Chapter 1

4.1. Introduction to Biology

Christoph Burgstedt / iStock.com

Page 4
4.1. Introduction to Biology
 4.1.1. What Is “Alive”?
Eva Onn / PPC

4.1.1. What Is “Alive”?

Learning objectives:
• To be able to identify which science topics belong to the field of biology.
• To be able to define “life”.
• To be able to explore the common ancestry of all life on Earth.

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4.1.1. What Is “Alive”?
 Knowledge
What is biology?
Biology is the science of life. Its name is derived from the Greek words «bios» (life) and «logos» (study).
Biologists study the structure, function, growth, origin, evolution and distribution of living organisms.
At least nine «umbrella» fields of biology are generally considered, each of which consisting of multiple subfields.

Biochemistry: the study of the material substances that Evolutionary biology: the study of the origins and
make up living things. changes in the diversity of life over time.
Botany: the study of plants, including agriculture. Genetics: the study of heredity.
Cellular biology: the study of the basic cellular units of Molecular biology: the study of biological molecules.
living things.
Physiology: the study of the functions of organisms and
Ecology: the study of how organisms interact with their their parts.
environment.
Zoology: the study of animals, including animal behavior.

These fields often overlap. For example, it is impossible to study zoology without knowledge about evolution,
4.1.1. What Is “Alive”?

physiology and ecology and you can’t study cellular biology without knowing biochemistry and molecular biology as
well.

Task
Fields of biology

There are many different fields of biology, each with their own distinct subfields. Research some of the different
fields of biology and their corresponding subfields then fill out the table below.

Fields of biology Subfields

Biochemistry Structural biochemistry, Metabolic biochemistry, Bio-organic chemistry

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4.1. Introduction to Biology
 Task
How do you know if something is alive?
At first this question appears to be very easy. However, technological advances make it more and more difficult to
define “alive.”
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4.1.1. What Is “Alive”?

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Read the following article from Australasian Science and afterwards write down your thoughts on citizenship for
robots.

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4.1. Introduction to Biology
 Interview

An AI professor explains: three concerns about granting citizenship to robot Sophia

By Hussein Abbass, Professor, School of Engineering and IT, UNSW-Canberra, UNSW

I was surprised to hear that a robot named Sophia was

granted citizenship by the Kingdom of Saudi Arabia.

The announcement last week followed the Kingdom’s

commitment of US$500 billion to build a new city powered
by robotics and renewables.

One of the most honourable concepts for a human being,

to be a citizen and all that brings with it, has been given to
a machine. As a professor who works daily on making AI
and autonomous systems more trustworthy, I don’t believe
human society is ready yet for citizen robots. To grant a
robot citizenship is a declaration of trust in a technology that
I believe is not yet trustworthy. It brings social and ethical
4.1.1. What Is “Alive”?

concerns that we as humans are not yet ready to manage. ITU Pictures / Wikimedia, https://fr.wikipedia.org/wiki/Sophia_(ro-
bot)#/media/Fichier:Sophia_at_the_AI_for_Good_Global_Sum-
mit_2018_(27254369347)_(cropped).jpg , https://creativecom-
mons.org/licenses/by/2.0/

Who is Sophia? Risk to citizenship

Sophia is a robot developed by the Hong Kong-based Citizenship – in my opinion, the most honourable status a
company Hanson Robotics. Sophia has a female face country grants for its people – is facing an existential risk.
that can display emotions. Sophia speaks English. Sophia As a researcher who advocates for designing autonomous
makes jokes. You could have a reasonably intelligent systems that are trustworthy, I know the technology is
conversation with Sophia. Sophia’s creator is Dr David not ready yet. We have many challenges that we need
Hanson, a 2007 PhD graduate from the University of to overcome before we can truly trust these systems.
Texas. For example, we don’t yet have reliable mechanisms
to assure us that these intelligent systems will always
behave ethically and in accordance with our moral values,
or to protect us against them taking a wrong action with
catastrophic consequences.

Here are three reasons I think it is a premature decision to

grant Sophia citizenship.

1. Defining identity
Citizenship is granted to a unique identity. Each of These and other technological identity management
us, humans I mean, possesses a unique signature that protocols are all possible, but they do not establish
distinguishes us from any other human. When we get Sophia’s identity – they can only establish hardware
through customs without talking to a human, our identity identity. What then is Sophia’s identity?
is automatically established using an image of our face,
iris and fingerprint. To me, identity is a multidimensional construct. It sits at
the intersection of who we are biologically, cognitively,
What gives Sophia her identity? Her MAC address? A and as defined by every experience, culture, and
barcode, a unique skin mark, an audio mark in her voice, environment we encountered. It’s not clear where Sophia
an electromagnetic signature similar to human brain fits in this description.
waves?

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4.1. Introduction to Biology
 Interview
2. Legal rights
For the purposes of this article, let’s assume that Sophia Sophia walks on wheels and has no skills for self-
the citizen robot is able to vote. But who is making the defence? Today, the artificial intelligence (AI) community
decision on voting day – Sophia or the manufacturer? is still debating what principles should govern the design
Presumably also Sophia the citizen is “liable” to pay and use of AI, let alone what the laws should be.
income taxes because Sophia has a legal identity
independent of its creator, the company. Sophia must also The most recent list proposes twenty-three principles
have the right for equal protection similar to other citizens known as the Asilomar AI Principles. Examples of these
by law. include: Failure Transparency (ascertaining the cause if
an AI system causes harm); Value Alignment (aligning
Consider this hypothetical scenario: a policeman sees the AI system’s goals with human values); and Recursive
Sophia and a woman each being attacked by a person. Self-Improvement (subjecting AI systems with abilities to
That policeman can only protect one of them: who should self-replicate to strict safety and control measures).
it be? Is it right if the policeman chooses Sophia because

3. Social rights
Let’s talk about relationships and reproduction. As a into other robots. These robots would also become
citizen, will Sophia, the humanoid emotional robot, be citizens. With no resource constraints on how many

4.1.1. What Is “Alive”?

allowed to “marry” or “breed” if Sophia chooses to? children each of these robots could have, they could easily
Students from North Dakota State University have taken exceed the human population of a nation.
steps to create a robot that self-replicates using 3D
printing technologies. As voting citizens, these robots could create societal
change. Laws might change, and suddenly humans could
If more robots join Sophia as citizens of the world, find themselves in a place they hadn’t imagined.
perhaps they too could claim their rights to self-replicate

Task
Do you think robots should be able to get citizenship? Justify your answer.
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4.1. Introduction to Biology
 Task

Life has no set, accepted definition on which all scientists agree. If you ask a biologist about the characteristics
of life you will get a different answer to that of a chemist or a physicist. Biologists have developed a list of eight
characteristics shared by all living organisms which are:

u Adaptation through evolution

v Cellular organisation

8 w Growth and development

Characteristics x Heredity
of Life y Homeostasis
z Metabolism
4.1.1. What Is “Alive”?

{ Reproduction
| Response to stimuli

Research and define the eight characteristics of life.

Adaptation through evolution Homeostasis

Cellular organisation Metabolism

Growth and development Reproduction

Heredity Response to stimuli

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4.1. Introduction to Biology
 Task
Research a chemist’s and physicist’s definition of life then discuss the different definitions of life.

Chemist’s definiton of life

Physicist’s definition of life

4.1.1. What Is “Alive”?

Task

Look at the following items. Imagine you would have to sort them. Which items would you group together? Justify
your answer.

Freepik

Page 11
4.1. Introduction to Biology
 Knowledge

Classifying organisms
There are millions of species on our planet. It would be the previous task. Taxonomy is the science of classifying
difficult if we just tried to describe and name each one organisms using morphological, behavioural, genetic and
individually. Although species can be very different from biochemical observations.
each other, many of them have similar features that
allow us to put them into groups, just like the objects of

Modern classification system

In the eighteenth-century Carl Linnaeus started the modern system of
putting species or organisms into certain groups and giving them scientific
names.
Each species is given a name using Latin words, so that the same name can
be used all over the world.
For example, the scientific name for human beings is ‘homo sapiens’.
4.1.1. What Is “Alive”?

Putting different species into different groups according to their

features is called classification.

There are seven major levels of classification: Kingdom, Phylum, Class,

Order, Family, Genus, and Species.
Alexandre Roslin — Nationalmuseum press photo
E. Onn / A. Velentini / PD via Wikimedia Commons
https://fr.wikipedia.org/wiki/Carl_von_
Linn%C3%A9#/media/Fichier:Carl_von_
Domain Linn%C3%A9.jpg

Kingdom Kingdom
All living organisms are first placed into three different domains
Phylum then kingdoms. There are six different kingdoms to classify
life on Earth, which are: archaea, bacteria, protista, fungi,
plantae, animalia.
Class

Order
Kingdom archaea Kingdom bacteria Kingdom protista
Family

Genus
Species
Kingdom fungi Kingdom plantae Kingdom animalia

A. Valentini / PPC

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4.1. Introduction to Biology
 Phylum
E. Onn / A. Velentini

Domain Organisms in a phylum share a set a characteristics that

distinguishes them from organisms in another phylum.
There are approximately thirty-five animal phyla, twelve
Kingdom
plant phyla, and seven phyla of fungi. The bacteria,
including the archaea, are grouped into roughly thirty-
Phylum four phyla, although the relationships between these
groups are not well established
Class Class
Class is a taxonomic rank (a taxon) consisting of
Order
organisms that share a common attribute; it is further
divided into one or more orders.
Family
Order
Genus Order is the taxonomic rank below the class and
comprises families sharing a set of similar nature or
Species character.

4.1.1. What Is “Alive”?

Family
A taxonomic group of one or more genera, especially
sharing a common attribute.

Species Genus
A biological species is a group of A genus is a group of closely related species.
organisms that can reproduce with one
another in nature and produce fertile
offspring.

Example of the
KINGDOM:
classification of Animalia
humans:
PHYLUM:
Chordata
CLASS:
Mammalia
ORDER:
Primates
FAMILY:
Hominidae
GENUS:
Homo Adult human
SPECIES: female and male
Homo sapiens
(Homo sapiens)
S. Coté / Freepik

Page 13
4.1. Introduction to Biology
 Task
Classify the following organisms.

Horse

Kingdom (Kingdoms)

Phylum (Phyla)

Class (Classes)

Order (Orders)

Family (Families)

Genus (Genera)
4.1.1. What Is “Alive”?

Species

Mango

Kingdom (Kingdoms)

Phylum (Phyla)

Class (Classes)

Order (Orders)

Family (Families)

Genus (Genera)

Species

Western honeybee

Kingdom (Kingdoms)

Phylum (Phyla)

Class (Classes)

Order (Orders)

Family (Families)

Genus (Genera)

Species

Page 14
4.1. Introduction to Biology
 Knowledge
Phylogenetic tree
Based on the similarities and differences between Simply put, the phylogenetic tree, often known as a
organisms and species a phylogenetic tree can be “tree of life” is constructed based on the evolutionary
constructed. relationship between different organisms and/or species.

Squids, Cuttlefish and Octopi

Crustaceans
Snails and Slugs
Tree of life Worms and Leeches
Jellyfish Animals
Insects
Bivalves Mammals
Urchins
Corals and Anemones Birds
Arachnids Reptiles and Amphibians
Bacteria Archaea Invertebrates Fish
Spirochetes Green Vertebrates

4.1.1. What Is “Alive”?

Halophiles Horsetails
Filamentous
Proteobacteria Gram Methanosarcina
bacteria Methobacterium Animals Club Mosses Ferns
positives Plants Plants
Cyanobacteria Methanococcus Hornworts Seed plants
Plantocmyces T. celer Fungi Mosses Gymnosperms
Ciliates Liverworts
Thermoproteus Flowering plants
Bacteroides Pyrodictium
Cytophaga Flagellates
Thermotoga Trichomonads
Aquifex Microsporidia
Diplomonads
Viruses Viruses
Living or non living? Eucaryota Diagram: S. Coté

Luca
S. Coté / PPC

descendants A B C D

The root of the tree represents the ancestral

lineage, and the tips of the branches represent the
descendants of that ancestor. As you move from the
times

tips to the root, you are moving backward in time

until you reach the Last Universal Common Ancestor
(LUCA).
ancestor

Task
Read different articles about LUCA, then share your information with the class.

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4.1. Introduction to Biology
 Chapter 2

4.2. Cells

CueImages / K6WR3F / Alamy

Page 16
4.2. Cells
 4.2.1. The Cell Theory

Ozgu Arslan/ iStock.com

4.2.1 The cell theory

Learning objectives:
• To be able to define cells as the basic unit on Earth.
• To be able to explain the shared attributes of all cells.

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4.2.1. The cell theory
 Task
What is a cell?
Research and write down a definition of cells.
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4.2.1. The Cell Theory

Task
Types of cells

There are many different types of cells. Research some different types of cells and print out or draw a picture of
them in the following table. Also, for each briefly state their function.

Picture Type of cells Function

1
Neuron A nerve cell is a basic functional unit of the nervous
system that transmits information from the body to
(Nerve cell) the brain and back again.

1. Neuron : Nicola Rougier / GPLv3 via Wikimedia, https://ast.wikipedia.org/wiki/Neurona#/media/Ficheru:Neuron-SEM.png

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4.2. Cells
 Task
Continued

Picture Type of cell Function

4.2.1. The Cell Theory

Knowledge
There are many different types of cells, however all cells possess these simple attributes.

1. A boundary between 2. Instructions for the cell to

inside and outside. build and maintain itself.

Animals cells Plant cells Fungal cells

Christogra4/ iStock.com Martin Almqvist / Alamy SDym Photography / Alamy

3. Machinery to execute the 4. Means to convert energy

instructions. into useful forms.

Page 19
4.2. Cells
 Knowledge

Two categories of cells on Earth

Prokaryotic cell
All cells on Earth can be classified as either prokaryotic cells or
eukaryotic cells. Eukaryotic organisms may be multicellular or
unicellular, but prokaryotes are always unicellular organisms.
Eukaryotic cells are larger and more complex than prokaryotes, and
usually contain organelles that are absent from prokaryotic cells.
This is because eukaryotes contain membrane-bound organelles
(like the nucleus, endoplasmic reticulum, Golgi apparatus, and
mitochondria), while prokaryotes do not.
Eukaryotic cell
A. Valentini / PPC

Types of prokaryotic cells

4.2.1. The Cell Theory

Prokaryotic cells are smaller and have a simpler structure than eukaryotic cells, as they do
not contain membrane-bound organelles. Prokaryotic organisms are always unicellular
and may be either bacteria or archaea. Bacterial and archaeal cells have the same basic
structure, but some of their components are made from different materials.

Bacterial cells
Bacterial cells have a cell membrane, cytoplasm, ribosomes, and free-floating loops of
DNA. Bacterial cells also have a cell wall made from a polymer called peptidoglycan (AKA
murein). Some bacteria have additional specialized structures, like the capsule (a sticky
layer of carbohydrates that surrounds the cell), or flagella (whip-like structures that allow
the bacterium to move).

Archaeal cells
Bacteria
Archaea are also unicellular prokaryotes, Nucleoid
and they contain many of the same
Pilus
structures that are found in bacteria
cells. However, they typically have a
different composition. For example, the
bacterial cell wall contains peptidoglycan, Pilius, Hamus,
or Cannulae
but the archaeal cell wall does not. The Ribosome
plasma membrane in bacterial cells (and
eukaryotes) is a lipid bilayer, but the Nucleoid
Cell wall and
plasma membrane of archaeal cells is a capsule Archaellum
lipid monolayer. Finally, the cell membrane
in bacteria contains fatty acids, while the cell
membranes of archaea contain a hydrocarbon Cytoplasm
called phytanyl.
Plasma membrane

Cell wall

A. Valentini / PPC
Archaea

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4.2. Cells
 Knowledge
Types of eukaryotic cells
The four types of eukaryotic cells are animal cells, plant cells, fungi cells, and protists.

Animal cells A. Valentini / PPC

Animal cells are the basic building blocks that make up all animals, including
birds, fish, reptiles, mammals, and amphibians. Like eukaryotic cells, they contain
membrane-bound organelles (such as a nucleus, mitochondria, Golgi apparatus,
and endoplasmic reticulum), and are surrounded by a plasma membrane.

Plant cells
Plants are made up of plant cells. Plant cells contain many of the organelles
common to all eukaryotes, but they contain additional structures that are
not found in animal cells. For example, plant cells are surrounded by a tough,
cellulose-based structure called the cell wall. They also contain organelles called
chloroplasts, which are the site of photosynthesis and allow plant cells to produce
carbohydrates from carbon dioxide, water, and light energy.

4.2.1. The Cell Theory

Fungi cells
The fungi kingdom consists of yeasts, mildews, molds, and mushrooms. Fungi cells
contain many of the structures and organelles found in plant and animal cells, like the
nucleus, cell membrane, mitochondria, Golgi apparatus, and endoplasmic reticulum.
However, they do not contain chloroplasts. They do have a cell wall but this is mainly
composed of a polysaccharide called chitin, rather than cellulose (as is the case in
plant cells).

A. Valentini / PPC
Protist cells
Protists are a highly diverse group of organisms, and kingdom protista is comprised
of all eukaryotes that are not animals, plants, or fungi. Protist cells contain all of the
membrane-bound organelles found in animal cells, and some types also contain
chloroplasts. They may also have a cell wall made from cellulose.

A. Valentini / PPC

A. Valentini / PPC

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4.2. Cells
 Knowledge

The first cell Life time line

It appears that life first emerged at least 3.8 billion years ago, 0
P Flowers
Earliest humans

approximately 750 million years after Earth was formed. The first h
a
Mammals
Dinosaurs
cells, called the last universal common ancestor (LUCA) consisted of n
r
Land life
-500
little more than an organic molecule such as RNA (Ribonucleic acid) z
c
Cambrian explosion

inside a lipid membrane. They gave rise to all subsequent life on Multicellular
life
Earth. How life originated and how the first cell came into being are -1 000

matters of speculation, since these events cannot be reproduced in P Earliest sexual

reproduction
r
the laboratory. o
t
The first cells were prokaryotes followed by eukaryotes which -1 500
e
r
scientists believe evolved from prokaryotes around 2.7 billion o
years ago. The primary distinction between these two types of -2 000
z
o
Eukaryotes

organisms is that prokaryotic cells do not have a membrane-bound i

c
nucleus, while eukaryotic cells have a membrane-bound nucleus. Oxygen crisis
-2 500
Inside this nucleus eukaryotes store their genetic material, while in Atmospheric
oxygen
prokaryotes, DNA is bundled together in the nucleoid region, but it is
4.2.1. The Cell Theory

A
not stored within a ­membrane-bound nucleus. -3 000
r
c Photosynthesis
h
e
a
n
-3 500 Earliest oxygen

Single-celled
LHB meteorites
H life
The endosymbiotic theory -4 000 a
d Earliest life
e (-4 100)
a Water
n Earliest water
-4 500 Earliest Earth (-4 540)

Endosymbiosis is a term used to describe two organisms living together Axis scale: million of years
Wikipedia contributors. (2023, November 28). Timeline of
with one inside the other. The word endosymbiont comes from two the evolutionary history of life. In Wikipedia, from https://
Greek root words: endo, meaning within, and symbios meaning, living en.wikipedia.org/w/index.php?title=Timeline_of_the_evolu-
tionary_history_of_life&oldid=1187391637
together.
An endosymbiont is a cell which lives inside another cell with mutual benefit. Many different types of eukaryotic
cells are believed to have evolved from these early prokaryotes that were engulfed by phagocytosis. The engulfed
prokaryotic cell remained undigested as it contributed new functionality to the engulfing cell (e.g. photosynthesis).
Over generations, the engulfed cell lost some of its independent utility and became a supplemental organelle. Two cell
organelles (“little organs of the cells”) that are believed to have once been independent, free-living bacterial prokaryotic
cells, which at some point have been engulfed by a eukaryotic cell, are mitochondria and chloroplast.

Overview of the process of endosymbiosis

Nucleus forming Cyanobacterium

Aerobic
bacterium
Ancestral Infolding of Endosymbiosis Ancestral
prokaryote plasma membrane eukaryote
A. Valentini / PPC

They resemble, in many ways, primitive single-celled prokaryotes. They have a double membraned structure
and possess their own unique DNA; distinct from the DNA of the cells nucleus. The outer membranes of the
mitochondrion and chloroplast resemble those found in eukaryotic or complex cells, while the inner membranes
resemble those found in prokaryotic or primitive bacterial cells.

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4.2. Cells
 Task

Model a prokaryotic cell

Create a 2D or 3D model of a prokaryote. There are

many different methods on the internet for creating a
model of a prokaryote . Some use bottles, others use
modelling clay or coloured card. Use the space below
to plan your model.

A. Valentini / PPC

4.2.1. The Cell Theory

Page 23
4.2. Cells
 NOTES

4.2. Cells
4.2.1. The Cell Theory

Page 24
4.2. Cells
4.2.2. Cell Structure and Function

A. Valentini / PPC

4.2.2 Cell Structure and Function

Learning objectives:
• To be able to identify a great variety of cells.
• To be able to identify cell organelles using a light microscope.
• To be able to explain the origin of new cells and that chromosomes are the
bearers of the cell’s instructions.

Page 25
4.2.1. The cell theory
 Microscopy
Ocular lens
(Eyepiece)
Body tube

A light microscope is an optical instrument

which allows us to view objects too small
to see with the naked eye. It is so-called Revolving
because it uses white or visible light to Arm nosepiece
illuminate the object of interest so it can Objectives
be magnified and viewed through one or a
series of lenses. Stage clips
Stage
Coarse adjustment Diaphragm
4.2.2. Cell Structure and Function

knob
Light source
Fine adjustment
knob

Base

Thomas-Soellner/ iStock.com

Task
Research the functions of the different parts of the light microscope and record them in the following table.

Part of the microscope Function

Ocular lens

Body tube

Revolving nosepiece

Objectives

Arm

Stage

Stage clips

Diaphragm

Light source

Coarse adjustment knob

Fine adjustment knob

Base

Page 26
4.2. Cells
 Knowledge

How to use the microscope:

1. Connect the light microscope to a power source and 7. Adjust the condenser for the maximum amount of
turn it on. light. Since you’re on the low magnification objective,
you may have to decrease the illumination. Use the
2. Move the stage down to the bottom by turning the
diaphragm under the stage to adjust.
coarse adjustment knob.
8. Now slowly rotate the fine adjustment knob until you
3. Turn the revolving nosepiece until the lowest
obtain a clearer image of your specimen.
magnification objective lens is in position.
9. Examine your specimen and create your drawings.
4. Mount your specimen onto the stage.
10. After you’re done viewing with the lowest magnifying
5. Use the stage clips to keep your slide in place. Make
objective, switch to the medium magnifying objective
sure the specimen is positioned in the center, right

4.2.2. Cell Structure and Function

and re-adjust the focus with the fine adjustment
under the lowest objective lens.
knob.
6. Look into the eyepiece and slowly rotate the coarse
11. Proceed to the high magnification objective once you
adjustment knob to bring your specimen to focus. Be
have it focused.
careful that the slide does not touch the lens.

How to stain a slide:

1. Place one drop of stain (iodine, methylene blue, or any 3. As soon as the stain has covered the area containing
other stain) on the edge of the coverslip. the specimen, you are finished. The stain does not
need to be under the entire coverslip. If the stain does
2. Place the flat edge of a piece of paper towel on the
not cover as needed, get a new piece of paper towel
opposite side of the coverslip. The paper towel will
and add more stain until it does.
draw the water out from under the coverslip, and the
cohesion of water will draw the stain in. 4. Be sure to wipe off the excess stain with a paper
towel.

Drawing specimens:
Membrane en miniscule
1. Use pencil - you can erase and shade areas viewing field, make sure your drawing reflects that.
For example:
2. All drawings should include clear and proper labels
S. Coté / PPC
(and be large enough to view
details). Drawings should be labeled
with the specimen name and Cell membrane
magnification.
3. Labels should be written on the
outside of the circle. The circle
indicates the viewing field as seen
through the eyepiece, specimens
should be drawn to scale - ie..if Nucleus
Nucleus
your specimen takes up the whole
Ameba (100x) Ameba (400x)

Page 27
4.2. Cells
 Advice
Troubleshooting:

Occasionally you may have trouble with working your ocular lens can be removed to clean the inside (ask
microscope. Here are some common problems and your teacher for help).
solutions.
3. I can’t see anything with the high magnification.
1. Image is too dark.
Remember the steps, if you can’t focus the low
Make sure your light is on and possibly adjust the magnification, you won’t be able to focus the high
diaphragm. magnification.
2. There’s a spot in my viewing field, even when I move 4. Only half of my viewing field is lit, it looks like there’s a
the slide the spot stays in the same place. half-moon in there.
Your lens is dirty. Use lens paper, and only lens paper You probably don’t have your objective fully clicked
to carefully clean the objective and ocular lens. The into place.
4.2.2. Cell Structure and Function

Task
Preparing a mount:
Plant cell: The following examples give you two choices
of observing plant cells, either using Elodea or onions.

Elodea (pondweed) cells

Materials: Method:
• Microscope slides 1. Pick off a healthy looking Elodea leaf, with your fingers
• Cover slips or small scissors and place it on the microscope slide.

• Paper towels 2. Add a drop of water onto the Elodea and a coverslip
and observe the mount using a microscope.
• Elodea
• Water

Onion cells
Materials: Method:
• Microscope slides 1. Place a small drop of water on a microscope slide.
• Cover slips 2. Cut the onion into sections. Take a piece from one of
• Pipettes the sections and peel off a small, thin piece of the
onion skin with either tweezers or your fingers.
• Water
3. Place the onion skin onto the drop of water on the
• Onion microscope slide.
• Knife 4. Cover the onion skin with a cover slip.
• Cutting board 5. Stain the onion skin with iodine ( the iodine will bind
• Tweezers to the starch in the cell wall and nucleus of the onion
cells, staining them, and making them easier visible).
• Iodine solution
6. Observe the mount using a microscope.

Page 28
4.2. Cells
 Task
Animal cell
Human cheek cells
Materials: Method:
• Microscope slides 1. Take a clean cotton swab and gently scrape the inside
of your mouth.
• Cover slips
2. Smear the cotton swab on the centre of the
• Paper towels or tissue
microscope slide for two to three seconds.
• Methylene blue solution (0.5% to 1% (mix
3. Add a drop of methylene blue solution and place a
approximately one part stock solution with four
coverslip on top. (Concentrated methylene blue is
parts of water))
toxic if ingested. Wear gloves and do NOT allow young
• Pipette children to handle methylene blue solution or have

4.2.2. Cell Structure and Function

• Sterile cotton swabs access to the bottle of solution.)
4. Remove any excess solution by allowing a paper towel
to touch one side of the coverslip.
5. Observe the mount using a microscope.

Fungi cell
Yeast
Materials: Method:
• Microscope slides 1. Dissolve the fresh yeast in the warm water (if you
use dried active yeast the dissolving will take a little
• Cover slips
longer).
• Fresh yeast (alternative dried active yeast)
2. Place a drop of the yeast mixture on the microscope
• Pipette slide.
• Small beaker with warm water 3. Place a coverslip on top.
4. Observe the mount using a microscope.

Extension: Bacteria
Yoghurt bacteria
Materials: Method:
• Microscope slides 1. Take a very small drop of yogurt with the toothpick and
smear it for two to three seconds on the slide.
• Cover slips
2. Place a small drop of methylene blue solution on
• Yogurt with live culture (eg: Actimel, Activia,
a microscope slide (optional). Wear gloves and do
Yakhult)
NOT allow young children to handle methylene blue
• Toothpicks solution.
• Paper towels or tissues 3. Place a coverslip on top. Remove excess solution
• Methylene blue solution (0.5 to 1%) Optional around the coverslip with a paper towel or tissue.
4. Observe the mount using a microscope.

Page 29
4.2. Cells
 Task
Microscopy of animal, plant and fungal cells (extension bacteria)
Prepare the mounts as previously described and draw your observations.

Plant cells: Specimen name...............................................

4.2.2. Cell Structure and Function

Magnification:.................................. Magnification:..................................... Magnification:....................

Animal cell: Specimen name...............................................

Magnification:.................................. Magnification:..................................... Magnification:....................

Fungi cell: Specimen name...............................................

Magnification:.................................. Magnification:..................................... Magnification:....................

Extension: Bacteria: Specimen name...............................................

Magnification:.................................. Magnification:..................................... Magnification:....................

Page 30
4.2. Cells
 Knowledge
Structure of animal, plant, fungal and bacteria cells

animal cellnucleus ribosomes

endoplasmic
plant cell A. Valentini / PPC
cell membrane
reticulum
plasma vacuole ribosomes
centrioles membrane endoplasmic
(centrosome) reticulum
mitochondrion

chloroplast
nucleolus
chromosomes

mitochondrion

4.2.2. Cell Structure and Function

A. Valentini / PPC

vacuole cytoplasm

Golki complex nucleolus cell wall

plasmodesma
Nucleus
bacteria cell
A. Valentini / PPC
(bacillus type) cytoplasm

flagela
ribosomes
chromosomes

capsule mesosome plasma pili

membrane

golgi apparatus yeast cell structures

lipid granule
(fungal cell)

vacuole
mitochondria

cell wall cytoplasm

membrane

nucleus
A. Valentini / PPC

Page 31
4.2. Cells
 Task
Comparing cells: animal, plant, bacteria and yeast
Chose a different colour for each cell organelle and if the organelle is present in the cell colour it in.

Cell part Animal Plant Bacteria Yeast

chloroplasts
4.2.2. Cell Structure and Function

cytoplasm

DNA

membranes

mitochondria

nuclei

vacuoles

walls

A. Valentini / PPC

Page 32
4.2. Cells
 Task
Research the functions of the following cell organelles

Cell organelle Function

nucleus

ribosomes

smooth endoplasmic

4.2.2. Cell Structure and Function

­reticulum

rough endoplasmic
­reticulum

golgi apparatus

lysosomes

mitochondria

chloroplast

cytoskeleton

vacuole

plasma membrane

cell wall

Page 33
4.2. Cells
 Task

Model an animal or plant cell

Create a 2D or 3D model of an animal or plant

cell. There are many different methods on the
internet for creating a model of an animal or plant
cell. Some use gelatin, others use modelling clay
or coloured card. Use the space below to plan
your model.

A. Valentini / PPC
4.2.2. Cell Structure and Function

Page 34
4.2. Cells
 Task
Optional: Specialised animal cells
Read the description of the following specialised animal cells and try to match them to the pictures.

......................................... ......................................... ......................................... ......................................... .........................................

......................................... ......................................... ......................................... ......................................... .........................................

4.2.2. Cell Structure and Function

A. Valentini / PPC

......................................... .........................................

......................................... .........................................
Red blood cell Nerve cells
A red blood cell has no nucleus. This lack of nucleus Nerve cells (or neurons) string together like wires to
gives it room to carry more oxygen from the lungs to carry electrical signals very quickly throughout the
other cells all over the body. Unlike most cells that stick body, especially the brain. The messages they carry
together to form large structures, red blood cells must include telling muscles to move and sensing (sight,
flow through blood vessels, so they are round and stay sound, touch, temperature, pain, etc.). Branches at the
separate. ends of nerve cells create complex networks of multiple
neurons connecting to each other.
Squamous cells
The barrier these flat cells form protects the body,
keeping moisture in and germs out. They are the top Intestinal cells
layer of skin and line our insides too, as in the mouth, After the stomach breaks down food, intestinal
blood vessels, lungs, heart, digestive system, and so on. absorptive cells take in nutrients through their
These scale-like cells overlap like shingles / roof tiles. “microvilli.» These tiny finger-like structures increase
the total surface area of the cell membranes, making it
Muscle cells easier to absorb lots of nutrients.
The muscles that move your fingers, arms, legs, and so
on are each made of millions of skeletal muscle cells
all bundled together. These long, thin fibers become Bone cells
shorter and thicker when they contract. Most cells have Bone cells deposit hard, calcium-rich material around
just one nucleus. Not these! They have many. themselves. Thin tunnels allow bone cells to stay
connected so that they can receive signals, oxygen, and
Macrophage nutrition.
A macrophage is a kind of white blood cell that crawls
around inside your body hunting for germs. When it
finds some, the macrophage reaches out and grabs it
with a gooey arm called a “pseudopod” (which means
“fake limb”).

Page 35
4.2. Cells
 Task
Optional: Specialised plant cells
Read the description of the following specialised plant cells and try to match them to the pictures.

A. Valentini / PPC
......................................... ......................................... ......................................... .........................................
4.2.2. Cell Structure and Function

......................................... ......................................... ......................................... .........................................

A. Valentini / PPC

......................................... ......................................... .........................................

......................................... ......................................... .........................................

Spongy leaf cells Palisade cells

Because they are round and don’t pack as closely Block-shaped palisade cells are full of chloroplasts. Their
together as other plant cells, spongy leaf cells are tall shape allows them to capture more light and carbon
surrounded by plenty of air space where gases move in dioxide for photosynthesis.
and out.
Root hair cells
Guard cells Found near the tips of roots, root hair cells stick out into
The walls of guard cells are thin on the outside and thick the soil. Water enters them easily through their thin walls.
on the inside. This structure helps them open and close Because roots are underground and in the dark, they have
holes that allow water vapor and gases in and out of no chloroplasts.
leaves.
Xylem Phloem cells
Xylem is made up of tube-shaped cells that bring water in
Phloem cells form long, tall tubes through which sugar
one direction: up to the leaves from the roots. As they die,
and other foods are sent back and forth around the plant.
the thick walls become thin, woody tubes.
Their walls have hole-filled ends called sieve plates. They
Epidermis cells have little cytoplasm and no nucleus.
The waxy, waterproof surfaces of epidermis cells protect
the plant. They lay close together to form a layer of skin
around the plant.

Page 36
4.2. Cells
 Knowledge

Cell division

Why do cells divide?

Cells divide for many reasons. For example, when you injure your
skin new cells are needed for healing the wound. Or cells divide
to replace old, dead, or damaged cells. Cells also divide so living
things can grow. When organisms grow, it isn’t because cells
are getting larger. Organisms grow because cells are dividing to
produce more and more cells. In human bodies, nearly two trillion
cells divide every day.

anusorn nakdee / iStock.com

4.2.2. Cell Structure and Function

How do cells know when to divide?
In cell division, the cell that is dividing is called the it is supposed to stop, this can lead to cancer. Some
«parent» cell. The parent cell divides into two «daughter» cells, like skin cells, are constantly dividing. We need to
cells. The process then repeats in what is called the cell continuously make new skin cells to replace the skin cells
cycle. Cells regulate their division by communicating with we lose. Did you know we lose 30,000 to 40,000 dead
each other using chemical signals from special proteins skin cells every minute? That means we lose around 50
called cyclins. These signals act like switches to tell cells million cells every day. This is a lot of skin cells to replace,
when to start dividing and later when to stop dividing. It making cell division in skin cells so important. Other cells,
is important for cells to divide so you can grow and so like nerve and brain cells, divide much less often.
your cuts heal. It is also important for cells to stop dividing
at the right time. If a cell cannot stop dividing when

How cells divide

Depending on the type of cell, there are two ways cells for basic growth, repair, and maintenance. In meiosis a
divide—mitosis and meiosis. Each of these methods of cell divides into four cells that have half the number of
cell division has special characteristics. One of the key chromosomes. Reducing the number of chromosomes
differences in mitosis is a single cell divides into two by half is important for sexual reproduction and provides
cells that are replicas of each other and have the same for genetic diversity.
number of chromosomes. This type of cell division is good

Mitosis cell division

Mitosis is how somatic—or non-reproductive cells—divide. Somatic cells make up
most of your body’s tissues and organs, including skin, muscles, lungs, gut, and
hair cells. Reproductive cells (sperm and eggs) are not somatic cells.
In mitosis, the important thing to remember is that the daughter cells each have
the same chromosomes and DNA as the parent cell. The daughter cells from
mitosis are called diploid cells. Diploid cells have two
complete sets of chromosomes. Since the daughter
cells have exact copies of their parent cell’s DNA,
no genetic diversity is created through mitosis in Two diploid cells
normal healthy cells. Mitosis cell division creates two DNA
replication

genetically identical daughter diploid cells. The major

steps of mitosis are as follows. Mitosis

A. Valentini / PPC

Page 37
4.2. Cells
 Knowledge
The mitosis cell cycle
4.2. Cells
Before a cell starts dividing, it is in the «interphase.» It
Cell growth
S. Coté / PPC

seems that cells must be constantly dividing (remember Phase

G1
there are 2 trillion cell divisions in your body every day), Cy
tok
in
but each cell actually spends most of its time in the Telo
esi
s
p hase
interphase. Interphase is the period when a cell is getting Cell Anaphas

Inte
e Cell
ready to divide and start the cell cycle. During this time, division

rphase
Metaphase division

Mitosis
cells are gathering nutrients and energy. The parent cell

ase
h ase
Prop
is also making a copy of its DNA to share equally between

io n
Ph
the two daughter cells.

c at
G2
Ph

S
Pre
ase

p li
re
pa
at
The mitosis division process has several steps or phases io
DN

A
nf
4.2.2. Cell Structure and Function

or
of the cell cycle—interphase, prophase, prometaphase, m it oté
Dia gra m : S . C

o sis
metaphase, anaphase, telophase, and cytokinesis—
to successfully make the new diploid cells. When down before mitosis and reassembles in each of the new
a cell divides during mitosis, some organelles are daughter cells. Many of the specifics about what happens
divided between the two daughter cells. For example, to organelles before, during and after cell division are
mitochondria are capable of growing and dividing during currently being researched.
the interphase, so the daughter cells each have enough
mitochondria. The Golgi apparatus, however, breaks

Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis

- Chromosomes - Chromosomes - Chromosomes - Centromeres split - Chromosomes - Animals cells: a

condense and continue to are lined up at the in two arrive at opposite cleavage furrow
become visible condense metaphase plate poles and begin to separates the
- Sister chromatids decondense daughter cells
- Spindle fibers - Kinetochores appear - Each sister (now called
emerge from the at the centromeres chromatid is chromosomes) - Nuclear envelope - Plants cells: a cell
centrosomes attached to a are pulled toward material surrounds plate, the precursor
- Mitotic spindle spindle fiber opposite poles each set of to a new cell wall,
- Nuclear envelope microtubules attach originating from chromosomes separates the
breaks down to kinetochores opposite poles - Certain spindle daughter cells
fibers begin to - The mitotic spindle
- Centrosomes move elongate the cell breaks down
toward opposite
poles - Spindle fibers
continue to push
poles apart

MITOSIS
A. Valentini / PPC

Page 38
4.2. Cells
 4.2.3. Single-Celled Organisms

wir0man / iStock.com

4.2.3 Single-Celled Organisms

Learning objectives:
• To be able to recognise that single-celled organisms make up the majority of
living things on earth.

Page 39
4.2.1. The cell theory
 Knowledge
Examples of unicellular organisms
Single-celled organisms
Single-celled organisms, also known
u All bacteria
as unicellular organisms are organisms E. Coli Streptococcus Halobacteria
consisting of one cell only which performs PHIL / PD via Wikimedia
all vital functions including metabolism, Rocky Mountain Laboratories
/ PD via Wikimedia
https://fr.wikipedia.org/ NASA / PD via Wikimedia
wiki/Streptocoque#/media/ https://fr.wikipedia.org/wiki/
excretion, and reproduction within this one https://fr.wikipedia.org/wiki/ Fichier:Streptococcus_py- Halobacteria#/media/Fi-
Escherichia_coli
cell. Single-celled organisms are neither ogenes.jpg chier:Halobacteria.jpg

plants nor animals, yet they are some of the v All protists
most important life forms on Earth. Single-
Amoeba Euglena Paramecium
celled organisms can either be prokaryotes Petit Rex / CC BY-SA 4.0 via
or eukaryotes. Examples of single-celled Wikimedia
https://en.wikipedia.org/wiki/
Barfooz / CC BY-SA 3.0via
organisms are bacteria, archaea, unicellular Amoeba#/media/File:Amoe-
Wikimedia
https://fr.wikipedia.org/wiki/
ba_proteus_with_many_pseu-
fungi, and unicellular protists. Even though dopodia.jpg
Param%C3%A9cie#/media/
wir0man / iStock.com Fichier:Paramecium.jpg
single-celled organisms are not seen by the
4.2.3. Single-celled organisms

naked eye, they have an indispensable role w Some algae

in the environment, industry, and medicine. Chlorella Chlamydomonas Saccharomyces
Mogana Das
Murtey et Patchamuthu
Some of them may also be infectious or NEON / CC BY-SA 3.0 via
Wikimedia
Dartmouth College / PD via
Wikimedia
Ramasamy / CC BY 3.0 via
Wikimedia
pathogenic to humans, animals, and plants. https://fr.wikipedia.org/wiki/ https://fr.wikipedia.org/wiki/ https://fr.wikipedia.org/wiki/
Chlorella_vulgaris#/media/ Chlamydomonas#/media/ Saccharomycetaceae#/me-
Fichier:Chlorella_vulga- Fichier:Chlamydomonas_ dia/Fichier:Saccharomyces_
ris_NIES2170.jpg (10000x).jpg cerevisiae_SEM.jpg

Task
Single-celled organisms are essential for the life and wellbeing of all other creatures on Earth. They can
produce useful substances, decay dead matter, and protect other creatures from some infections.
Research and briefly describe the function of the following single-celled organisms.

Single-celled
Function
organism

Phytoplanktons

Amoebae

Nitrosomonas and
Nitrobacter

Euglena

Page 40
4.2. Cells
 Task
Microscopy of pond water or hay infusion. You could also do microscopy of yeast cultures or yogurt
if you have not already done this during the previous section.
Prepare the mounts as previously described and draw your observations.

How to make a hay infusion

Put a small handful of hay or other dry plant band) and place it in a warm, bright spot (at least
material like leaves or moss into a large (approx. 1L) at room temperature, but without direct sunlight).
jar and add about 500mL of water. Ideal is water The infusion can start to smell especially with too
from a pond or aquarium. Cover the jar loosely much hay, this should be taken into account when
(e. g. with a piece of kitchen towel and a rubber choosing the location.

Materials: Method:

4.2.3. Single-celled organisms

• Jar of pond water or hay infusion 1. Place a drop of the pond water or hay infusion
on the microscope slide.
• Microscope slides
2. Place a coverslip on top.
• Cover slips
3. Observe the mount using a microscope.
• Pipette

Specimen name: .............................................................................

Magnification: ................................................ Magnification: ................................................ Magnification: ................................................

Specimen name: .............................................................................

Magnification: ................................................ Magnification: ................................................ Magnification: ................................................

Page 41
4.2. Cells
 4. Tissues
2. Molecules
Chapter 3

4.3. Levels of Organisation

in Living Things
1. Atoms

5. Organs and organ systems

3. Cells

6. Organisms

7. Community

9. Biosphere
8. Ecosystem

Page 42
4.3. Levels of Organisation in Living Things
 4.3.1. Levels of organisation
from chemical elements
to multicellular organisms

S. Coté / PPC

4.3.1 Multicellular organisms

Learning objectives:
• To be able to name the chemical elements of which organisms are composed.
• To be able to identify the principal categories of molecules in organisms.
• To be able to explain the levels of organisation in multicellular organisms.

Page 43
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Knowledge
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Elements of life - CHNOPS

The six most common elements in all living things

are Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen
(O), Phosphorus (P), and Sulfur (S). They are often
abbreviated as CHNOPS. These six elements are very
good at constructing complex biomolecules, the
molecules involved in life. These six elements also make
up organic molecules, all of which contain carbon and
hydrogen, as well as inorganic molecules.

Carbon
Freepik
Carbon forms strong covalent bonds (where electrons involved in the metabolism of energy in even the
are shared between two atoms). Carbon can bond with simplest cell structures. Oxygen is not required for all
up to four atoms at the same time. Therefore, many organisms on Earth to survive (some microorganisms
kinds of molecules can be created from carbon. Along thrive in the absence of oxygen) however, oxygen is still
with the other five elements (H, N, O, P, & S) carbon present in those organisms in the form of water and
makes up carbohydrates, proteins, nucleic acids, and organic molecules.
lipids. From a molecule like methane (CH4) to complex
molecules like long hydrocarbons (such as those found Phosphorus
in fossil fuels) carbon’s versatility makes it essential to all
life as we know it. Phosphorus can be found in the backbone of the
DNA molecule. Phosphorus has a vital role in energy
Hydrogen metabolism since it makes up a cell’s energy molecules.
These molecules are ATP and ADP, each named for
Hydrogen is a simple element with the ability to form the number of phosphorus atoms attached: adenosine
a single bond with other atoms. Two hydrogen atoms tri-phosphate (ATP, 3 phosphorus atoms) and adenosine
bond with one oxygen atom to form water molecules di-phosphate (ADP, 2 phosphorus atoms).
(H2O). Water forms when two hydrogens bond with
one oxygen. The human body consists of approximately Sulfur
70% of water. Hydrogen can also attach (bond) with
carbon, creating long hydrocarbon chains that make up Sulfur is the heaviest of the basic six elements. Sulfur is
carbohydrates and lipids, as well as to nitrogen to make primarily found in protein molecules, and sulfur to sulfur
up nucleic acids and proteins. bonds are involved in the tertiary structure or shape of
proteins. Protein shapes are very important. They are
important because protein function and specificity are
Nitrogen dependent on their geometry (shape).
Nitrogen bonds well to carbon and hydrogen and is
therefore involved in the assembly of a variety of organic
compounds. In addition to carbon, hydrogen and oxygen,
nitrogen is the main element that makes up proteins
and nucleic acids. Nitrogen is vitally important to DNA
molecules, since the structure of the DNA molecule is
built from protein and nucleic acid molecules.

Oxygen

With hydrogen, oxygen makes up water. Therefore,

oxygen is a vital element found in living organisms.
Oxygen is also found in organic molecules and is heavily

Page 44
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Task

4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Important elements found in lesser quantities in organisms

Research and briefly describe the functions of the following important elements found in small quantities in
organisms.

Element Function in organisms

Calcium (Ca)

Potassium (K)

Sodium (Na)

Chlorine (Cl)

Magnesium (Mg)

Iron (Fe)

Page 45
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Knowledge
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Molecules

Atoms form chemical bonds with other atoms molecule of ozone (O3). If a molecule forms from
when there is an electrostatic attraction between atoms of two or more different elements, we call
them. This attraction results from the properties and it a compound. A common compound everyone is
characteristics of the atoms’ outermost electrons, familiar with results from the chemical bonding of
which are known as valence electrons. two atoms of hydrogen with one atom of oxygen to
form a molecule of water (H2O). Water is the most
When two or more atoms chemically bond together,
abundant molecule in living organisms. In cells,
they form a molecule. Sometimes the atoms are
water accounts for 70% or more of total mass.
all from the same element. For example, when
three oxygen atoms bond together, they form a

Biological macromolecules

Just as you can be thought of as an assortment of Nucleic acids store and transfer hereditary
atoms or a walking, talking bag of water, you can information, much of which provides instructions for
also be viewed as a collection of four major types of making proteins.
large (macro) biological molecules: carbohydrates
Proteins themselves have perhaps the broadest
(such as sugars), lipids (fats and oils), proteins, and
range of functions: some provide structural support,
nucleic acids (such as DNA and RNA).
but many are like little machines that carry out
That is not to say that these are the only molecules specific jobs in a cell, such as catalyzing metabolic
in your body, but rather, that your most important reactions or receiving and transmitting signals.
large molecules can be divided into these groups.
Together, the four groups of large biological
molecules make up the majority of the dry mass of a A. Valentini / PPC
cell. (Water, a small molecule, makes up the majority
of the wet mass).
Large biological molecules perform a wide range of
jobs in an organism.
Carbohydrates store fuel for future energy needs,
Lipids are key structural components of cell
membranes.

Task
Research the CHNOPS elements that each macromolecule contains.

Macromolecule Elements involved

Carbohydrate

Lipid

Protein

Nucleic acid

Page 46
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Knowledge

4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Functions and examples of biological macromolecules

Biological
Buildind blocks Functions Examples
macromolecule
Carbohydrates Monosaccharides Provide cells with quick/ Glucose, sucrose, starch,
short-term energy, source cellulose, chitin
(simple sugars) of dietary fiber

Sugar
Tetiana Zhabska / Alamy

Lipids Fatty acids and glycerol Provide cells with long- Fats, phospholipids,
term energy, make up waxes, oils, grease,
biological membranes steriods

Fatty acid

Bacsica/ iStock.com

Proteins Amino acids Provide cell structure, send Keratin (found in hair
chemical signals, speed up and nails), hormones,
chemical reactions, etc enzymes, antibodies
Amino
acid
Dr_Microbe/ iStock.com

Nucleic acids Nucleotides Store and pass on genetic DNA, RNA

information

Nucleotide

Horizon International Images

/ Alamy

Page 47
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Task
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Testing food for carbohydrates, proteins and fats

Get a selection of food, especially ones where you expect carbohydrates, proteins and fats within. For example:
biscuits, yoghurt, crisps, milk, butter, cereals and pasta. Perform the following tests on them and record your
findings on the following lab report.

Tests for carbohydrates:

Benedict’s test – for simple (reducing) sugars:

1. Make a solution of the substance to be tested in a boiling tube.

2. Add Benedict’s solution (blue).

3. Heat tube for about 2 minutes in a water bath.

A colour change from blue to brick red shows the presence of simple sugars.

Iodine test – for starch (complex carbohydrates):

1. Solid food - Add a few drops of the iodine solution (orange) to a chunk of food on a spotting tile.

2. Liquid food – Add a few drops of iodine solution to the food sample in a boiling tube.

A colour change in the iodine from orange to blue / black indicates the presence of starch.

Test for proteins:

Biuret test – for proteins:

1. Place food type into a boiling tube or on a spotting tile.

2. Add equal amounts of sodium hydroxide and copper sulfate (Biuret test) to the sample.

A colour change in the test solution from blue to lilac indicates the presence of protein.

Test for fats:

Emulsion / Ethanol test – for fats and oils:

1. Add ethanol to a small amount of the food sample with some water.

2. Shake the tube gently to mix.

3. Heat gently in a water bath for a few minutes.

The formation of a cloudy precipitate in the tube indicates the presence of fat / oil.

Page 48
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Task

4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Laboratory report

Title ( Give the experiment a clear title)

Purpose of the experiment (what do you want to investigate?)

Hypothesis (What do you think will happen?)

Equipment list (List all the equipment that you have used during the experiment. Make sure you list every
piece of equipment that you have used.)

Page 49
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Task
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Risk assessment (Identify all the equipment, chemicals or procedures which could pose a risk to you and describe
what you do to prevent any accidents.)

Equipment/Procedure Danger Precautions (What will you do to prevent an accident?)

Method (Write it like a recipe. Never include he/she/it/we/you or I)

Tests for carbohydrates:
Benedict’s test – for simple (reducing) sugars:
1. Make a solution of the substance to be tested in a boiling tube.
2. Add Benedict’s solution (blue).
3. Heat tube for about 2 minutes in a water bath.

Iodine test – for starch (complex carbohydrates):

1. Solid food - Add a few drops of the iodine solution (orange) to a chunk of food on a spotting tile.
2. Liquid food – Add a few drops of iodine solution to the food sample in a boiling tube.

Test for proteins:

Biuret test – for protein:
1. Place food type into a boiling tube or on a spotting tile.
2. Add equal amounts of sodium hydroxide and copper sulfate (Biuret test) to the sample.

Test for fats:

Emulsion / Ethanol test – for fats and oils:
1. Add ethanol to a small amount of the food sample with some water.
2. Shake the tube gently to mix.
3. Heat gently in a water bath for a few minutes.

Page 50
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Task

4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Drawing of the experiment (Draw and label the setup of the experiment.)

Results (Results should be presented in the easiest way to read as possible. For example: tables, drawings,
sentences or graphs)

Page 51
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Task
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Conclusion (Write here what happened and what you found out in a scientific way. Include the SCIENCE
here! Comment on if this is what you expected.)

Evaluation (Write here how your experiment went. Did it go well or not and why? Also comment on what you
would change the next time if you were to do the experiment again to make it better. )

Page 52
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Knowledge

4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Levels of organisation in living things

In the previous section we learned how elements, when chemically combining together form
molecules. Now we will take a look at the following levels of how living things are organised from
smallest to largest.

Atoms

Atoms are the basic units of matter and the building blocks of all Electron
things. Atoms are made up of three particles: protons, neutrons
and electrons. Nucleus
Proton
Protons and neutrons are heavier then electrons and reside in
the centre of an atom, which is called the nucleus. Electrons are
extremely lightweight and exist in a cloud orbiting the nucleus.
Neutron
Freepik
Molecules

Molecules are made up of atoms that are held together by chemical

bonds. These bonds form as a result of the sharing or exchange of
electrons among atoms.

Freepik
Macromolecules

A macromolecule is a very large molecule, such as protein,

commonly created by polymerization of smaller subunits
(monomers). They are typically composed of thousands of atoms
or more. The most common macromolecules in biochemistry are
biopolymers (nucleic acids, proteins, carbohydrates and polyphenols)
and large non-polymeric molecules (such as lipids and macrocycles).

iStock.com / Dr_Microbe
Organelles

Organelle literally means "little organs". As the body is composed of

various organs, the cell, too, has "little organs" that perform special
functions. They are membrane-bound compartments or structures
of a cell. A eukaryotic cell contains many organelles, for example,
the nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria,
and chloroplast (plastid). However, not all these organelles are found
in only one cell or in an organism. The chloroplast, for instance, is
abundant in plant cells but not in animal cells. A. Valentini / PPC
MICHAEL ABBEY / BSIP

Cells

The cell (from Latin cella, meaning "small room") is the basic
structural, functional, and biological unit of all known living organisms.
A cell is the smallest unit of life that can replicate independently, and
cells are often called the "building blocks of life".
Christogra4/ iStock.com

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4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Knowledge
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

Tissues

Animal cells and plant cells can form tissues, like muscle tissue. A living tissue is made from a group of cells with a
similar structure and function, which all work together to do a particular job. Here are some examples of tissues:

- muscle

- the lining of the lungs

- phloem (tubes that carry dissolved sugar around a plant)

- root hair tissue (for plants to take up water and minerals from the soil)

Nephron / CC BY 3.0 via Wikimedia

https://commons.wikimedia.org/wiki/File:Skele-
Organs tal_striated_muscle.jpg,
https://creativecommons.org/licenses/by-sa/3.0/
deed.en

An organ is made from a group of different tissues, which all work together to
do a particular job. Here are some examples of organs:

- heart - brain

- lung - leaf

- stomach - root

Organ systems Rob Walls / CWM02M / Alamy

An organ system is made from a group of different organs, which all work
together to do a particular job. Here are some examples of organ systems:

circulatory system nervous system

respiratory system reproductive system

digestive system leaf canopy

Organism
Freepik

An individual living thing that can react to stimuli, reproduce, grow,

and maintain homeostasis. It can be a virus, bacterium, fungus,
plant or an animal.

- Human

- Animal

- Plant
A. Valentini / PPC

Page 54
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Systematic study of the Systematic study of the Systematic study of the Systematic study of the
structure and behaviour structure and behaviour structure and behaviour structure and behaviour

Example:
of the physical and natural of the physical and natural of the physical and natural of the physical and natural
world through observation, world through observation, world through observation, world through observation,
experimentation, and the experimentation, and the experimentation, and the experimentation, and the
testing of theories against testing of theories against testing of theories against testing of theories against
the evidence obtained. the evidence obtained. the evidence obtained. the evidence obtained.
Levels of organisation in living things
Task

Freepik
Science Science Science Science
correct vertical order onto the next page as shown in this example.

Tous les textes et images sont exactement les memes

Biology, Chemistry, Biology, Chemistry, Biology, Chemistry, Biology, Chemistry,

Environmental Science , Environmental Science , Environmental Science , Environmental Science
Geography, Mathematics Geography, Mathematics Geography, Mathematics Geography, Mathematics
and Physics. and Physics. and Physics. and Physics.
On the following page you will find pictures of different levels of organizations in living things, as well as the
description of the level (black) and some examples (blue) of each. Cut out all of the boxes and glue them in the

Page 55
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
 Task
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms

4.3. Levels of Organisation

The smallest unit of
an element which
These are the
smallest units A specialised
A living thing
which can Groups of the

in Living Things
still shows the of life. They are subunit, usually respond to same type of
characteristics of surrounded by a within a cell, that stimuli, is capable cell. They are
that element. They membrane or a has a specific of reproduction, grouped together
are used to build wall. Some may function. growth and to perform
molecules. Non- be specialised for development, and a particular
living particular jobs. maintenance of function
homeostasis as
a stable whole. It
is made of organ
systems working
together Composed of
A group much larger
These are made of A group of of organs numbers of
atoms. They have different which works atoms than
different chemical tissues which together ordinary
and physical performs to perform molecules.
properties from the a specific a certain
atoms which make function. function. Freepik

them. Non-living. Freepik

Organ System
Level
Molecular Level Atomic Level
Tissue Level Cell organelle Freepik A. Valentini / PPC
Freepik Level
A. Valentini / PPC

Organism Cell Level

Macromolecular Level Organ Level Freepik
iStock.com / Dr_Microbe Freepik H2O (water), N2
Muscle cell, Carbon, (nitrogen), O3
Epithelium (lining), Guard cell, Root Hydrogen, (ozone), CaO
Nervous tissue, hair cell, Red Oxygen, (calcium oxide),
Connective tissue, blood cell, Nerve Nitrogen, NaCl (table salt)
Transport tissue (e.g. cell Sodium,
xylem), Mesophyll Heart, Brain, Potassium,
(photosynthetic Kidney, Leaf, Magnesium
tissue) Flower, Plant
Chloroplast, Circulatory
stem
Mitochondria, system, Nervous
Human, Mouse, system, Plant
Nucleus,
DNA, Oak tree, transport
Membrane,
Glucose, Seaweed, Bread system,
Cell Wall
Protein, mould (Mucor) Respiratory
Fat system

Page 56
4.3.1. Levels of Organisation from Chemical Elements to Multicellular Organisms
4.3.2. Reproduction in Multicellular
­Organisms

Lise Gagne / iStock.com

Science History Images / Alamy

4.3.2 Reproduction in Multicellular Organisms

Learning objective:
• To be able to explain asexual and sexual modes of reproduction.

Page 57
4.3.2. Reproduction in Multicellular Organisms
 Knowledge
xxx
Reproduction in multicellular organisms Sexual reproduction

Living organisms need to reproduce to sustain

their species. Some species reproduce sexually
and combine their DNA to produce a new
organism. Sexual reproduction requires both
an egg and sperm that combine to create a
new organism that possesses a combination
4.3.2. Reproduction in Multicellular Organisms

of genes from both parents. Organisms can

interact with each other to achieve this goal,
or the egg and sperm can travel via other
organisms or wind or water currents. This olando_o / IStock.com, Freepik
offspring, while it contains genetic traits of each of its parents, is genetically
unique. This process results in diversity in populations, which improves the
odds of survival in a changing environment. Asexual reproduction
Other organisms reproduce asexually
and create offspring completely on their
own. With no other organism involved, all
offspring are genetically identical to the
parent. This method of reproduction is
common among single-celled organisms
and plants and animals with simple
organisations. It tends to occur more rapidly
than sexual reproduction, allowing these
Anatoliy Stepura / iStock.com
species to grow at a faster rate. From the outset, offspring are able to live
independently, needing nothing from the parent.

Some species are capable of both sexual and asexual reproduction. The simplest organisms have no sex
organs, so asexual reproduction is a necessity. Other species, such as corals, may reproduce either sexually
or asexually, depending on conditions. Though it occurs infrequently, some species surprise scientists
by adapting to asexual reproduction, sometimes where the species or even an individual organism had
reproduced sexually in the past. This is most common in species in captivity and in those where no males are
present to further the species but is also in evidence in sharks and snakes in the wild where the populations
included both male and females of the species.

Zoonar GmbH / Alamy

Sea ​​anemone

Marco_de_Benedictis / iStock.com Common black carpenter ant

Strawberry plant

SR/ iStock.com

Page 58
4.3.2. Reproduction in Multicellular Organisms
 Task

Sexual vs. asexual reproduction

Research the advantages and disadvantages of both sexual and asexual reproduction. Record your
findings in the table below

Advantages Disadvantages

4.3.2. Reproduction in Multicellular Organisms

Sexual reproduction

Asexual reproduction

Page 59
4.3.2. Reproduction in Multicellular Organisms
 Knowledge
xxx
Types of asexual reproduction

There are many different types of asexual reproduction. Four major types are:
TarikVision / iStock.com

1) Binary fission
4.3.2. Reproduction in Multicellular Organisms

Single parent cell doubles its DNA, then divides into two
cells. Usually occurs in bacteria.

Parent cell Cell division

New daughter
cell
Illustration of a budding in hydra, a multicellular organism

2) Budding
Small growth on surface of parent breaks off, resulting
in the formation of two individuals. Occurs in yeast and
some animals like the hydra.

Tiny bump Parent hydra Bud grows Bud breaks

appears on develops bud off to become
parent hydra independent
hydra
Anatoliy Stepura / iStock.com

Illustration of regeneration in flatworm

3) Fragmentation head regrows

new tail
Organisms break into two or more fragments that
develop into a new individual. Occurs in many plants, as
well as some animals (like coral, sponges, and starfish).

tail regrows
new head

iStock.com / anuwat meereewee

Parent flatworm
divided into two

4) Parthenogenesis
An embryo develops from an unfertilized cell. Occurs in
invertebrates, as well as in some fish, amphibians, and
reptiles.

S. Coté / PPC

Page 60
4.3.2. Reproduction in Multicellular Organisms
 Task
Another type of asexual reproduction is vegetative propagation

New plants can be produced from vegetative structures such as the roots, stems, and leaves
of some plants. The process can be natural or artificial.

Research a method of vegetative propagation of plants and experiment with it. For example
take a cutting, then care for your plant. Complete the table below.

4.3.2. Reproduction in Multicellular Organisms

I will use the following method of vegetative propagation of plants: _______________________________

Materials needed for the experiment:

Method of my chosen vegetative propagation:

1.

2.

3.

4.

5.

6.

Are there any risk(s) involved when doing the experiment? If so how will an accident be prevented?

Picture of my plant (drawing or photo):

Page 61
4.3.2. Reproduction in Multicellular Organisms
 Knowledge
xxx
Sexual reproduction

Sexual reproduction is the process in which new organisms are created, by combining the genetic
information from two individuals of different sexes. The genetic information is carried on chromosomes
within the nucleus of specialized sex cells called gametes. In males, these gametes are called sperm and in
females the gametes are called eggs.

During sexual reproduction the two gametes join together

4.3.2. Reproduction in Multicellular Organisms

Father
in a fusion process known as fertilization, to create a zygote, 2n
n
which is the precursor to an embryo offspring, taking half
of its DNA from each of its parents. In humans, a zygote
contains 46 chromosomes: 23 from its mother and 23 from
its father. The combination of these chromosomes produces Fertilization
an offspring that is similar to both its mother and father but Mother 2n 2n
is not identical to either. 2n

Freepik et S. Coté/PPC

Meiosis

Meiosis is a type of cell division that reduces the Meiosis begins following one round of DNA replication
number of chromosomes in the parent cell by half in cells in the male or female reproductive organs.
and produces four gamete cells. This process is
required to produce egg and sperm cells for sexual
reproduction. During reproduction, when the sperm The process is split into meiosis I and meiosis II, and
and egg unite to form a single cell, the number of both meiotic divisions have multiple phases. Meiosis I
chromosomes is restored in the offspring. is a type of cell division unique to gamete cells, while
meiosis II is similar to mitosis (You will learn more
about mitosis in Year S5).
Meiosis begins with a parent cell that is diploid,
meaning it has two copies of each chromosome. The
parent cell undergoes one round of DNA replication
followed by two separate cycles of nuclear division.

The process results in four daughter cells that are

haploid, which means they contain half the number of
chromosomes of the diploid parent cell.

Meiosis has both similarities to and differences from

mitosis, which is a cell division process in which a
parent cell produces two identical daughter cells.

A. Valentini / PPC

Page 62
4.3.2. Reproduction in Multicellular Organisms
 Task

Research the role of insects in flowering plant reproduction as well as the crisis in bee
population.

Role of insects in flowering plant reproduction:

4.3.2. Reproduction in Multicellular Organisms

The crisis in bee population:

Page 63
4.3.2. Reproduction in Multicellular Organisms
 Chapter 4

4.4. Communication

Wavebreakmedia Ltd IW-200629 / Alamy/ 2C59028

Page 64
4.4. Communication
 4.4.1. Chemical Communication

iStock.com / undefined undefined

4.4.1 Chemical Communication

Learning objectives:
• To be able to understand that the communication system is universal to
multicellular organisms.
• To be able to explain how hormones may have multiple targets and effects.

Page 65
4.4.1. Chemical Communication
 Knowledge
The endocrinesystem

What is the endocrine system?

The endocrine system is a network of glands and organs in the body that produces hormones.
Hormones are chemicals that coordinate different functions in your body by carrying signals through your blood
to your organs, muscles and other tissues. These signals tell your body what to do and when to do it. Your body
makes over 50 hormones, and many of them interact with each other.
Several glands make hormones, including the hypothalamus, the pituitary gland, the pineal gland, the thyroid
gland, the parathyroid glands, the adrenal glands, the islets of Langerhans (in the pancreas), the ovaries and
the testes. Each gland makes one or more hormones. Hormones are important for almost all of the cells in the
body to work. They influence metabolism, growth and development, tissue function, reproduction, sleep, mood
and many other functions. Some hormones influence almost all cells in the body. Others only influence a small
number of cells in specific a organ (target organ).
4.4.1. Chemical Communication

Hypothalamus
Some glands ‘talk to’ other glands, telling
them to release particular hormones.
For example, the pituitary gland releases Pineal gland
hormones that tell the thyroid gland, the
adrenal glands, the ovaries and the testes to Pituitary gland
release hormones.
Thyroid gland

How does the hormonal system work? Parathyroid glands

(behind thyroid)

When a hormone is released from a gland, Adrenal glands

it travels in the bloodstream through the
body. It passes by most cells, but eventually
reaches its target.
Islets of Langerhans
(in pancreas)
When it reaches its target, it attaches to a
particular type of cell, known as a receptor
cell. The hormone then triggers the receptor
cell to do something. It can make cells grow Ovary
faster, release another hormone, absorb (in female)
sugar from the blood, withhold water from
the kidneys, or one of many other important
functions in the body. Testis (in male)

A. Valentini / PPC

Page 66
4.4.1. Chemical Communication
 Knowledge
Task
Fill in the table:

Gland Hormone Effect

Hypothalamus
Dopamine
Vasopressin

Pineal gland Melatonin

Pituitary gland Growth hormone

(GH)

Follicle-stimulating

4.4.1. Chemical Communication

hormone (FSH)

Luteinizing

hormone (LH)
Thyroid gland Thyroxine

Calcitonin

Parathyroid Parathyroid
gland
hormone (PTH)

Adrenal glands Aldosterone

Adrenaline

Islets of Insulin
Langerhans
Glucagon

Ovaries Estrogens

Progesterone

Testes Testosterone

Page 67
4.4.1. Chemical Communication
 Knowledge
Growth in plants and wnimals

Growth hormone in plants Growth hormone in animals

4.4.1. Chemical Communication

Human Growth
Auxin
Hormone (HGH)

Auxin molecules Liver

Cell elongation
Bone

Pituitary gland
Elongated cells

Skeletal muscle

Adipose tissue
A. Valentini / PPC
MedicalStocks / Alamy Stock Vector / 2A6EPJJ
Frepik / S. Coté / PPC
Plants use a variety of hormones to control their
growth and development. A family of hormones
called auxins, which promote growth, are The pituitary gland produces growth
commonly found in plants. For example, auxins hormone (also referred to as human
play a part in phototropism, an occurrence that growth hormone or HGH). The growth
involves plants bending or moving towards the hormone influences our height, bone
light. The shoot tip is responsible for directional length and muscle growth. Growth
movement by the plant in response to sunlight, hormone levels increase during
as this is the area where auxins can be found. childhood and peak during puberty.
When the sun is overhead, auxin is distributed
evenly in the shoot tip. When sunlight hits on a
side, auxin moves to the shaded area, inducing
cell elongation.

Page 68
4.4.1. Chemical Communication
 Task
S. Coté / PPC
Experiment with plant hormones
Age faster with apples

Don't worry - people who eat apples don't grow

old faster. But what will happen with other fruits is
something you can explore in this experiment

Equipment needed:
- one ripe apple
- two green bananas and/or two green tomatoes

4.4.1. Chemical Communication

- two bowls

Method:
1. Place a ripe apple together with a green tomato in a bowl.
2. For comparison, put the other tomato in the second bowl.
3. Place both bowls at a large distance from each other but in similar conditions and wait a few days.
(If you do not have green tomatoes, you can also use green bananas.)

Drawing of the experiment:

Results:

_____________________________________________________________________________________________________________________
_____________________________________________________________________________________________________________________
_____________________________________________________________________________________________________________________
Conclusion:
(Research the scientific reason for your results)

______________________________________________________________________________________________________________________
______________________________________________________________________________________________________________________
______________________________________________________________________________________________________________________
______________________________________________________________________________________________________________________
______________________________________________________________________________________________________________________

Page 69
4.4.1. Chemical Communication
 Task

Propagate a golden pothos with S. Coté / PPC

and without rooting hormone

Equipment needed:

- One or two golden pothos plants

(alternatively you can use any other plant
suitable for propagation)
- Scissors
- Rooting hormone powder (e.g. TakeRoot®
from Garden Safe ®)
- Two 250 ml beakers
4.4.1. Chemical Communication

Method:

1. Cut two 10 cm sections off a stem just below the root node. (The
root nodes are the small brown nodes on the golden pothos’ stems).
Try to find a 10 cm section of stem that is healthy and has at least 3
leaves on it.

2. Remove all leaves off the bottom 5 cm of the stem of both cuttings.

3. Dip the stem of one of the cuttings in the rooting hormone powder.

4. Label two 250 ml beakers; one “with rooting hormone” and the
other one with “control”.

5. Fill both beakers with enough water.

6. Put each plant cutting into the corresponding beaker.

A. Valentini / PPC
Results:
Describe any differences you have noticed after a few weeks between both of your plants.

___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________

Page 70
4.4.1. Chemical Communication
 Task
Read the following article from the newspaper StarTwo on Wednesday 17th June 2009 and then research
bisphenol A. Record your findings on the next page.

It is not possible to exploit this article. It would be better to

rewrite it or find a newspaper from which we can
buy the article :( .

The full article from StarTwo on Wed 17th June 2009 : the hearts of women, permanently damage the DNA
of mice, and appear to be pouring into the human
Hormone Experts are worried by a chemical called
body from a variety of unknown sources. BPA, used
bisphenol A, which some politicians want taken out
to stiffen plastic bottles, line cans and make smooth
of products and which consumers are increasingly

4.4.1. Chemical Communication

paper receipts, belongs to a broad class of compounds
shunning. They said they have gathered a growing
called endocrine disruptors. The United States Food
body of evidence to show the compound, also known
and Drug Administration is examining their safety, but
as BPA, might damage human health. The Endocrine
there has not been much evidence to show that they
Society issued a scientific statement last week calling
are any threat to human health. “We present evidence
for better studies into its efforts. Studies presented
that endocrine disruptors do have effects on male and
at the group’s annual meeting show BPA can affect

Photo bébé et biberon

Page 71
4.4.1. Chemical Communication
 The effects of Bisphenol A:
4.4.1. Chemical Communication

Page 72
4.4.1. Chemical Communication
 4.4.2. Nervous System

iStock.com / libre de droit

4.4.2 Nervous System

Learning objectives:
• To be able to understand neurons, nerves and the nervous system.
• To be able to explain the action of mind-altering drugs on neurotransmission in
the brain.

Page 73
4.4.2. Nervous system
 Knowledge
xxx
Evolution of the nervous system
Brains, centralized nervous systems and nets Diffuse nerve nets Nets and ‘brain’
S. Coté / PPC PPC, F. Garcia
6 7 8

Nerve Nerve nets 5

1 2
nets

Brachiopoda

Mollusca

Annelida
Arthropoda

Ptizpulida

Nematoda

Phoronida
Neurons
Echinodermata
Xenoturbellida

Hernichordata

Scyphozoa
Hydrozoa

Anthozoa
Muscles
Chordata

Cubozoa
Nerve nets Nerve nets Mesoderm
Ecdysozoa Lophotrochozoa
Nerve
4.4.2. Nervous System

Nerve nets Nerve nets

Protostomia
nets
Deuterostonia Origin of neurons
~20 million years
S. Coté / PPC Nerve nets
Nerve nets
UrBilaterian 4
Origin of neurons in
Eumetazoans 3
Hexactinellida No neurons
Demospongiae
No neurons No muscles
Calcarea Placozoa
Porifera No muscles Ancestral
Ctenophora
UrMetazoan
>580 Mya Choanoflagellata

Phylogenetic Tree of Life

Bacteria Archaea Eukarya
Spirochetes Green You are
Halophiles
Filamentous here
Proteobacteria Gram Methanosarcina
bacteria Methobacterium Animals
positives Plants
Cyanobacteria Methanococcus
Plantocmyces T. celer Fungi
Thermoproteus Ciliates
Bacteroides Pyrodictium
Cytophaga Flagellates
Thermotoga Trichomonads
Aquifex Microsporidia
Diplomonads

Luca Diagram: S. Coté

1. Hiroaki Nakano, Hideyuki Miyazawa, Akiteru Maeno, Toshihiko Shiroishi, 5. iStock.com / LeeYiuTung
Keiichi Kakui, Ryo Koyanagi, Miyuki Kanda, Noriyuki Satoh, Akihito Omori & 6. Kevin Raskoff / National Oceanic and Atmospheric Administration / do-
Hisanori Kohtsuka / CC BY-SA 4.0 via Wikimedia Common maine public via Wikimedia Common
2. iStock.com / bennymarty 7 et 8. iStock.com / Wirestock
3. Bernd Schierwater / CC BY 4.0 via Wikimedia Common
4. Orin Zebest / CC BY 2.0 via Wikimedia

Page 74
4.4.2. Nervous System
 Task
Knowledge

The nervous system

Central nervous
system: brain and
spinal cord The nervous system is the major controlling, regulatory,
and communicating system in the body. It is the centre of
all mental activity including thought, learning, and memory.
Together with the endocrine system, the nervous system is
responsible for regulating and maintaining homeostasis (the
ability of the body or a cell to seek and maintain a condition
of equilibrium). Through its receptors, the nervous system
keeps us in touch with our environment, both external and
internal.

Like other systems in the body, the nervous system is

composed of organs, principally the brain and spinal cord,
which make up the central nervous system, and sensory

4.4.2. Nervous System

Peripheral and motor nerves, which constitute the peripheral nervous
nervous system. Together they carry out the complex activities of the
system nervous system.

Types of neurons

Based on their roles, the neurons found in the human

nervous system can be divided into three classes: sensory
neurons, motor neurons, and interneurons.
Freepik

Task
Research the anatomy (structure) and the function of the different types of neurons.

Type of neuron Anatomy (structure) Function Picture or Drawing

Sensory neuron

Motor neuron

Interneuron

Page 75
4.4.2. Nervous System
 Knowledge

Sending and receiving messages

Neuron cell body Synapse

Axon of previous
neuron Neuron cell body

Electrical signal
Nucleus

Nucleus
4.4.2. Nervous System

Synapse Dendrites Axon Axon Dendrites

A. Valentini / PPC

Messages, in the form of electrical impulses, When neurons communicate, an electrical impulse
constantly travel back and forth between the brain triggers the release of neurotransmitters from the
and other parts of the body. Neurons are responsible axon into the synapse. The neurotransmitters cross
for carrying these messages. There are about 100 the synapse and bind to special molecules on the
billion neurons in the human brain. other side, called receptors. Receptors are located
on the dendrites. Receptors receive and process the
A neuron has three main parts: the cell body,
message.
dendrites and axons. The cell body directs all activities
of the neuron. Dendrites extend out from the cell What’s particularly interesting about
body and receive messages from other nerve cells. neurotransmission is that each neurotransmitter
An axon is a long single fiber that transmits messages can bind only to a very specific matching receptor.
from the cell body to the dendrites of other neurons A neurotransmitter binds to a receptor in much the
or to other body tissues, such as muscles. same way a key fits into a lock. After transmission
has occurred, the neurotransmitter is either broken
A protective covering called the myelin sheath, covers
down by an enzyme (a chemical that speeds up
most neurons. Myelin insulates the axon and helps
some of the body’s processes) or is reabsorbed
nerve signals travel faster and farther.
into the neuron that released it. The reabsorbed
Messages travel along a single neuron as electrical neurotransmitters can be reused at a later time.
impulses, but messages between neurons travel
differently. The transfer of information from
neuron to neuron takes place through the release
of chemical substances into the space between
the axon and the dendrites. These chemicals are
called neurotransmitters, and the process is called
neurotransmission. The space between the axon and
the dendrites is called the synapse.

Page 76
4.4.2. Nervous System
 Knowledge
The Synapse
1. Electrical impulse
2. Axon of the pre-synaptic neuron
3. Mitochondria
4. Vesicle
5. Neurotransmitter
6. Synaptic gap / synaptic cleft
7. Receptor
8. Post-synaptic neuron
9. Post-synaptic membrane
2
10. Synaptic knobs 11

4.4.2. Nervous System

31 10
41

61 5
7
81 9
A. Valentini / PPC

Task

Explain how messages are passed on from neuron to neuron by completing the following text. Make sure
that you identify each of the parts labeled 1 – 10 in the diagram.
Where two neurons meet there is a small gap called a synapse. An electrical impulse (1) cannot
directly cross the gap so a different mechanism has to be used.

____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________

Page 77
4.4.2. Nervous System
 xxx
Knowledge
Reflex arc
Remember, there are three main types of neuron: sensory neuron, motor neuron and interneuron.
These different types of neurons work together in a reflex action. A reflex action is an automatic (involuntary) and
rapid response to a stimulus, which minimizes any damage to the body from potentially harmful conditions, such as
touching something hot. Reflex actions are therefore essential to the survival of many organisms.

A reflex action follows a general sequence of stimulus – receptor – sensory neurons – interneurons – motor
neurons – effector - response and does not involve the conscious part of the brain. This is why the response is so
fast.
Spinal cord
The nerve pathway followed by a reflex action is
2. Afferent or (in cross section)
called a reflex arc. For example, a simple reflex arc
sensory neuron
happens if we accidentally touch something hot.

1. Receptor in the skin detects a stimulus (the

4.4.2. Nervous System

change in temperature).
3. Integration 2. Sensory neuron sends electrical impulses to a
Interneuron centrer relay neuron, which is located in the spinal cord of
4. Efferent or
the central nervous system (CNS).
motor neuron
3. Interneurons connect sensory neurons to motor
1. Receptor neurons.
4. Motor neuron sends electrical impulses to an
effector.
5. Effector produces a response (muscle contracts
to move hand away).
Organisms are able to modify a reflex action and
overcome it, but this uses the brain and has to be
learnt. For example, keeping hold of a hot object
requires a nerve impulse to be sent to the motor
A. Valentini / PPC
Stimulus neuron of the reflex arc to interfere with the
normal reflex action to drop the object.

Task
Research different reflexes and briefly explain their purpose, or what they are protecting us from.

Reflex Purpose ( what they are protecting us from)

Page 78
4.4.2. Nervous System
 Task
Test your reaction time

The reaction time is the time taken for a person to respond to a S. Coté / PPC
stimulus.

Equipment:
- 30 cm ruler
- Partner

Method:
1. One person holds the ruler with the arm stretched out. The
fingers should be on the highest measurement.
2. The other person hovers with their slightly open thumb and
index finger over the 0 at the bottom of the ruler.

4.4.2. Nervous System

3. The first person holding the ruler drops the ruler at any moment.
4. The other person tries to catch the ruler with their thumb and
index finger as fast as possible.
5. Repeat the test three times and each time record the number
(cm) at which the ruler was caught.
6. Calculate the average.
7. Now swap with your partner and repeat all steps.

Results:
Conclusion:
Explain in detail how this works, or what happens.
Test 1

Test 2 _____________________________________________________________________________
_____________________________________________________________________________
Test 3 _____________________________________________________________________________
_____________________________________________________________________________
Average _____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________

Page 79
4.4.2. Nervous System
 xxx
Task

The nervous system of an insect

(Analyse, describe and draw the nervous system of an insect of your choice)
4.4.2. Nervous System

Compare the nervous system of your insect to that of vertebrates.

(You can create a table to compare them, write about it or produce a well labelled drawing.)

Page 80
4.4.2. Nervous System
 Task
Create a table in order to compare and contrast the endocrine and the nervous system.

Nervous system Endocrine system

Parts of the system

Types of message

4.4.2. Nervous System

Method of transmission

Speed of transmission

Length of effect

Effectors

Page 81
4.4.2. Nervous System
 Knowledge
xxx

Drugs and the synapse

What is a drug?
A drug is any substance (with the exception of food and water) which, when taken into the body, alters the
body’s function either physically and/or psychologically. Some drugs may be legal in certain countries while
others are illegal.
Psychoactive drugs affect the central nervous system and alter a person's mood, thinking and behaviour.
Psychoactive drugs may be divided into four categories: depressants, stimulants, hallucinogens and 'other'.

Depressants: Drugs that decrease alertness by slowing down the activity of the central nervous system (e.g.
heroin, alcohol and analgesics).

Stimulants: Drugs that increase the body's state of arousal by increasing the activity of the brain (e.g. caffeine,
nicotine and amphetamines).
4.4.2. Nervous System

Hallucinogens: Drugs that alter perception and can cause hallucinations, such as seeing or hearing something
that is not there (e.g. LSD and 'magic mushrooms').

Other: Some drugs fall into the ‘other’ category, as they may have properties of more than one of the above
categories (e.g. cannabis has depressive, hallucinogenic and some stimulant properties).

Drugs can increase

the amount of Drug
neurotransmitters that molecule
are made, so there
is more inside each
vesicle.

They can block

the release of
neurotransmitters.

They can counteract the

clean-up enzymes that
break down the transmitter.
They can block
the reuptake of They can destroy
neurotransmitters. neurotransmitters in the
synapse.

They can mimic a particular neurotransmitter,

binding to that neurotransmitter’s postsynaptic
A. Valentini / PPC receptors and either activating them or increasing
the neurotransmitter’s effects.

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4.4.2. Nervous System
 Task

Research three different drugs and for each one explain, how they effect the human body and especially the
nervous system.

Name of the drug: ____________________________________________

Effect on the human body:

Effect on the synapse:

4.4.2. Nervous System

Name of the drug: ____________________________________________

Effect on the human body:

Effect on the synapse:

Name of the drug: ____________________________________________

Effect on the human body:

Effect on the synapse:

Page 83
4.4.2. Nervous System
 xxx
Task

Groupwork: Imagine you are an employee at the European Centre for Disease Prevention and Control
(ECDC) and your task is to produce an information video for school children on drugs in order to prevent
teenage drug use. Your target audience is 11 to 14 year-olds. The length of the video should be between 2 min
and 5 min. Use the space below to plan your video.

https://www.ecdc.europa.eu/en
4.4.2. Nervous System

ECDC / CC BY 4.0

Page 84
4.4.2. Nervous System
Notes

4.4.2. Nervous System

Page 85
4.4.2. Nervous System
 Chapter 5

4.5. Transport

iStock.com / Ian Groves

Page 86
4.5. Transport
 4.5.1. Absorption and Uptake

S. Coté / PPC

4.5.1 Multicellular Organisms

Learning objectives:
• To be able to understand how organisms take in the materials and energy they
need.

Page 87
4.5.1. Absorption and Uptake
 Knowledge
During year 1 you learned that all living organisms need Types of nutrition
water and energy to grow and reproduce, maintain
their structures, and respond to their environments.
The different organisms have different means to AUTOTROPHS HETEROTROPHS
absorb/uptake the materials and energy needed. There (autos : self ; trophos : feed) Obtain energy through intake &
are two categories autotrophs and heterotrophs. digestion of organic substances
Autotrophs are known as producers because they Use simple inorganic substances (animal / plant tissue)
are able to make their own food from raw materials and either light energy
and energy. Heterotrophs are known as consumers (photosynthesis) or chemical
energy (chemosynthesis) to
because they consume producers or other consumers. synthesise food.

Task
4.5.1. Absorption and Uptake

Research some organisms that are autotrophs and some that are heterotrophs.

Autotroph organisms
(light energy)
Autotroph organisms
(chemical energy)
Heterotroph organisms

Let’s investigate the absorption and

uptake by humans (vertebrates) and
plants in more detail and compare
them. We start with humans;
humans are heterotrophs. They
obtain their energy from consuming
producers, or other consumers. In
year 1 you learned that humans take
in the nutrients needed when eating.
The macromolecules in the food
need to be broken down in order for
the body to be able to absorb those
nutrients. The process of digestion is
doing exactly this job. Let’s revise the
digestion process.

S. Coté / PPC

Page 88
4.5.1. Absorption and Uptake
 Task
The digestive system
Label the organs of the digestive
system :

4.5.1. Absorption and Uptake

A. Valentini / PPC

Organ Function
Teeth and tongue Mechanically break down food into smaller pieces.
Salivary gland Produces salivary to lubricate the food, chemical digestion through enzymes.
Epiglottis Seals off the windpipe during eating in order to not accidentally inhale food.
Oesophagus Muscular tube connecting the throat to the stomach.
Stomach Secretes acid and enzymes that digest food, the acid also kills bacteria and the
stomach is churning the food to enhance digestion.
Liver Produces bile which is needed for the digestion and absorption of fat.
Pancreas Secretes digestive juices.
Gall bladder Stores bile.
Small intestine Nutrients are being absorbed into the blood stream.
Large intestine Water is being absorbed into the blood stream.
Rectum Stores faeces until it is released.
Anus Controls the expulsion of faeces.
Appendix Unknown. One theory is that it acts as a storage house for good bacteria.

Page 89
4.5.1. Absorption and Uptake
 Knowledge
Bile production in liver
Liver and pancreas
Food does not travel through the liver or pancreas, but
they are important parts of the digestive system.
After the stomach, food travels to the small intestine.
The enzymes in the small intestine work best in Bile stored in
alkaline conditions, but the food is acidic after being gall bladder
Hepatic duct
in the stomach. The liver produces a substance called
bile which neutralises the acid to provide the alkaline
conditions needed in the small intestine. Digestive enzymes
produced in pancreas
The pancreas produces important digestive enzymes.

Pancreatic duct
4.5.1. Absorption and Uptake

Bile duct Duodenum

Bile production in liver A. Valentini / PPC

Enzymes
Enzymes are special proteins that can break down large molecules into small molecules.
Different types of enzymes can break down different nutrients:

- carbohydrase or amylase enzymes break down starch

into sugar.

- protease enzymes break down proteins into amino

acids.

A faire moi
même sur
- lipase enzymes break down fats into fatty acids and
glycerol.
illustrator, rond
en 3D
S. Coté / PPC

Page 90
4.5.1. Absorption and Uptake
 Knowledge

Once the large food molecules are broken down into smaller ones they can be absorbed in the small intestine. This
means that they pass through the wall of the small intestine and into our bloodstream. Once in the bloodstream,
the digested food molecules are carried around the body to where they are needed. Only small, soluble substances
can pass across the wall of the small intestine. Large insoluble substances cannot pass through.

Sabrina, tell me if I’m removing content from the names of the various elements.

4.5.1. Absorption and Uptake

iStock.com / VectorMine

Task
Describe the way the villus and microvilli look:
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________

Why do you think the villi and microvilli look this way (think about their function):
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________
___________________________________________________________________________________________________________________________

Page 91
4.5.1. Absorption and Uptake
 Knowledge

Once the small intestine has absorbed most of the nutrients from the food, the circulatory system passes them
on to other parts of the body to store or use. Glucose for example needs to be transported to the cells in order
to be turned into energy through a process called cellular respiration. Cellular respiration is a series of chemical
reactions that break down glucose to produce ATP (energy). There are two types of cellular respiration – aerobic
respiration (with oxygen) and anaerobic respiration (without). Most aerobic respiration takes place in the cells’
mitochondria while anaerobic respiration takes place within the cells’ cytoplasm. Aerobic respiration releases a lot
more ATP energy than anaerobic respiration.

Task

State the chemical word equation for aerobic cellular respiration :

+( )
4.5.1. Absorption and Uptake

+ +

State the chemical word equation for anaerobic cellular respiration :

+( )

Now compare and contrast aerobic respiration and anaerobic cellular respiration :

- Occurs in the ___________________ - Occurs in the ___________________

Requires
- _____________________ oxygen ______________ - _____________________ oxygen

- Produces _____________________ - Produces _____________________

- Releases ______________ of ATP - Releases ______________ of ATP

energy energy

Page 92
4.5.1. Absorption and Uptake
 Knowledge
Now we will take a closer look at the absorption and
uptake of plants.
Most plants are autotrophs, they produce their own
food through a process call photosynthesis. During
photosynthesis light energy is converted into chemical
energy.
During photosynthesis, plants produce glucose from
simple inorganic molecules, carbon dioxide and water
with the help of light energy. The light energy required
is absorbed by a green pigment called chlorophyll in
the leaves. Chlorophyll is located in chloroplasts in plant
cells, particularly the palisade and spongy mesophyll
cells (see leaf diagram on the next page).
Oxygen is also produced by the plant during this
process, therefore photosynthesis is largely responsible

4.5.1. Absorption and Uptake

for producing and maintaining the oxygen content
of the Earth’s atmosphere, and supplies most of the
energy necessary for life on Earth.
iStock.com / Baks

Task

With the help of the above text, create the chemical word equation for photosynthesis :

Sunlight

+ +
What do you think? Where do the substances needed for photosynthesis come from and how do they get into the
plant?
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________

Page 93
4.5.1. Absorption and Uptake
 Knowledge

How do the substances needed for photosynthesis

get inside the plant? Cuticle Upper epidermis Palisade layer
Plants obtain the gases they need through their leaves.
They require oxygen for respiration and carbon
dioxide for photosynthesis.
The gases diffuse into the intercellular spaces of
the leaf through pores, which are normally on the
underside of the leaf - stomata. From these spaces
they will diffuse into the cells that require them.
Stomatal opening and closing depends on changes in
the turgor (the rigid state of fullness of a cell) of the
guard cells. When water flows into the guard cells by
osmosis (next page), their turgor increases and they Spongy layer
Lower epidermis Vein
expand. Due to the relatively inelastic inner wall, the Stomata
4.5.1. Absorption and Uptake

guard cells bend and draw away from each other,

A. Vallentini / PPC
so the pore opens. If the guard cells loose water the
opposite happens and the pore closes.

Diffusion

Diffusion is a physical process where molecules of a material move

from an area of higher concentration (where there are many
molecules) to an area of lower concentration (where there are fewer
molecules) until the concentrations of the solutions have reached
equilibrium (molecules evenly spread). Diffusion usually takes place in
liquids or gases.
A. Vallentini / PPC

Task
Drop some ink or food colouring in a glass of water in order to observe diffusion. Describe what happened:
_____________________________________________________________________________________________________________________
_____________________________________________________________________________________________________________________
_____________________________________________________________________________________________________________________
_____________________________________________________________________________________________________________________

Colourful celery S. Coté / PPC

Fill a beaker with water, add food colouring and celery (it works best
when some leaves are on the celery). Leave it for a few days then cut the
stem and observe what has happened. Describe what happened:
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________

Page 94
4.5.1. Absorption and Uptake
 Knowledge
A. Vallentini / PPC

Osmosis

Osmosis, like diffusion, is another important type of mass

transport. This time the movement of water or solvent
is through a semipermeable (or selectively permeable)
membrane from a region of low solute concentration to
a region of high solute concentration. Unlike diffusion,
osmosis can only take place in liquids. Osmosis is a form
of passive transport, meaning it does not require energy
to be applied. What causes osmotic pressure is different
concentrations of solutes on the two sides of the membrane. When Root Soil particle
osmosis happens, water moves from the side of the membrane with a
lower amount of osmotic pressure to the side of the membrane with the
higher amount. An important example of osmosis is the movement of liquid
(solvent) molecules across a cell membrane into a cell with a higher solute

4.5.1. Absorption and Uptake

concentration. Plant root hairs for example take up water from the soil
through osmosis. Osmosis is a fundamental part of cell biochemistry, but
also has mechanical applications and usages. Water
Air Root hair

Task
The text needs to be changed. We don’t have
Gummy bear osmosis experiment 1 the rights.

Gummy bears have a selectively permeable coating which will allow water molecules to diffuse across, but
inhibiting other larger molecules. In this osmosis experiment the water molecules move into the bear, thus
enlarging it.

Material: Method:
- Gummy bears 1) Take 2 gummy bears that are the same colour and similar size and record their
mass.
- Two beakers
2) Put one gummy bear in each beaker. Fill one beaker with water so that the bear
- Water
is submerged, but measure the amount of water you use as this information will
- Paper towels be useful later on. The other cup remains dry (no water). This is your control bear
- Balance which will prove the bear does not enlarge without water!
3) Leave both bears overnight and then compare gummy bears by looking at them
and weighing both bears and record the results.
4) Calculate the mass gained by the enlarged bear by subtracting the weight before
from the mass after. Check the weight of the control bear as well, as this may have
changed too.

Results:
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________

Page 95
4.5.1. Absorption and Uptake
 Task
Osmosis experiment 2, modelling a cell

Material: Method:
- 600 ml Beaker 1. Fill the beaker with 500 ml of water.
- Visking tube 2. Add some iodine solution to the water.
- Pipette 3. Cut two pieces of string each approx. 20
cm long.
- Starch solution
4. Cut an approx. 30 cm piece of Visking tube
- String
and soak it in water.
- Scissors S. Humphries / PPC
5. Tie one end of the Visking tube with the string.
- Pencil
6. Fill the Visking tube with the starch solution using the pipette.
- Iodine solution
7. Tie the other end of the Visking tube with the string and rinse
4.5.1. Absorption and Uptake

the outside of the visking tube with water.

Drawing: 8. Tie both ends of the Visking tube together.
9. Submerge about ¾ of the Visking tube into the beaker with
water with the help of the pencil.
10. Observe (it will take approx. 30 min until you see first
changes) and record your results.
S. Humphries / PPC S. Humphries / PPC

Results:
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________

Conclusion:
Explain what happened in a scientific way. Make sure you explain what each part of the experiment
represented.
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________

Page 96
4.5.1. Absorption and Uptake
 Task
Now you learnt that most plants produce their own food (glucose)
during photosynthesis. But what about cellular respiration? Do you think
cellular respiration takes place in plants? Justify your answer.

_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
A. Vallentini / PPC
_______________________________________________________________________________
_________________________________________________________________________________________________________________________

4.5.1. Absorption and Uptake

_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________

Some plants are parasitic plants. Most parasitic plants are those which lack chlorophyll in them and depend on
others for their nutrition.
Groupwork: Research a parasitic plant and introduce your researched plant to the class. Use the space below for
your research notes.

Note: Parasitic plants are different from carnivorous plants like the Venus flytrap, which catch insects for
protein but still make their own sugars using sunlight and are thus still green. Parasitic plants steal all or nearly
all their food directly from other plants.

Page 97
4.5.1. Absorption and Uptake
 NOTES
4.5.1. Absorption and Uptake

Page 98
4.5.1. Absorption and Uptake
 4.5.2. Transport Within the ­
Organism

iStock.com / Thomas-Soellner

4.5.2. Transport Within the Organism

Learning objectives:
• To be able to explain the different types of transport/circulatory systems.

Page 99
4.5.2. Transport Within the Organism
 Knowledge
xxx
Transportation in living organisms is the movement of food, water, and oxygen to different parts of their body. The
closed circulatory system is responsible for transportation in all mammals, fish, birds, reptiles, and amphibians.
Some invertebrates, like earthworms, octopuses, and squids, also have a closed circulatory system. The main parts
of the circulatory system are blood, blood vessels, and the heart. Blood is pumped through different types of blood
vessels by the heart.

Blood
Blood consists of: plasma, red blood cells, white blood cells, and platelets. Blood has many different functions,
including transporting oxygen, carbon dioxide, nutrients and hormones around the body.
4.5.2. Transport Within the Organism

Plasma
Plasma is the liquid component of blood. It is a mixture of water, sugar, fat, protein, and salts. The main job of the
plasma is to transport blood cells throughout the body along with nutrients, waste products, antibodies, clotting
proteins, chemical messengers such as hormones, and proteins that help maintain the body’s fluid balance.

Red blood cells (also called erythrocytes)

Red blood cells contain a special protein called hemoglobin, which helps carry oxygen from the lungs to the rest
of the body and then returns carbon dioxide from the body to the lungs so it can be exhaled. Blood appears red
because of the large number of red blood cells, which get their colour from the hemoglobin.

White blood cells (also called leukocytes)

White blood cells protect the body from infection. They are much fewer in number than red blood cells, accounting
for about 1 percent of the blood.

Platelets (also called thrombocytes)

Unlike red and white blood cells, platelets are not actually cells but rather small fragments of cells. Platelets help
the blood clotting process (or coagulation) by gathering at the site of an injury, sticking to the lining of the injured
blood vessel, and forming a platform on which blood coagulation can occur.
White blood cell

Platelet

Red blood cell

Comparison of a human red blood cell,

erythrocyte, a white blood cell, leukocyte
and a platelet thrombocyte. SEM X2500.
DR STANLEY FLEGLER / BSIP

Page 100
4.5.2. Transport Within the Organism
 Knowledge
Blood vessels
Blood vessels are tubes that carry blood throughout the
Artery
body. They form a closed loop, like a circuit, that begins
and ends at the heart. There are three main types of blood
vessels called arteries, capillaries and veins.
Arteries: These strong, muscular blood vessels usually
carry oxygen-rich blood from the heart to the body. (There
is an exception from the heart to the lungs. That artery
carries deoxygenated blood.)
Capillaries: These tiny blood vessels have thin walls.

4.5.2. Transport Within the Organism

Capillary Oxygen and nutrients from the blood can move through
the walls and get into organs and tissues. The capillaries
also take waste products away from the tissues. Capillaries
are where oxygen and nutrients are exchanged for carbon
dioxide and waste.
Veins: Unlike arteries, veins usually carry deoxygenated
blood back to the heart. (There is an exception from the
lungs to the heart. That vein carries oxygen-rich blood.)
Veins have thin, less elastic walls and most veins have
valves that open and close. These valves ensure blood flow
Vein and keep the blood flowing in one direction.

Freepik / S. Coté / PPC

Task
Identify one special feature of the arteries, of the capillaries and of the veins and explain why they are
important:

Special feature Function

Arteries

Capillaries

Veins

Page 101
4.5.2. Transport Within the Organism
 Knowledge
The heart Superior vena
cava
The heart is a fist-sized organ that
pumps blood throughout the body. It
is the primary organ of the circulatory
system.
Aorta
Pulmonary
artery
Pulmonary
Left vein
4.5.2. Transport Within the Organism

Atrium
Right Atrium Mitral
valve
Pulmonary Aortic
valve valve
Left
Triscuspid ventricle
valve Right
ventricle

Inferior vena cava

Pericardium
A. Valentini / PPC

Task
Explain how blood flows through an organism with a closed circulatory system. Make sure you name all the correct
blood vessels and all of the parts of the heart. Start with the following.

Deoxygenated blood from all over the body arrives at the right atrium through the superior and inferior venae cavae...

______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

_______________________________________________________________________________________________________________________________

Page 102
4.5.2. Transport Within the Organism
 Knowledge
Plants have primarily two types of tissues that help transport water, minerals, and nutrients. Those tissues
are the xylem and phloem. Xylem and phloem are both transport vessels that combine to form a vascular
bundle in higher order plants. The vascular bundle functions to connect tissues in the roots, stem and leaves
as well as providing structural support.

Xylem
Mature xylem consists of elongated dead cells, arranged end to end to form continuous vessels (tubes).
Xylem does not contain any cytoplasm and is impermeable (fluids are unable to pass through) to water. The
outer wall of the xylem is quite tough containing a woody material call lignin. Xylem is responsible for the
transportation of water and mineral salts from the roots to different parts of a plant.

4.5.2. Transport Within the Organism

Phloem
Phloem consists of living cells arranged end to end. Unlike xylem, phloem vessels contain cytoplasm, and this
goes through the holes in the sieve plates from one cell to the next.
Phloem transports glucose and amino acids up and down the plant. This transport of dissolved material
within a plant is called translocation. In general, this happens between where these substances are made
(the sources) and where they are used or stored (the sinks).

Freepik / S. Coté / PPC

Any applied chemicals to the plant, such as pesticides, also move through the plant by translocation.

Sabrina checks that the text matches what you want. If it

doesn’t, I’ll put back exactly what’s written in the pps.

Page 103
4.5.2. Transport Within the Organism
 Knowledge
Ostia
In contrast to a closed circulatory system, (openings in heart)
Dorsal blood vessel

4.5. Transport
arthropods (including insects, crustaceans, and
most mollusks) have an open circulatory system.
In an open circulatory system, the blood is not
enclosed in the blood vessels, but is pumped into a Hearts
cavity called a hemocoel.
The blood is called hemolymph because it mixes
with the interstitial fluid. As the heart beats and
the animal moves, the hemolymph circulates
around the organs within the body cavity,
reentering the heart through openings called ostia
4.5.2. Transport Within the Organism

(singular: ostium). This movement allows for gas Body cavity

and nutrient exchange. Feepik / A. Valentini / PPC

An open circulatory system does not use as

Tubular heart much energy to operate and maintain as a
closed system, however there is a trade-off
with the amount of blood that can be moved
Ostia
to the organs and tissues that require high
(openings in heart) levels of oxygen.
In fact, one reason that insects with wing
spans of up to 70 cm are not around today
is probably because they were outmatched
by the arrival of birds 150 million years ago.
Birds, having a closed circulatory system, are
thought to have moved more agilely, allowing
them to obtain food faster and possibly to
prey on the insects.

Blood flows around

body cells

Feepik / S. Coté / PPC

Task
Comparing the differences of transportation methods in plants, certain animals and insects. Complete the
following table:

Mammals, fish, birds,

Variable Plants Insects
reptiles and amphibians

Transport system Closed circulatory system Xylem and phloem Open circulatory system

Composition of the
transport system

Substances
transported

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 4.5.3. Waste Disposal
Aboussoir Maoulida / PPC

4.5.3. Waste Disposal

Learning objectives:
• To be able to explain how plants dispose of oxygen.
• To be able to explain how heterotrophs dispose of CO2 and complex organic
molecules.

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 Task

State the waste products of a monkey (heterotroph):

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________
S. Coté / PPC
______________________________________________________________
4.5.3. Waste Disposal

State the waste products of plants:

______________________________________________________________ Photos Stéphane

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________
S. Coté / PPC

State the waste products of an insect in this case a grasshopper:

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________

______________________________________________________________
S. Coté / PPC
______________________________________________________________

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4.5.3. Waste Disposal
 Knowledge
Human excretion

Excretion is a process in which metabolic waste is eliminated from an organism. In vertebrates this is primarily
carried out by the lungs, kidneys, and skin. The excretory system consists of organs which remove these
metabolic wastes and toxins from the body. In humans, this includes the removal of urea from the bloodstream
and other wastes produced by the body. The removal of urea happens in the kidneys, which is the primary
excretory organ in humans, while solid wastes are expelled from the large intestine.

The kidneys Urinary tract

The kidneys are paired, bean-shaped organs located

in the abdomen, on either side of the spine, under Kidney
the diaphragm. Blood enters the kidneys via the renal
artery and exits them via the renal vein.
The kidneys are made of a large number of structural
and functional subunits called nephrons. These

4.5.3. Waste Disposal

nephrons perform the primary task of filtering blood
and removing waste products by producing urine. The
urine is transported from the kidneys via the ureter,
where it is stored by the bladder prior to excretion.
Ureter

Structure of the kidney Urethra

A. Valentini / PPC

Medulla
Each nephron snakes between the outer cortex of the
Renal artery kidney and the inner medulla, with different activities
occurring at each site. Consequently, the composition
of blood entering the kidney (via the renal artery)
differs to that exiting the kidney (via the renal vein).

Renal vein

Renal pelvis

Cortex
Ureter
A. Valentini / PPC

Blood in the renal vein (i.e. after the kidney) contains: Structural organisation of the kidney’s
- Less urea (large amounts of urea is removed via the
nephrons to form urine).
- Less water and solutes / ions (amount removed will Cortex
depend on the hydration status of the individual).
- Less glucose and oxygen (not eliminated, but used
by the kidney to generate energy and fuel metabolic
reactions).
Medulla
- More carbon dioxide (produced by the kidney as a
by-product of metabolic reactions). A. Valentini / PPC

Kidney Nephrons

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4.5.3. Waste Disposal
 Task
iStock.com / BENCHAMAT1234
Urinalysis

Urinalysis is a simple test that looks at a small sample of

urine. It can help identify medical problems that need
treatment. In a hospital a student nurse was asked to take
a urine sample from five different patients and test them.
After she took the samples she noticed that she forgot to
label the different urines, therefore she didn’t know which
samples belonged to which patient. She tested the different
samples anyway and hoped that she would be able to
match the urine samples to the patients.

Materials needed:
The teacher or lab assistants need to prepare five urine
- The five different urine samples labelled A - E samples for each group prior to the experiment. Urine
- White paper can be imitated by using herbal tea bags. Leave one urine
4.5.3. Waste Disposal

untouched. Add glucose to another urine. Leave the tea

- Universal indicator paper bag in for longer in another sample in order to get a darker
- Urine analysis sticks which test for glucose colour. Add protein (such as powdered egg) to another
and protein (such as Combur 5 Test® HC) sample and finally, add some alkali to the last sample (pH
needs to be above 9).
- Paper towels

Method:
1. Hold a white piece of paper behind each urine sample and look at it. Make a statement about its colour and
transparency in the results table below.
2. Open the urine samples and dip a piece of universal indicator paper in each sample.
3. Put the universal indicator paper on a paper towel and record your results in the results table.
4. Insert a fresh urine analysis stick into each urine sample and for each record the presence or absence of glucose
and protein.
5. Then match the patients (following page) to the urine samples using the description of the medical conditions of
each patient.
Results:

Colour and Presence of Presence of

pH Patient
transparency glucose protein

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 Task

Patient 1
Was recently diagnosed with diabetes and was Patient 2
admitted to the ward in order to regulate his blood Was admitted to the ward with kidney failure.
sugar. Having sugar in your urine is usually a sign Kidney failure can result in a pH higher than 8.
of very high blood sugar levels which is typical for
a diabetic person.

Patient 3

4.5.3. Waste Disposal

Is due to go home today
after she has been
released by the doctor
following an appendix
removal.

Freepik

Patient 4 Patient 5
An 11 years old boy who was admitted An elderly patient who has Alzheimer’s.
with the fever that has lasted for over It is summer and the patient hasn’t drink
three days now. Such a severe fever can much water therefore she is severely
cause a short-term presence of protein dehydrated.
in urine.

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 Knowledge

Other excretory organs

Lungs Skin
A major product that must be excreted The skin is a secondary excretory organ since
from all animals is carbon dioxide. Carbon sweat glands in the dermis can remove salts
dioxide is created in the cells, as they undergo and some excess water. The skin also has
aerobic respiration. This waste product is sebaceous glands that can secrete waxy lipids.
removed from the cells and transferred to the
bloodstream. When the blood reaches the
lungs it is exchanged for oxygen and released
into the atmosphere.
4.5.3. Waste Disposal

S. Coté / Freepik / PPC

Liver Large intestine

The liver is the main detoxifying organ of The liver is also necessary for the removal of the
the body, especially for nitrogenous wastes. decomposed hemoglobin, some drugs, excess vitamins,
The cells of the liver play host to biochemical sterols, and other lipophilic substances. These are
processes that create ammonia from amino secreted along with bile and finally removed from the
acids. Since ammonia is extremely toxic, it body through feces. The large intestine, therefore, plays
is quickly converted to urea before being a role in excretion, especially for hydrophobic particles
transported in the blood towards the kidneys. (tending to repel or fail to mix with water.).

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 Knowledge
Plant excretion

Excretion is one of the most important life

processes that help to regulate life. However,
animals are more biologically complex than plants,
which is why a plant’s excretion system is much
simpler than that of animals. The numerous
metabolic reactions produce useful products, as
well as unwanted toxins. When accumulated, these
toxins can be fatal. An excretory system gets rid of
these toxins or metabolic waste to ensure a longer,
healthier life. Freepik

Plants excrete through stomatal pores on their

leaves. The major metabolic reactions occurring in
a plant that produce this waste are photosynthesis
and cellular respiration.
The gaseous waste produced of photosynthesis is S. Coté / PPC
oxygen. Excess oxygen is an undesirable toxin for

4.5.3. Waste Disposal

the plant which is released through the stomata
into the surrounding air. Plants obtain a voluminous quantity of carbon dioxide from
animals, and in return, plants replenish us with oxygen. In
this way, plants and animals share a symbiotic relationship.
They live and benefit from each other. The absence of one
would fatally affect the survival of the other.

The gaseous waste produced when a plant cell respires is carbon dioxide. The carbon dioxide oozes
through its stomata and is simultaneously used as the reactant for photosynthesis. Similarly, some of
the oxygen produced by photosynthesis is utilized for cellular respiration.

When plants have more water in their leaves than

Gas exchange in plants they need, they get rid of this extra water through
a process called transpiration. During transpiration,
Vein
water evaporates from the stomata of the leaves
Upper epidermis
into the air.

Palissade chlorophyll
Plants also excrete nitrogenous compounds that
are produced in protein metabolic reactions.
Palissade mesophyll Some metabolic reactions also produce organic
“waste”, of different forms. These include gums,
Lower epidermis various oils, latex, resins and a multitude of
Water Stoma crucial products that we borrow from plants.
These substances are found on barks, stems and
Photosynthetic CO2 O2 Water vapor colourful leaves.
products
A. Valentini / PPC

Plants can also store the waste in organs that are destined to fall off (like autumn leaves) or die off (like the
leaves and stalk of a bluebell which is dying back in the summer, leaving the bulb underground).
Some plants will actively secrete waste compounds (allelochemicals) into the soil, occasionally using them as
chemical weapons against other competing plants e.g. conifers and some palms such as cohune.

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 Task
Plant excretion

Materials needed:
- Elodea cutting
- Test tube
- Sodium bicarbonate (baking soda)
- Beaker with water
- Lamp
- Filter funnel

Method:

1. Fill the beaker with enough water to completely submerge the filter funnel.
2. In order to improve results add a little sodium bicarbonate to the water.
4.5.3. Waste Disposal

3. Cut one elodea stem at an angle and use your fingers to crush the end of the stem.
4. Insert the elodea into the beaker and place the filter funnel on top of it.
5. Completely fill the test tube with water.
6. Using your finger close off the top of the test tube and insert it into the beaker upside down.
7. Gently remove your finger from the opening of the test tube and manoeuvre the test tube whilst staying under
water on top of the filter funnel.
8. Switch on the lamp and observe any bubbles given off.
9. This experiment might need to run over the duration of a few days.
10. Once enough oxygen has collected in the test tube you can remove the test tube gently (you will have to cover
the opening with your finger as soon as all of the water has come out).
11. Test the gas with a glowing match or splint. If it relights this is proof that oxygen is the gas in the test tube.

Sabrina can you doing this picture with your device ?

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 Knowledge
Insect excretion

Insects have a circulating fluid system called hemolymph. Within this fluid the excretory system (Malpighian
tubules) which connects to the digestive system of the animal is submerged within this fluid.
Malpighian tubules are slender tubes normally found at the junction between the midgut and hindgut. Each
tubule consists of a single layer of cells. The number of tubules varies between species although most occur
in multiples of two. Tubules are usually bathed in hemolymph.
Midgut Hindgut
The Malpighian tubules branch off from the Haemolymph::
Haemolymph
intestinal tract and actively uptake nitrogenous Salt, uric acid, water
Into Tubules
wastes (as uric acid) and water from the
hemolymph. The tubules then pass these
materials into the gut to combine with the
Excretion::
Excretion
digested food products. Some solutes, water Uric acid and faeces
and salts are reabsorbed into the hemolymph Out
at the hindgut, whereas uric acid and
undigested food are excreted via the anus. Haemolymph:
Haemolymph:
Malpighian tubules Salt and water

4.5.3. Waste Disposal

A. Valentini / PPC Recycled

Task
Grasshopper dissection

The Malpighian tubules can easily be seen in grasshoppers and dissected out. For this you need to make
sure that the grasshopper is submerged in water throughout the dissection in order to remove the intestinal
tract with the Malpighian tubules easily. If you use previously boiled water there won’t be any air bubbles in
the way.
Materials needed: Method:
- Lab coat 1. Examine the outside of your grasshopper.
- Gloves 2. Cut off all of the legs and wings with the scissors so that
- Googles you are left with the grasshopper body only.
- Dissecting pan 3. Using your scissors cut from the bottom of the
grasshopper towards the head along the back. Make
- Tweezers sure that you are staying right under the edge of the
- Dissecting scissors exoskeleton.
- Pins 4. Open the grasshopper along your cut and pin each side on
the dissecting pan using the dissecting pins.
- Water (enough to cover the grasshopper)
5. Pour the water over the grasshopper until it is fully
- Grasshopper
submerged.
- Magnifying glass (optional)
6. Locate the Malpighian tubules.
7. Using tweezers gently remove the Malpighian tubules and
examine them.

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 Chapter 6

4.6. Control

iStock.com / Libre de droit

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4.6. Control
 4.6.1. Control of the Self

iStock.com / iLexx

4.6.1 Control of the Self

Learning objectives:
• To be able to explain the competing interests of individual cells and the organism
as a whole.
• To be able to describe cancer as a failure to control “selfish” cells.
• To be able to identify risk factors for cancer in humans.

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4.6.1. Control of the Self
 https://www.cancerresearchuk.org/terms-and-conditions
Knowledge
It’s not possible to keep this article. The site prohibits it. You
What is cancer? need to rewrite it
All cancers begin in cells. Our bodies are made up of billions of cells. Cancer starts with changes in one cell or a
small group of cells.
Usually, we have just the right number of each type of cell. This is because cells produce signals to control how
much and how often the cells divide. If any of these signals are faulty or missing, cells might start to grow and
multiply too much and form a lump called a tumour.

Normal Cancer
A primary tumour is where the
cancer starts. Some types of
cancer, called leukaemia, start Large, variably shaped
from blood cells. They don't nuclei
form solid tumours. The cancer
cells build up in the blood and
sometimes the bone marrow. Many dividing cells;
4.6.1. Control of the Self

For a cancer to start, certain Disorganized arrangement

changes take place within the
genes of a cell or a group of cells.
Variation in size and shape

Loss of normal features

Sabrina please find the photos on Alamy, istock or
BSIP

Genes and cell division

Different types of cells in the body do different jobs, however all cells also share similarities.
They have a nucleus which is the control centre of the cell. Inside the nucleus are chromosomes made up of
thousands of genes. Genes contain long strings of DNA (deoxyribonucleic acid), which are coded messages that tell
the cell how to behave.
Each gene is an instruction that tells the cell to make something. This could be a protein or a different type of
molecule called RNA (ribonucleic acid). Together, proteins and RNA control the cell. They decide:

- what sort of cell it will be

- what it does
- when it divides
Nucleus containing
- when it dies chromosones made up of
thousands of genes

A. Valentini / PPC

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4.6.1. Control of the Self
 https://www.cancerresearchuk.org/about-cancer/what-is-cancer/how-cancer-star
Knowledge
It’s not possible to keep this article. There are no
Gene changes within cells (mutations) authorisations :(
Genes make sure that cells grow and make copies (reproduce) in an orderly and controlled way, and are
needed to keep the body healthy.

Sometimes a change happens in the genes when a cell divides. This is a mutation. It means that a gene has
been damaged or lost or copied too many times.

Mutations can happen by chance when a cell is dividing. Some mutations mean that the cell no longer
understands its instructions. It can start to grow out of control. There have to be about six different mutations
before a normal cell turns into a cancer cell.

Mutations in genes may mean that:

a cell starts making too many proteins that trigger a cell to divide
a cell stops making proteins that normally tell a cell to stop dividing
abnormal proteins may be produced that work differently to normal.

4.6.1. Control of the Self

It can take many years for a damaged cell to divide and grow and form a tumour big enough to cause
symptoms or show up on a scan.

How mutations happen

Mutations can happen by chance when a cell is dividing. They can also be caused by the processes of life
inside the cell, or by things coming from outside the body, such as the chemicals in tobacco smoke. Some
people can inherit faults in genes that make them more likely to develop a cancer.

Some genes get damaged every day and cells are very good at repairing them. But over time, the damage
may build up, and once cells start growing too quickly, they are more likely to pick up further mutations and
less likely to be able to repair the damaged genes.

Some common forms of cancer?

A Wright’s stained
Cancer may occur anywhere in the body. In women, bone marrow
breast cancer is one of the most common. In men, it’s aspirate smear from
prostate cancer. Lung cancer and colorectal cancer a person with B-cell
affect both men and women in high numbers. Among acute lymphoblastic
children (ages 0 to 14 years), the most common types leukemia.
of cancer are leukemia. Leukemia is a group of blood
cancers that usually begin in the bone marrow and
result in high numbers of abnormal blood cells.

VashiDonsk / CC BY SA 3.0 via Wikimedia

https://en.wikipedia.org/wiki/Leukemia#/media/
File:Acute_leukemia-ALL.jpg

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 Knowledge
The birth and death of cells

The growth and replication of cells is often described G2

as a cyclic process with two main phases: interphase,
when the cell grows and replicates DNA in preparation The cell «double checks» the
duplicated chromosomes for
Mitosis
for cell division, and mitosis, during which the actual error, making any needed
repairs
division of the cell into two daughter cells occurs. k inesis
Cyto
The events occurring in this cyclic process are
summarized in the diagram on the right in which S In
terp a s e
G1
h
Each of the 46
interphase events are shown with green arrows and chromosomes is
Cellular contents excluding
mitosis is shown in brown. Note that cells may also exit duplicated by
the cell. the chromosomes,
the cycle and enter a G0 phase either temporarily or are duplicated.

more or less permanently.

G0
Cell cycle arrest
S. Coté / PPC

In cells that are actively growing and dividing, such as misaligned. The many factors that regulate the cell cycle
4.6.1. Control of the Self

those in an embryo, the cycle is completed frequently play an important role in the aging process, because
as cells divide over and over during the embryo growth as cells age their capacity to replicate diminishes to
and development. In adults the need for growth and the point that they are no longer able to divide. As
development has passed, and most cells remain in the this occurs, the ability to replace damaged or lost
G0 phase during which they perform their specialized cells dwindles and ultimately results in a decline in
functions, but they no longer replicate (e.g., nerve and tissue strength and cellular and organ function that is
muscle cells). Nevertheless, even in fully developed characteristic of aging.
adults, certain cells retain the ability to replicate and
give rise to new daughter cells to replace cells that are
damaged or lost due to wear and tear. Regulation of the Aging and p53
cell cycle is of critical importance to the aging process.
Replication should only occur when there is a need for Protein 53 (p53) is a tumor suppressor protein that is
growth and development (in embryos and the young) encoded by the TP53 gene. The p53 protein has been
or when there is a need to replace damaged or lost extensively studied because the gene that encodes it
cells. Thus, the cycle is influenced by growth factors and has been found to be mutated in approximately half
by proto-oncogenes (Mutations in a proto-oncogene of all human cancers. Stopping cell growth at the G1
may cause it to become an oncogene, which can cause checkpoint is mediated by p53 which is rapidly activated
the growth of cancer cells) that favour replication and in response to damaged DNA. Following the stopping
by anti-oncogenes that produce proteins that inhibit of cell division, p53 will also induce either cell death
replication. These various factors interact to regulate through apoptosis or permanent loss of the ability of
the cell cycle in cells that have retained the capacity to a cell to proliferate (senescence). The accumulation of
divide. senescent cells contributes to aging because it leads
to reduced tissue renewal and repair. Several studies
In addition, there are cellular processes that constitute conducted in both mice and humans on mutant p53
checkpoints that prevent the cell cycle from proceeding genes have supported the notion that increased cancer
if errors have occurred. The first checkpoint occurs protection by mutant p53 can also lead to a shortened
during the G1 phase which provides an opportunity for life span.
cellular processes to repair damaged DNA before the
cell enters the S phase when replication occurs. This
prevents the daughter cells from inheriting damaged
DNA, which would result in mutations. There are also
other checkpoints in S and G2 phases that check for
damaged DNA and failure of DNA replication. The
final cell cycle checkpoint occurs at the end of mitosis
and checks for any chromosomes that have been

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 Knowledge

Apoptosis
Apoptosis, also known as programmed cell death, is a regulated process that takes place throughout life and
serves to eliminate unnecessary or damaged cells. Apoptosis takes place during embryonic development
as a means of reshaping tissues during normal growth and development, and it provides a mechanism for
eliminating worn out or damaged cells throughout life. Age-related diseases such as Alzheimer disease and
Parkinson's disease have been linked to an increase in apoptosis where cells that might otherwise continue
to support proper tissue functioning are eliminated. There are many pathways and proteins that regulate
apoptosis, such as p53, that are able to sense cells that are damaged or no longer needed. The image below
illustrates a cell undergoing apoptosis.
Pre-Apoptotic Cell Early Apoptotic Cell Late Apoptotic Cell
Apoptotic
bodies

4.6.1. Control of the Self

Membrane Nuclear
blebs fragments
A. Valentini / PPC

Once molecular signals trigger apoptosis, catabolic (Catabolism is the break down of complex molecules)
processes are initiated in the cell. Various enzymes begin to break down cellular components and fragment
nuclear DNA. The chromatin condenses, the cell begins to shrink and irregular bulges in the plasma
membrane known as blebs form. The cell eventually breaks into several smaller pieces known as apoptotic
bodies containing the cell components and the nucleus. The apoptotic bodies are then taken up by
macrophages and removed.

Autophagy
Autophagy is another mechanism by which cell death can occur. Like apoptosis, it is a highly regulated process that
plays a normal role in cell growth, development and homeostasis. Autophagy allows a starving cell to reallocate
nutrients from unnecessary processes to more essential ones, and it also plays an important housekeeping role by
removing misfolded or aggregated proteins, clearing away damaged
Lysosomal hydrolase
organelles, such as mitochondria Lysosome
and endoplasmic reticulum, as VESICLE
well as eliminating intracellular ELONGATION Autolysosome
pathogens. In addition, autophagy
degrades proteins to enable their
replacement and also degrades
damaged proteins that are no
longer functional. Isolation
membrane Autophagosome
VESICLE DOCKING & VESICLE BREAKDOWN &
NUCLEATION FUSION DEGRADATION
A. Valentini / PPC
Summary of Autophagy

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 Task

Most cancers occur randomly, however certain factors and behaviours make human cancer more likely.
Research those factors and explain how you might prevent them and then present them.
4.6.1. Control of the Self

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 Task

Optional: Create posters which make students aware of cancer causing factors and behaviours and display
them around school.

Space for brainstorming and ideas for your poster:

4.6.1. Control of the Self

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 Task
Optional: Research different cancer treatments and explain how they work.
4.6.1. Control of the Self

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 Task

Optional: Plan and organise a charity event in your school and donate the money to a cancer organisation.

Space for brainstorming and ideas for your charity event:

4.6.1. Control of the Self

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 Task

Optional: Research sources of help and support for those affected by cancer, both local and national.
4.6.1. Control of the Self

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