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Junior Certificate Biology
Animal and Plant Cells
All living things are made of tiny building blocks called cells. Cells are extremely small and can
only be seen with a microscope. There are two major types of cells, animal and plant cells. Their
structures and functions are shown below.
Plant cell
Animal cell
Cell membrane
Chloroplast
s
Nucleus
Cell wall
Vacuole
Cytoplasm
Part
Function
Nucleus
Controls all cell activities,
growth, cell division etc.
Membrane
Controls the passage of
substances in and out of the
cell.
Cytoplasm
Jelly-like substance which
provides food for the cell.
Vacuole
Mops-up excess water and
salt and stores sugar. Are
small in animal cells and large
in plant cells.
Chloroplast
Contain green chlorophyll
which are used to makes food
for the plant cell [plant only]
Cell wall
Gives strength to plant cells
only]
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Junior Certificate Biology
The differences between animal and plant cells
 Animal cells have no cell wall.

Animal cells have no chloroplast.

Animal cells have small vacuoles.
Using a light microscope
Eye piece
Focus
Objective
lens
Stage
There are four major parts of a microscope,
 Eyepiece – This is the lens which you look through.
 Focus – This allows you to focus on the sample being examined.
 Objective lens – This lens is placed directly in front of the object being examined.
 Stage – This a platform on which the sample is placed for viewing.
Mandatory experiment: to examine plant cells under a light microscope.
 Place some onion tissue on a slide.
 Cover with iodine stain.
 Leave for a minute.
 Examine with the microscope, using the different lenses.
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Junior Certificate Biology
Onion
cells

A tissue is a group of similar cells with a special function (heart tissue or nerve tissue).

An organ is a group of tissues that work together to carry out a special function. The
heart is an organ which consists of muscle tissue, blood tissue, blood vessels, valve tissue
and others, all doing the job of pumping blood.

A system is a group of organs working together (the digestive system).
Growth results from cells dividing to form new cells.
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Junior Certificate Biology
Chapter 3 – Food
All living things need food. We need food for three main reasons,
1. To give us energy.
2. For growth and repair.
3. For protection against disease.
The five major nutrients in our food are given in the table below.
Food type
Carbohydrate
 Starch
 Sugar
 Fibre
Fat [lipids]
Protein
Function
Sources
Provides energy
Provides energy
Prevents
constipation
Stored energy
Insulation
Source A/D
vitamins
Growth and Repair
Bread, pasta
Sweets, biscuits.
Fruit and vegetables.
Butter
Margarine
Fried food
Vitamins
A vision
D bones
C joints
Eggs, meat, dairy
products
Fish oil
Milk, sunlight
Citrus fruits, potatoes
Minerals
Ca bones
Fe red blood cells
Milk, cheese, salmon
Liver, cabbage
Balanced diet
A balanced diet is one which has the
right amount of all five food groups
needed to stay healthy.
The average daily energy requirement
for a teenager.
Boy – 12,000 kJ
Energy from food
The energy content of food is
measured in kilojoules or kilocalories.
Both are mentioned on food packets.
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Girl – 10,000 kJ
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Junior Certificate Biology
The food pyramid
1. Place a small quantity of the
food which you want to test
into a test tube.
2. Add 2 drops of iodine indicator.
3. If starch is present in the food
sample it will turn blue/ black.
4. Repeat for different food
samples
Sugar,
crisps
Meat, fish
poultry
Dairy products
Mandatory experiment; To test for
the presence of glucose.
Fruit and vegetables
Bread, potatoes, rice, pasta
food and
benedict's solution
The food pyramid shows us roughly how
much of type of food we should be
eating every day.
Only small amounts from the top of
the pyramid and large amounts from
the bottom.
boiling water
Mandatory experiment; To test for
the presence of starch.
1. Place a small quantity of the
food which you want to test
into a test tube.
2. Cover with Benedict’s solution
(blue).
3. Place the test tube into boiling
water.
4. If glucose is present in the
food sample the solution will
turn from blue to brick red.
5. Repeat for different food
samples.
iodine
(red)
food sample
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Junior Certificate Biology
Mandatory experiment; To test for
the presence of protein (the Biuret
test).
1. Add a small amount of the food
to be tested to a test tube.
2. Add an equal amount of Biuret’s
reagent.
3. Shake the test tube. If a
permanent violet colour develops
in the mixture protein is present.
3. Note the rise in temperature.
4. If it is releasing heat it must
contain energy.
THE DIGESTIVE SYSTEM
The digestive system in humans is group
of organs working together to break
down food.
Mandatory experiment; To test for
the presence of fat in a food sample.
1. Crush a sample of the food
against a piece of brown paper.
2. If a permanent translucent spot
is left on the paper then fat is
present in the food sample.
Mouth
oesophagus
Liver
Small
intestine
Mandatory experiment; To investigate
the conversion of chemical energy in
food to heat energy.
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Large
intestine
Anus
Organ
1. Set a crisp alight using a Bunsen
burner.
2. Once it is burner unaided, hold a
thermometer near it.
Stomach
Function
Mouth
Food is mixed with saliva
and chewed. Amylase
enzyme breaks down the
starch.
Oesophagus
A tube which brings the
food from the mouth to
the stomach by muscular
action.
Stomach
Churns the food and
mixes it with digestive
juices and acid. Acid kills
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Junior Certificate Biology
Pancreas
Liver
Small
intestine
bacteria.
There are four types of teeth.
Produces digestive
enzymes.
Produces bile to break
down fats.
Incisors
Sharp flat front teeth
used to cut food.
Canines
Pointed teeth for tearing
food.
Premolars
Flat back teeth for
grinding food
Produces enzymes and
carries out the final
breakdown of the food.
Food is absorbed into
the bloodstream here.
Large
intestine
Water passes back into
the bloodstream from
here producing solid
waste.
Anus
Waste food is released
through here.
Molars
Larger flat back teeth for
grinding food.
Chemical digestion
Chemical digestion involves the use of
special chemicals, called enzymes, to
breakdown the large food molecules
(proteins, fats and carbohydrates) into
smaller ones.
An enzyme can be defined as a
biological catalyst. A catalyst is a
chemical which speeds up a chemical
reaction without itself being used up.
The five stages of Nutrition
1. Ingestion – taking in food.
2. Digestion – breaking down the
food by chewing and churning or
by enzyme.
3. Absorption – passing of food into
the blood stream.
4. Assimilation – this is where body
cells use the food for energy,
growth and repair.
5. Egestion – getting rid of waste
food through the anus.
How enzymes work
 The substance acted-on by the
enzyme is called the substrate.
 The substance formed by the
enzyme action is called the
product.
 The enzyme works by grabbing a
substrate molecule, breaking it
down and then releasing the
products when they are formed.
An example of this is amylase enzyme.
It grabs starch molecules, breaks them
down into maltose molecules and then
releases them.
A second enzyme called maltase then
breaks down the maltose into glucose.
Physical digestion of food
The physical digestion of food is
carried out by (i) muscle action, the
stomach and intestinal walls crush the
food by squashing it, or (ii) crushing,
using teeth to cut and grind the food.
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Junior Certificate Biology
RESPIRATION AND BREATHING
Mandatory experiment; To show the
action of amylase enzyme on starch.
A
Respiration is the release of energy
from food. Aerobic respiration requires
oxygen and can be written as a word
equation;
B
water at 37oC
Glucose + oxygen →
carbon dioxide + water + energy
Starch only
Starch and amylase
enzyme
The human breathing system
1. In test tube A put starch only.
2. In test tube B put some starch
and a few drops of amylase
enzyme solution.
3. Place both in a beaker of warm
water. The enzyme works best in
warm conditions.
4. After 10 minutes, take out a
small amount of A and B and test
them with iodine solution.
5. ‘A’ will turn blue/ black due to
the presence of starch.
6. ‘B’ will not change the colour of
the iodine because the enzyme
has converted all of the starch
to maltose.
7. Test both test tubes with
Benedict’s solution.
8. A shows no reaction to it.
9. B changes the blue benedict’s
solution to brick red. This shows
that test tube B now contains
sugar. This must be due to the
presence of the enzyme.
Voice
box
Rings of
cartilage
Trachea
Bronchus
Diaphragm
Organ
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Function
Voice box
Makes sounds when air
passes through it.
Trachea
Wind pipe. Passes air
to the lungs.
Rings of
cartilage
Keep the windpipe open
at all times.
Bronchus
A branch from the
trachea to each lung.
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Junior Certificate Biology
The blood now goes back to the
heart with a new supply of
oxygen.
 The heart can then pump it
around the body.
Not all animals use lungs for breathing,
fish use gills and insects use spiracles.

Bronchioles
Small air passages
which bring air to the
alveoli.
Alveoli
Air sacs surrounded by
blood vessels. Gas
exchange occurs here.
Diaphragm
A sheet of muscle
which helps to draw air
in and out of the lungs.
Gas exchange in the lungs




Air enters the alveoli from the
bronchiole tubes. It is carrying a
fresh supply of oxygen.
The oxygen moves from the
incoming air into the blood
capillary.
At the same time carbon dioxide
and water vapour move out of the
blood capillary into the alveolus.
This exchange of gases is made
possible because of the very thin
walls of both the capillary and
the alveolus.
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The effects of smoking
1. It causes lung cancer because
cigarette smoke contains
carcinogenic chemicals.
2. It causes bronchitis because the
smoke irritates the lungs causing
them to produce more mucus.
3. Carbon monoxide replaces oxygen
in the blood. The heart needs to
pump blood under greater
pressure to ensure an adequate
supply of oxygen to cells. This
puts a strain on the heart and
can lead to heart attacks.
4. Smoking during pregnancy
reduces the oxygen supply to the
baby.
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Junior Certificate Biology
Mandatory experiment; To
demonstrate that expired air has
more carbon dioxide than inhaled air.
Experiment; To show that respiration
produces carbon dioxide gas.
stopper
A
woodlice
B
limewater
limewater
A
B
1. Set up the apparatus as shown.
2. After a few hours, the limewater
in test tube ‘A’ will have turned
milky-white because the
respiring woodlice will have been
producing carbon dioxide gas.
3. The limewater in ‘B’ will remain
unchanged as there is no
respiration occurring here.
Expired air
 Blow through ‘A’.
 This forces the air that you
exhale to pass through the
limewater.
 Time how long it takes for the
limewater to turn milky-white.
Experiment; To show that respiration
produces water vapour.
Inspired air
 Suck air through ‘B’.
 This forces the inhaled air to
bubble through the limewater
before it enters your lungs.
 Time how long it takes to turn
the limewater milky-white.
stopper
woodlice
Results and conclusions
The exhaled air turns the limewater in
seconds while the inhaled air takes
several minutes. Therefore, we can
conclude that exhaled air contains more
carbon dioxide.
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blue cobalt
chloride
paper
A
B
1. Set up the apparatus as shown.
2. After a few hours, the blue
cobalt chloride paper in test
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Junior Certificate Biology
tube ‘A’ will have turned pink
because the respiring woodlice
will have been producing water
vapour.
4. The paper in ‘B’ will remain
unchanged as there is no
respiration occurring here.
CIRCULATION
The circulation system in consists of the
blood, arteries, veins, capillaries, and the
heart.
The Blood
Experiment; To show that respiration
produces heat energy.
Thermos
flask
A
Red blood cells
B
live
peas
White
blood
cells
dead
peas
Platlets
Red blood cells

cotton wool

thermometer




Set up the flasks as shown.
The temperature will rise in ‘A’
because the live peas are
respiring and producing heat.
The dead peas produce no heat.
The cotton wool keeps in the
heat as does the thermos flask.


White blood
cells


Protect against
disease.
1000 times less
numerous than rbc’s.
Platlets


Tiny bits of cells.
Cause blood clotting.
Plasma

Liquid part of the
blood.
Carries gases, food
and wastes.

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Most numerous blood
cell.
Contain haemoglobin
which carries
oxygen.
Have no nucleus.
Dip in middle.
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Junior Certificate Biology
Functions of the blood
1. Transport

The food, carbon
dioxide, and vital
chemicals are carried
around the body by the
plasma.
Rbc’s carry the oxygen.
2. Defence
against
disease



3. Regulates
Body
temperature

Some wbc’s digest
bacteria.
Others make antibodies
to kill bacteria.
Clotting stops entry of
infection to the body.
The heart
 The heart is a pump and pumps
blood through the arteries under
pressure.
 It is made of a special type of
muscle, cardiac muscle, which never
tires.
 The average adult heart rate is 70
beats per minute.
Distributes the body’s
heat
evenly.
The Blood vessels
There are three types of blood vessels:
arteries, veins, and capillaries.
Arteries





Veins





Carry blood to the heart.
Blood flows slowly.
Thin muscular walls.
Wide lumen.
Valves to prevent backflow.
Capillarie
s



Connect arteries to veins.
Thin-walled, one cell thick.
Blood cells fit through one at a
time.
Carry blood away from the heart.
Blood pumped under pressure.
Thick muscular walls.
Narrow lumen.
No valves.
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Passage of blood through the heart
 Blood enters the heart through the
vena cava from the body.
 The right atrium fills up with blood.
 The right atrium contracts and
pushes the blood into the right
ventricle.
 The right ventricle then contracts
and sends blood out of the heart, to
the lungs, via the pulmonary artery.
 This is the only artery in the body
which has a low oxygen supply.
 In the lungs the blood absorbs
oxygen and returns to the heart via
the pulmonary vein.
 This is the only vein in the body
which is rich in oxygen.
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Junior Certificate Biology


The left atrium fills with blood and
then pushes the blood into the left
ventricle.
When the left ventricle contracts,
it pushes blood out of the heart,
through the aorta, and around the
body.
EXCRETION
Heart disease
Heart disease is caused by the blocking of
the arteries that feed the heart itself.
Heart disease can be prevented by,
 Regular exercise.
 Healthy diet.
 Not smoking.
 Avoiding stress.
Experiment; To determine the effect of
exercise and rest on pulse rate
1. Locate your pulse at the wrist with
two of your fingers (not your thumb,
as it has a slight pulse).
2. Using a stop watch record the number
of beats in 15 seconds.
3. Multiply your answer by 4.
4. Repeat this twice more.
5. Get your average pulse rate.
6. Repeat steps 1-5 after a period of
exercise.
7. Compare the two pulse rates.
Experiment; To determine the effect of
exercise and rest on breathing rate
Repeat the procedure as for the above
experiment but count the number of
breaths per minute.
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Excretion is the removal of wastes made in
the body.
There are three main excretory organs in the
body:
1. The lungs – which excrete water and
carbon dioxide. If you blow through
limewater, it turns milky white. This
shows that carbon dioxide is present in
your breath. If you breathe out on a
piece of blue cobalt chloride, it will turn
pink. This shows the presence of water
vapour in the air we breathe out.
2. The skin - which excretes salt and
water (sweat) from the blood vessels
near the surface of skin.
3. The kidneys – which excrete salts,
water and urea (urine).
Renal
artery
Renal
vein
Kidney
Ureter
Bladder
Urethra
Kidney
Filters the blood and
removes salt, water and
urea.
Renal
artery
Brings blood to the kidney
Renal vein
Carries blood away from
the kidney
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Junior Certificate Biology
Ureter
A tube which passes the
urine made by the kidney
to the bladder.
Bladder
Stores up to 0.5 litres of
urine.
Urethra
Passes urine out of the
body.
2. Protection – the skeleton
provides protection for many
parts of the body. The brain,
ears and eyes are all protected
by the skull. The ribs protect the
heart, lungs and major blood
vessels.
3. Movement – the skeleton along
with the muscles and nerve
tissue allows us to move freely.
The human skeleton
Bone
Bone is a combination of soft living cells
(gives flexibility) and non-living calcium
salts (hard rigid part). The living cells
produce the non-living part of the bone.
Skull
Collar bone
Humerus
The Vertebral column
This is a stack of flattened bones,
hollow in the middle, which carry the
spinal cord out from the brain into the
body. The main job of the column is to
protect this cord. It also acts as an
anchor for the rib cage and the bones
of the arms and legs. Each of the bones
are separated from each other by discs
of cartilage, which act as shock
absorbers.
Breast bone
Radius
Ulna
Femur
Knee cap
Tibia
Fibula
The three functions of the skeleton
1. Support – the skeleton holds-up
all of our delicate internal organs
and carries a considerable weight
of tissue.
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Joints
Joints are formed where bones meet.
There are different kinds of joints:
1. Fused joints – the bones are
fixed together in a manner which
allows no movement. (The hip
bone is a number of bones fused
together to make one piece.)
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Junior Certificate Biology
2. Ball and socket joints – allow
movement in several directions.
(hip joint, shoulder joint)
3. Hinge joints – allow movement in
one plane only, like the hinges of
a door. (elbow, knee, fingers)


Moveable joints

Ligaments are tough elastic
fibres that join bone to bone.
 Cartilage is a soft but
reasonably tough tissue which
acts as a shock absorber
between the bones and
prevents them rubbing off each
other.
 The synovial fluid fills the cavity
surrounding the joint and acts as
a lubricating fluid.
 The synovial fluid and cartilage
act together to prevent friction
between the bones.
Antagonistic movement
Biceps
Triceps



Ligament
Muscles work by contracting
(getting smaller) and relaxing
(full size).
The muscles are joined to bone
by tendons. These are the
narrow tough parts at both ends
of the muscle.
The biceps muscle contracts and
pulls up the bones of the lower
arm.
At the same time, the triceps
relaxes.
To return the arm to its original
position, the triceps contracts
and the biceps relaxes.
This type of movement, where one
muscle is contracting while the other is
relaxing, is called antagonistic
movement.
Synovial
fluid
Cartilage
Muscles
 Muscles are made from bundles
of muscle cells called muscle
fibres. The fibres are collected
together in bunches called
muscles.
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Junior Certificate Biology
A sensory nerve carries messages to
the brain.
Nervous system and sense organs
_________________________
We have five senses, hearing, touch,
taste, smell and sight. These senses
are controlled by five sense organs, the
ears, the skin, the tongue, the nose and
eyes, respectively. These organs are
connected to the brain by the nerves of
the nervous system.
The nervous system
 The nervous system consists of
the brain and spinal cord (called
the central nervous system,
CNS) and all of the nerves
connected to the CNS.
 Each of the nerves consists of a
bundle of nerve cells.
 Each nerve cell can be up to 1
metre in length.
 The nerve (bundle of nerve cells)
is rather like an electrical cable
as it sends messages as electrical
signals.
How the nervous system works
 The sense organs pick up a signal
from the environment around us.
 A signal is sent along a sensory
nerve cell to the brain.
 The brain sends back a response
along a motor nerve to a muscle,
or some other organ, to carry out
a response.
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A motor nerve carries messages away
from the brain.
Reflex action (emergency response)
 If you put your hand on a hot
stove by mistake, delayed action
might result in serious injury.
 The usual response is too slow.
 A signal is sent from your hand
to the spinal cord and takes a
short-circuit back along a motor
nerve to the muscle of the arm,
causing it to move.
 This kind of action is called, a
reflex action.
The eye
Retina
Lens
Cornea
Pupil
Iris
Ciliary
muscle
Optical
nerve
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Junior Certificate Biology
Lens
Focuses light on the
retina.
Retina
Light sensitive cells.
Sends signal to optic
nerve.
Human reproduction
The male reproductive system
Gland which
makes
seminal fluid
Optical
nerve
Sends signal to brain.
Ciliary
muscle
Changes the shape of
the lens to help focus.
Pupil
The hole in the middle
of the iris.
Iris
Cornea
Sperm
duct
Penis
Controls the amount of
light entering the eye.
Clear outer layer.
Allows light in.
Helps to focus light.
17
Testis
Testis
Makes sperm cells and sex
hormones.
Sperm
cell
Made in testes. The male
gamete (sex cell)
Sperm
duct
Carries the sperm cells
from the testes.
Glands
Produce fluids for the
sperm cells to move about
in and also food supply.
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Junior Certificate Biology
The female reproductive system


Fallopian
tube
Uterus
Ovary
Vagina
Ovary
Produces egg cells.
Produces sex hormones.
Fallopian
tube
Carries the egg from the
ovary to the uterus.
Vagina
Holds the penis during
intercourse.
Uterus
Also called the womb.
Holds and protects the
baby during pregnancy.
Cervix
Opening of the uterus.
Sex organs mature.
Sperm cells made.
In girls
 Breasts develop, Growth of body
hair, Eggs mature and released,
Periods start and menstrual cycle
starts.
The menstrual cycle
From early teenage years up to the
menopause, in her late forties, a woman
will undergo a series of monthly
changes, which will affect her
reproductive system and her health and
well-being generally. This series of
monthly changes is often referred to as
her menstrual cycle. The menstrual
cycle occurs in a number of stages.
Puberty – The time between the ages
of 10 and 15 when hormone changes, in
both boys and girls, cause the body to
mature.
In boys
 Voice deepens
 Growth of hair on face, chest,
and underarms.
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Junior Certificate Biology
Menstrual cycle
1. Menstruation
(period)
Day 1 – 5
 Shedding of
extra lining of
the uterus.
 Blood loss.
 Unfertilised
egg passed out.
2. Repair stage
4. Rest stage
3. Ovulation
Day 15 – 28
 The extra
lining stays
built up in case
fertilisation
occurs.
Day 14
 The egg is
released from
the ovary into
the fallopian
tube.
Day 6 – 13
 Extra lining
builds up on the
uterus.
The fertile period
This is the time in the month in which a
woman is most likely to become
pregnant if she has sexual intercourse.


Sperm cells can survive for 3
days.
Egg cells can survive 4 days.
19
How a baby is made
1. Sexual intercourse
 During intercourse, the man’s
penis becomes filled with blood.
This causes an erection which
allows the penis to be placed
inside the vagina.
 A mixture of sperm cells and
seminal fluid (semen) is
ejaculated from the penis at the
opening of the uterus, the cervix.
2. Fertilisation
 The sperm cells, 200 million of
them, swim up through the
uterus towards the fallopian
tube.
 Only a few thousand make it to
the egg.
 Several sperm cells surround the
egg cell but only one fertilises it.
 Fertilisation is the fusion of the
male sperm cell and the female
egg cell to form a zygote.
Fertilisation takes place only in
the fallopian tube.
3. Pregnancy
 Once fertilisation occurs the
woman’s periods will stop and she
will not menstruate until after
the baby is born.
 Pregnancy lasts, on average, 40
weeks.
 After a week, the baby is a ball
of 200 cells, and implants itself
(buries itself) in the wall of the
uterus (this where the extra
lining is needed).
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Junior Certificate Biology






For the next 40 weeks the baby
gets all it needs from its mother
with the help of this lining.
After 8 weeks the baby is a fully
formed, but miniature, version of
a new-born baby.
The baby is held in a fluid-filled
sac (called the amniotic sac)
which protects it.
It gets all its food and oxygen
through and umbilical cord and
placenta.
Wastes and carbon dioxide also
pass out this way.
In this way the baby continues to
grow until birth
4. Birth
 The birth process begins with
contractions of the uterus
(labour).
 The amniotic sac bursts and the
contractions increase in severity.
 The mother must push with the
contractions to push the baby
out.
 Eventually, the baby will be born,
head first.
 The umbilical cord is cut and
clamped.
 The placenta passes out shortly
afterwards.
Fertilisation
occurs here
Baby grows
here
Genetics

Genetics is the study of the
inheritance of characteristics. Many of
our physical characteristics are passed
from generation to generation e.g. hair
colour, eye colour, height etc.

The nuclei of ordinary human body cells
contain 46 chromosomes, found as 23
pairs of chromosomes.

These chromosomes are chemicals
which appear as thin threads in the
nucleus, when viewed under the
microscope. They are made of protein
and a chemical called DNA.

Each chromosome is divided into
segments called genes. Each gene
controls a different characteristic.
Genes


20
Egg is
released from
here
Chromosome
Genes can be dominant or recessive.
A Dominant gene always shows in the
physical appearance of the person.
G. Nugent
Junior Certificate Biology




A recessive gene is hidden if the
dominant gene is present.
Example; in humans, eye colour is
controlled by two genes, the gene for
blue eye colour and the gene for brown
eye colour.
The gene for brown eyes is dominant
and is denoted by a capital letter ‘B’.
The gene for blue eyes is recessive and
is denoted by a lower case letter ‘b’.
There will always be two genes controlling the
characteristic, so a person with BB will be
brown-eyed, a person with bb will be blue-eyed
and a person with Bb will be brown-eyed (since
B is the dominant)
21
G. Nugent
Junior Certificate Biology
Plant structure
Part
Root
Stem
Leaf
Flowers
Buds
The equation for photosynthesis
The process of photosynthesis can be
summarized by the word equation below.
Function
1. Anchorage.
2. Absorb water and minerals.
3. Store food.
Carbon + water + chlorophyll + sunlight →
Glucose + oxygen
This can also be written in chemical symbols;
1. Hold leaves up to the light.
2. Hold up flowers
3. Transport water and food.
1.
6CO2  6H 2 O  light CHLOROPHYL
L  C6 H 12O6  6O2
The structure of the leaf
The leaf is adapted to photosynthesis in the
following ways;
 It is flat and thin to allow the maximum
light to be absorbed.
 The inner cells of the leaf have chlorophyll
for carrying out photosynthesis. The
chlorophyll is stored in structures called
chloroplasts.
 There are air spaces in the leaf to allow
carbon dioxide and oxygen gas to circulate
inside the leaf.
 There are tiny pores on the underside of
the leaf to allow gases in and out of the
leaf.
To make food by
photosynthesis.
1.To make fruit and seeds for
reproduction.
1. To make new flowers and
leaves.
Photosynthesis
Photosynthesis is the food-making process
which takes place in the leaves of plants. The
leaves of green plants take simple ingredients
and turn them into food.
There are four ingredients needed for
photosynthesis:
1. Sunlight (artificial lighting will do) - as
long as there is light photosynthesis can
take place.
2. Carbon dioxide – This gets into the
leaf through the pores on the underside
of the leaf.
3. Water – Enters the plant through the
roots and makes its way up the plant to
the leaves in special vessels called
xylem vessels.
4. Chlorophyll – This a green coloured
substance found in leaf cells. It absorbs
the sunlight which the leaf uses for
photosynthesis.
22
Experiment; To test a leaf for starch.
Leaves make glucose in photosynthesis but
store it as starch. If we can show the presence
of starch in the leaf we can demonstrate that
photosynthesis has taken place.

Place a leaf in boiling water. This
softens the leaf cells and makes it
easier to take out the chlorophyll from
the leaf.
boiling
leaf
water
5
4
6
2
1
5
7
3
11
4
8
3
9
2
6
7
8
9
1
10
hot plate
G. Nugent
Junior Certificate Biology

Transport in Plants
Place the leaf into boiling alcohol. This
removes the chlorophyll from the leaf.
The flow of water from the roots to the leaves
is called the transpiration stream.
boiling
alcohol
Transpiration is the loss of water vapour
from the surface of the leaf.
boiling
leaf
water
5
4
6
2
1


5
7
3
11
4
8
3
9
2
6
Water is lost from the leaf through tiny pores
on the undersurface called stomata. As water is
lost from the leaf more is sucked into the
leaves through the xylem vessels.
7
8
9
1
10
hot plate
Place the leaf back into boiling water.
This re-softens the leaf.
The leaf is placed on a dish and covered
with iodine. If starch is present then
the leaf will go blue black in colour.
Experiment; To show that photosynthesis
produces oxygen gas.
 Set up the apparatus as shown in the
diagram below.
 Shine light on the plant and leave it for
a couple of hours.
 After this length of time the test tube
should be full of gas.
 Remove the test tube carefully and test
the gas with a glowing splint. If the
splint relights the gas is oxygen.
The functions of transpiration are:
1. To transport water through the plant.
2. To carry minerals up from the roots to
the leaves.
3. To cool the plant.
The factors which affect the rate of
transpiration;
1.
2.
3.
4.
5.
23
Sunlight – bright sunlight causes the
pores to open and a lot of water to be
lost.
Heat – warm temperatures cause the
pores to open and a lot of water loss.
Wind – a gentle wind will cause pores to
open and loss of water.
Humidity – low humidity (dry air)
increases the amount of water loss
from the plant.
Soil water – high amounts of water in
the soil means high intake of water by
plants. This will result in a lot of water
lost by the plant.
G. Nugent
Junior Certificate Biology
Experiment; To demonstrate transpiration


The only explanation for this is that the
roots must have absorbed the water.
Note; The layer of oil is to prevent the
water level from dropping due to
evaporation.
Experiment; To the show the movement of
water in plants







Set up a potted plant, as shown above.
Leave the plant in sunlight for several
hours.
The bag will become ‘fogged-up’.
Test this liquid from the inside of the
bag with blue cobalt chloride paper.
The paper will turn pink, indicating that
the liquid is water.
Experiment; To show the absorption of water
by the roots



Use the same set-up as for the previous
experiment, except use red dye food
dye instead of water.
After several days, remove the plant
and rinse off the excess dye.
Cut across the root and examine the cut
section. You should note a red spot in
the middle of the root.
Cut across the stem and examine the
cut section. You should note several red
spots around the outside of the stem.
This demonstrates that water travels
up the middle of the root and along the
outer cells of the stem.
Sensitivity in Plants
A tropism is the growth response of a plant
to a stimulus.
Phototropism is the growth response of a
plant to light. The stem of a plant always
grows towards the light and the root will grow
away from the light.
Geotropism is the growth response of a plant
to gravity. A stem always grows away from
gravity and the root always grows towards
gravity (downwards).



Set up a plant, as shown above.
Leave the plant in sunlight for several
hours.
After several hours, it will be noted
that the level of water in the test-tube
has fallen.
24
G. Nugent
Junior Certificate Biology
Experiment; To show geotropism in plants



Record your results.
The plants which were getting light
from one side only were all growing
towards the light.
The plants which were getting light
from above were growing straight up.
Sexual Reproduction in the
Flowering Pant.





Set up the apparatus as shown.
Several seeds have been planted in
different positions (upside-down,
sideways, right-way-up etc.)
The seeds are left for several weeks
and observed daily.
The observations are recorded.
You will find that no matter in what
position the seed is planted, the root
always grows down and the shoot always
grows upwards.
Steps in the reproductive cycle of the
flowering plant;
 Flower formation.
 Pollination.
 Fertilisation.
 Seed and fruit formation.
 Dispersal of seeds.
 Germination.
Flower formation
Stigma
Petal
Carpel
Anther
Style
Experiment; To show phototropism in plants
Ovary
Filament
Sepal
Sepal;
Petals ;
Anther ;


Place two potted plants in two closed
boxes, one with a window at the side
and the other with a window on the top
of the box.
Examine the plants in both boxes again,
after several days.
25
Leaves to protect the flower
from drying out.
To attract insects.
To produce pollen grains.
Stigma;
To catch pollen grains.
Ovary;
Contains the ovules for
reproduction.
Nectarines;
Sugary food to attract
insects
G. Nugent
Junior Certificate Biology
Pollen grain
Pollination
This is the transfer of pollen from the anther
to the stigma of the same plant (selfpollination) or a different plant of the same
species (cross-pollination).
Plants can be pollinated by insect or wind.
Insect pollinated
Wind pollinated
Large bright flowers
to attract insects.
Small, dull flowers.
Scent
No scent
Nectaries (food for
insects)
No nectaries
Anthers and stigmas
remain in the flowers.
Anthers and stigmas
hang outside flowers.
Male nucleus
Stigma
Pollen tube
Style
Ovary
Egg
nucleus
Fertilisation is the fusion of a male gamete
nucleus and a female gamete nucleus to form
a zygote.
Fertilisation
 The pollen lands on a stigma.
 A tube grows down through the stigma,
style and ovary.
 The tube enters the ovary which contains
an egg cell.
 The male nucleus (male gamete) passes
down the tube and enters the ovary, where
it fuses with the female egg nucleus (the
female gamete).
 The fertilised the egg cell is called a
zygote. The zygote becomes the seed.
Seed and fruit formation
 The fertilised egg cell forms the seed.
 The ovary wall will swell with food to form
the fruit.
 The fruit protects and nourishes the seed.
Seed dispersal
Seeds can be dispersed by four methods:
 Wind dispersal – seeds dispersed by
this method have flying attachments.

26
Animal dispersal – seeds dispersed by
this method are either nice to eat or
sticky and will cling to the clothes of
humans or the fur of animals.
G. Nugent
Junior Certificate Biology




Self-dispersal – some plants have pods
which explode and scatter the seeds
(pea plants).
Soon after this, the plumule (the young
shoot) grows upwards and pushes over
the ground.
Once the leaves are above ground they
start making food and can now live
independently.
Experiment; To show that water, oxygen and
heat are needed for germination
Water dispersal – water lilies and other
plants which live in water produce seeds
which float and can be carried by rivers
to a place where they can grow into new
plants.
Germination is the growth of a seed into a
new plant.
For a seed to germinate three conditions are
needed:
 Water
 Oxygen
 Heat
If any one of these conditions is missing, the
seed will not germinate.


What happens?
 The seed soaks up water and swells.
 The seed coat bursts and the radicle
(the young root) starts to grow
downwards.


27
Set up the apparatus as shown below.
The seeds in A will germinate because
they have warmth, oxygen and water.
The seeds in B will not germinate
because they are lacking water.
The seeds in C will not germinate
because they are lacking oxygen (boiled
water has no oxygen)
G. Nugent
Junior Certificate Biology

The seeds in D will not germinate
because they are too cold.
Animals depend on animals
 For food – foxes eat rabbits and other
small animals. Fleas live on the fur and
skin of animals.
Ecology
Ecology is the study of living organisms and the
ways in which they interact with each other and
the environment.
A Habitat is the place where an organism lives.
Each habitat has its own community of plants
and animals.
Interdependence
Animals and plants in a habitat depend on each
other for food and shelter and survival.
Food chains
A food chain is a feeding relationship which
exists between organisms in an ecosystem e.g.
Grass - eaten by a rabbit - eaten by a fox
In practice, individual food chains do not exist
on their own but as interconnected food chains
called food webs.
Food web from a woodland habitat
Animals depend on plants
 For food – rabbits eat grass, greenflies
eat leaves, bees get nectar from
flowers.
 For shelter – crows make their nests in
trees, pheasants make their nests in
high grass, squirrels make their homes
in tree hollows, beavers use branches of
trees to make a dam.
Plants depend on animals
 For pollination – bees and other
insects carry pollen from flower to
flower so that seeds for the next
year will be made.
 For scattering seeds and fruit –
some fruits are tasty and are eaten
by animals who pass them out in their
droppings miles away. Others are
sticky and cling to the fur and are
knocked off at a later time.
Plants depend on plants
 For support – ivy clings to trees for
support. Pea plants need support also.
 Shelter – large trees in a forest
provide shelter for small plants such as
bluebells, ferns and moss.
28
Producers are green plants because they can
produce their own food.
Consumers are organisms which eat the food
produced by plants (directly by eating plants or
indirectly by eating other animals).
Herbivores eat plants only e.g. rabbits, horses,
cattle, greenfly.
Carnivores eat animals only e.g. foxes,
ladybirds.
Decomposers are organisms which feed on dead
plants and animals e.g. bacteria, fungi,
earthworms, dung beetles. Decomposers are
important because they release minerals and
nutrients into the soil.
G. Nugent
Junior Certificate Biology
Pyramid of numbers
Make a simple map (woodland habitat)
Fox
Tree
s
Rabbit
Lake
Grass
Roadway
Scale = 10m:1cm






Plants absorb the sun’s energy to make
food.
When herbivores eat the food the
energy is passed to them.
When the carnivores eat the food the
energy is passed on to them.
In this way the energy of the sun is
passed up the food chain.
However, each organism wastes a lot of
energy, so less and less gets passed on
each time.
This why the numbers of organisms
decreases as you go up the food chain.
Measurements
 Air, water and soil temperatures can be
taken with a thermometer.
 Light can be measured with a light
meter.
Collecting animals and plants
Plants can be collected easily because they are
rooted to the ground and can’t move around.
A variety of methods need to be employed to
gather animals.
A pooter (catching insects and small animals)
Ecology (studying a woodland
habitat)
A study of a habitat involves the following
stages:
 Make a simple map of the habitat.
 Measure and record environmental
factors (temperatures, light intensity,
soil composition etc.)
 Collect samples of animals and plants.
 Identify and record all the animals and
plants found in the woodland.
 Estimate the numbers of plants and
animals.


Nets

Point one of the tubes at an insect and
suck in.
The suction will draw in insects to the
container where they be identified.
Various types of nets can be used to
catch butterflies and insects.
Beating tray
29
G. Nugent
Junior Certificate Biology


A beating tray is a large sheet of
plastic or cloth which is positioned
under a tree or bush.
The tree is shaken and animals of all
sizes will fall out of the tree and onto
the sheet where they can be captured
and later identified.
When he does a trap door is sprung
closed and the animal is caught.
Identification of animals and plants
 This is done using biological keys.
 A biological key is a book of questions
and answers, which may used by a
student or investigator, to identify
animals or plants.
 The key, which we will use, is for wild
flowers. We will use it to identify a
plant (daisy).

Pitfall trap
 A jar is placed in a hole in the ground
and covered by a stone or piece of
timber, as shown below.
 Animals which crawl under it fall into
the alcohol and can be later collected
for identification.
Follow the questions.
Q.1 What colour are the flowers?
 Yellow (2)
 White or greenish-white (87)
 Red or reddish (192)
 Blue or bluish (292)
 Green or brown (342)
We go to question 87.
Ground
Q.87 Is the plant growing in water?
 Yes (88)
 No (93)
We go to question 93.
Alcohol
Tullgren funnel
Q.93 How do the leaves grow?
 Alternate (94)
 Opposite (141)
 Basal only (171)
We go to question 171.
Lamp
Soil
Gauze
Q.171


We go
Funnel
Beaker of
water


The lamp shines on a soil sample.
The animals in the soil move away from
the light and fall into the beaker of
water.
Mammal trap
 A trap with bait and a spring-lock door.
 The animal to be caught has to go all of
the way into the trap to get the bait.
30
Do the flowers grow singly?
Yes (172)
No (184)
to question 172.
Q.172 Are the flowers regular?
 Yes (173)
 No (183)
We go to question 173.
Q. 173 How many petals has each flower?
 3 or 6 (174)
 5 (175)
 Over 6 (182)
We go to question 182.
In fact 182 identifies the plant as a daisy and
gives a photograph.
G. Nugent
Junior Certificate Biology
would can be given by,
Mandatory experiment:
(i) Using a quadrat to estimate the density,
the number per m2, of daisies in a habitat.
 A quadrat is a 0.5m x 0.5m square,
made from wood, plastic or metal.
 Throw the quadrat at random (without
looking).
 Count the number of daisies in the
quadrat. This is the number in 0.25m2.
 Multiply your answer by 4 to get the
number of daisies in 1m2.
 Repeat this procedure for twenty
quadrats, thrown in your habitat.
 Record your results each time and enter
them in a table
Quadrat number
1
2
8 100 800


 40%
20 1
20

To investigate the effect of light intensity
on the distribution of plants close to a tree
standing in a field.
Tree
Number of daisies
1
19
20
Average
 Calculate the average number of daisies
per m2. This is referred to as the
density.




(ii) Using a quadrat to find the frequency of
daisies, in a habitat.

1m

1m



This means that every time you throw a
quadrat there is a 40% chance of
finding daisies in it.
Throw the quadrat twenty times in the
chosen habitat.
Each time record whether or not there
are daisies present.
If, in the twenty quadrats, daisies were
present in eight quadrats, the
frequency of daisies in the habitat
31
2
3
4
From the base of a tree, lay down a line
transect.
This is a long piece of cord with a knot
tied at regular intervals.
Record the plants found under each
knot there.
Examine your results and determine if
the distance from the base of the tree
has any effect on the number of plants
present.
The greater the distance from the base
of the tree, the more plants growing.
This is because there is more light
further from the base of the tree.
Competition is the struggle between organisms
of the same species and different species for
available food and resources.
 Plants compete with each other for
light water minerals and space.
Dandelions compete with grass for
water. Dandelions compete with other
dandelions for light and space.

Animals compete for food, territory,
shelter and space. Hedgehogs and
thrushes compete with each other for
G. Nugent
5
Junior Certificate Biology
snails in a woodland habitat. Blackbirds
compete with other blackbirds for
territory by fighting and using loud
shrill singing.


Adaptations
Animals and plants have, over a long time,
changed their structures (become adapted) so
that they can compete with each other for
resources.
 Dandelions have developed deeper roots
so that they can absorb water from
lower down in the soil than grass plants,
which have very shallow roots.
 Rabbits are very well adapted to their
environment. They have excellent
hearing and sight to hear and see
predators. They are camouflaged so
that they are difficult for predators to
see.
Conservation and Pollution
Conservation is the wise use of our
environment and its resources.
Pollution is the addition of unwanted, harmful
wastes to our environment, causing damage.
Pollution of our environment can happen in a
number of ways:
Air pollution
 Smoke and soot from fires and
industry blacken buildings and slows
down photosynthesis in plants.
 Dust from quarries, saw mills, and
factories causes lung diseases.
 Carbon dioxide and sulphur dioxide
from the burning of fossil fuels dissolve
in rain water to form acid rain. Acid
rain damages crops, stonework and
metal objects.

Pesticides kill insect pests etc. but
when washed into the soil they cause
problems. These chemicals can be
passed up the food chain.
Fertilisers, if overused, cause river
pollution when they get washed into
rivers and lakes.
Acid rain leaches important nutrients
from the soil.
Water pollution
 Fertilisers spread onto the land get
washed into the soil and then into the
rivers and lakes where they cause
serious problems. They cause pond
weeds to grow very fast and cover the
surface of the river. This cuts out light
from the other plants in the river and
they die. Also, the bacteria needed to
breakdown all this extra pondweed uses
up all the oxygen in the water. Fish die
from lack of oxygen.
 Sewage and slurry have a similar
effect as the fertilisers.
 Oil spillages cause harm by pouring
poisonous substances onto beaches etc.
Waste disposal solutions
 Incineration – releases harmful gases.
 Landfill – releases harmful effluents
into the soil.
 Dumping at sea – nuclear waste is
disposed of like this.
 Recycling – paper, glass, plastics, and
metals can be recycled.
Soil pollution
32
G. Nugent
Junior Certificate Biology
Microbiology



Microbiology is the study of micro-organisms
(microbes). Micro-organisms are organisms
which can only be seen with the aid of a
microscope. The three types of microorganisms are,
 Viruses
 Bacteria
 Fungi

Benefits of bacteria
 Soil – In the soil they break down dead
plants and animals into nutrients for
growing plants.
 Cheese – Bacteria are in cheese making.
 Yogurt – Bacteria turn milk into yogurt.
 Silage – Bacteria breakdown sugars in
grass into acids which preserve the
grass.
Viruses
Protein coat
Harmful effects of bacteria
 Diseases – cause food poisoning
(salmonella and botulism), meningitis,
appendicitis.
 Food spoilage – food spoils because
bacteria breakdown the food molecules.
DNA
strand







They are single-celled.
They are larger than viruses.
They feed, grow, reproduce, respire,
excrete, move and are sensitive to their
surroundings.
They are found on and in all living and
non-living things.
Viruses consist of a strand of DNA (or
RNA) covered by a protein coat.
They are not living cells because they
have no cytoplasm, nucleus or vacuoles.
They cannot feed, respire, grow, move
or excrete.
They can reproduce inside living cells.
This is the only activity of living things
that they carry-out.
Viruses cause diseases; colds, flu,
measles, mumps, chicken pox, rabies and
AIDS.
Antibiotics do not work against viruses.
But, our white blood cells make
antibodies against viruses.
Bacteria
 Bacteria are living cells. They have
cytoplasm, vacuoles etc.
Fungi
Fungi are living things. They can be unicellular
(yeast) or multi-cellular ( moulds and
mushrooms).
Benefits of fungi
 Brewing – yeast is used in brewing.
 Baking – yeast is also used as a raising
agent in baking.
 Food – mushrooms are edible.
 Antibiotics – penicillium notatum is used
to make penicillin.
Harmful fungi
 Disease – ringworm and athlete’s foot.
 Food spoilage – bread and fruit moulds.
 Poisonous – some mushrooms are
poisonous.
Biotechnology means using living things to
make useful substances for humans.
Experiment; To show the presence of microorganisms in the air and soil.
33
G. Nugent
Junior Certificate Biology
A
Petri dish +
Sterile agar
Un-opened







B
Petri dish +
sterile agar
Opened for
10 minutes
C
Petri dish +
Sterile agar
Sprinkled
with soil
Set up the apparatus as shown above.
Allow the three dishes to sit upsidedown in a warm room for two days.
Examine the plates.
Record your results.
A should remain clear.
B and C should have lots of bacterial
and fungal colonies growing on the
plates, showing that soil and air contain
micro-organisms.
Bacterial colonies appear as shiny
dots of liquid on the plates and fungal
colonies appear as fluffy or powdery
growths.
34
G. Nugent