
cilia
trachea
bronchusbronchiole
left lungdissected toshowinternal
cluster ofalveoli
from pulmonaryartery to pulmonary
vein
nasal cavity
capillaries
Structures involved in the exchange of gases in humans.
Air enters the body through the nostrils. The nasal cavity warms the air,
filters it and removes dust. The air then moves into the throat region or
pharynx (pronounced farrinks). It enters the largest air tube–the trachea
(pronounced track–ee–ah) through the opening called the glottis.
The epiglottis is a flap of tissue that closes over the glottis and stops food
going down the wrong way when we swallow.
The trachea branches into two bronchi (pronounced bron–key).
Each bronchus (singular) branches into smaller air passages called
bronchioles (bron–key–oles) and these end in very thin–walled alveoli
(pronounced al–vee–oh–lie), singular alveolus. Blood capillaries are
wrapped closely around the alveoli.
It has been estimated that the total surface area of the alveoli of an adult
male is about one third the area of a tennis court. A large surface area
obviously allows for a greater quantity of gases to be exchanged.
The thinness of the walls of the alveoli allows for rapid diffusion of
oxygen into the blood and carbon dioxide out of the blood. The moisture
in the alveoli walls allows gases to dissolve.
14 Patterns in nature
blood from body(low in oxygen, high in carbon dioxide)
blood capillary
blood cell
oxygen
carbon dioxide
wall of alveolus
air inhaledair exhaled
blood to rest of body(high in oxygen,low in carbon dioxide)
Movement of material in an alveolus.
Composition of inhaled and exhaled air is shown in the table below.
Gases Percentage in inhaled air(%)
Percentage in exhaled air(%)
oxygen 21 16
carbon dioxide 0.04 4
nitrogen about 80 about 80
water vapour varies according to thehumidity of the air
more than in inhaled air
Air passages
Rings of cartilage keep the trachea and bronchi open and prevent them
closing when the air pressure inside the body falls. The lining cells of
the air passages have numerous cilia (sill–ee–ah). These are minute
hair–like projections that sweep to and fro.
Mucus is secreted by special gland cells, also present in the lining or
epithelial (ep–e–theel–e–al) cells. Dust particles and bacteria in the air
are trapped by the mucus film. The movements of the cilia sweep them
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Part 7: Transporting materials in animals 15
away in the mucus to the larynx and the mucus is swallowed or
coughed up.
The nose hairs and mucus also trap dust and foreign particles.
Around the lungs is a membrane, the pleural (ploo–ral) membrane, which
covers the outside of the lungs and the inside of the chest cavity.
It contains a fluid that lubricates the surface so that there is no friction
between the tissues during breathing movements.
The mechanism of breathing
In mammals, breathing refers to the movements of the chest that result in
air entering and leaving the lungs.
The movement of air in and out of our chest is bought about by changes
in the pressure of the air in the chest cavity. This pressure varies because
the volume of the chest cavity varies. The chest cavity is airtight and
enclosed by ribs with intercostal (inter–cos–tal) muscle between them.
At the base of the chest cavity is the diaphragm (die–ah–fram).
The diaphragm is the muscular sheet separating the chest (also called
thorax) and abdomen.
At rest, the diaphragm is curved upwards. The intercostal muscles relax
at the same time and the ribs move downwards and inwards.
These collapsing movements reduce the size of the chest cavity, increase
the pressure of the air in the lungs and thus force it out.
During inhalation, the diaphragm contracts and flattens, being more taunt
or tight in this state. At the same time, the intercostal muscles contract
and move the rib cage up and outwards. This increases the volume of the
chest cavity and reduces the pressure of the air in it. Air thus moves into
the lungs. You can check these movements by placing your fingers over
your rib cage as you inhale and exhale.
Complete Exercise 7.3.
16 Patterns in nature
Investigative technology
Much of what is known about the structure and function of living
things has been directly associated with the improvements in
technology available.
New technology is increasing the range of investigative methods in
research laboratories, industry, environmental management and in the
medical profession. The use of radioisotopes have improved productivity
and gained information that cannot be obtained in any other way.
Radioisotopes produce radioactive emissions that can be easily detected.
This property makes radioisotopes very useful as tracers.
Radioactive materials can be tracked through a process, system or
organism. Examples of use include mapping pathways of nutrients and
toxins through ecosystems, absorption of nutrients by plants and tracing
metabolic pathways. Increasingly medical diagnosis is making use of
tracers for organ and tissue function.
Many chemical elements have isotopes. (Isotopes have the same number
of protons but a different number of neutrons in the nucleus of an atom.)
Some isotopes are unstable and emit alpha or beta particles and
sometimes gamma radiation.
Tracers can be used to follow movement of substances in large amounts
or at molecular or even atomic levels. The observations are made by
measuring the radioactivity or by measuring the relative abundance of the
stable isotopes. The instruments used for detecting the tracers pathway
include electroscopes, scintillation counters, the Geiger–Müller counter
and the mass spectrometer.
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Part 7: Transporting materials in animals 17
Radioactive tracers
Radiation is used in nuclear medicine to diagnose the functioning of
organs such as the liver and kidneys. Radioactive tracers are used which
emit gamma rays for very short periods of time. Radioactive materials
are introduced into the body orally, by injected or they are inhaled.
An image of the organ showing the location of the radioisotope is used in
diagnosis. An unusual pattern indicates a malfunction in the organ.
Bone and other tissue can be seen much more clearly using these imaging
techniques than by x–rays.
Blood flow to the brain, liver and kidney function and bone growth can
be diagnosed using radioisotopes as tracers. The amount of radioisotope
given to patient is a very small dose, only enough to obtain an image for
diagnosis.
Technetium–99 is a very common isotope used in medicine.
It has a half–life of six hours. Technetium–99 emits low energy gamma
rays so the patient receives only a very low radiation dose.
Geiger counters
A Geiger counter is a machine that measures radioactivity.
In the experiment on the following page radioactive carbon was taken in
by the leaves through the process of photosynthesis. The Geiger counter
was used to measure the amount of radioactive carbon in the leaves and
in the fruit. The next day the readings showed that the radioactive carbon
had moved from the leaf to the fruit.
18 Patterns in nature
Geiger counter
Geiger counter
sugar with radioactive carbon on scraped leaf
Day 1
tomato fruit
HIGH
LOW
Geiger counter
Geiger counter
sugar with radioactive carbon on scraped leafDay 2
tomato fruit
LOW
HIGH
Gather information from secondary sources on the use of radioisotopes in
tracing the path of elements through living plants and animals.
You will need to carry out a search of secondary information sources such as
contacting research institutions such as ANSTO, CSIRO or the Internet.
Conventional sources such as libraries will have many references you can
use and may be a good place to start.
Process the information by answering the questions in Exercise 7.4.
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Part 7: Transporting materials in animals 19
Exercises - Part 7
Exercises 7.1 to 7.4 Name: _________________________________
Exercise 7.1: Transport systems in animals
Compare the roles of the excretory, respiratory and circulatory systems in
the body. systems
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Exercise 7.2: Circulatory systemsa) What is the role of the circulatory system in humans?
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20 Patterns in nature
b) What is the difference between open and closed circulatory systems?
Give examples.
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c) Which system is more efficient – open or closed circulatory system?
Give reasons.
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Exercise 7.3: Comparison of gas exchange
Identify and compare the gas exchange surfaces in an insect, a frog a fish
and a mammal by filling in the table below.
Organism Name of gasexchange structures
Surface Area/Volumeratio
Gas exchangestructuresinternal/external
insect high
skin low externalfrog
lungs high
fish
mammal internal
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Part 7: Transporting materials in animals 21
Exercise 7.4: Radioactive tracers
Discuss the role of radioisotopes as tracers in medicine. What are the
issues? Provide points for and against the use of radioactive materials in
medicine.
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