Preliminary Biology
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Module 1 - Cells as the Basis of Life
Module 2 - Organisation of Living
Things
Module 3 - Biological Diversity
Module 4 - Ecosystem Dynamics
Working Scientifically Skills
Module 2: Organisation of Living Things

Chapter 1: Organisation of cells
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Chapter 2: Nutrient and gas requirements
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Inquiry question: How are cells arranged in a
multicellular organism?
Inquiry question: What is the difference in nutrient and
gas requirements between autotrophs and
heterotrophs?
Chapter 3:Transport

Inquiry question: How does the composition of the
transport medium change as it moves around an
organism?
Give me...
5
4
3
2
1
Specialised animal cells
Red blood cell, nerve cell, sperm cell, egg cell and white blood cell
Organelles found in cells
Nucleus, cell membrane, cell wall and cytoplasm
Differences between plant and animal cells
P – cell wall, vacuole and chloroplasts
Differences between a eukaryotic and prokaryotic cell
E- have nucleuses, P- unicellular and multicellular
Specialised plant cell
Root hair cell
Module 2 – Organisation of living
things
Chapter 2: Nutrient and gas requirements
Inquiry question: What is the difference in nutrient and gas requirements between autotrophs and heterotrophs?
What is the difference in
nutrient and gas
requirements between
autotrophs and
heterotrophs?
Chapter 2: Nutrient and Gas Requirements
Inquiry question: What is the difference in nutrient and
gas requirements between autotrophs and heterotrophs?
Investigate the structure of autotrophs through the examination of a variety of
materials, for example:
- dissected plant materials
- microscopic structures
- using a range of imaging technologies to determine plant structure
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All living organisms require many different substances for
their efficient functioning.
Inorganic and organic materials are essential nutrients for
both autotrophs and heterotrophs.

These nutrients are required to:
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supply energy to the organism and
provide the raw materials to be used in building the structure of cells
and living tissue.
Majority of autotrophic organisms are plants.
Structure of plants
A.
i.

The root system is responsible for:
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The root system
anchoring the plant and
absorbing both inorganic and organic nutrients from the soil.
Roots have:
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Structural adaptations that help them absorb water.
Specialised cells that increase surface area and maximise water
and mineral uptake.
Internal root structure
Cross section (Transverse section)
root hair
epidermis
transport vascular tissue
cortex
phloem
xylem
Longitudinal section
root hair
cortex
xylem
phloem
epidermis
zone of cell elongation
cell division occurs here
root cap
ii.

The shoot system (Stem)
The stem provides:
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structural support and
acts as a transport pathway between the roots and the leaves.
Revision

The stem contains three types of tissues:
1. Dermal tissue: Makes up the outer layer of the stem and
provides waterproofing as well as protection and control of gas
exchange
2.Vascular tissue: Consist of the xylem and phloem tissue
organised in vascular bundles. They provide structural support
and enable transport of materials.
3. Ground tissue: Fills in around the vascular tissue. It is used for
Photosynthesis, stores photosynthetic products and helps
support the plant.
Internal stem structure
The position and
shape of the
vascular system
changes due to the
different
requirements of a
plant from root, to
stem, to leaf!
https://ib.bioninja.com.au/higher-level/topic-9plant-biology/untitled-6/stem-tissue.html
The shoot system (Leaves)
iii.

The main function is to:
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absorb sunlight and carbon dioxide and
produce glucose through the process of photosynthesis.
Leaves have specialised cells that can be divided into 3
distinct layers:

Upper epidermis and lower epidermis
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A layer of cells covering the entire leaf.
Secrets a water proof waxy layer called the cuticle.
Forms a protective barrier.
Prevents water loss.
Mesophyll

Photosynthesis takes place here.
Thin, waxy
waterproof layer.
Transparent and
usually thin.
Epidermis
and cuticle
(combined)
Photosynthesis
Transports water and
products of photosynthesis.
Internal leaf structure
Let’s label!
Video Activity
Watch the previous video again and suggest why a vascular
system in plants may be an evolutionary advantage.
Classwork/Homework
KISS Worksheet 4 – Test-Style Questions
Investigate the structure of autotrophs through the examination of a variety of
materials, for example:
- dissected plant materials
- microscopic structures
- using a range of imaging technologies to determine plant structure
B.


Plant structure – Imaging technologies
Development of technologies that are much more
advanced than light and electron microscopes has led to a
greater depth of understanding of not only plant
structure but also plant functioning.
Advancements have allowed scientist to:
1.
2.
3.
capture an image
manipulate it
process it using advanced computer models
i.

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
MRI (magnetic resonance imaging)
Uses radio waves and a magnetic field to take a series
of images of the plant structures that are used to
produce a computer-generated 3D image of the
structure.
Can be combined with other technologies such as PET
(position emission tomography) to provide greater
detail as well as functional information about transport
and processes.
Both MRI and PET involve the detection of radiation
produced by a radioisotope.
Image of maize roots
produced by MRI and PET
technologies.
ii.
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X-ray computed microtomography (micro-CT)
Used to gain a much deeper knowledge of the internal
structure of a plant.
Non-destructive process and like the CT scan used in
hospitals, but smaller
Images produced from different angles are
reconstructed into a 3D computer-generated image
which is then analysed from every angle and spatial
arrangement, allowing all internal tissues of the plant to
be studied.
Research Task
Gather, process and analyse information from secondary
sources (the internet as well as the handout provided) to
discuss the use of radioisotopes in increasing our
understanding of plant structure and function.
Classwork/Homework
Complete the following worksheets from the worksheet
booklet:
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9.1 – Gas exchange in plant leaves
9.4 – The role of roots
9.5 – Plant structure and adaptations
9.6 – Transport in plants
Example 1: Phosphorus-32
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Plants take up phosphorus-containing compounds from
the soil through their roots.
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By adding a small amount of radioactive phosphorus-32
to fertiliser and then measuring the rate at which radioactivity
appears in the leaves, it is possible to calculate the rate of
uptake of phosphorus from the soil.
The information gathered could help plant biologists to identify
plant types that can absorb phosphorus quickly.
Example 2: Carbon-14

Radioisotope carbon-14 was
used to explain the details of
how photosynthesis occurs.
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Plants were exposed to
CO2 containing a high
concentration of radioactive
carbon-14. At regular
intervals, the plants were
analysed to determine which
organic compounds contained
carbon-14 and how much of
each compound was present.
From the time sequence in
which the compounds
appeared and the amount of
each present at given time
intervals, scientists learned
more about the pathway of
the reaction.
Investigate the structure of autotrophs through the examination of a variety of
materials, for example:
- dissected plant materials
- microscopic structures
- using a range of imaging technologies to determine plant structure
Dissected plant materials
Microscopic structures
C.
D.
i.
ii.
Part 1: Dissecting Celery
Part 2: Observing plant cells under the microscope
i.
Part 1: Dissecting Celery
Background Information:
 Xylem is specialised vascular tissue for the transport of
water and dissolved mineral nutrients from the roots to
the leaves.
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Movement occurs in only one direction- upwards from the
roots.
Water that is taken up travels to the leaves and can escape
through stomates, causing low water pressure at the leaves.
Water from the roots is constantly replacing water lost from
the leaves - this is known as the transpiration stream.
Aim:
1. To observe the movement of water through plant
xylems.
2. To observe dissected plant materials under the
microscope and identify microscopic structures which
are present in autotrophs.
3. To identify that transpiration rate is greater when leaves
(macroscopic structures) are present (Chapter 3).
Hypothesis:
 If celery is kept in water with red food dye, then
water transport will become evident by redstained stems and/or leaves after some time.
 If celery stems are cut across after being placed
in red-coloured water, xylem in the vascular
bundles will be found to be stained red.
 If celery is kept in red-coloured water, those
stems with leaves intact will have a faster
movement of water to the stem i.e. Faster
transpiration rate.
Equipment:
 Celery with leaves still attached – similar size (20cm)
 Beaker 500mL
 Red food dye
 Water
 Scalpel
 Ruler
 Microscopic slide
 Light microscope
 Cover slip
 Stopwatch
 Paper towel
Method
PART A:
1.
Wear disposable gloves.
2.
Fill the beaker with 300 mL of water and add a couple of
drops of red dye.
3.
Choose 4 celery stems of the same length remove the leaves
of 2 and place them in the beaker upright in a shaded, but
well-ventilated area.
4.
Leave in beaker for ~ 40 minutes.
5.
Cut across each stem at 1cm intervals up the stem to
determine the distance that the coloured water was
transported. Record data in the table.
6.
Calculate the rate of transpiration for each treatment.
PART B:
1. Leave the stems in the stained water overnight.
2. Cut the stems longitudinally and vertically to determine
where the water has travelled,
3. Slice thin sections and mount them on a microscope
slide.
4. Focus the section of the xylem under the microscope
and record observation.
Results:
Table 1: Rate of transpiration in a celery stem with and without leaves
With leaves
Without leaves
Stem 1 Stem 2 Average Stem 1 Stem 2
Average
Distance travelled
in 40 minutes (cm)
Transpiration
rate/minute
22
23
22.5
17
4
10.5
0.55
0.58
0.56
0.43
0.1
0.26
Discussion:
1. Explain the transport of water through plants.
2. Construct diagrams of cross sections of stems to
illustrate xylem in vascular tissue.
3. Explain why transpiration was faster in the celery with
leaves.
4. Describe the appearance of xylem tubes.
ii.
Part 2: Observing plant cells under the microscope
Background Information:
 The shape and position of the vascular bundle changes
from the roots, through the stem and to the leaves due to
the varied requirements of these organs.
Aim:
To use the light microscope to
observe and identify the xylem,
phloem and stomata in prepared
slides.
Equipment:
 Light microscope
 Prepared slides
Method:
After you carry out the experiment
write up a method!
Results:
Fill in the table on page 14-15.
Investigate the function of structures in a plant, including but not limited
to:
- tracing the development and movement of the products of photosynthesis
- the movement of water (added)
Photosynthesis is the process whereby most autotrophic
plants use inorganic materials in the environment to
produce organic materials which are broken down to
produce energy.
Photosynthesis occurs within the
chloroplast of cells.
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Each chloroplast has an inner and
outer membrane which together
regulate the movement of materials
in and out.
Inside there is a fluid called stroma
and a highly complex inner thylakoid
membrane which fold to form a
system of stacks called grana,
between which are flat membrane
sheets called lamellae.
Chloroplasts are found mostly in
palisade mesophyll cells with some
found in the spongy mesophyll layer.
The development of products
from photosynthesis
Photosynthesis requires:
A.
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Carbon dioxide
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Used by plants for photosynthesis.
Obtained from the air surrounding the
leaves.
Exchange of gases takes place through the
stomata and can be temporarily stored in
the air spaces within the mesophyll layer.
Rate of photosynthesis depends on the
concentration of carbon dioxide available
in the environment.

Water
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Used to keep the cells in the plant alive.
Water molecules are split to form molecules of oxygen gas and
hydrogen ions which produce ATP energy and can be used later in
aerobic respiration to produce further ATP molecules.

Light energy
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Energy from the sun is absorbed by the pigment found within
chloroplasts called chlorophyll.
Chlorophyll (or other pigments) is necessary for photosynthesis to
occur.
When water levels are low in the plant, the stomata close
to reduce excess water loss, this reduces the amount of
carbon dioxide available for photosynthesis.
Photosynthesis produces:

Oxygen
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Produced as a by-product
of photosynthesis.
Required for aerobic
respiration.
Oxygen that is not used up
is then transported out of
the plant via the stomates if
the guard cells are open.

Glucose
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The main product of photosynthesis.
Stored in plants as starch if it is not used up in aerobic respiration.
Travels around the plant to its required location or storage space via
the vascular bundle (transported by the phloem).
Investigate the function of structures in a plant, including but not limited
to:
- tracing the development and movement of the products of photosynthesis
- the movement of water (added)
The movement of the products of
photosynthesis
The products of photosynthesis are moved around the
plant through:
i.
the phloem or
ii.
exists the plant leaves either through stomata or
lenticels.
B.
ii.

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
Stomata
Gas exchange occurs through a structure called stomata.
Stomata are the openings to an air space usually located
in the lower epidermis of a leaf.
Each stoma (singular) consists of two highly specialised
epidermal cells called guard cells.

Stomata regulate the exchange of gases between the
plants internal and external environments, by changing
shape which causes the pore to open or close.
When plants have open
stomata, there is an
exchange of
photosynthetic gasses
(CO2 and O2) as well
as the loss of water
vapour due to
transpiration.


Lenticels are pores through which gaseous exchange
occurs in the woody parts of plants such as the trunks
and branches of trees.
The diffusion of oxygen, carbon dioxide and water vapour
take place through lenticels, relatively slowly.
Chapter 2: Nutrient and Gas Requirements
Inquiry question: What is the difference in nutrient and
gas requirements between autotrophs and heterotrophs?
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
Investigate a range of secondary-sourced information to evaluate processes, claims and
conclusions that have led scientists to develop hypotheses, theories and models about the
structure and function of plants, including but not limited to:
- photosynthesis
- transpiration-cohesion-tension theory
Poster
In groups of 4, use the information provided to analyse the
claims and hypotheses, theories and models about the
structure and function of plants in relation to
photosynthesis and the transpiration-cohesion-tension
theory.
PART 1: You will choose either photosynthesis OR
transpiration-cohesion-tension theory and create a poster
which covers the points on pg 25 of your booklet.
PART 2: You will be given a copy of another groups poster,
which you will need to critique using the points provided.
Resources provided on pg 26 of your booklet!
Chapter 2: Nutrient and Gas Requirements
Inquiry question: What is the difference in nutrient and
gas requirements between autotrophs and heterotrophs?



Investigate the gas exchange structures in animals and plants through the
collection of primary and secondary data and information, for example:
- microscopic structures: alveoli in mammals and leaf structure in plants
- macroscopic structures: respiratory systems in a range of animals
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

Gas exchange is an important function for both plants
and animals.
Gas exchange removes waste products that can affect
metabolism or alter the functioning of organisms and
provides the organism with gasses that are required for
it to survive.
Plants and animals have evolved various microscopic
and macroscopic structures that assist in gas exchange.
Investigate the gas exchange structures in animals and plants through the
collection of primary and secondary data and information, for example:
- microscopic structures: alveoli in mammals and leaf structure in plants
- macroscopic structures: respiratory systems in a range of animals
A.


Leaf structure in plants
(microscopic
structures)
Gas exchange in plants
occurs through a structure
called the stoma (plural
stomata) - the opening to
an air space located in the
lower epidermis of a leaf.
Each stoma consists of two
highly specialised epidermal
cells called guard cells,
which surround a pore,
creating an opening
through the epidermis and
cuticle.

Stomata regulate the exchange of gases and water
between a plant’s internal and external environment.

They change shape, which causes the pore to open and close.

When plants open their stomata to allow carbon dioxide gas in for
photosynthesis, oxygen gas is released, and water is lost as water
vapour during the process of transpiration.


Stomata are usually open during the day to increase the
rate of photosynthesis when sunlight is available.
The stomata close when light levels drops and the plants
do not need any more carbon dioxide for photosynthesis.

When the guard cells are:

Turgid (swollen)
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
The stomatal opening is large, allowing water and gases to enter and
exit the leaf.
The guard cells become swollen when potassium ions (K+)
accumulate and the potential water potential of the guard cells
decreases.

Flaccid

When guard cells loose water, the cells become flaccid and the
stomatal opening closes, preventing water and gas from leaving the
leaf.
Investigate the gas exchange structures in animals and plants through the
collection of primary and secondary data and information, for example:
- microscopic structures: alveoli in mammals and leaf structure in plants
- macroscopic structures: respiratory systems in a range of animals
Respiratory systems of animals (microscopic and
macroscopic structures)
Gaseous exchange occurs in all animals and involves the
movement of gases between their internal and external
environments by diffusion across cell membranes.
B.

Organisms must exchange oxygen and carbon dioxide
with their environments to maintain normal cell
functioning.



Oxygen is essential for all cells to carry out cellular respiration
to release energy from the nutrients they have consumed.
As a result of this process, carbon dioxide is produced and
must be removed as it is toxic and can decrease the pH of
blood and other cells in the body interfering with enzyme
activity.
The respiratory system enables this gaseous exchange
between the organism and its environment.

The respiratory system contains organs that are made up of
specialised tissue. Different animals possess different
respiratory organs but they all have common exchange
structures to ensure efficient functioning and maximum
exchange of gasses. They all:




Have a large surface area that has been enhanced by folding
branching or flattening. This large surface area allows a faster rate of
diffusion to supply oxygen and to remove carbon dioxide.
Have a moist, thin surface to ensure that oxygen and carbon dioxide
dissolve for easier diffusion - thinnest decreases the distance that the
gasses need to travel.
Are in close proximity to an efficient transport system that will
transport the gasses to and from all cells in the body.
Have a greater concentration of required gasses on one side of the
membrane than the other so that a concentration gradient is
maintained.
i.

Mammals (Humans)
The gaseous exchange surfaces in mammals are located in
the lungs, and are known as alveoli (single - alveolus).


Each thin walled alveolus is composed of an air sac that is
connected to the external environment and is surrounded by
tiny thin-walled blood vessels called capillaries.
Capillary walls are one cell thick and they only allow one red
blood cell to pass through at a time, allowing for efficient
exchange of gasses.

There are 3 key steps in the process of respiration before
the air is able to exchange gasses with the blood:

Nasal cavity


Air is drawn in through the nose and passes into the nasal cavity and
pharynx (the back of the throat).
The nose filters, moistens and warms the air for the airways.

Airways


The air then passes to the trachea which then splits into two bronchi
and then further branches off into bronchioles.
The trachea and bronchi are lined with cells covered in cilia and
secrete mucus which traps particles of dust or bacteria while the cilia
push the partials towards the pharynx.

Alveoli



Air enters the terminal air sacs called alveoli where gas exchange
takes place.
Alveoli are microscopic and there are approximately 286 million
alveoli in each human lung.
There is a constant supply of oxygen to cells through the capillaries.
Alveoli
 The alveoli in the lungs have all the features that allow for
efficient gas exchange:

The increased surface area is achieved by the approximately 286 million
microscopic alveoli that are supplied by 280 million capillaries.



Each alveolus has a thin lining made of flattened cells that are in a single layer,
facilitating the efficient diffusion of gases across a very small distance.
The surface area of all parts of the respiratory system is moist. The air inside
the alveoli is saturated with water vapour and the mucus lined epithelium
reduces the evaporation of this water.


Each alveolus has folding of the thin interior lining, thus further increasing surface
area.
This ensures that the oxygen and carbon dioxide that diffuse across the gaseous
change surface are in a dissolved form enhancing the efficiency of diffusion.
The numerous blood capillaries that closely surround the outside of each
alveolus ensure that all alveoli are in close contact with the blood.
Lung ventilation
 The lungs are located in the chest cavity, which is
completely enclosed and under a small negative pressure
that keeps the lungs expanded.
 The floor of the chest cavity is the muscular diaphragm.
Malfunctions of the respiratory system in humans
 Asthma


A condition in which the cells lining the airways are sensitive to
foreign particles in the air such as pollen.
Small airways swell and fill with mucus and become
constricted.

Emphysema


Caused by the breakdown of air sacs in the lungs.
Reduces the lung surface area available for gas exchange.

Pneumonia

Caused by an infection that causes the lungs to become
inflamed, and the air sacs to fill with white blood cells and fluid.
Classwork/Homework
Complete the following worksheet from the worksheet
booklet:


8.7 – Gas exchange in humans
Gas exchange worksheet
ii.

Insects
Insects do not have lungs or blood capillaries because
they are small, they can achieve the exchange of gases
using a much simpler system.

Insects exchange gasses directly through a network of
tubes called tracheae which branch through the body.

They take in and expel air through structures called
spiracles (breathing pores).

Spiracles have valves to regulate their opening and closing.


This ensures they are not continually exposed to the drying effects of
the environment.
Abdominal muscles and the insects overall body movement,
controls the movement of air into the insects’ body through
these spiracles.
iii.

Fish
Gases such as oxygen, have a low solubility in water so
their concentration in water is much lower than in the
air.

As a result, fish have evolved features that allow the maximum
amount of oxygen absorption from their aquatic environment.

Fish possess gills which are formed from infolding of the
body wall.


They consist of curved bony gill arches with rows of folded gill
filaments that form an increased surface area for gas exchange.
They use the oxygen dissolved in water.
1.
2.
3.
As the fish swims, it opens its mouth so that water enters
and flows over the gills.
The fish then lifts its gill coverings, called gill slits to let out
the water.
As oxygen-rich water flows over the gills, gaseous exchange
takes place with the blood vessels lining the gill filaments.
iv.

Amphibian – Adult frog
Frogs are partly aquatic
(tadpole) and partly terrestrial
(adult).

Adult frogs have retained
certain respiratory
characteristics, typical of simple
aquatic organisms as well as
developing terrestrial features
(e.g. simple lungs).

Adult frogs use three surfaces for gaseous exchange:

The skin is the main site for respiration when the frog is in
water or when it is relatively inactive on land.

The skin is very well supplied with blood vessels.

The floor of the mouth is large and well supplied with blood
capillaries.


It serves as a pump, ventilating the lungs.
Some gaseous exchange may also occur across the inner lining of the
buccal cavity.

They have two simple, sac-like lungs and, although internal they
are not greatly folded like those typical of mammals.


Frogs only use their lungs for gaseous exchange when they are
physically active (e.g. during hopping and when on land).
The nostrils have valves which close to prevent the entry of water
into the lungs during swimming.
Classwork/Homework
Complete the following worksheet from the worksheet
booklet:

8.8 – Gas exchange in animals
Lung Dissection - DEMONSTRATION
Background Information
The lungs make up part of your respiratory system. When
you breathe, oxygen travels into the lungs to be used by the
rest of the body. When you inhale, the diaphragm contracts
and the lungs inflate.
Aim
 To observe the structure of the lungs and its movement
when breathing occurs.
 To relate the structure of the lung to how they work
when we breath.
Materials
 Sheep’s lung
 Dissecting tray
 Scalpel
 Forceps
 Safety glasses
 Safety gloves
 Electric pump
Risk Assessment
What is the risk?
Why is it a risk?
How do we reduce the
risk?
Method
1. Place the lungs facing forward on the dissecting tray.
2. Observe the structure and texture of the lungs.
3. Identify the different components of the respiratory
system you are able to observe.
4. Insert an electric pump into the trachea and exhale to
fill the lungs with air.
5. Observe and record the changes that occur when
modelling inhaling of the lungs.
6. Dispose of the lungs and gloves into the bio-hazardous
waste bag.
Results/Discussion
1. Describe the texture of the lungs. What is the reason
for this?
2. Identify 3 different structures of the respiratory system.
3. What change was observed as air was blown into the
lungs?
4. How does this organ (lung) change the composition of
the red blood cells passing through capillaries around it?
Building a model to demonstrate breathing
Aim
To model the action of the diaphragm in inhalation and
exhalation.
Materials
 1L Soft drink bottle
 Sticky tape
 2 Straws
 2 Balloons (medium)
 1 Balloon (large) to cover the end of the bottle
 Retractable utility knife/Scalpel
 Blue-tac
Risk Assessment
What is the risk?
Why is it a risk?
How do we reduce the
risk?
Method
1. Watch the YouTube Video “How to make lungs with
balloons”.
https://www.youtube.com/watch?v=6oMFAMqSlq4
2. Build a model to demonstrate how the actions of the
diaphragm inflate and deflate the lungs, using the
instructions in the video and the diagram.
3. To ensure your model works, pre-blow the balloons to
stretch them before placing them on the model and
ensure that your model is airtight.
Results
Draw a diagram of your model and label each of the parts
of the model with the name of the actual part of the
respiratory system that it represents.
Chapter 2: Nutrient and Gas Requirements
Inquiry question: What is the difference in nutrient and
gas requirements between autotrophs and heterotrophs?




Trace the digestion of foods in a mammalian digestive system, including:
- physical digestion
- chemical digestion
- absorption of nutrients, minerals and water
- elimination of solid waste

Digestion is the breaking down of large and complex food
particles into much smaller and simpler particles.


The aim of digestion is to break down the particles into
substances that are small enough to be absorbed through the
intestinal walls and into the bloodstream.
There are 2 types of digestion:


Physical
Chemical

Digestive enzymes can only act on the external surface of
food particles.


The smaller the particles are, the larger the surface area to
volume ratio is, resulting in faster breakdown of food and
absorption of important nutrients.
As large food molecules are broken down, salivary enzymes
are added to begin the chemical process of digestion.

Physical digestion continues along the digestive pathway
through the mechanical movements of the muscles
(churning) which further assist in the breakdown of food.
Pathway through the digestive system
i.


Mouth
After food enters the mouth,
physical/mechanical digestion begins
the process of breaking down food.
Teeth break the food up into
smaller pieces with greater surface
area for the more efficient action of
enzymes.

The salivary enzyme, amylase is released into the mouth,
mixed with the food and begins the breakdown of
complex carbohydrates such as starch into the simple
sugar, maltose.

Saliva produced from the salivary glands, lubricates the
food and along with the tongue and action of chewing,
form a ball shape called the bolus - this is easy to swallow.
ii.

Epiglottis
As the bolus moves from the mouth, it passes the
entrance to the trachea which is closed off by the
epiglottis (flap of skin).

This is essential to prevent food from passing down in to the
respiratory system and directs the bolus into the oesophagus.
iii.

Oesophagus
As the bolus enters the
oesophagus, it travels along the
soft-walled, muscle-ringed tube to
the stomach.


The bolus of food is pushed down
due to muscular contractions
(peristalsis).
Chemical digestion of starch
continues along the oesophagus.
iv.

Stomach
At the entry and exit of the stomach, there are narrow
openings whose opening and closing are controlled by
circular sphincter muscles.

These control the movement of substances into and out of the
stomach.

Once inside the stomach, relaxation and contraction of
the stomach walls continue the mechanical digestion.


The bolus breaks up into pieces that combine with gastric
juices found within the stomach to form a mixture (chyme).
Gastric juices secreted from the wall of the stomach contain:





water
hydrochloric acid (HCl)
pepsinogen (released by cells in the stomach wall, and upon mixing
with HCl activates to become pepsin)
pepsin (begins the breakdown of protein into peptide)
The chyme remains in the stomach for approximately 6 hours.
v.
Small intestine
The chyme from the stomach enters the small intestine
gradually through a sphincter.

The small intestine facilitates the
absorption of nutrients such as
glucose into the blood stream
through tiny projections called
villi which line the intestinal wall.


Villi increase the surface area for
much more efficient diffusion.
Villi are moist and once cell thick
with a large supply of capillaries.

The highly folded small intestine is approximately 7 meters
long in an adult and can be broken down into 3 regions:
1. Duodenum (start of the small intestine)

Food entering this section stimulates the release of a hormone
which intern simulates the release of pancreatic juices into the
area.


This juice contains enzymes amylase, trypsin and lipase which continue
the breakdown of proteins and carbohydrates.
Here bile can also be added if there are lipids present.
Jejunum (middle section)
2.
Most absorption of digestive products occurs here.
Has adaptations which increase the surface area available for the
adsorption of essential nutrients.




The products of digestion move into the cardiovascular system via
diffusion or active transport into the surrounding capillaries.
The tiny projections along the wall of the small intestines (villi), are
moist and are once cell thick; they have a rich supply of blood
through capillaries that are wrapped around it.
Ileum (end region)
3.

Passes the remaining material into the large intestine.
During the process of absorption in the small intestine:
The liver produces bile for
the breakdown of fats
which is stored in the gall
bladder until needed.
The pancreas produces
digestive enzymes, hormones
(insulin and glucagon) and
sodium bicarbonate.
vi.


Liver
Acts on the bloodstream coming from the small intestine.
Converts excess glucose into glycogen and removes
absorbed toxins from the body.
Large intestine
When all of the required digestive products have been
absorbed in the small intestine, the remaining materials
move to the large intestine.
vii.



This material is composed of substances such as water, salts
and dietary fibres.
The large intestine has 2 main sections:
1.
2.
Colon
Rectum
Colon
1.


In the colon, water and some salts are absorbed back into the blood
stream, compacting the undigested material into a more solid
structure.
Vitamins A and K are produced by bacteria in the colon acting on
the undigested matter and is absorbed into the blood stream.
Rectum
2.

The remaining waste material known as faeces moves into the
rectum and is egested from the body through the anus.
Classwork/Homework
Complete the following worksheet from the worksheet
booklet:


Activity 2: Digestive system diagram
Activity 3: Chemical and mechanical digestion
Chapter 2: Nutrient and Gas Requirements
Inquiry question: What is the difference in nutrient and
gas requirements between autotrophs and heterotrophs?





Compare the nutrient and gas requirements
of autotrophs and heterotrophs
Diffuses through the respiratory surface
Not required
Diffuses into roots
Produced by photosynthesis
Move into the plant through the roots
by diffusion and active transport
Activity – Summary + Questions
i.
ii.
Create a summary in your booklet, using the information on
‘Comparing nutrient and gas requirements’ to compare the
nutrient and gas requirements of autotrophs and
heterotrophs.
Use your summary, to answer Q1-3 on pg 163, in your
booklet.