Patterns in Nature
Topic 13: Movement of Chemicals in Plants and Animals
Part of the Patterns in Nature Module
Biology in Focus, Preliminary Course
Glenda Childrawi and Stephanie Hollis
DOT Point(s)
 Explain the relationship between the requirements of cells
and the need for transport systems in multicellular
organisms.
 Compare the roles of the respiratory, circulatory and
excretory systems
 Compare open and closed circulatory systems using one
vertebrate and one invertebrate as examples
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Movement of Chemicals
For the normal functioning of
plants and animals, chemical
substances needed by the
organism must be transported
into and around the body.
Waste substances also need to be
transported from where they are
produced to the outside of the body.
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Movement of Chemicals
Examples of the movement
of chemicals from the
external environment into
the organism include:
 Oxygen from the air into
an animal for respiration
 Carbon dioxide from
the air into a plant for
photosynthesis
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Movement of Chemicals
Examples of the movement of chemicals from inside an
organism to the outside include:
 Wastes such as carbon dioxide or urea out of an animal
 Oxygen produced by photosynthesis carried out of a plant
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Movement of Chemicals
Examples of the movement of chemicals within the organism
from the site where they have been produced to the site where
they will be used or expelled:
 Food carried from leaves in plants to storage organs
 Oxygen carried from the lungs of an animal to the muscle
cells where energy is required
 Carbon dioxide carried from the muscle cells where it is a
waste to the lungs where it can be expelled
 Chemical messengers such as hormones from glands
where they are produced to organs where they act (in
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animals)
Movement of Chemicals
If the chemicals that are
being moved into the
body, within the body or
out of the body are gases,
this movement is termed
gaseous.
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Movement of Chemicals
When gases move into and out of an organism they need to
move across the surface of the body. In some organisms this
could be a general movement across the entire body surface,
but in most, a special surface area has been developed for this
to occur. This is called the respiratory surface.
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What process do you think this gaseous exchange involved???
The Respiratory System
The terms breathing, respiration and gaseous exchange are all
related but do not mean the same thing.
 Respiration: a biochemical process occurring in all cells
(inside mitochondria) in which energy is released from
nutrients (food) that had combined with oxygen.
 Breathing: a mechanical rhythmic process to allow an
organism to inhale and exhale
 Gaseous exchange: a physical process where gases move
by diffusion, often across cell membranes.
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The Respiratory System
The respiratory system enables organisms to take in oxygen and
remove carbon dioxide from their bodies. It allows gaseous
exchange between an organism and its external environment.
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The Respiratory System
Gaseous exchange may take place externally (between the
external environment and internal environment) or internally
(between different parts of an organism's internal environment) For
example, In mammals:
 Externally: oxygen moves into the lungs, across the surface
of the air sacs and into the blood stream. Carbon dioxide
moves out of the bloodstream into the air sacs and out of the
lungs
 Internally: Oxygen moves from the bloodstream out of a
blood vessel, into the surrounding cells. Carbon dioxide
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moves from the cells into the bloodstream.
The Respiratory System
The respiratory system is made up of tissues and organs that are
specialised for gaseous exchange. In animals the respiratory
organs are varied, such as lungs in mammals, gills in fish and a
tracheal system in insects.
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See handout figure 4.2 (Bio in Focus Text pg 158)
Movement of Chemicals
In large, multicellular organisms, special systems called
transport systems, are needed to ensure the efficient
movement of substances within their bodies.
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We’ll now explore these special systems.
Transport Systems
We already know, unicellular organisms are so small that their
surface area to volume ratio is adequate (large enough) to allow
them to rely on simple diffusion to supply their bodies with the
requirements needed to survive.
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Transport Systems
Multicellular organisms are
bigger in size and so their total
surface area to volume ratio is
smaller. Cells near the centre
of these organisms would be
way to far away from the
surface for substances from the
outside environment to reach
them efficiently by diffusion and
osmosis.
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Transport Systems
Some large organisms are also very active and need more
nutrients and oxygen to provide them with the energy they
need. They also produce more wastes which need to be
removed. To efficiently do this an effective transport system is
required.
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Transport Systems
An effective transport systems have the following features:
 A system of vessels in which substances are transported
 A way of ensuring the materials flow in the correct direction
 A medium in which the chemicals can be carried
 A mechanism to ensure substances are released where they
are needed and picked p from where they are not needed.
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In animals this system is called the circulatory system.
The Circulatory System
The Circulatory system carries substances needed by the body
from their point of entry into the body (or from their site of
production) to the parts of the body where they will be stored or
used.
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The Circulatory System
In animals, nutrients are carried in a fluid medium (most often
the blood) that circulates the body, picking up and dropping off
chemicals.
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The Circulatory System
The main functions of the circulatory system are:
 Transport of gases (oxygen and carbon dioxide), nutrients, waste
products, hormones and antibodies.
 Maintenance of a constant internal environment (pH, ions,
blood gases and osmotic pressure)
 Removal of toxins and pathogens
 Distribution of heat
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The Circulatory System
A circulatory system is classified as closed or open depending
on the flow of its transport fluid.
 Closed Circulatory System: the transport fluid flows in
vessels only. (characteristic of all vertebrates such as fish, frogs,
reptiles, birds and mammals)
 Open Circulatory System: at some stage of circulation
the transport fluid leaves the vessels and enters spaces or
cavities in the body bathing the organs directly. (characteristic
of invertebrates such as spiders, insects, crabs and snails)
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The Circulatory System
In both open and closed circulatory systems, the blood vessels
are responsible for the transport of blood and its contents, but
the capillary networks (closed system) or fluid in the body cavity
(open system) carry out the other functions to maintain a stable
internal environment.
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The Excretory System
We’ve discussed how chemicals enter and are moved around
the body, the last thing we will look at is how waste chemicals
are removed from the body which is called excretion.
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The Excretory System
Excretion involves
expelling metabolic wastes
(wastes that have been made
by cells as a by-product of
metabolism) from the body.
This is not the same as passing
undigested food or faces
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The Excretory System
Nitrogenous wastes
are the main
excretory wastes in
vertebrates and are
toxic if they
accumulate in the
body. As their name
suggests, they
contain the chemical
element nitrogen
which cannot be
stored in the body.
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The Excretory System
The most common examples of nitrogenous wastes that are
excreted are the substances urea, uric acid and ammonia. These
wastes are transported from where they have been produced to
where they will be excreted.
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The Excretory System
The main function of the excretory system is to remove
metabolic wastes from the transported medium (blood) and to
expel them to the outside.
 Nitrogenous wastes, together with water and substances
like salts, they combine to form urine in mammals. The
kidneys act as organs of excretion and send this material to
the bladder where it is removed from the body.
 Carbon dioxide is transported to the lungs where it is then
exhaled and removed from the body
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Activity
-Hand out summary of excretory system found on the teacher
resource CD
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Homework
-Students to complete ‘Comparing these systems in mammals’
activity found on teacher resource CD
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