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IGCSE Biology

Section 1: The nature and variety of living organisms

Most living organisms have eight life processes in common:
§ Nutrition (needing food)
§ Excretion (removing waste products)
§ Movement (of all or part of organism)
§ Growth and development
§ Respiration (getting energy from food)
§ Response to stimuli (changes in surroundings)
§ Reproduction (producing offspring)
§ Controlling their internal environment
There are 6 major classification groups for living organisms:
Name
Cell Structure
Energy
Cell Wall
Plant
Multicellular
Photosynthesi Made of
s, using
cellulose
chlorophyll
...

Animal
Multicellular
...

Have nervous
organisms
...

Store as
glycogen
...
g
...

Store energy as
glycogen
...



Bacteria
(Prokaryotes)

Tiny, singled
celled organisms
...


Secrete
enzymes that
digest food
outside cells,
and then
absorb
digested
products
...

Some
photosynthesi
s (e
...
algae)
some feed on
other
organisms
(e
...

protozoa)


Chitin

Divisions
Flowering (cereals
(maize), sunflowers,
peas) and non-flowering
(mosses and ferns)
Vertebrates (with
backbone e
...
fish,
mammals, birds,
reptiles) and
invertebrates (insects,
worms, starfish)
Multicellular fungi are
made of mycelium, a
tangled network of
thread-like structures
called hyphae
...
g
...
g
...
Some are
microscopic, some are
very large (e
...

seaweeds)
...
g
...

Some have
flagella for
movement
...
Some
photosynthesis, most
feed on dead or living
organisms
...
g
...


Virus

Core or genetic
Don’t respire
...

Are all parasites
and can only
reproduce inside
living host
...
All natural virus cause
disease
...
g
...



Pathogens (cause disease in other organisms) include bacteria, virus, protoctists and fungi
...
g
...
Specialized cells group together to form
a tissue
...
g
...
An organ system involves different organs working together to carry out functions in
the body e
...
the digestive system or the circulatory system
...

Vacuole
Filled with cell sap to keep the cell turgid

Carbohydrates:
Glucose C6H12O6
Fructose, fruit sugar
Lactose, milk sugar
Sucrose, table sugar
Starch- long chain glucose, polymer, plant tissue
Glycogen- animal tissue
Cellulose- cell walls, cant digest but forms dietary fibre
Lipids: Animal fats solid @ room temp, plant fats ‘oils’ liquid @ room temp
Proteins: Peptides are short chain amino acids
Amino acids (20 types), function is determined by shape, shape is
determined by order of amino acids
...

Protein deficiency called Kwashiorkor is common



Name
Carbohydrates

What
Sugars
and
starches

Atoms
Source
Carbon,
Bread, pasta
hydrogen and and rice
oxygen

Proteins

Long
chains of
amino
acids

Carbon,
hydrogen,
oxygen,
nitrogen and
sulfur

Mea
t,
and cheese
fish

Role
Provide energy for cells
...

Growth and repair and
enzymes
...

Protein: biuret turns blue (little protein) to purple/lilac (lots of protein) when heated
...
They
speed reactions up and control them, without being use up
...

When the substrate
attaches to the active
site, the reaction
takes place and
products are formed
...
E
...


Diffusion is the net overall movement of particles from an area of high
concentration to an area of lower concentration, until an equilibrium is
reached
...

It can be affected by concentration, temperature and available surface area
...
g
...


In active transport, substances move against a concentration gradient or across a selectively
permeable membrane
...
This occurs when
cells need more than 50% of a substance, the first 50% is reached using diffusion
...
Flaccid cells cause
plant to wilt
...

Factors that affect rate:
Surface Area- larger surface area means more
area for molecules to diffuse through, so
increased rate
Temperature- increase temperature means
increase kinetic energy, so molecules collide with
cell wall more frequently
...

Investigations:
Demonstrate diffusion using agar blocks dyed
with potassium permanganate
...



Green plants absorb light energy using
chlorophyll in their leaves
...
The glucose is used
in respiration, or converted into sucrose
for transport, cellulose for cell walls or
starch and stored
...
This is photosynthesis
...
NT
...

To show photosynthesis is taking place in presence of
oxygen use aquatic plant such as Canadian pondweed

in bright light
...


To show chlorophyll is needed for photosynthesis, use variegated (green and white) leaf
...


To show carbon dioxide is needed for photosynthesis, remove carbon dioxide from air surrounding
plant using soda lime
...


Can investigate effect of light intensity and temperature on photosynthesis, on pondweed (count
bubbles produced)
...


Energy requirements vary with
activity levels, age and pregnancy
(development of fetus and extra
body mass cause increase)

Ingestion: Food made up of large insoluble
molecules is taken in by the digestive system-
food enters mouth
Digestion: The digestive system
breaks down large insoluble
molecules into molecules, which
are soluble and small enough for
the body to absorb
...

Assimilation: The small molecules
are used to build large molecules
(e
...
body tissues)
...

citrus) + veg
Fish liver oils, sunlight,
cream
Dairy products, fish,
veg, bread
Red meat, liver, eggs,
green leafy veg
...
Sunlight makes Vitamin D
Makes bones and teeth
Makes haemoglobin in red blood cells to
carry oxygen
Solvent
...


Digestion- chewing, saliva, amylase ready for peristalsis
...
This is the contractions of two sets of
muscles in the walls of the gut
...
Their wave-like contractions
create a squeezing action, moving down the gut
...
Starch è glucose

• Proteases catalyse the breakdown of
proteins into amino acids in the stomach and small
intestine
...
Lipids è fatty acids + glycerol


Bile:
After the stomach, food travels to the small
intestine
...
Bile is an
alkaline substance produced by the liver and
stored in the gall bladder
...
This is important, because it
provides a larger surface area in which the
lipases can work
...

Stored in gall bladder
...


You can determine energy content of a food sample by
burning it and using it to heat a measured sample of water
...

(Weigh crisp, set on fire, heat water
...
) Q=(mcΔT) ÷ mass of food (g)
...
Villus (singular), Villi (plural)
Up to 7 meters long! Increases surface area so
more nutriets can be absorbed + maximized
time food spends being broken down by
enzymes
...


Really long

Villi have good blood supply

Respiration releases energy for cells from glucose
...

Respiration is a series of reactions in which energy is released from glucose
...
It can be summarized by this equation:
glucose + oxygen → carbon dioxide + water (+ energy)

Not enough oxygen may reach the muscles during exercise
...

Anaerobic respiration involves the incomplete breakdown of glucose
...
The waste product is lactic acid
rather than carbon dioxide and water:
Cells: glucose → lactic acid (+ little energy)
Yeast: glucose è ethanol and carbon dioxide ( + energy)

Energy released during respiration is used by the organism in several ways
...
For example:
§
§

Plants make amino acids from sugars, nitrates and other nutrients
These amino acids are then built up into larger molecules – proteins


The gas exchange system takes air into and out of the body to supply oxygen and remove carbon
dioxide in humans
...


In plants gas exchange is caused by respiration (produces carbon dioxide) and photosynthesis
(produces oxygen)
...


Adaptation
Purpose
Flattened shape

Larger surface area to absorb light and carbon dioxide

Thin

Short diffusion distance for carbon dioxide to diffuse into leaf cells, and
oxygen to diffuse out of leaf cells

Stomata

Can open to allow diffusion of carbon dioxide into the leaf from the
atmosphere, and the diffusion of oxygen and water vapour out of the
leaf- allow gas exchange
...




Fill a test tube quarter full with HCIS, attach
a leaf to a bung and put in the test tube;
observe the indicator colour in different
light intensities
...

It then passes through the trachea and one
of the two bronchi into one of the lungs
...

This is where gas exchange takes place -
oxygen passes out of the air into the blood,
and carbon dioxide passes out of the blood
into the air in the alveoli
...


the diaphragm contracts, pulling downwards to increase the volume of the chest
...

When you exhale:



3
...

5
...





the intercostal muscles relax, the ribcage drops inwards and downwards
the diaphragm relaxes, moving back upwards, decreasing the volume of the chest
...


The lungs contain millions of tiny air sacs called alveoli
...


Smoking has bad effects on your health:
1
...
Carbon monoxide reduces amount of oxygen that can
be carried by blood
Cilia are destroyed so dirt and bacteria are not removed, more mucus
Emphysema- walls of alveoli are damaged and break down so gas exchange is not efficient
Lung cancer- tar and other chemicals can cause cells to mutate
Smoking also affects circulatory system and increases risk of heart attacks and strokes
...


Transport: Unicellular organisms- including fungi and bacteria- have a large surface area to volume
ratio and they are small and so the diffusion distance is short, meaning diffusion happens very
quickly
...
This wouldn't support the organism; so they have developed
transport systems, like the ventilation system and the circulatory system which speed up diffusion
enough to support themselves
...

Carries sucrose and amino acids around the
plant (translocation- movement of dissolved
material within a plant)

Xylem: dead cells, cell walls coated in lignin,
impermeable to water, no cytoplasm
...



Water is taken up from the soil by the root hair cells and moves across the root by osmosis
...
g
...

1
...
It is ‘pulled’ up ‘transpiration pull’ via the xylem
2
...
Therefore water travels via osmosis into spongy mesophyll
3
...
Water is then lost through stomata, and evaporates into the air
...

1
...
Weigh again after a certain amount
of time
3
...
Transpiration in cactus is reduced
because spikes instead of leaves, and
spikes have smaller surface area
...

§ White blood cells (defend body against attacks by microbes)
⇒ Phagocytes; engulf bacteria and digest them, contain
digestive enzymes, lobed nucleus, granular cytoplasm
⇒ Lymphocytes; large round nucleus, clear cytoplasm,
produce antibodies (proteins) in response to antigens
(foreign molecules)
...
Also make memory cells for a
secondary immune response
...

§ Platelets (help clot blood)- see hemophilia (genetics), missing protein so blood cant clot
...
It is mainly water)
Carbon monoxide- has a higher affinity than oxygen to hemoglobin so binds tighter preventing
oxygen being carried around body
...

Humans have a double circulation- the pulmonary circulation to lungs (pick up oxygen) and
systemic circulation to body
...


The Immune Response: The white blood cells protect the body against pathogens
...
You can be given artificial immunity to a disease by
vaccination
...
Your lymphocytes produce
antibodies to the anitgens of the pathogen, and memory cells ready for a secondary immune
response, but you are not at risk to the disease
...


Blood Clotting is caused by platelets
...
Prevents blood loss and pathogens and other microorganisms entering
...
These
contract to force blood
into the ventricles
...
Both
sides of the heart fill and empty together
...
ventricle è pulmonary arteryè lungs
The heart beats around 70 times a minute; this is controlled by the pacemaker region of the heart
...

During exercise cells need more food and oxygen, and more carbon dioxide is produced so heart
beats more rapidly
...



Arteries: Blood in the arteries is under high pressure generated by the
heart
...
The arteries have:

thick outer walls

thick layers of muscle and elastic fibres
...



Veins: The blood in veins is under lower pressure than the blood in arteries,
because blood is flowing into heart, not away
...



Unlike arteries, veins have one-way valves in them to keep the blood moving in the correct
direction
...
Capillaries have thin walls - only one
cell thick - that allow them to effectively perform their function
...

Excretion is… the process by which waste products of metabolism are removed from the body
...



E
...

Water (created during respiration)
Urea (excess protein that cannot be stored)
Sweat (SECRETION RATHER THAN EXCRETION- BUT WATER IS EXCRETED)

Faeces are NOT excreted (they are made in body)
...



• Blood is brought to kidney via renal artery,
from the heart
...

• Urine leaves the kidney through the
URETERS, two tubes, and is then stored in the
bladder
...

• The SPHINCETERS can contract in order to
hold back urine
...



Blood is filtered by the kidney in the
nephron
...
Because the blood
arrives at high pressure, it is
squeezed through the glomerulus and
some is filtered into the Bowman’s
Capsule
...
The
process is called ultrafiltration
...
Except for water- not all the water
is filtered because otherwise with no water the blood would become thick and sticky
...

Therefore all of the glucose, some of the water and some of the salts are reabsorbed back into the
blood in the first convoluted tube (proximal convoluted tube)
...


Water is also reabsorbed back into the blood from the collecting duct
...
A longer Loop of Henle produces concentrated urine because there are more
places for water to be reabsorbed into the blood
...
g
...

Therefore URINE contains: water, urea and salts
...

Osmoregulation is Kidney: Too Little/More water
1
...
PITUITARY GLAND releases (less) ADH
(ANTI-DIURETIC HORMONE)
...
Kidney maintains/reduces blood water level
4
...
Blood water levels return to normal
...


Coordination and Response

Living organisms are able to respond to changes in their environment
...
E
...
blood glucose levels, body
temperature (thermoregulation), blood water content (osmoregulation)
...
g
...

In order for an organism to respond to any changes in its surroundings, a coordinated response is
required
...
g
...
g
...
g
...
The effector is always a muscle or a gland

STIMULUS
RECEPTOR
EFFECTOR
Flashing light
Eye
Eye lid muscle
Smell of cooking bacon
Nose
Salivary gland
Music
Ear
Ear drum
Cut finger
Skin
Finger muscle

Plants need light and water for photosynthesis
...


Part
of
plant
Shoot

Light stimulus
positive phototropism (grows
towards the light)
negative phototropism (grows
away from the light)

Root

Gravity stimulus
negative gravitropism (grows against the force
of gravity)
positive gravitropism (grows in the direction of
the force of gravity)

Response in plants:
- Very slow compared to animals
- Long lasting
- (Like a hormone)
There are two main types of tropism:

Similar to hormones



positive tropism – the plant grows towards the stimulus
negative tropism – the plant grows away from the
stimulus
...
In shoots, auxins cause more
growth
...
The
auxins move away from sunlight, onto darker side
and cause cell elongation (in stem)
...

Remove or cover shoot tips and apply artificial
hormones to show responses
...

(Clinostat holds plant and slowly rotates in a
vertical plane so that gravity both upwards and
downwards on a plant)
...

The Nervous System:
• Central Nervous System (CNS)- brain and spinal cord
• Peripheral Nervous System (PNS)- all nerves that come off CNS, to other parts of the body
...
g
...
g
...
g
...
Always a muscle or a
gland
• The response- the action e
...
contracting a muscle, secreting a hormone
...


Reflex:
• Simple reflex- a rapid automatic response which follows a sensory stimulus, it is not under
conscious control, it is involuntary e
...
knee jerk reflex
...
It is under conscious control and is voluntary
...
g
...

A neuron is a nerve cell, which carries an impulse within the nerve
...
Chemicals are able to
cross the gap and travel through the neuron
...
Can be found
between sensory neurons and relay
neurons, or motor neurons and
relay neurons
...
Also, synapses allow the
output of one neuron to be the
result of integration of information from many other cells
...
Electrical impulse arrives at synapse
2
...
Neurotransmitter is broken down in second neuron, energy is converted to electrical energy
(electrical impulse is generated)
There are also electrical synapses- the gap is so small that electrical impulses can travel straight
across
...

As a result the image is inverted
The brain interprets the image the right way up-
it’s the brain the ‘sees’ things not the eye
...
Impulse travels to
brain via optic nerve
...


The iris
...

In dark: muscles relax, pupils dilate, more light into eye
...

- Near object, lens is more convex (rounded), ciliary
muscles contract, suspensory ligaments slacken
- Far object, lens is less convex (flatter), ciliary muscles
relax, suspensory ligaments are stretched




Hormones are chemicals secreted by glands in the body
...
The bloodstream transports hormones from the glands to the target organs
...
This evaporates, removing heat energy
from the skin
...

Too cold- When we get too cold: Vasoconstriction
Muscles contract rapidly - we shiver
...

o Blood vessels leading to the skin capillaries become narrower - they constrict -
letting less blood flow through the skin and conserving heat in the body
...
They lie flat when we are warm, and
rise when we are cold
...

o

Section 3: Reproduction and Inheritance

In asexual reproduction a single parent creates genetically identical offspring
...

Sexual reproduction happens
when a male gamete and a
female gamete join
...

gland
liver and heart
ovary
oestrogen
ovaries, uterus, Controls puberty and the menstrual cycle in
pituitary gland females; stimulates production of LH and
suppresses the production of FSH in the pituitary
gland
...


fertilisation
...

no scent - no need to attract insects
Controls blood water level by triggering uptake of
no nectar - no need to attract insects
water in kidneys
...

pollen very light and smooth - so it can be blown in
the wind and stops it clumping together
Triggers egg release and progesterone production
anthers loosely attached and dangle out - to release
in ovaries
...

stigma hangs outside the flower - to catch the
drifting pollen
stigma feathery or net like - to catch the drifting
pollen
Sexual reproduction allows some of the genetic information from each parent to mix, producing
offspring that resemble their parents, but are not identical to them
...
Animals and plants can reproduce using sexual reproduction
...

The pollen grain land on the stigma and a pollen tube is grown down through the style towards the
ovary
...

The fertilized egg cell develops into an embryo, the ovule becomes the
seed and the ovary forms the fruit
...

Self-pollination- transfer of pollen
from the anther of a plant, to its
stigma- no genetic variation
...



Structure
Sepals
Petals
Stamens
Anthers
Stigma
Ovary
Nectaries


Function
protect the unopened flower bud
may be brightly coloured to attract insects
the male parts of the flower consisting of the anther held up on the filament
produce male sex cells (pollen grains)
...
Seeds use their stored food as
they germinate until new leaves open and photosynthesize
...
Plant hormones are
often used to encourage new roots to develop
...
After a few weeks, new roots develop and a new plant is
produced
...


Or naturally; some plants produce side branches with plantlets on
them
...
Other plants, such as
strawberries, produce runners with plantlets on them
...
They have two functions:
o

to produce sperm (the male gametes or sex

o

cells)

to make the hormone testosterone

Sperm duct and glands: The sperm pass through the sperm
ducts, and mix with fluids produced by glands (seminal
vesicles)
...

This mixture is called semen
...
A ring of muscle ensures that
urine and semen do not get mixed up
...
Ova are the
female gametes or sex cells
...

Oviducts: Each ovary is connected to the uterus by an
oviduct (fallopian tube)
...
Every month, an ovum (egg) develops and
becomes mature, and is released from an ovary
...

Uterus and cervix : The uterus is a muscular bag with a soft
lining
...
The

cervix is a ring of muscle at the lower end of the uterus
...

Vagina and urethra: The vagina is a muscular tube that leads from the cervix to the outside of the
woman's body
...
The opening
to the vagina has folds of skin called labia that meet to form a vulva
...
It passes urine out of the
body from the bladder
...

It also reduces levels of FSH produced by pituitary and
increases levels of LH
Progesterone stimulates growth of blood vessels in the
lining of the uterus getting ready for pregnancy
...

Follicle Stimulating Hormone (FSH) stimulates ova in the
follicles of the ovary to develop
...

Luteinizing hormone (LH) stimulates the release of a
mature egg from ovary
...







If sperm fertilizes an ovum and forms a zygote in the
Fallopian tube, a pregnancy begins
...
It also takes urea and carbon
dioxide from fetus into the mother’s blood and secretes the hormone progesterone which maintains
the pregnancy
...

Changes occur at puberty because of hormones:

testosterone - produced by the testes - controls the development of male secondary
sexual characteristics


oestrogen - produced by the ovaries - controls the development of female secondary sexual
characteristics

Changes during puberty
Boys only
Voice breaks
Hair grows on face and body
Body becomes more muscular
Testes start to produce sperm
cells

Boys and girls
Pubic hair grows
Underarm hair
grows
Sexual organs
grow and develop


Girls only
Voice deepens gradually
Hips get wider
Breasts develop
Ovaries start to release egg cells - menstruation starts


Inheritance
§
§
§
§

Nucleus of a cell contains chromosomes
...

Different forms of the same gene are called alleles (pronounced al-eels)
...

Alleles are dominant or recessive:
§ the characteristic controlled by a dominant
allele develops if the allele is present on one or both
chromosomes in a pair
§ the characteristic controlled by a recessive
allele develops only if the allele is present on both
chromosomes in a pair



For example, the allele for brown eyes is dominant, while the allele for blue eyes is recessive
...
An individual will
only have blue eyes if they inherit two copies of the allele for blue eyes
...







Ratio of red to white is 3:1


A pedigree diagram shows a specific gene in a family
...
)

In this diagram, the mother and two sons have a
different genes to the others:




Human body cells have 23 pairs of chromosomes in the nucleus
...
They are XY
in females, the two sex chromosomes are the same (homogametic)
...






female







X

X

X

XX

XX

male

Y

XY

XY



Ratio of girls to boys is 1:1
Therefore it’s the father that determines the gender of the child
...

Mitosis is a type of cell division
...
It produces two new
cells that are identical to each other, and to the parent cell
...

The cycle starts as the number of organelles - the different parts of the
cell - increases
...


Diagram of the stages of mitosis

Before a cell divides, its chromosomes are copied exactly
...
As each of the two strands separate,
new strands are made alongside each of them, thereby making two
new copies
...
It is used to produce male and female gametes
...
The gametes are sperm or eggs, and only
contain half as many chromosomes (23)
...

Meiosis produces four cells, each with half number of chromosomes, and formation of genetically
different offspring

At fertilisation, the
nuclei of the sperm and
an egg join to form the
zygote
...
It also means the zygote contains a complete set of chromosomes from each parent
...

Variation in a species is the differences between the members of a species
...

Environmental is caused by some action after birth (e
...
)
Some variation is a bit of both
...
It
doesn't happen very often or on purpose
...

Evolution is the process by which the range of organisms on Earth changes
...

Natural Selection meas that organisms adapt and change to new conditions, this can continue
indefinitely eventually forming a new species because organisms are so different that they can no
longer interbreed
...
) These mutations can
mean that they are no longer affected by a certain antibiotic, this makes it easier for them to survive
...

There are things that make you more likely to have a mutated gene, these include: ionising radiation
and chemical mutagens like some chemicals in tobacco
...
They can estimate the size of a population
...



word
producers
primary
consumers
secondary
consumers

meaning
Green plants and algae
...

Usually eat plant material - they are herbivores
...

Usually eat animal material - they are carnivores
...


predators
prey
scavengers
decomposers

Kill for food
...

Feed on dead animals
...

Feed on dead and decaying organisms, and on the undigested parts of plant and animal
matter in faeces
...
This means that the top trophic levels
receive very little energy unless they live in very fertile habitats
...


Some of the available energy goes into growth and the production of offspring
...


§ preventing animals moving around too much
§ keeping their surroundings warm
Mammals and birds maintain a constant body temperature using energy released by respiration
...
Keeping pigs and chickens in warm sheds with little space to
move around allows more efficient food production
...
Therefore, a balance
must be reached between the needs
of farmers and consumers and the
welfare of the animals
...
That leaves just 1 per cent of the world's water as
fresh water on land or in the air
...

Carbon Cycle:
Combustion (burning wood and fossil fuels
to release CO2)
Photosynthesis (removes CO2 from air)
Decomposition (release CO2 through
respiration)
Respiration



Nitrogen is essential for the formation of amino acids in proteins
...

There's lot of nitrogen in air – about 78% of the air is nitrogen
...
Only nitrates are useful to plants, so we are
dependent on other processes to convert nitrogen to
nitrates in the soil
...
Nitrogen gas is converted to nitrate compounds
by nitrogen-fixing bacteria in soil or root nodules
...
The Haber process converts nitrogen gas
into ammonia used in fertilizers
...

2
...
The plant may be eaten by an animal,
and its biomass used to produce animal protein
...
Urea and egested material is broken down by
decomposers
...

4
...

5
...
This is usually in waterlogged soil
...

6
...

Pollutant
Typical effect
smoke
Deposits soot on buildings and trees, causing them damage
...

carbon
poisonous gas
monoxide
carbon
greenhouse gas that contributes to global warming
dioxide
sulfur
contributes to acid rain
dioxide


A green house gas is one that absorbs heat reflected by the earth; this heat is then trapped in the
earth's atmosphere warming the earth
...
Gasses that do this include: water vapour, carbon dioxide, nitrous oxide,
methane and CFCs
...
As the numbers of rice fields and cattle
have increased, so has the amount of methane in the atmosphere
...
In addition, if the fallen trees are
burned or left to rot, additional carbon dioxide is released into the atmosphere
...

Water pollution: is caused by the discharge of harmful substances into rivers, lakes and seas
...

pollutant
fertilisers
sewage
toxic chemicals

typical effect
damage to aquatic ecosystems- eutrophication
kills aquatic organisms and harms human health
kill aquatic organisms and harm human health






Eutrophication: The resulting increase of nitrate or phosphate in the water encourages algae
growth, causing an ‘algae bloom’
...

Decomposing bacteria in water multiple and aerobic respiration decreases oxygen levels in water
causing anoxic water, some species die/suffer
...

This process is called deforestation
...

This control means that all the limiting factors for plant growth can be
set to the optimum conditions; this will result in more growth, so
higher yield
...

Fertilisers make crops grow faster and bigger so that crop yields are
increased
...

Fertilisers provide plants with the essential chemical elements needed for growth particularly
nitrogen, phosphorus and potassium
...


ü Pesticides are used to kill pests that reduce crop yield
...
Fast and accurate to apply
...

û They can harm other wildlife
...

Pesticides can leech into the soil and possibly pollute rivers or surrounding habitats
...



Yeast (bacteria) can be used in the fermentation reaction of glucose to form beer
...

2
...

4
...


2C2H5OH + 2CO2

Barley seeds are germinated (in warm water- malting)
Germinating seeds break down sugar stores, releasing sugar
After, barley seeds are roasted to kill them and dried
...


Investigate the carbon dioxide production by yeast, in different conditions
...
Pour a layer of paraffin on top to make sure no
oxygen-containing air gets in
...
If carbon dioxide then clear
liquid will turn cloudy
...


Production on yoghurt:
1
...

2
...
Milk is cooled to 40-45C and inoculated with lactic acid bacteria (Lactobacillus bacteria)
4
...
Thickened yoghurt is stirred and cooled to 5C

The stirrer turns the blades, this evens out the mixture:
making sure the temperature and concentration is the same
through out; and increasing the contact between the microorganisms and other components
...
The temperature and
PH both need to be monitored so that they can be kept at
the optimum level for the enzymes
...


The air inlet gets oxygen into the fermenter
...
A sparger/agitator makes the air into very small
bubbles; this means they have a larger surface area and can dissolve easily
...


Nutrients are needed in the fermenter so the micro-organism can grow
...

However… diseases can spread quickly, waste and excess food can cause water pollution
and eutrophication, wild fish stocks are depleted to make food for farm fish
...
(There is always some variety within species
...
In
plants- disease resistant, heavy cropping, ability to survive in difficult conditions
...

Genetic Modification and Engineering:
This involves cutting a gene out of one organism
(using restriction enzymes), and inserting it into the
DNA of another (use ligase enzyme)
...
An organism that
receives a new gene
from a different species
is called transgenic, or
genetically modified
...




Using viruses for
genetic
engineering

Insulin production:
Previously was produced by slaughtering cattle, some people were allergic, moral? Vegetarians?
Expensive so not available to everyone
...



GM crops:
Plants have been modified to improve food production, mainly by plants which are resistant to
disease
...

However, pests may become resistant to the chemicals in the plants that make them pest resistant,
and diseases too
...
Also the consequences of GM crops interbreeding with wild organisms
...
This can be used commercially to produce clones
with desired characteristics
...

Disadvantages: all plants are identical so are all
vulnerable to new disease or changes in conditions
...
Successfully done with Dolly the Sheep, but still unreliable
and unsafe and many failures
...
Egg cell from different sheep is placed inside
...
Cell develops into an embryo
...
The proteins are
secreted in the animal’s milk
...




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