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The key to a smarter way of revising. Download sample: REVISE Edexcel AS/A level Biology Revision Guide samples (PDF, Mb). Designed for hassle-free. Authors: REVISION GUIDE BIOLOGY. 3 Classification. 4 Vertebrates and invertebrates. 5 Species. Hi guys, I'm new to the Edexcel system. I sat my no there isnt any as biology revision guide.:(where .

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Edexcel Biology AS Revision Notes - Free download as PDF File .pdf), Text File .txt) or read online for free. Revision Notes for Edexcel Biology AS. Feel free to. Download as PDF, TXT or read online from Scribd. Flag for . Welcome to your Edexcel A2 Biology Revision Guide. can be found at the back of the book. A-level biology edexcel - revision notes AS Watch. start new bio rev ( KB). 1. reply . do you have a pdf for the cgp revision guide plz! 0. reply.

Part of the Edexcel A level Science series. Designed for hassle-free classroom and independent study, our Revision Guides are designed to complement the Student Books with a range of specially designed features such as the one-topic-per-page format, practice questions, knowledge checks and skills checks. Write the first. Please note there is no delivery charge for digital products. Ordering on educational establishment account?

Most solar radiation Some infrared is absorbed by the is absorbed by Earth's surface. This gives us information about temperatures and C02 levels in the past.

By sampling at different levels in the peat we are sampling at different ages. They may bo th be i nfrared radiation fluctuating in s te p for some other from the Earth reason. To answer these questions we need to look at evidence from many different sou rces. It a l lows radiation to reach the Earth from the S u n. We can look at tree ring widt hs If the climate is warmer and wetter then the rings are wider.

Other gases also have this effect. Analysis of the pollen can tell us which plants were gr owing and so what the climate was like when the peat was formed. Some infrared warming the emitted by the troposphere. Earth's surface Remember that just because there escapes and cools is a correlation it does not mean down the Earth. Some of this energy is trapped by C02 and the Earth warms up. They would only release the C02 they had Plants take i n C02 i n photosynthesis.

Q1 List three sources of evidence that can be used to investigate cli mate dioxide in the atmosphere. These -- models get better all the time but they are li mited by lack of computing powe r. The increase in the use of biofuels as opposed to fossil fuels could also help because the C02 released in burning the fuel will only have been recently fixed in photosynthesis. This is because we a l ready have a n understanding of the cycling of carbon in nature.

Until recently. On the wild side The data support the theory of global warming betng r. Science is telling us about a possible future problem. One way of reducing C02 levels would be to grow plants to use as fuel. Identify the processes that Q2 What is the likely advantage. Deforestation is thought chopping down rainforest to grow palms for oil releases to be an important cause of C02 increase in the air. Looking at the cycle it can be seen that there are a number of ways we could intervene to offset this.

Suggest one disadva ntage. It is well worth learning the carbon Reforestation will increase the removal of carbon dioxide from the atmosphere due to cycle because you can work out an increase in photosynthesis. It is clear that there are a n umber of inputs and outputs to and from the atmospheric reservoir of C Jsed by humans. The Natural Environment and Species Survival Global warming will i mpact on the climate in many ways.

All of this will affect plants and ani mals in three main ways: Global warming Rising temperatures. Possible effecrs of global warming and climate change on living things. Insects may north may extend southward. In other areas the risk might be drought. Temperature affects enzymes and therefore whole organisms.

This might mean an increase in the risk of flooding in some areas. In many reptiles. Rainfall patterns are also likely to be effected. Organisms may g row faster if temperatures rise by a few degrees. In Britain a rise i n temperature might mean warmer. There is little doubt that global warming is happening. Q1 What do we mean by an enzyme's optimum temperature?

Q2 Phenology is the study of seasonal events.. It soon becomes clear that data are bei n g in terpreted with various hidden agendas and then this becomes the news rather than the science itself.

Quickly the debate becomes politicised and then the usual impassionate meth odology of sc i en ce bec ome s sid eli n e d. Th ere are other variables which might affect the rat e such as sali n ity. It is import ant to keep these controlled or monitored du r in g the experiment.

In this practical we want to vary temperature independent variable and see how it affects the number of shr imps hatched dependent variable. In both especially those involving animals. The people who will give them this are often not the scientists but politicians. It is quite normal for scientists to disagree but this topic is also a matter for public debate. Non-scientists may not understand the uncertainty and naturally want a clear answer. Give one event that may be U1 List some of the ethical affected by rising temperature for animals and one for plants.

It is also aspects of experiments you do.. Always consider the ethical b oth to make the data valid. What conclusions p eopl e reach are often coloured by who funded the research they are doing. The optimum temperature. L D D Discuss how understanding of the carbon cycle could carbon cycle help reduce atmospheric C02 levels. L D D The effects of global Describe the effects of global warming on plants and animals distribution. Energy transfer Calculate net pnmary productivity from the equation: L D D warming Explain the effects of increasing temperature on enzymes in living things.

L D D Describe succession to a climax community. D1scuss how a person's point of view might affect the conclusions they reach about actio1s to take on L D D global warming. Describe the role of gene mutation and natural Speciation and evolution selection in evolution. L D D Investigating numbers and Describe an ecological study of a habitat to create valid. L D D Describe an investigation of the effect of temperature on development of organisms. L07 D D abundance and Calculate efficiency of energy transfer between trophic levels.

L D D Explain how the concept of niche explains distribution and abundance of organisms. L08 D D I ecosystems Explain how biotic and abiotic factors control distribution and abundance of organisms. L D D Describe the validation of new evidence supporting the theory of evolution. I Describe the modelling of trends in glcbal warming and the limitations of this approach. The use of a quadrat would gain a mark.

Some have an enzyme which breaks A basic answer would mention genetic mutation as the origin of resistance or down the antibiotic. The number of species in each quadrat to gain full marks. An excellent answer would mention these points and go on to discuss how the selection pressure leads to antibiot ic-resistant bacteria being able to reproduce.

The device that could be used along the transect line. The idea that number of species recorded down again until the quadrat would be placed randomly.

A transect nota quadrat is used and you need to discuss estimation of distribution and abundance of an organism. An excellent answer would describe laying out a line. In this case random placing is not appropriate. Many answers discuss the ability of the bacteria to break down the antibiotic.

The rest of the answer is not have a pump which pumps the antibiotic out of relevant to the question asked. Some have a resistant mention that antibiotics create a selection pressure when misused.

Such an answer gains no credit at all. A line would be laid out and a quadrat placed This is quite a typical answer in which there is some truth. Note carefully the word 'become' in this questi o n. A basic answer would mention the quadrat but be unclear as to how to place or use it for a specific purpose. This might be because they now bacteria which gives them resistance to antibiotics On the wild side 1 A transect can be used to study trends in the abundance and distribution of organisms Describe one method you could use to estimate the abundance o f an organism at intervals along a transect line.

Tray 3 contained only non-tolerant plants and Tray 2 had a mixture of equal n umbers of both types. June 2 Agrostis tenuis is a grass that g rows near old copper mines in north Wales. Tray 1 contained only tolerant plants. Copper is usually very toxic to plants but some Agrostis plants c a n tolerate copper in the soil and grow on waste tips from the copper mines.

The Natural Environment and Species Survival 1 The diagram below summarises the light-dependent reactions of photosynthesis. Li g ht Product A t. The total dry mass of the plants in each tray was measured. Electron carriers Product B. C electro ns electrons Chlorophyll. The arrangement of the plants and the results are summarised below.. NPP u:: On the wild side 3 Su r '' Aver seed lings were planted and kept under controlled conditions for 20 days. The I frequency of an allele.

The results are shown i n the graph below. June l. NPP a n d respiration. A and B June 4 The tolerance of plants to copper ions in the soil is under genetic control. The table below sh Plants need nutrients such as nitrogen..

Micro-organisms are crucial to the decomposition process These nutrients are locked into the tissues of the plants and any animals that might eat them. The products of external digestion are absorbed by the m icro-organism and broken down in microbial respiration.

Bacteria a n d fungi produce a range o f enzymes that are released on t o the dead organic matter. The stage of larvae on a dead body can be used to estimate time of death.

The process of decomposition allows the nutrients to be recycled The carbon cycle is a good example of how nutrients are recycled a n d how micro-organisms help. There are five m a i n ways that scientists g o about this Decay and decomposition Once the plant or a n i m a l dies the nutrients can be released only through decay. So the muscles become fixed. This happens within about hours depending on temperature. The community of examin ations where you are asked species present when the body is found allows the stage of to do calculations.

Th i s stiffening is called rigor mortis. The stiffness wears off again after about 36 hours in cooler conditions as the muscle tissue starts to break down.

E nzym es in the gut start to break down the wall of the gut and then the surrounding area. During the first 24 hours after death the temperature of the body when it is found can be used to work out how long ago the person died.

This provides a n estimate of time of death assuming any eggs were All the m ethods used to indicate laid soon after death. There is a succession of species. U1 Desc ri b e two wa ys in which succ ession on a body is simila1 to succession on a sand dune Q1 List three i nd i cators that can be used to work out time of death.

Remember this in change. The stiffness occurs because muscle contraction relies on ATP. The signs of decomposition.. Topic 6: As cells die they release enzymes which help to break down tissues. Otherwise you may the po s itive electrode.

The sequences of repeated bases are called short tandem repeats STRs. The fragments separate into invisible bands. These non-coding sections are called i ntrons. The steps in the production of a DNA profile or fingerprint. The negatively charged DNA moves towards the positive electrode. It is rather like chromatogra phy. The data can also be presented a s a graph o r as a series of numerical values. Scientists look a t the short tandem repeats at many loci to build u p a unique pattern for that individual.

This is because of t h e variety found in the sections of DNA which are not used to code for proteins. DNA fragments continuing the repeated sequences are created using reestriction enzymes or the polymerase chain Do not try just to remember a reactions. People and a l l other organisms vary i n regard to t h e number o f these repeats they carry a t each locus. Green Book 6. If a potential difference diagram like this.

Edexcel A2 Biology Revision Guide Edexcel a Level Sciences | Photosynthesis | Metabolism

DNA is cut into fragments. The fragments move at different rates according to their size get it in the wrong sequence and and charge. DNA double strands split and stick to the membrane. In addition there is now also a technique called the polymerase chain reaction PCR which allows tiny amounts of DNA to be a mplified into quantities large enough to use in DNA p rofiling. The technique allows us to identify biological material with a high degree of confidence.

Scientists look for short. Together they form one of the most powerful techniques we have for criminal investigation and a range of other situations where total certainty about the identity of a sample is requi red. There can be up to several hundred copies of the STR at a single locus. Everyone's DNA is u nique. Its influence on forensic science has been hJge. Membrane placed in bag X-ray film is used to detect the with DNA probe.

Small fragments with fewer repeats travel faster and end up closer to the not realise it! Topi c 6: Infec tion. Q1 Which parts o f t h e DNA are used for profiling? Q1 The family tree of every ra cehorsP. The process relies on DNA primers. This is a good example of developments in science and technology allowing us to answer questions which we would previously not have been able to add ress. Confirming the ped i g ree of domestic animals such as racehorses.

Explain why it is easi Q2 Why is it necessary for forensic scientists to look at 1 0 or more short to identify humans using DN1 tandem repeats when creating a DNA profile?

Transcription means 'to make a full copy of'. A peptide bond is formed template strand A pairs with U. It only becomes a prote in when folded and. The whole process is shown below.: The mRNA copy is not direct. A pairs with T.. We now know this is not correct. These changes are made to the mRNA before it is used in translation. Using three bases gives the next amino acid to be attachec 64 codons which is more than enough.

As long as the codon starts with CC the amino acid proline will be put into the polypeptide. Amino acids are non-overlapping Each set of three bases forms one triplet. This offers some protection against mutation. The triplets do added one at a time in a repeating not overlap. Q3 Link each description in list A with the correct term in list B. Explain what this means and why it is significant.

Most genes code for many proteins and this is achieved by post-transcriptional changes in the mRNA. Q2 The DNA code is degenerate. The following responses are non-specific: No cell wall.

The initial symptoms of an HIV in fection are fevers. The Natural Environment and Species Survival Infectious diseases in humans are caused mainly by bacteria singular: All symptoms can then then disappear for years but eventually patients suffer from weight loss.

I Can live independently. Nucleic acid enclosed in prote in coat. You need to be aware of the differences between them. Blood bacterial cell walls. In TB the first infection may have no symptoms but tubercles form in the lungs due to the imflammatory response of the person's immune system. Both viruses and bacteria may enter the bodies of living things and.

TB bacteria also target cells of the immune system so the patient cannot fight other infections well. Finally there are severe symptoms such as dementia. Often have mucus-based cuter May have outer membrane of host cell surface capsule.

The patient develops a serious cough. Average diameter 0. We can illustrate this by looking at tuberculosis. Kaposi's sa rcoma and opportunistic infections such as TB and pneumon1a. These phagocytes in clude and capillaries to become by breaking down the neutrophils and monocytes which more permeable. Some bacteria may survive inside the tubercles. In active TB. In some cases the bacteria invade glands and the CNS central nervous system.

All of this can be fatal.: They lie dormant. Circular strand of DNA is the geneti c material. Bacteria have a prokaryotic cellular structure with organelles but viruses do not. Infectio n. B memory cell viru s-infe'.. Macrophages identify 6. T killer and T memory Q2 Why might a fever be a good thing if you have an infectious disease7 cell s. Both types respond to foreign non-self antigens such as proteins on the surface of bacteria and viruses. The immune response. Use a presenting cell.

Q1 Draw a table to distinguish between the roles of B cells including B memory and B effector cells and T cells T Q1 Give two differences and two similarities between viruses and bacteria.

T memory cells a They alert the immune system to the presence of the foreign antigens. Macrophages are also involved. These live naturally on the skin and out-compete pathogens. We can also use antibiotics to f1ght bacterial infections There are two kinds of antibiotics: These antibodies can p rotecti on produces toxins or protect against any against the memory antigen invading pathogen invading cells which fragments that the mother has pathogen they make it means that the encountered.

Major routes of entry ofpathogens and the role of barriers in protecting the body from infection. The mucus is then swallowed and passed into the digestive system. These compete with pathogens for food and space which helps to protect us. When bacteria are no longer affected by an antibiotic they are said to be resistant to it Green Book 6. We can acquire immunity in different ways: Injected with to ant1gen antibodies cross the antibodies that by getting wea kened I placenta and are also can provide the disease.

Gastrointestinal tract. Sebum is an oily fluid which is made by the skin and can also kill microbes. In addition the gut has its own bacteria. The harmless bacteria also excrete lactic acid which deters pathogens. The Natural Environment and Specie5 Survival Pathogens organisms that cause diseases enter the body through areas not covered by skin: As an additional line of defence the skin has its own microbes.

Respiratory tract. This means A simple procedure can be carried out to investigate bacteria and antibiotics for the that new mutations occur quite core practical It is important to follow safe.

Anything in in exams. Bigger areas indicate a better antibiotic antibiotics on bacteria. Q1 What theory would you hope to test with the practical above7 Write a scientific question to answer. Hospitals try to combat this in a number of ways. Consequently they will produce A sterile nutrient agar plate is seeded with many mutations in the time it woulc suitable bacteria. IL nl Lack of details like Look for clear areas around the antibiotic discs investigate the effect of different this often lose candidates marks or wells.

The TB bacterium produces a thick waxy coat which protects it from the enzymes of the macrophages. Incubate below 30 oc for about 24 hours. I us1ng a stenle p1pette. This is because bacteria will not grow in an empty plastic dish. The protein coat of HIV is constantly changing which means that the immune system can't target and destroy it.

Describe how the polymerase chain reaction can be used to give more DNA for analysis. L06 0 0 Describe how DNA fragments can be separated by electrophoresis. Explain antigens and antibodies and how plasma cells. Infectious discJscs und Distinguish between the structure of bacteria and viruses. L D D Describe investigations of the effects of antibiotics on bacteria. L D D Describe the way in which our understanding of infections acquired in hospitals can be used to L D D reduce their occurrence through codes of practice.

L D D Explain how people develop natural.: Distinguish between bacteriostatic and bactericidal antibiotics.: Describe how micro-organisms are involved in decomposition L D D Infection prevention and Describe the routes of entry of pathogens into the body and skin.

Explain how changes that happen after transcription can give rise to more than one protein L04 0 0 from one gene. L02 overlapping and degenerate.: Distinguish between roles ofT helper. L08 0 D 0 0 the immune Explain the symptoms of bacterial and viral disease L response to include those ofTB and infection by HIV Describe non-specific immune responses: Almost everyone coug hs at some point dur ing most days so.

An excellent answer would suggest qualified coughing i e cough ing up blood or excessive coughing as well as the appearance of tubercle s.

It is not TB which does system and therefore become more active.. A 'weakened immune system' does not address TB would take advantage of a weakened immune the specific aspect of the immune system which HIV affects. The diagram below. E Jnd C. One treatment for HCV infection is injections of interferon. In each case the antibiotic was added at 7 hours. The N atura l Environment and Species Survival 1 The graph below shows the changes in population size of bacterial cultures grown.

Suggest an explanation for the change in the response to antibiotic A. She took the pupae and larvae to her laboratory. She recorded the temperature in the room and she collected the larvae and pupae of several species of insect from the body. June One of the first species to be seen was the blowfly. It has been found that these resistant 'Jiru. June 4 On 26th September. Records of weather conditions for the area were consulted and the time of death was determined to be 14th or 15th September.

June 3 HIV can damage the human immune system. She was asked to determine the time of death. Key ooc. The excited electrons that are taken up by electron carriers follow pathway B. Give reasons for your answer. The data for four of these trees are given as a percentage of the total tree pollen sample..

An estimate of the age of the sample at each depth was also made. Copy and complete the table by putting a cross in the box if the structural feature is present. J [] 5 b The table below shows the number of new TB cases recorded in and in from four different geographical regions. These data exclude people who are HIV positive. L I 98 If they had been included suggest how the data would differ.

G ive an explanation for your answer. Suggest two reasons tor this. MRSA can survive treatment with several antibiotics. An i nfection with MRSA is difficult to treat It is i mportant to use an a n ti biotic that is effective against specific bacteria. Describe in outline how you could test the effectiveness of an antibiotic on a specific bacterium in the laboratory Include aspects of the method that ensure safe working. A transect was used which extended i nland from a beach. Quadrats were used at nine positions along the transect.

The percentage cover of selected species was recorded in each quadrat as well as the n u m ber of r: The results are shown in the two tables below.

Edexcel A2 Biology Revision Guide Edexcel a Level Sciences

Number of 1 1 5 11 18 7 5 6 7 species found. Mass of organic 0. Common heather Corsica pine Use the Information in the table to suggest how the resu lts of the study could be explained by succession. Bones can move in relat i on to one another at joints. Different types of joint a l low d iffere nt degrees of movement.

Ligaments are made of elastic connective tissue. They hold bones together and restrict the amount of movement possible at a joint.

Tendons are cords of non-elastic fibrous tissue that anchor muscles to bones. Skeletal muscles are those attached to bones a n d are normally a r ranged i n antagonistic p a ir s T h i s means that there are pairs o f m uscles which p u l l i n opposite direct ions Flexors contract to flex, or bend a joint, e.

Remember that m u s c l e s c a n't stretch themselves. It is the pull Each skeletal muscle i s a bundle of millions of muscle cells called fibres.

Each muscle created by the contraction of the cell may be several centimetres long and contains several nuclei. It conta ins m a n y antagonistic muscle that stretches a myofibrils which are made up of the fibrous proteins actin thin fi l a ments and m u s c l e when it is in a relaxed state.

The cytoplasm inside a m u scle cell i s called the sarcoplasm. The specialised synapse see page 63, Topic 8 between neurones and muscle cells is called the neuromuscular junction.

The p refi x myo- refe rs to 'muscle' and sarco- to 'flesh' i. When the muscle contracts the thin actin filaments move between t h e thick myosin f i l a m ent s shorte n i n g the length ,.

The arrangement of actm and myosin filaments in a sarcomere when relaxed A and contracted B. Myosin head cannot bind i to move together with the threads of tropomyosin.

Actin filaments are associated with two other proteins. ATP comes from respiration electron transport chain anaerobic respiration glycolysis lots of myoglobin dark red pigment to store little myoglobin and few capillaries The 02 and lots of ca pilla r es to supply Q3 Explain why muscles are arranged in antagonistic pairs. Topic 7: RJn for your life Myosin filaments have flexible 'heads' that can change their orientation.

V blocked by Ca2' attaches to actin p tropomyosin. Jo upright myosin forms position. This muscle has a light colour gives the muscle a dark colour fatigue resistant fatigue quickly low glycogen conten t high glycogen content low levels of creatine phosphate high levels of creatine phosphate Q1 Give one reason why fast-twitch muscles are more likely to get t i red faster than slow-twitch muscles.

The variation in gametes comes from;. Each individual makes many gametes, each of which is genetically different. This creates a huge number of potentially different embryos as which two gametes are selected for fertilization is largely random.

If the number of different gametes made by both parents is n, therefore the total number of possibilities is n2, which is huge! Whichever way up the pair are aligned will affect the combination of alleles in the gamete. When the chromosomes are paired up during metaphase sections of DNA are swapped between chromatids this is called crossing over. This means that alleles which were previously linked with others i.

Part of Ovum Adapted for… Nucleus Contains only one copy of each chromosome haploid. Follicle cells Secrete chemicals that secrete the acrosome reaction. Zona pelludica Hardens once sperm has entered ova, stops further cells entering. Tail Made from motor proteins, which use ATP to propel the sperm forwards. The acrosome swells and bursts when the sperm embeds in the zona pellucida zona pellucida releases chemicals that trigger this. The enzymes in the acrosome digest the follicle cells and the zona pellucida and allow the cell membranes to fuse.

Cytoplasm Very little cytoplasm, which means cells are small and therefore can be released in large numbers. Fertilization is the successful fusion of two haploid gametes to create a diploid cell a zygote.

The zygote then divides rapidly by mitosis to become an embryo. The sperm is attracted to the ovum by hormones released by the follicle cells surrounding the ovum. When the sperm reaches the ovum it embeds its head in the zona pellucida, triggering the acrosome reaction.

The acrosome swells and bursts, releasing proteolytic enzymes. Sperm membrane fuses with ovum membrane and the sperm nucleus enters the ovum by endocytosis. Pollen grain grows a pollen tube down into the stigma.

The pollen nucleus is at the tip of the tube. The pollen tube reaches an ovum and the nucleus enters it by endocytosis forming a zygote. Stem Cell: Pluripotent Cell: Multipotent Cell: Stem Cells are very useful because they can be used to grow replacement organs.

However, it is not yet possible to get a differentiated cell to revert to being a stem cell. Therefore, stem cells tend to be harvested from embryos, which causes serious ethical problems.

Cells become specialized or differentiated by progressively switching genes off. This is sometimes done by adding methyl groups to the gene, which stop it being opened in transcription.

In addition, some genes may require a transcription factor to activate them i. Usually the TF is a hormone e. Steroids - think about their effects , but sometimes it can be an environmental factor e.

The phenotype is a product of the genotype and the environment. For some genes the environment has minimal effect e. You need to know 4 examples. Some animals have fur colour that is a product of the environment e. Siamese cats should have black fur all over as their genotype codes for the enzyme tyrosinase that converts tyrosine into melanin which is a dark protein — remind yourself of Albimism in 1.

However, the enzyme is denatured by body heat, so only the cold parts of the animal are black tail, ears etc and teh rest is white. Is controlled by many genes, each with a range of alleles, making it an example of polygenetic inheritance i.

In addition, diet has a huge effect on height. MAOA enzymes break down neurotransmitters released by nerves in the brain. Mutations of MAOA are the genetic component to these conditions, but environmental factors such as stress levels also have a profound effect. A tumour is a ball of cells dividing quicker than they should. Tumours that split apart and spread around the body metastasis are the most dangerous malignant.

Oncogenes — speed cell cycle up Tumour Supressor Genes — slow cell cycle down. Mutations in either of these genes can cause tumours. Although mutations occur naturally, the environment can have an effect e. Discontinuous variation: Usually controlled by one gene where the environment has little effect. Continuous variation: Usually controlled by many gene polygenes where the environment has a large effect.

Notes 2: Animal and plant cells are both eukaryotic cells, they have common eukaruyotic features. However, plant cells also have some features unique to them. Cell wall: A structure made from cellulose fibrils and pectin cross- links. It strengthens the cell and allows it to be turgid without bursting. A junction between adjacent cells where the cytoplasm of one cell joins the cytoplasm of the other. Used for intercellular communication. Plant cells are strong because they are wrapped in a protective layer of cellulose.

This forms the cell wall. Because cellulose has no side branches the chains can be packed closely which increases the strength of the hydrogen bonds further. Individual cellulose chains are packaged together into microfibrils.

The microfibrils wind around each other forming cellulose fibres. The cell wall is build from layers of these fibres. Secondary cell wall: Forms later, cellulose fibres laid down at right angles to those in the primary wall. Provides much greater strength. These tend to form as a cap to the vascular bundles in the stem.

Sometimes the sclerenchyma can be extracted by humans for making into rope e. Sustainable - they are not a limited resource as, although they are used, they can be replanted. Carbon neutral - do not contribute to rising CO2 levels although they may give off CO2, replanting uses the CO2 up again. Plant materials are used as fibres wood, cotton etc as they have a high tensile strength and can be used in clothing, building industry etc.

Oils from plants can be used as biofuels and starch can be used in packaging, glues, absorbants as well as for food. Mineral Function in plant Nitrate Used to make amino acids, which the plant uses to form proteins Calcium Used to make pectin for cell walls Magnesium Central ion in the chlorophyll molecule. Transport of substances e. Maintain turgor 5. Solvent for chemical reactions 6. Gamete distribution. William Withering experimented with foxglove extract as a cure for dropsy oedema caused by congestive heart failure.

He also killed someone. His studies, though important are NOT ethical and do not follow the basis of modern clinical trials. Stage Purpose of stage Pre-clinical 1. Proposed drug is tested in a lab with cultured cells to testing see the general effects of the drug 2.

Proposed drug is given to animals to see the effects on a whole animal. Any side effects away from target cells are noted. Clinical Trials — 1. A small group of healthy volunteers are given different Phase 1 doses of the drug. They are told what the drug does 2.

The effects of the different doses are assessed to try and determine the optimum dose 4. A small group of people with the disease are given the Phase 2 drug.

Studies are very similar to Phase 1 3. The optimum dose is worked out Clinical Trials — 1. A large group of people with the disease are given Phase 3 optimum doses of the drug 2.

The patients are either given the drug or a placebo in a double-blind test 3. The results are analysed 4. The number of species, the number of individuals within those species and the number and variety of alleles those individuals.

Where a species is found only within a particular niche in a particular ecosystem. Species richness: Can be measured in different ways;. Genetic diversity: The greater the diversity, the more likely the species is to survive environmental change or disease.

A niche is the specific part of the ecosystem in which a species lives and any adaptations the species has that make it successful there. Adaptations can be;. Behavioural e. Iguana on the Galapagos islands dive for seaweed - they are the only lizards to venture into the sea.

Physiological e. It loads O2 much more efficiently at altitude see end of Topic 1. Anatomical e. The smaller claw is, rather disappointingly, used for feeding. More offspring are born than can survive O2: There is variation within a species. Eventually the isolated population cannot reproduce with the originals.

The taxonomic classification system follows a hierarchy of groups the 5 Kingdoms at the top, individual species at the bottom in which all species are categorised according to their anatomy. However, this is not necessarily the best approach as species with similar anatomies e. A better system is based on molecular phylogeny i. The best molecule to examine is DNA. A recent proposal along this line the three domain theory argues that all organisms evolved into three broad groups;.

Archaea — those species that exhibit characteristics of both i. Seed banks and Zoos help because they allow us to preserve biodiversity, reintroduce species, set up captive breeding programmes, educate people about ecology and generate money from tourism. However, be aware that some species those that have a lot of leaned behaviours e. A single layer of cells often with long extensions called root hairs, which increase the surface area enormously.

A single plant may have root hairs. A single layer of tightly-packed cells containing a waterproof layer called the casparian strip. Symplast pathway: Apoplast pathway: The cell walls are quite thick and very open, so water can easily diffuse through cell walls without having to cross any cell membranes. However the Apoplast pathway stops at the endodermis because of the waterproof casparian strip. At this point water has to cross the cell membrane and enter the symplast pathway.

This effectively water-proofs the Stele, which stops water loss higher up the root. Water moves from high water potential to low water potential by osmosis. However, most soils are dry especially in the desert and the water potential of the soil is low. The answer is that plant roots take up lots of ions from the soil, which lowers the water concentration of their cytoplasm enough for water to enter the root by osmosis, even if the soil if very dry.

The ions are taken up by active transport, by proteins in the cell membrane of the root hairs. This uses up lots of energy uses lots of ATP. Because of the low water potential root cells become very turgid. This creates a small pressure, which forces water up the xylem in the stem.

This is called Root Pressure. In small plants root pressure is very important for transpiration. In woody plants it does not have a significant effect.

Different kinds of cells form wide and Transverse Section T. The xylem vessels form continuous pipes from the roots to the leaves. Water can move up through these pipes at a rate of 8m h-1, and can reach a height of over m. Water evaporates out of the leaves and causes low H H pressure in the leaves.

This creates a suction or tension force which sucks water H H up the stem O 3. Because water molecules are polar they stick to each other and the entire column of water in the Xylem moves H H upwards.

This mechanism is called the cohesion-tension theory. Flag for inappropriate content. Related titles. Jump to Page. Search inside document. Understanding the jargon: This gives water some useful properties; Property Explanation Less dense as a solid Arctic ecosystems float, ice insulates water beneath it etc High SHC Cells do not heat up or cool down easily, therefore can hold a fairly stable temp.

Found in muscle and liver cells for energy storage 3. Insoluble, so no osmotic effect in tissues 4. Compact shape, so good for storage Starch 1. Actually made from two molecules in combination; Amylose and Amylopectin 2. Found in Amyloplasts starch grains inside plant cells for energy storage 4. Insoluble, so no osmotic effect in tissues 5. Main component of cell walls as it is a very strong structural molecule 3.

Insoluble… for obvious reasons! The opposite of a condensation reaction is a hydrolysis. This requires; 1. OR an enzyme e. Amylase Tests for Sacharides: Triglycerides are used for; 1. They form fats.

They form oils. Test for a triglyceride Emulsion test: Vol Amoeba Large SA: Therefore require a mass transport system and specialized exchange organs In humans the mass transport system is the circulatory system and the heart. The names of the two sets of valves in the heart 4. The cardiac cycle 5. When ventricular pressure rises above pressure in the arteries the semi-lunar valves open 2 Blood leaves the heart 0.

Key Points: Relatively small lumen Vein: Large lumen decreases effect of friction Capillary: The sequence of atherosclerosis is as follows; 1. Endothelial layer on the inside of an artery is damaged 2. Inflammation an A2 topic of the artery wall occurs 3. White blood cells move into the artery wall 4. Cholesterol begins to accumulate at the site of damage 5. Platelets are activated by substances released by the damaged artery wall 2.

Platelet plus releases chemicals which activate thromboplastin 4. Thromboplastin initiates the clotting cascade Thromboplastin There is a real danger of the blood clot becoming dislodged from the site of formation. If this occurs; - in the brain a stroke occurs - in the coronary arteries, CHD or even an infarction might occur - anywhere else, ischaemia and even gangrene are possible 1.

Two explanations; 1. Three problems with this, however; 1. It has the following effects; 1. The major side effect is kidney failure. Vasodilators — dilate blood vessels, reducing blood pressure. Remove LDL from the circulation Associated with liver failure.

Anticoagulants As the second stage of atherosclerosis is associated with blood clotting thrombosis , anticoagulants block the clotting process. Blood clots slowly. Platelet inhibitory drugs These work in the same way as anticoagulants but target platelets, which are required to activate the clotting process.

We get cholesterol from two sources; 1. Diet 2. It is made by the liver Lipoproteins also made by the liver ferry cholesterol around in the bloodstream and play a role in pushing the liver towards making more cholesterol, or excreting more cholesterol. If two sets of data follow the same pattern they are correlated If two sets of data follow the same pattern because one factor directly affects the other they are causal In order to assess whether data is correlated or causal scientists experiment, the idea being to try and falsify the Null Hypothesis that one factor does not affect the other.

Things to watch out for; 1. Quite quickly the risks stack up… Oxygen Dissociation Curve This is not mentioned on the syllabus, but it is in the text book.

The prudent man learns it anyway… Remember, each Haemoglobin Hb can bind up to 4 O2 molecules. It is only given up if the Hb passes through tissues with very low PO2 When the line shifts position 1. Acids tend to be - carbonic acid made from CO2 - lactic acid made in anaerobic respiration Both acids are produced when O2 is in short supply, so it makes sense for Hb to give up more O2 in these circumstances.

There are a few theories about how the water actually gets through, but these are the best so far; 1. These are gated channel proteins Facilitated Diffusion proteins 1 2 3 Protein channel has an active site specific to a particular hydrophilic molecule. Active Transport proteins As above, but the movement is against the concentration gradient.

Test for Protein: Therefore; The specific sequence of specific amino acids determines the shape of the protein and, therefore, its function. New nucleotides diffuse into the fork and hydrogen bind with their complementary partners 3. A Gene e.

Gene opens up. Hydrogen bonds break between bases 2. RNA nucleotides attracted to complementary bases and form hydrogen bonds. Complementary RNA copy of gene now made.

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Biology Revision

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