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Title: GCSE Biology Exam 2
Description: These are concise, exam-focused notes made using the WJEC specification and BBC Bitesize. Notes on practicals are included. (I achieved an A.) Topics are also sold separately.
Description: These are concise, exam-focused notes made using the WJEC specification and BBC Bitesize. Notes on practicals are included. (I achieved an A.) Topics are also sold separately.
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2
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Assumptions made in capture/recapture techniques
•
•
•
•
no death
no immigration
no emigration
The marking technique does not affect the chances of survival
...
2: Cell division and stem cells
Mitosis
• enables organisms to grow and replace worn out cells and repair damaged
tissues
• produces two daughter cells that are genetically identical and have the same
number of chromosomes as the mother cell
• if uncontrolled, causes cancer
Meiosis
• enables the formation of gametes
• produces four daughter cells that are genetically different and have half the
number of chromosomes of the mother cell
Stem cells
• the cells in mature tissues that do not lose the ability to differentiate in both
plants and animals
• able to treat damaged or diseased tissue
• provide a medical tool
The benefits of using your own stem cells
• no rejection
• no need to find a donor
• no need for tissue typing
The use of embryonic stem cells
• raises particular ethical issues
The bodies of multicellular organisms
• consist of a variety of different cells that are adapted for particular functions,
which originate from undifferentiated stem cells that have the capacity to
develop into specialised cells
4
2
...
Insurance companies may receive stored DNA who could analyse your DNA for
predisposition to disease
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C (cytosine) pairs with G (guanine)
...
g
...
g
...
g
...
g
...
g
...
7
Phenotypic features
•
(most) the result of multiple genes rather than single gene inheritance
Gametes
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•
sex cells
sperm and eggs
Sex determination in humans
•
In human body cells, one of the pairs of chromosomes, XX or XY, carries the genes
which determine the sex
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X
X
X
XX
XX
Y
XY
XY
Selfing
•
where pollen from one plant lands on the stigma of the same plant
8
2
...
g
...
sometimes too slow for organisms to adapt to new environmental conditions and so
organisms may become extinct
proposed by Alfred Russell Wallace and Charles Darwin, who were both working on the
ideas of evolution and natural selection at around the same time
Evolution
•
ongoing, as illustrated by antibiotic resistance in bacteria, pesticide resistance and warfarin
resistance in rats
The human genome
•
important, because it uses information from DNA to develop new ways to treat, cure or even
prevent disease
Mutations
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•
•
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changes in existing genes, resulting in new genes
occur at random
sometimes beneficial or harmful
more likely after exposure to ionising radiation
Cystic fibrosis
•
•
•
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an inherited disease
causes the production of thick mucus that blocks the bronchioles
arises as a mutation
can be inherited as a recessive allele
Gene therapy in cystic fibrosis sufferers
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•
•
•
•
has potential to treat cystic fibrosis
not straightforward, as the introduction of genes is not sufficient, as they should be able to
work within the body
has difficulties targeting the appropriate cells
not a cure for the underlying condition
involves introducing the genes into the lung tissue via an inhaler
10
2
...
g
...
The retina
•
•
•
The pupil
•
•
a hole in the centre of the iris
allows light to enter
The blind spot
The iris
•
•
•
muscles that alter the size of the pupil
to control the amount of light
entering
where the optic nerve leaves the eye
where there are no light-sensitive
cells
The optic nerve
The lens
•
a light sensitive layer
where images are formed
where impulses are sent to the optic
nerve
•
changes shape to focus light onto
retina
12
carries impulses from the retina to
the brain
Homeostasis
•
regulating the conditions inside the body to keep them constant and protected from harmful
effects
Hormones
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•
•
chemical messengers
carried by the blood
control many body functions
Glucose levels
•
need to be kept within a constant range
Insulin
•
•
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•
a hormone
a protein
released by the pancreas into the blood
causes the liver to reduce the glucose level by converting glucose into insoluble glycogen
then storing it
Diabetes
•
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a common disease in which a person has a high blood glucose level
detected by glucose in urine using Benedict’s solution
Type 1 diabetes
•
caused by the body not producing insulin
Type 2 diabetes
•
caused by the body cells not properly responding to the insulin that is produced
The methods of treating diabetes
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•
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regularly injecting insulin
a low sugar diet
a low carbohydrate diet
a possible transplant of pancreatic tissue
13
Metabolism
•
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operates only within a narrow range of temperature and pH
requires appropriate nutrients and water
The structure of a section through the skin
Blood
vessels
•
Body temperature regulation when too warm
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•
vasodilation
sweating
Vasodilation
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•
The arterioles get wider
...
The amount of heat loss from the skin increases
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The sweat travels up the sweat duct
...
The sweat evaporates and takes excess body heat with it
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The hair is raised
...
Vasoconstriction
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•
•
The arterioles get narrower
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The amount of heat loss from the skin decreases
...
illustrated by the control of glucose levels by insulin and glucagon and by the control
of body temperature
Phototropism
•
•
the positive response of plant shoots to light
due to a plant hormone called auxin
Gravitropism
•
the positive response of plant shoots to gravity
15
Lifestyle choices
•
affect some conditions
Alcohol
•
•
•
changes various chemical processes in the body, including reaction time
may cause people to become dependent on, addicted to and suffer withdrawal
symptoms without it
can cause long-term physical damage, e
...
liver, circulatory and heart diseases
Drugs
•
•
misused
affect people’s bodies
Obesity and type 2 diabetes
•
There is a link between rising levels of obesity and increasing levels of type 2
diabetes
...
6: Role of kidney in homeostasis
The structure of the excretory system
Kidney
Ureter
•
The location of the nephrons
•
start in the cortex of the kidney and loop down into the medulla and back to the cortex
The structure of a nephron
•
The functions of the nephron
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•
to regulate the level of water and salts in the blood
to remove urea from the blood
17
The location of the kidney
•
in the back of the abdomen
The structure of the kidney
•
The functions of the kidneys
•
•
to regulate the water content of the blood
to remove waste products of metabolism from the blood (excretion)
The location of the nephrons
•
start in the cortex of the kidney and loop down into the medulla and back to the
cortex
18
The process of filtration under pressure
•
The diameter of the blood vessels entering the capillary knot is wider than the
diameter of the blood vessels leaving the capillary knot
...
Waste
•
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a solution containing urea and excess salts (urine)
passes from the kidneys in the ureters to the bladder where it is stored before being
passed out of the body
The indication of disease in the kidney
•
by the presence of blood or cells in the urine
The indication of diabetes
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by the presence of glucose in the urine
The regulation of the water content of the blood
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The kidneys produce dilute urine if there is too much water in the blood
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The role of anti-diuretic hormone (ADH)
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The concentration of blood is monitored by the brain
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This results in the urine becoming more concentrated
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Patients need to spend many hours a week attached to a dialysis machine
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The counter-current system ensures that a diffusion gradient for urea is always maintained
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The donor kidney may be rejected by the body and attacked by the immune system, unless
drugs are taken which suppress the immune response
...
Patients no longer have diet restrictions
...
There is a risk of organ rejection
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Patients need to make regular doctors’ appointments to detect signs of organ rejection
...
7: Microorganisms and their applications
The safe use of basic aseptic techniques involved in inoculating, plating and incubating
microorganisms
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Bacteria and fungi can be grown on nutrient agar in a Petri dish, to produce an agar
plate
...
An inoculating loop is used to transfer bacteria and is sterilised before and after use
by heating it to red heat in a Bunsen flame
...
After inoculation the lid of the Petri dish should be secured in place by strips of
adhesive tape for safety reasons
...
For safety reasons, plates and equipment should be sterilised after use
...
However, the clumping of bacteria can cause inaccuracies in counting
...
Freezing stops bacterial growth
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In a fermenter, the supply of air, the temperature and pH can be controlled to
enable maximum growth to take place
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After incubation, the culture medium is filtered and the penicillin
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8: Disease, defence and treatment
Microorganisms
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mostly harmless
many perform vital functions
Pathogens
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type of microorganism
cause disease
include bacteria, viruses, fungi and protists
The structure of a bacterial cell
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•
•
•
a cell wall
a cell membrane
cytoplasm
no distinct nucleus
The structure of a virus
•
•
a number of genes…
…surrounded by a protein coat
Communicable diseases
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•
caused by bacteria, viruses and fungi
spread by contact, aerosol, body fluids, water, insects and contaminated food
AIDS (Acquired Immune Deficiency Syndrome)
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caused by HIV (Human Immunodeficiency Virus), which infects lymphocytes
spread by blood to blood contact, especially during sexual intercourse
can cause infection with a variety of microorganisms, e
...
tuberculosis or pneumonia
can be prevented through the use of condoms and the use of disposable gloves
where there is any danger of contact with contaminated blood
can be treated with antiviral agents when taken throughout life to prevent the
multiplication of the virus inside cells
22
Chlamydia
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the most common sexually transmitted disease in Britain
caused by the bacterium Chlamydia trachmitis
spread during sexual intercourse via the vagina and urethra
can cause infertility in adults and conjunctivitis and pneumonia in babies during the
process of birth if the mother is infected
can be prevented by the use of condoms
can be treated with antibiotics, such as tetracycline or erthyromycin
Malaria
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kills over a million people in the world each year
caused by the single celled organism Plasmodium
spread via female mosquitoes of the genus Anopheles, which bite humans and inject
Plasmodium into the blood stream
causes a fever when it destroys red blood cells in humans
can be prevented through killing mosquitoes with insecticide, releasing large numbers of
infertile male mosquitoes, biological control of mosquitoes, the use of mosquito nets,
the use of repellents and a vaccine against Plasmodium
can be treated through killing Plasmodium with anti-malarial drugs, such as paludrine or
daraprim
Antibiotics
•
•
•
(e
...
penicillin) were originally medicines produced by living organisms, such as fungi
are now often chemically modified and so are semi-synthetic or synthetic
help to cure bacterial disease by killing the infecting bacteria or preventing their growth
but do not kill viruses
Resistant bacteria
•
•
•
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bacteria resistant to antibiotics
caused by the use of antibiotics in animal feed
caused by over-prescription for humans
e
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MRSA
MRSA control measures
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•
hand washing
thorough cleaning of hospital wards
use of alcohol gels
MRSA screening
23
Preventative measures for some conditions
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•
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good hygiene
clean water
an improved diet
vaccination
drugs (such as antibiotics)
How the body defends itself from disease
•
•
•
•
the skin
blood clots
phagocytes
lymphocytes
The skin
•
•
forms a barrier against microorganisms
The community of microorganisms on the skin (the skin flora) make it difficult for
pathogens to become established
...
24
Vaccines
•
•
•
•
•
contain antigens derived from a disease-causing organism
protect against infection by stimulating the lymphocytes to produce antibodies
specific to that antigen
generally use ‘non-active’ microorganisms, antigens or parts of antigens to stimulate
an immune response
The specific response is relatively slow if the body has not previously encountered
the relevant antigen
...
Vaccines which protect against bacteria and viruses may be produced
...
This memory provides immunity following a natural infection and after vaccination
...
However, the risk of contracting a
serious disease is far greater
...
A controversy provoked by Dr Andrew Wakefield’s 1998 research claiming that the
MMR vaccine holds links with autism saw a 15% drop in parental participation in the
MMR vaccination programme in some countries
...
Double blind trials
•
Neither the patients nor the doctors are told if they are in the trial group or the
placebo group
...
26
Monoclonal antibodies
•
identical specific antibodies produced from B-lymphocytes fused with tumour cells
forming a hybridoma, which divides rapidly in laboratory conditions to form a clone
The medical uses of monoclonal antibodies
•
•
•
•
diagnosis of diseases
tissue typing for transplants
monitoring the spread of malaria
supporting chemotherapy for cancers
The use of monoclonal antibodies in the diagnosis of diseases
•
•
•
Immunoassays are used in the diagnosis of diseases caused by Chlamydia trachmitis, HIV
and Plasmodium
...
The extent of the infection is related to the extent of the labelling
...
Monoclonal antibodies can be used against helper T-cells (T-lymphocytes) so Blymphocytes, normally causing rejection, are prevented from functioning
...
Monoclonal antibodies will detect the presence of Plasmodium in the bloodstream (even
if they are dead or killed by anti-malarial drugs) as they have specific antigens and will
attach to the labelled monoclonal antibodies
...
The use of monoclonal antibodies in supporting chemotherapy for cancers
•
•
•
•
The destruction of cancer cells can be targeted with the use of monoclonal antibodies
...
Monoclonal antibodies that act against tumour markers can be produced
...
27
Investigation into factors affecting the abundance and distribution of a species
Method
1
...
3
...
5
...
Roll two 20 sided dice to determine the coordinates
...
Count the number of daisy plants within the quadrat
...
Repeat steps 2-4 for at least 25 quadrats
...
biting and stinging insects
Risk
adverse skin response
Control measure
Cover skin at all times
...
Use insect repellent
...
•
•
•
•
Data for mown and unmown areas could be compared
...
It is important to use random sampling techniques in reducing/eliminating bias
...
28
Investigating into variation in organisms
Method
1
...
2
...
3
...
Analysis
1
...
2
...
Risk assessment
Hazard
•
•
Risk
Control measure
No significant risks are associated with this investigation
...
In reality, some snails may have better camouflage than others, which may affect sample
size
...
Ask your first volunteer to sit in the chair with good upright posture and eyes looking
across the room
...
Have the volunteer place their forearm (the part of the arm from elbow to hand) so it
extends over the edge of the table
...
Ask the volunteer to place their thumb and index (pointer) finger on either side of the
bottom of the vertically placed ruler
...
4
...
5
...
6
...
Their job will be to
catch it with their thumb and forefinger as soon as they sense it dropping
...
Drop the ruler
...
The lower the number, the faster the reaction time
...
Conduct five trials with the same volunteer, dropping the ruler from 2 cm above their
fingers each time
...
Repeat the experiment with at least five other volunteers and record your results in a
suitable table
...
Use a conversion table to convert the distance measured to a reaction time for each
volunteer
...
Discuss the extent to which your results support the hypothesis
...
1
...
30
Test artificial urine samples for the presence of protein and glucose
Method (for glucose)
1
...
3
...
Using a 10 cm3 measuring cylinder, add 5 cm3 of Sample A into a test tube
...
Observe and record any colour change
...
Method (for glucose)
1
...
3
...
5
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Using a syringe, add 2 cm3 of Biuret solution
...
Observe and record any colour change
...
Analysis
1
...
Risk assessment
Hazard
Biuret solution is an irritant
...
Risk
Biuret could get on to the
skin when putting into the
test tube
...
scalding of skin
31
Control measure
Wash hands immediately if
amylase gets on to them
...
Wear eye protection
...
Investigation of the effect of antibiotics on bacterial growth
Method
1
...
Wipe down the working area thoroughly
with the disinfectant
...
Work very close to a lit Bunsen burner
...
3
...
4
...
5
...
6
...
Divide the base into four sections by drawing a cross with
the marker pen
...
7
...
Raise the lid of the
Petri dish at an angle and place the disc onto the agar in the centre of section A
...
Repeat step 5 for the other 3 discs
...
9
...
Tape the lid securely
...
10
...
11
...
Analysis
1
...
Risk assessment
Hazard
Bacteria can be pathogenic
...
burning skin when placing
discs on plate
32
Control measure
Wash hands
...
Seal plate so that it is not
opened
...
Do not touch tip of forceps
after flaming
Title: GCSE Biology Exam 2
Description: These are concise, exam-focused notes made using the WJEC specification and BBC Bitesize. Notes on practicals are included. (I achieved an A.) Topics are also sold separately.
Description: These are concise, exam-focused notes made using the WJEC specification and BBC Bitesize. Notes on practicals are included. (I achieved an A.) Topics are also sold separately.