Biology B5

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Without a skeleton you'd be jelly like

The job of the skeleton is to:

  • support the body
  • allow it to move
  • protect vital organs

Vertebrates all have an internal skeleton

Advantages of an internal skeleton:

  • can easily grow with the body
  • its easy to attach muscles to it
  • its more flexible than an internal skeleton
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Different Animals

Worms= Hydrostatic- body is made of incompressible liquid against which muscles contract

Shark= Skeleton made of cartilage

Insects= exoskeleton- a skeleton on the outside of the body made of chitin

Mammals= endoskeleton- skeleton made up of mostly bone inside the body- feature of all vertebrates

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Bone is made of living cells

  •  they grow
  • can repair themselves

Long bones are hollow- makes them lighter than solid bone of the same size, also makes them stronger- making them more efficient for movement

Hole in the middle is filled with bone marrow

  • =spongy substance that makes new blood cells
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Bones start off as cartilage in the womb

=living tissue that looks and feels rubbery

As you grow cartilage is replaced by bone

  • blood vessels deposit calcium and phosphorus in the cartilage
  • which eventually turns to bone- ossification

You can tell if someone is still growing by the amount of cartilage they have present

Even when your fully grown the ends of bones remain covered with cartilage

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The damage of bones and cartilage

  • both made of living tissue- can get infected
  • bones can be fractured
  • elderly people suffer more from broken bones as they often suffer from osteoporosis- where calcium is lost from the bones- makes the bones brittle and softer so more likely to break
  • A broken bone is more likely to injure tissue
  • shouldn't move anyone with suspected broken bone especially if its a spinal fracture as could damage spinal cord which can lead to paralysis
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Fractures of Bones

There are 3 types of fracture:

  • Simple Fracture= involves just one bone and is a clean break, bone is not out of place and tissues around it aren't damaged
  • Compound fracture= involves other tissues, the bone may stick out from skin so may get infected so surgery is needed
  • Greenstick fracture= incomplete fracture, bone is not completely separated usually happens in children
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-allow the bones to move

  • bones at a joint are held together by ligaments- ligaments have tensile strength (can pull them and they won't snap) also are pretty elastic
  • the ends are covered in cartilage to stop the bones rubbing together- can be slightly compressed, like a shock absorber
  • membranes at joints release oily synovial fluid to lubricate the joints allowing them to move more easily

different joint:

  • Hinge- like the knee or elbow
    • can go backwards and forwards but not side to side
  • Ball and socket- like hip or shoulder
    • can move in all directions and can also rotate
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Muscles and Bones

  • Bones are attached to muscles by tendons
  • muscles move bones at a joint by contracting (becoming shorter) they can only pull on bones to move a joint- can't push
  • this is why muscles usually come in pairs (antagonistic pairs)
  • when one muscle in the pair contracts the joint moves in one direction, when the other contracts it moves in the opposite direction
  • Biceps and triceps are an antagonistic pair of muscles
    • when the biceps contracts it pulls the lower arm upwards
    • and when the triceps contract the lower arm is pulled back down
    • together work as a lever where the elbow is a pivot
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Replacing Joints

If hip or knee joints get damaged or diseased can be replaced with artificial joints


  • less pain and discomfort
  • able to walk better


  • length of legs may be different causing difficulty walking
  • doesn't last forever and must be replaced after 12-15 years
  • surrounding tissues may become inflamed and painful
  • risk of infection
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Open and closed Circulatory system

Humans have a closed circulatory system where blood is enclosed in blood vessels

Insects have open circulatory systems were they have blood filling the open space in the body

amoeba's don't have a circulatory system as they get everything by diffusion and osmosis

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Single and double Circulatory systems

Single- Have two chambered hearts

  • animals like fish have them

In a double circulatory system the blood goes through the heart twice in each circuit so is more efficient as it has more power 

The heart is made of muscle, they have their own blood vessels to supply oxygen and food that they need to provide enough energy to contract

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Humans Double Circulatory System

  • In any circulatory system the heart acts like a pump
  • heart contracts pushing blood around the body
    • arteries take blood away from the heart
    • blood flows through capillaries in organs
    • blood returns to the heart in veins
  • As the blood travels around the body it loses pressure
    • arteries have the highest pressure and veins the lowest
  • have a 4 chambered heart
  • different organs need different volumes of blood depending on what your doing
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The cardiac Cycle

Sequence of events in one complete heartbeat= cardiac cycle

1. Blood flows into two atria (valves closed and heart valves open)

2. The atria contract pushing the blood into the ventricles (valves closed, heart valves open)

3. The ventricles contract, forcing the blood into the aorta and the pulmonary artery (valves forced open by pressure from ventricles, heart valves close automatically)

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Claudius Galen and William Harvey

Claudius Galen was an ancient Greek Doctor

  • he cut up animals to study them and new about the chambers in the heart
  • he thought arterial blood was made by the heart while blood in veins was made by the liver and was sucked through veins by the heart and consumed by the organs

William Harvey

  • showed what the valves did
  • showed that the heart was a pump
  • he showed that the same blood was circulated around the body over and over
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Heart Rate

When you exercise your muscles need more oxygen

  • so your heart pumps faster to deliver more oxygenated blood to your muscles
  •  small arteries control blood flow by getting wider- vasodilation- and getting narrower- vasoconstriction

Hormones also affect heart rate

  • e.g. adrenaline is released when you get a shock or your in danger it increases heart rate to make sure the muscles have plenty of oxygen
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The heart has a pacemaker

  • The heart is told how fast to beat by pacemaker cells
  • These cells produce a small electric current which spreads to the surrounding muscle cell making them contract
  • two clusters of these cells
    • sino-atrial cells (SAN)- stimulate atria to contract
    • atrio-ventricular node (AVN)- stimulates ventricles to contract
  • In one complete heartbeat the SAN produces electric current first which spreads to the atria (they contract) this stimulates the AVN to produce an electric current (ventricles contract) this process ensures the atria always contract before the ventricles
  • An artificial pacemaker can be used to control heartbeat if the pacemaker cells don't work properly. Its a device implanted under the skin which has a wire going to the heart
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ECGs ans Echocardiograms

These are ways in which doctors can measure how well the heart is working

Electrocardiogram (ECG)- shows the electrical activity of the heart- can show:

  • heart attacks
  • irregular heartbeats
  • general heart health

(draw picture:)

Echocardiogram- an ultrasound of the heart which can show:

  • enlarged heart- showing heart failure
  • decreased pumping ability- could indicate disease called cardiomyopathy
  • valve function- torn, infected or scarred heart valves can cause problems
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Ways the heart can go wrong

Hole in the heart:

  • usually something your born with
  • It's a gap in the wall separating either the two ventricles or the two atria
  • Oxygen rich blood on the left-hand side of the heart (should go to the body) leaks into right side of heart and goes back to the lungs
  • means the heart has to pump extra hard

Valve damage

  • can be damaged be heart attacks, infections or old age
  • damage can cause them not to open properly causing high blood pressure
  • may allow blood to flow in both direction- valves need replacing

Coronary Hear disease (CHD)

  • when the arteries that supply blood to muscle of heart get blocked with fatty deposits, often causes heart attacks, treated by coronary bypass operation
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Surgery to fix heart problems

different surgeries:

  • heart transplant- an entirely new heart from a donor
  • can have new bits fitted such as valves and pacemakers
  • can get a heart assist device- take over the pumping duties of a failing heart
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Affects of lifestyle on circulatory system

Unhealthy lifestyle:

  • eating too much saturated fat can raise level of cholesterol in the blood which can clog up blood vessels and lead to coronary heart disease
  • eating too much salt can raise blood pressure putting strain on your heart

Drinking alcohol: regular drinking can raise blood pressure and increase fat levels

Smoking: can increase blood pressure and is major cause of heart disease

Stress: continual or excessive stress raises blood pressure


  • certain recreational drugs raise heart rate and blood pressure- effect is not permanent buts its dangerous for anyone with heart problems
  • cannabis increases heart rate, and causes complex changes in blood pressure
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Red and White blood cells

Red and white blood cells have platelets used in clotting

Red blood cells carry oxygen:

  • are small and have biconcave shape to give large surface area for absorbing and releasing oxygen
  • contain haemoglobin which gives colour and reacts with oxygen to form oxyhaemoglobin
  • don't have a nucleus
  • flexible so can fit through tiny capillaries

White blood cells

  • produce antibodies to fight microbes
  • produce antitoxins to neutralise toxins produced by microbes
  • flexible shape helping them to engulf micro-organisms
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Clotting Blood

When you're injured your blood clots to prevent too much bleeding.Platelets clump together to 'plug' the damaged area (are small fragments of cells that help blood clot)

In a clot, platelets are held together by a mesh of a protein called fibrin (also needs other proteins called clotting factors)

Some substances affect the way the blood clots:

  • Vitamin K: needed for the blood to clot properly- found in green vegetables
  • Alcohol- moderate intake of alcohol slows blood clotting
  • cranberries- evidence suggests they slow clotting

too little clotting means you could bleed to death and get loads of bruises, too much clotting can cause strokes and deep vein thrombosis (DVT)

people who are at risk of stroke and DVT can take drugs like warfarin, heparin and aspirin to prevent blood from clotting to reduce risk

haemophilia is a genetic condition where the blood can't clot easily as clotting factor can't be made by the body, can be injected

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Blood Type

If your in an accident or having surgery you may lose a lot of blood which needs to be replaced by a blood transfusion

People have different blood groups or types, you can wither be A, B, O or AB

These letters refer to the type of antigens on the surface of a person's red blood cells (an antigen is a substance that can trigger a response from a person's immune system)

red blood cells can have A or B antigens (or neither, or both)

blood plasma can contain anti-A or anti-B antibodies

if an anti-A antibody meets an A antigen the blood clots up and goes wrong- agglutination

The antibodies are acting as agglutinins

O blood can be given to anyone

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Table to show blood type

draw table to show blood type

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Organ replacement

Organs can be replaced by living or dead donors

  • living donors can donate whole or parts of organs, for example can donate a kidney or a piece of your liver, to be a living donor you must be fit and healthy, over 18 and a close family member
  • organs from people who have recently died or who are brain dead can be transplanted
  • to donate any organ you must meet the criteria (relatively young, similar body weight, close tissue match, family consent etc)
  • there is a shortage of donors:
    • can join the NHS organ donor to show your willing to donate organs when you die
    • some people say it would be easier for doctors to use the organs of people who have died- use of opt-out system instead
  • success rates of transplants depend on lots of things- type of organ, age of patient, skill of surgeon etc.
  • transplants involve major surgery, can be problems with rejection or taking immunosuppressive drugs
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Ethical issues of organ donation

  • religious reasons people think that a persons body should be buried intact
  • others think life or death is up to God
  • others worry that doctors might not save them if their critically ill and their organs are needed for transplant- safeguard for this though
  • also worried people may be pressured into being a living donor
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Mechanical replacements

Mechanical replacements can be used- don't have problems of rejection but:

  • pacemakers need a battery that needs replacing
  • artificial valves don't work as well as natural ones- blood doesn't flow through as easily so need blood thinning drugs

Sometime temporary mechanical replacements are used to keep someone alive could be for a few hours, several months or several years

  • a heart-lung machine keeps patients blood oxygenated and pumping during heart or lung surgery
  • a kidney dialysis machine can filter a patients blood- whilst waiting for a kidney transplant
  • modern ventilators are used to ventilate a patients lungs if they stop breathing
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Inspiration (breathing in) an Expiration (breathin


  • intercoastal muscles (between the ribs) and diaphragm (the muscle beneath the lungs) contract and increase the volume of the thorax
    • muscles between ribs pull ribcage and sternum up and out
  • A pleural membrane inside the thorax pulls on another pleural membrane attached to the lungs, expanding them decreasing the pressure inside your lungs, drawing air in


  • Intercoastals and diaphragm relax
  • thorax volume decreases
  • air is forced out
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Lung Capacity

Doctors measure lung capacity using a machine called a spirometer- help diagnose and monitor lung diseases

The patient breathes into the machine for a few minutes, and the volume of air that is breathed in and out is measured and plotted on a spirogram

  • total volume of air you can fit in lungs= total lung capacity (normally 6 litres)
  • the volume of air you breathe in (or out) in one normal breath= tidal volume
  • even if try to breathe out really hard there's always some air left in your lungs to make sure they stay open= residual volume
  • total lung capacity-residual volume=vital capacity (amount of useful air)
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Cilia and Mucas

The respiratory tract is lined with mucus and cilia (little hairs) which catch dust and microbes before they reach the lungs

the cilia beat, pushing microbe filled mucus out of the lungs as phlegm

goblet cells secret mucus

sometimes the microbes get past the body's defences and cause infection

  • lungs as prone to infections as are a dead end
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Human Gaseous exchange in the lungs

Air enters body through mouth or nose, goes into trachea (windpipe)

  • the trachea splits into two tubes called 'bronchi' one going to each lung
  • the bronchi spilt into progressively smaller tubes called bronchioles and at the end there are small bags called alveoli where gaseous exchange take place

Alveoli are efficient at gaseous exchange as they have:

  • large surface area
  • moist surface to help carbon dioxide and oxygen dissolve
  • thin lining so gases don't have to diffuse as far
  • good blood supply
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Gaseous exchange in amphibians

Adult amphibians have simple lungs, but their skin plays an important part in gaseous exchange

oxygen moves into the animal and carbon dioxide moves through the skin- has to be kept moist

this means the skin can't be waterproof which means the amphibian would lose too much water if it lived in a dry environment

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Gas exchange in fish

occurs at the gills

a constant supply of oxygen-rich water flows through the open mouth of the fish and is then forced through the gill slits (highly folded to increase surface area)

water helps to support gills- keep seperate from eachother

If fish weren't in water their gills would stick together and they would suffocate

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Lung disease

causes of lung disease:

  • Industrial materials- e.g. asbestos, can cause cancers as well as asbestosis which is where lung tissue is scarred.
  • Genetic causes- e.g. cystic fibrosis, is an inherited lung condition, causes lungs to produce a really thick, sticky mucus that clogs up the lungs
  • Lifestyle causes- e.g. smoking can cause lung cancer, this is when cells divide out of control forming a tumour
  • Asthma- means lungs are overly sensitive to certain things (e.g. pet hair, pollen, dust, smoke) when they encounter these things the airways constrict making it hard to breathe
    • symptoms of a asthma attack= shortness of breath, coughing, wheezing, tight chest
    • muscle relaxant is inhaled from an inhaler to open up the airways
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The Kidneys

The Kidneys are excretion organs

have 3 main roles:

  • removal of urea from the blood, urea is produced in the liver from excess amino acids
  • adjustments of ion levels in the blood
  • adjustment of water content of the blood

they do this by filtering stuff out of the blood under high pressure and then reabsorbing useful things

end product= urine

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Nephrons are the filtration units in the kidneys

1) Ultrafiltration

  • a high pressure is built up which squeezes water, urea, ions and glucose out of the blood and into the capsule
  • membranes between the blood vessels and the capsule act like filters, so big molecules like proteins and blood cells are not squeezed out, they stay in the blood

2) reabsorption

  • All the sugar is reabsorbed (involves process of active transport against concentration gradient
  • sufficient ions are reabsorbed (active transport) excess ions are not
  • sufficient water is reabsorbed, according to level of ADH

3) release of wastes, urea, excess ions and excess are not reabsorbed so continue out the nephron into the ureter down the bladder as urine

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Water content controlled by the kidneys

The amount of water reabsorbed in the kidney nephrons is controlled by a hormone called anti-diuretic hormone (ADH)

The brain monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed

The whole process of water content regulation is controlled by a mechanism called negative feedback, this means if the water content gets too high or too low a mechanism will be triggered that brings it back to normal

(draw diagram)

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Urine isn't always the same

The amount and concentration of urine depends on 3 things:


  • when it's hot you sweat (which evaporates, cooling down the skin), sweat contains water too so there is water loss
  • This means the kidney will reabsorb more water into the blood. This leaves only a small amount of excess water that needs to be got rid, so only a small amount of quite concentrated urine will be produced


  • exercise makes you hot, so you sweat to cool down, produces same affect as heat- concentrated, small volume of urine

Water Intake:

  • not drinking enough water will produce concentrated urine. drinking lots produces lots of dilute urine
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Dialysis filters

  • patients who have kidney failure can't filter their blood properly- but a dialysis machine can do this for them
  • dialysis has to be done regularly to keep the dissolved substances at the right concentration and to remove waste
  • dialysis fluid has the same concentration of salts and glucose in blood plasma
  • the barrier is permeable things like ions and waste substances not big molecules like proteins, so the waste substances and excess ions and water move across the membrane into dialysis fluid
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Menstrual Cycle has 4 stages

Stage 1- Day 1 the bleeding starts- the uterus lining breaks down for about 4 days

Stage 2- the lining of the uterus builds up again- from day 4 to 14 into a thick spongy layer of blood vessels ready to receive a fertilised egg

Stage 3- An egg is developed and then released from the ovary at about day 14

Stage 4- the wall is maintained for about 14 days until day 28, if no fertilised egg has landed on the uterus wall by day 18 then the spongy lining starts to break down again

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Four Hormones controlling the menstrual cycle

1. FSH- (follicle stimulating hormone)

  • produced in the pituitary gland causes an egg to develop in one of the ovaries
  • stimulates the ovaries to produce oestrogen

2. Oestrogen

  • produced in the ovaries, causes the lining of the uterus to thicken and grow
  • stimulates the production of LH and inhibits production of FSH

3. LH (luteinising hormone)

  • produced by the pituitary gland, stimulates the release of an egg at day 14

4. progesterone

  • produced in the ovaries, maintains the lining of the uterus when the level of progesterone falls the lining breaks down
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Infertility treatment

Artificial Insemination (AI): where a man's sperm is placed into a woman's uterus without having sex, used if problem with sperm reaching egg

FSH injections: some women have low levels of FSH which means their eggs don't develop properly so they can't get pregnant, FSH injections increase fertility

In vitro fertilisation (IVF) : where woman's eggs are fertilised outside the body, woman is given hormones to stimulate egg production, several eggs are collected and mixed with the mans sperm. You need sperm, eggs and a healthy uterus any of these can come from someone else:

  • some women can't produce eggs, can use donated eggs
  • some women produce eggs but always miscarry- can be implanted into surrogate mother

Ovary transplants: some women don't have ovaries, can transplant a healthy ovary donated by someone else

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Arguments against fertility treatment

  • It's just not natural- if can't have a child its not meant to be
  • In IVF not all the fertilised eggs are implanted back into the woman, some people think throwing away the extra fertilised eggs is denying a life so is morally wrong
  • IVF increases chance of multiple pregnancies this can be a danger to the mother's health and possibly a financial burden
  • what happens if the surrogate mother doesn't want to give up the child?
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Foetus Growth

Doctors can screen a foetus for genetic disorders before its born- can check for problems like downs syndrome and cystic fibrosis

2 ways:

1. Amniocentesis- use a long needle to remove some of the fluid surrounding the baby containing skin cells and the DNA can be analysed

2. another method (chrionic villus sampling) involves taking a sample of the placenta

ethical issues:

  • is it right to abort a foetus with a genetic defect?
  • minor defects like cleft lip might become grounds for abortion?
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Things that influence growth

Growth happens when cells divide by mitosis and identical cells are made

The size of an adult is mainly influenced by genetic factors by also external factors:

  • diet- a poor diet that is low in proteins or minerals may mean the child doesn't grow as much as the genes would allow
  • exercise- exercise builds muscle, and wait bearing exercise can increase bone mass, exercise stimulates the release of growth hormone

growth hormone is produced in the pituitary gland

sometime hormonal or genetic factors affect growth. Gigantism (extreme height) is often the result of a tumour of the pituitary in childhood, dwarfism (extreme shortness) is caused by genetic factors

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Moitoring a Baby's growth

A baby's growth is monitored after birth to make sure its growing normally.

three measurements: length, mass and head circumference

Babies vary in size so doctors aren't usually concerned uncless a baby's size is above the 98th percentile or below the 2nd percentile or if there is an inconsistent pattern

growth charts can pick up things like obesity, malnutrition, dwarfism, water on the brain

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Life expectancy

Life expectancy has increased, because:

  • medical advances means fatal conditions can be treated
  • places of work and housing are safer and healthier
  • people are better of so can afford a healthier diet and lifestyle
  • more information available about health issues

problems with people living longer:

  • the population grows leading to possible shortages of housing and more environmental pollution
  • number of older people increases so the state might not be able to give pensions to everyone
  • older people have more medical problems increasing costs on the tax payer
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this was REALLY useful for last minute revision!! 

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