This is for my biology revision 



Approximately 30 million different types of living things.

Each different type of organism is called a species and these are organised into groups. This process is called CLASSIFICATION 

USEFUL IN CLASSIFICATION: number of legs, habitat, reproductive behaviour, colours/patterns size 

LESS USEFUL IN CLASSIFICATION: blood group, gender, size 

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Naming species

Many different animals have many different names in different countries and to avoid confusion between scientists there has to be names for certain animals. 

The name is given in the Latin language and are decided by an international committee of scientists. The scientific name is made up of two parts the genus and the species for the purple top shell snail it is name Gibbula umbilicalis 

The scientific name is always written in italics or underlined to define it. 

If two species have similar genus' then they are usually related in some way. 

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Living Things

The three main group living things are split up into are: ANIMALS, PLANTS AND BACTERIA.

These are then split up further into more complicated groups 

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Animals adapt to the conditions they need to live in to survive. 

For example:

The shore crab has: Pincers - for feeding and protection; Coloration for camouflage against the sea bed; a flattened body - to squeeze under rocks and crevices; Gills (modified) - to be able to breath on land and in the sea and Hard carapace to protect the inner organs 

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The number of one species will often depend on many factors, such as the availability of resources and the number of other species. Pollution is a key affect on the population of an animal in water and air. 

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Water pollution

Biological measure of water purity (BMWP). The BMWP can be tested by biological indicator species. Some species will only live in clean water where as others have a higher pollution tolerance. 

Each species is given a BMWP score such as the nymph of mayfly is 10 and cannot tolerate any pollution in water so would only be found in clean waters. 

A bloodworm larva can be found in polluted water and has a BMWP score of 2 

The main chemical pollutant found in water is nitrogen which is found in two main forms:

Ammonium form the decay of waste organic matter, dead bodies, faces and urea. 

Nitrate from excessive use of fertilizer 

Increases in these levels can cause decreasing amounts in oxygen levels and and decreased PH which makes water more acidic. 

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Lichens are plant like organisms formed from fungus and algae, growing closely together. 

They grow together as they are in a symbiotic relationship which means that they both benefit from living together. 

Lichens can survive extreme conditions but are very sensitive to air pollution and so we can use them to see how much pollution is in an area

There are three main forms of lichen which are:

CRUSTY:More tolerant of pollution

LEAFY:Tolerates some pollution 

SHRUBBY: Tolerates very little pollution 

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Effects on the enviroment

Deforestation has a global effect as it effects everyone. With less trees more CO2 is emitted into the atmosphere, this contributes to global warming. Habitat destruction which means loss of species and polar ice caps melting and flooding destroys habitats. 

The Cardiff bay barrage has a local effect. There is permanently water in the harbor which means we lose inter tidal feeding and birds start to feed elsewhere. 

ENVIRONMENTAL IMPACT ASSESSMENT, these are carried out to find out the impact of development on the environment. Developers must produce an ES environmental statement to find out the likely effect son the environment if development continues. 

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Modern farming methods and industries can have a serious impact on the environment


the death of a lake or sream caused by too much nitrogen. 

Excess fertiliser washes into lakes and streams 

Encourages algae bloom

Blocks sunlight so plants die

Decomposers use up oxygen to respire

Fish suffocate and die

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fertilizer - Excessive use can cause eutrophication (( USE MANURE))

pesticides - Can taint crops with chemicals the pest it kills may be prey for another species ((BIOLOGICAL CONTROL INTRODUCE A NATURAL PREDATOR))

Disease control - TB expensive for screening, culled if carrying disease, vaccinations to prevent diseases, badgers culled as they are thought to spread the disease (( VACCINATIONS, PREVENT CONTAMINATION FROM OTHER FARMS))

battery methods - Chickens are cramped scrawny and disease spreads quickly between them. Vaccines, not many will sell, expensive (disease control)  ((FREE RANGE))

(( )) << Double brackets = other ideas for modern farming methods. 

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Bio accumulation describes the way in which poisons are concentrated along a food chain. 


Plankton >>> Sculpin >>> Herring >>> humans 

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sunlight is the energy provided for photosynthesis 

Through photosynthesis the light energy is turned into chemical energy, in the form of glucose a simple sugar. 

Production of glucose in photosynthesis

Carbon dioxide + water >>> oxygen 

The food created can be used in : 

  • respiration 
  • stored for later use
  • Converted into other chemicals for growth

Arrows in food chain symbolizes the flow of energy. 

The problem with food chains is they don't show you what every organism eats.

So we can use food webs  

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feeding pyramids

Biomass is always in the same shape like a triangle

Pyramids of numbers can be any shape 

Energy pyramids are pyramid shaped as energy is always lost up a food chain. 

producers lose energy through light reflection

Herbivores lose energy through movement growth and heat loss from respiration  

Carnivores lose energy through movement growth and heat loss from respiration

Both above lose energy through excretion

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Carbon cycle

Carbon is passed on in feeding through carbohydrates, Carbon dioxide is used by plants and produces by animals 

in the carbon cycle there are 6 boxes 11 labelled arrows and 1 non labeled arrow

[animals] [plants] && [decomposers] respire >>> back to [CO2 in the atmosphere]

photosynthesis >>> to [plants] from [C02] 

[plants] && [animals] die both with death and no decay >>>  which leads to [decomposers] and die with decay >>> which leads to [formation of fossil fuels] 

[plants] lead to [animals] through feeding >>> 

[animals] are the only ones who excrete>>>   [formation of fuels] lead to [burning of fossil fuels] which with the last arrow of combustion>>>> takes us back to[ C02]

>>>>  = labelled arrow [ ] = in a box 

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Nitrate is produced naturally through: 

  • Legumes (beans, peas rice)
  • Lightning ( by providing energy to chemically join nitrogen and oxygen) 
  • Soil bacteria

In the nitrogen cycle there are 5 boxes and 8 labelled arrows one of which is a lightning bolt. 

Nitrogen in the atmosphere, fixation and lighting brings us near to soil nirogen fixing bacteria (nitrogen >> nitrites >>nitrate) Assimilation to plants and protein leading to feeding plants and protein both die and decay to soil denitrifying bacteria 

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DNA >>> Gene >>> Chromosome >>> Nucleus >>> Cell 

Information to determine individuals characteristics are found in the nucleus in the cell.

The many thousand of pieces of information are arranged onto structures called chromosomes, which are usually arranged in pairs. 

Humans have 46 chromosomes arranged in 23 pairs. Each of these pices of information are determined by genes.

These genes have different forms . Each form of gene is called an allele which are made up of the molecule DNA

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DNA is the chemical which forms our genes; its the basic genetic material of all living things.

A gene is a piece of DNA which contains the information to make a particular protein. These proteins determine how cells function DNA is a complex molecule which has two main parts:

SUGAR PHOSPHATE BACKBONE: this forms the main structure of the molecule (DNA molecules can also be know as the double helix)

BASE PAIRS: The sequence of these molecules carries the genetic information. 

It ii wound up to save space and hydrogen bonds join the bases together 

A=T C=G 

=>=>= <<<this is what the DNA molecule looks like with many joined up together in base pairs. 

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DNA profiling

DNA profiling was discovered by Alec Jeffries 

It is produced by cutting up the enzymes then each piece of DNA forms a different bband 

DNA finegr print identifies closely related individuals by their similar bonding patterns 

Two uses of DNA profiling are for paternity tests ( you need both the motehr and fatehr) 

Identifying a SUSPECT in a crime. 

DNA fingerprints can be kept on record without the individual knowing about it 

People will be worried they will be found guilty of a crime they have not committed 

It is unethical, insurance companies could discriminate and privacy concerns

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The technique of Designer babies is called preimplantation. 

The baby is made in a test tube and then inserted into the mothers womb. 

The baby is made to help another sick child. 

They therefore must be matching embryos. It would suffer pain but no real harm would come to it. 

You collect sperm and eggs from the parents and you create multiple you find matching embryos and implant one into the mothers womb.

98% chance of the baby being a match to the ill child. 

It is illegal to change the gender hair colour eye colour race or any physicalities to fit preferences.

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Parents pass on genetic information to us; the information is found in the nucleus of the GAMETES or sex cells 

The human gametes are called sex cells 

male = sperm female = eggs

Each gamete provides half the information needed for a new organism so that when connected there aren't double the amount needed so there are 23 in each gamete. 

Kangaroo chromosomes 

6 pairs = 12 chromosomes 

so 6 chromosmes wil be present in a kangaroo gamete 

chromosomes are somatic and hold nearly all the information the last two are the sex chromosomes ** = female xy = male 44 

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To find our more about inheritance we must look at something to prove it, the first person to study inheritance was Gregor Mendel.

He used peas for his theory as they:

  • reproduce very quickly 
  • They have obvious characteristics 
  • Each characteristic has a very distinct form

pure bredding is when two homozygous individuals are bred, self fertilize is when soemthing has both male and female parts and can fertilize itself 

Mendel studied many characteristics her are four:

Tall/dwarf ((height)) small/wrinkly ((seed form)) white/purple ((flower colour)) green/yellow ((pod colour)) white/green ((Seed colour))

He had F1 generations and F2 generations F2 always came out with a ratio 3:1


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Genetic diseases

The patterns of inheritance demonstrated by mendel can be applied in many different situations including the inheritance of genetic diseases


Sickle cell anaemia is a blood disease caused by a recessive allele. 

The sickle cell has a longer crescent shape and smaller surface area. 

The sickle cells can block blood capillaries and starve organs of oxygen.Transplants of bone marrow offer a possible cure by providing a source of normal blood-making cells 

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huntington's disease

A progressive genetic disorder of the nervous system, which affects muscle coordination and leads to dementia. It typically becomes noticeable in middle age and usually leads to death in about 20 years. It is a DOMINANT allele 

You either have it or don't you cannot be a carrier of Huntington's disease. 

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Genetic modification

Recent scientific advances mean that we can choose genes which can control certain characteristics and swap them between species. These genetically modified (GM) organisms contain recombinant dna

organism produced in this way include:

Bacteria which produce human insulin for diabetics

Goats which contain a medicine in their milk to treat people with emphysema 

Soya plants which have been given a herbicide resistant gene 

To produce GM plants an enzyme is sent into the gene where it cuts a piece out of the DNA and then replaces it with the DNA of another plant

This would be beneficial as products wouldn't go out of date as quickly they could be bigger and healthier. The reasons against are centered around the ethical side of GM and how it is not right and could be used dangerously and in bad ways.

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Living things differ from one another. ''The differences between individuals of the same species'' . Humans vary in many different ways through hair colour, eye colour, accent shoe size. Variation has two main cause GENETIC and ENVIRONMENTAL. 

Genes (sections of DNA which control characteristics)  are the cause of genetic variation between individuals 

Environmental variation can be caused by the lifestyle one chooses: whether one smokes or not, whether you drink, diet, exercise and the climate or culture you are brought up in.

Continuous variation - every individual has the characteristic but it differs and varies in each individual (e.g. we all have eyes but some have blue, green, hazel, brown etc.) 

Discontinuous variation - is when you either have the characteristic or you don't (e.g. the ability to roll your tongue)

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Sexual reproduction

Organisms reproduce to pass on their genes and for variation 

Sexual reproduction produces offspring that are genetically different from the parents. This is because the offspring receives a set of genes from its father and a set of genes from its mother. 

Fertilization is when an egg from the mother combines with the sperm from the father and creates and embryo that is UNIQUE!

egg + sperm = gamete (sex cells) 

An embryo is an organism that is at the very early stage of development. It has a full set of chromosomes and has resulted from fertilization. 

ADVANTAGES - Variation of genes - ability to adapt to changing environments

DISADVANTAGES - It's slow, you need two parents and you cannot produce many

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Sometimes an organism can reproduce with only one parent. 

Offspring produced this way are called clones and are genetically identical to each other.


It's fast, produces lots of offspring quickly, you only need one parent


No variation, Cannot adapt to changing environments, all susceptible to the same diseases. 

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A mutation is a change in a gene or chromosome 

Mutations can occur at random as a result of existing genes changign to form new genes 

Most mutations have no effect but some can be BENEFICIAL and others can be HARMFUL 

Mutated genes are inherited by offspring form their parents 

Mutation rates can be increased by conditions in the environment 

For example they are increased by Ionising radiation (Electromagnetic waves which are energetic and highly penetrable. They increase the rate of mutation by damaging DNA. 

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Sources and uses of ionising radiation

Ultraviolet light: From exposure to the sun's rays and sun beds 

X-rays: Used in hospitals for diagnosis and treatment 

Gamma rays: Sterilized medical equipment and ''irradiated food'' (sterilized food to keep it fresher for longer)

Increased exposure to these sources of ionising radiation can increase mutation rates.  

Something that causes a mutation is a mutogen 

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Microwaves mobile phones and sun beds

nine is the age recommended for the minimum age a child should be in use of a mobile. Our body absorbs microwaves because of the water that we contain 

Microwaves are thought to cause severe headaches genetic damage and cancer, but this is not proven yet. 

Sun beds give off radiation constantly, these rays are fast and frequent and are some of the most dangerous. The argument also says that actually there is no evidence to show that UV rays give cancer where as smoking has. 

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Harmful mutations

The inheritance of mutated genes can cause genetic disease such as cystic fibrosis a recessive genetic disease passed form parent to offspring so it is genetic. In the bronchioles of the lungs excess mucus is produced which makes it harder for the sufferer to breath.

The mucus also traps bacteria making the sufferer more susceptible to infections.

The pancreas is also unable to function properly so people suffering from CF have excessive appetites but fail to gain weight. 

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Gene therapy

There is currently no cure for CF but work with gene therapy is being developed which helps sufferers. 

Gene therapy involves taking mutated faulty genes and replacing them with normal genes. 

The perfect genes are inhaled into the airways in sticky liposome bubbles which joins with the cell membrane of the cells which line the airway and then enters the nucleus. 

The problem with gene therapy is that it's difficult to get the normal gene into the cells lining the airways. It also doesn't replace all the faulty genes. 

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Natural selection ''survival of the fittest''

Only the individuals with USEFUL inherited CHARACTERISTICS will SURVIVE and go on to REPRODUCE. This means that the genes for these characteristics will be passed on by offspring. This theory was proposed by Charles Darwin in 1859  

  • Organisms produce lots of offspring 
  • There is variation among the offspring 
  • Variation can SOMETIMES be caused by mutations
  • There is a struggle for existence 
  • Organisms with useful characteristics are more likely to survive reproduce and pass on the gene to their offspring. 
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Charles Darwin

In 1831 Charles Darwin set sail to the galapagos islands in the HMS beagle 

His theory was the THEORY OF EVOLUTION 

The definition of this highly known title is a gradual change in a species over time 

Finches produce lots of offspring 

There is a mutation that leads to different shaped beaks 

There is competition for food, that is a struggle for existence

These birds with different shaped beaks are more likely to survive, reproduce and pass on the gene for different shaped beaks to their offspring 


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Camoflauge and standing out

Camouflage is essential for the survival of some animals mostly those who are prey to hide from predators and to protect their young just like peppered mtohs, chameleons, sloths and many more animals. 

But some animals choose to stand out to attract mates, to warn of predators and to attract pollinators

Plants have brightly coloured petals to attract insect for pollination.

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Species may struggle to survive for various reasons

  • Lack of variation 
  • Competition for food 
  • Competition fro mates 
  • Increase in predators 

dodos, mamouths and saber toothed tigers have all become extinct.

Fossils are the remains or traces of plants or animal species from the past

Bones teeth and shells fossilise as these are the hard parts of the animal. The soft parts decay by decomposers.

CARBON DATING is used to find out how old the species in a fossil is by testing the amount of carbon dioxide

Whole species can be found if they have been preserved in ice, tar, peat  or amber.

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Evolution is ongoing

Overuse in antimicrobial chemicals in homes and hospitals has lead to an increase in superbugs. They have formed resistance (when an organism that was once killed by a chemical no longer is) to products like antibiotics. 

This can be explained using Charles Darwins theory of evolution as it can also be related to rats and their resistance to Warfarin. 

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RESPONSE AND REGULATION- detecting changes

We are able to detect changes using our sense organs; these are groups of receptor cells. These receptor cells can detect changes in the world around us; each of these changes is called a STIMULUS.We have five main sense organs that detect a different stimuli (plural)

Sense organs   Stimulus     Sense                      

Eye                   Light          sight

Ear                   Sound       Hear 

Nose                Chemical   Smell 

Taste               Chemical   taste

Ear                  Gravity      Balance 

Skin: pressure, heat, texture ... touch

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(2) RESPONSE AND REGULATION- detecting changes

The information that the sense organs collect is sent to the central nervous system to be processed. The central nervous system consists of the brain and the spinal cord. This information is carried as electrical impulses along nerves and neurons

These responses are divided into steps:

  • Stimulus - This is the change that is detected 
  • Receptor - These are the cells that can detect change
  • Co-ordinate - this organises information in the brain
  • Effector - Causes the body to do something 
  • Receptor - what the body does                                                                    For a ball this would be the steps in action:
  • The moving ball 
  • In the eye
  • The brain
  • Muscles in the arm 
  • Catches the ball
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The six senses are: Sight, Sound, touch, taste, Smell, balance 

Electronic signals are sent through the nervous system 

The retina is the back of the eye

The pupils size controls the amount of light entering the eye

The optic nerve carries messages from the eye to the nerve 

The inner ear controls our balance 


A pilot uses sight and balance to fly a plane 

G-force makes your body feel heavy and makes your eyes temporarily blind or looses the picture

Fingers have many receptor cells so are very sensitive to touch 

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Plant responses

Plants also respond to stimuli like light water and gravity 

This ability to grow in response to a stimulus is called tropism 

Positive tropism is when a plant grows towards a stimulus

Negative tropism is when a plant grows away from a stimulus

Plants have developed Tropic responses so that they grow towards light and water. 

Plant tropism:

Phototropism - grows in the direction of light  

Gravitropism - grows in the response to gravity  

These are controlled by a hormone

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plant responses (2)


Positive phototropism: stem tip, towards the light, gets more light for photosynthesis

Negative phototropism: Root tip, away from light, will grow towards water and has no chloroplasts

Positive gravitropism: Root tip, Towards gravity, gets more water

Negative gravitropism: Stem tip, Away from gravity, gets more light

To move a plant in a direction of light the hormone builds up wight on the side where the light is coming from making it heavier on that side to bend that way and grow towards it.

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If conditions change to much in our body we would all die very quickly. To make sure conditions stay constant we have systems that are adapted to do this 

Conditions: Temperature, blood sugar, water content, oxygen, carbon dioxide

Organ         Skin               pancreas/liver    Kidneys       Lungs        Lungs  


Reason:   To prevent       To prevent us   Stops us       For            To prevent it                                                                                                                     

                 overheating  becoming hyper dehydrating chemical    reaching toxin  

                                        / hypo glycemic                      reactions   levels

                                                                                      in cells

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Temperature control

  • Vasodilation (widening) of capillaries ((too hot)) - capillaries widen, more blood can flow, more heat can be lost
  • Vasoconstriction (narrowing) of capillaries ((too cold)) - Capillaries narrow, less blood can flow, less heat is lost 
  • Erection of hairs ((too cold)) - A layer of air is trapped on the skin forming a layer of insulation
  • Hairs lying flat ((too hot)) - No air trapped so no layer of insulation 
  • Sweating ((too hot))  - sweat evaporates of the skin, cooling us down
  • Shivering ((too cold)) - Muscles contract generating heat 

High temperatures would increase sweat because the heat would evaporation will increase.

Negative feedback is used in body control where receptors and brain detect rise or fall in temperature and then a cooling or warming mechanism starts. 

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Negative feedback is a change away form the ideal 

If too much water enters a cell it ruptures 

If the cells overheat then they ground to a halt and die 

Hypothalamus measures body temperature by producing sweat or making you shiver 

when your body goes below 35 degrees c then you get hypothermia nad death occurs at >25 degrees c

Your body releases glucagon when your body sugar is too low

Alcohol affects homeostasis because it stops the feeling of heat 

nephrons (the structural and functional part of the kidney, its role is too filter the blood and excrete products as urine)  produces glucose, water salt, urea/urine

Homeostasis is how the body keeps conditions inside it the same.

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Controlling blood glucose

Blood glucose rises when people eat and decreases when you do exercise. If these changes are not controlled it is dangerous. To regulate blood glucose two main organs are used. 

The pancreas (which creates the hormone) and the liver (where the hormone is carried to in the bloodstream. 

High blood glucose: Pancreas produces the hormone insulin which it sends to the liver and converts glucose to glycogen and blood sugar levels drop 

Low blood glucose: Pancreas produces the hormone glucagon which it sends to liver and converts glycogen into glucose which make the blood sugar level increase. 

Negative feedback is the mechanism in our body that responds when conditions change form the ideal and returns conditions back too normal. This is where blood glucose control is controlled. 

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Diabetes is a common condition in which the pancreas does not prodcue enough INSULIN (protein). Hyperglycaemia ((too much glucose)) induces exhaustion and blurred vision/ Hypoglycaemia ((too little glucose)) causes the brain to become starved of energy; causing confusion, fits, unconsciousness and even comas. Type 1 diabetes is where someones blood levels rises fatally high. They cannot produce insulin 

Treatments include:

  • Diet - eat little amounts of glucose at regular time intervals 
  • Injecting insulin - Either before or after eating a meal. It converts the excess glucose into the storage form glycogen 
  • Pancreatic transplant - Healthy cells from a healthy pancreas are put into diabetics pancreas from a dead person
  • Medication - tablets reduce glucose levels by :-Reducing the amount of glucose made by liver, revising the amount of glucose absorbed by your stomach and improving the effects of insulin
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Testing for Diabetes

Diabetes is tested through someones urine.

Add benedicts reagent to a sample and then heat

If there is high amounts of glucose in the urine then it will turn orange/red otherwise it usually stays blue 

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