BIOLOGY UNIT 2 NOTES BY Maaz Chati
DNA is a double stranded molecule, mole cule, with the two twisted strands joint by Hydrogen bonds. Each twisted strand is a polynucleotide which is made up of lots of single nucleotides via condensation. This is a single nucleotide Every Nucleotide has ! components "ugar called Deo#yribose$ deo#yribose is a carbohydrate A %hosphate &roup A Nitrogenous 'rganic (ase )contains nitrogen* "ingle +ing (ases ytosine - Thymine Double +ing (ases Adenine - &uanine A T with / H0(onds$ & 1 with ! H0(onds. Also this means there will be the same percentage pe rcentage of Adenine as there is Thymine and the same percentage percentage of &uanine as there is of ytosine. This form of DNA found in all eu2aryotes. However, in di3erent cells, there will be di3erent percentages of e ach pair of bases as each e ach cell produces D455E+ENT %+'TE4N" and has D455E+ENT &ENE" and has D455E+ENT DNA (A"E "E67ENE". DNA is also a polymer as it is made of monomers )nucleotides*. DNA in eu2aryotes, 'N89 'N89 E:4"T" 4N N78E7", this is why red blood cells do not have DNA, as they have no nucleus 5unction 5unc tion of DNA "tore information 5eature How it helps 5eature How it helps "ugar0%hosphate %rovides strength Double heli# %rotects wea2 H0(onds bac2bone oiling &ives compact shape Hydrogen (onds Allows chain to split for translation "e;uence of bases Allows info to be stored
/ bases, the ma#imum number of amino acids they could code for is >/. "ome amino acids have > triplet code whilst other amino acids have /0? triplet codes. 4.e. /0? di3erent triplets would all code for the same amino acid. ells may be genetically identical, but di3erent in appearance, this is because >* Di3erent Di3erent genes genes are e#pre e#pressed ssed in each each /* Therefore Therefore producing producing di3erent di3erent en@ymes en@ymes How di3erent se;uences of bases code for di3erent proteins >* %roteins %roteins are are made made of chains chains of amino amino acids acids /* Each amino acid has its its own own triplet triplet code Therefore in applications such as if you 2now the amino amino acid se;uence of a substance, you could ma2e an arti=cial gene coded for that substance as ! bases code for one amino acid, therefore a correct base se;uence can be wor2ed out. 4n Eu2aryotic ells, there are many base se;uences that do not code for an amino acid, they are 2nown as 4ntrons 4ntrons,, also there are many non0 coding strands and strands and addition of bases by mutations, mutations , therefore for these reasons, the number of bases will be more than the number of amino acids multiplied by ! as the triplet code suggests. 4n %ro2aryotic ells >* ells >* DNA molecules are circular /* DNA molecules are not associated with proteins 4n Eu2aryotic ells, DNA molecules are associated with proteins and coil up to form a structure called H+'<'"'
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Number*, but when they combine with another "e# ell the Diploid Number )? chromosomes* is restored. Allele Di3erent Allele Di3erent form of the same gene positioned in the same locus, one allele is inherited from each parent, sometimes they are the same, e.g. Eye colour from dad is blue and from mom is also blue, sometimes they are di3erent, and however one will be the dominant one, e.g. Eye colour col our from dad is blue but from mom it is i s brown.
* %rocess >* +andom lining up of homologous chromosomes )+andom Assortment* /* rossing over of chromatids to form recombinant chromosomes. Also, an e#change of alleles between chromatids 4mportance of * Halves Halves chromo chromosom some e number number /* +estores +estores full chromosome number at fertilisation !* 4t also introduces variation Through this process, process, meiosis provides provides &enetic Cariation Cariation through >* +andom +andom 4ndependent 4ndependent assortment assortment of homologous homologous chromosome chromosomes s /* ros rossi sing ng ove overr !* +educing chromos chromosome ome number ma2es ma2es random fertilisati fertilisation on possible possible 7sually in the =rst stage of meiosis, DNA in each chromosome replicates to give two chromatids which have two copies of the gene, one on each chromatid. Also the homologous chromosomes in the =rst stage are separated by spindle =bres. How homologous chromosomes cross0over hromosomes in homologous pair twist around each other hromatids brea2 and rejoin to chromatid on sister chromosome Advantage of changing diploid cells into haploid cells in gamete production 5ertilisation restores restores diploid number How crossing over can contribute to genetic variation "ections of chromatids are e#changed, sections have di3erent di 3erent alleles and therefore new combination of alleles Homologous hromosomes each homologous pair consists of a maternal and paternal version of the same chromosome, since the homologous chromosomes contain the same genes$ this also means we have two copies of each gene, one from each parent. hy DNA base se;uences of homologous chromosomes are almost the same >* Homologous Homologous chromosom chromosomes es have the the same gene at the the same loci loci /* Di3erent Di3erent alleles alleles usually have have only small small di3erences di3erences in base base se;uence se;uence Although homologous chromosomes carry the same &ENE", they are N'T genetically identical (ecause although both have same genes at the same loci, the alleles alle les are di3erent )Alleles are di3erent forms of the same gene* • •
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4f aft after er <4T'" <4T'"4", 4", a cell cell loo2 loo2s s li2 li2e e this this
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an you see how there is ! homologous pairs )? chromosomes* above after mitosis and after meiosis there are three chromosomes, one chromosome from each homologous pair "ometimes, abnormal "e# ells occur, this is due to >*
The di3erence between se# se# cells and normal body cells >* "e# "e# ells ells ar are haplo haploid id /* (ody (ody ells ells are are diplo diploid id 4f an organism has an odd diploid number )e.g. !!* 4t cannot undergo * auses auses Cari Cariati ation on in phenoty phenotype pe /* "election "election of di3erent di3erent phenotypes phenotypes in di3erent di3erent enviro environment nment eventually leads to species change The greater the number of di3erent di3erent alleles that all members of a species posses, the greater the genetic diversity, the greater the genetic diversity, the more li2ely that a species will adapt to environmental change.
There are stages stages 4nterphase, 4nterphase, %rophase, cycle. hen the units of DNA have doubled, it i t means the DNA has replicated. Hence the diploid number has doubled. %rophase hromosomes become visible, nuclear envelope disappears, and nucleolus disappears, also chromosomes coil and shorten * No visible chromosomes /* Cisible nucleus 4f there were no "pindle 5ibres 5ibres hromatids will not separate * hro hromo moso some mes s shorte shorten n /* hromosome hromosomes s contain contain two identical identical chroma chromatids tids !* hromo hromosom somes es move move to e;uator e;uator of cell cell * They then attach attach to individu individual al spindle spindle =bres =bres * "ister "ister chromatids chromatids separat separate e and move move to opposite opposite poles poles ?* Each pole pole receives receives identical identical copies copies of each each chromosom chromosome e I* Nuclear Nuclear envelope envelope forms forms around around each group group of chromoso chromosomes mes ancer ells •
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>* ancer ancer ells ells often often have have damage damaged d DNA /* Therefore when this cell containing faulty DNA divides divides it divides uncontrollably and +A%4D89 +A%4D89 producing cancer !* The time cancer cancer cells spend spend at each phase phase during mitosis mitosis is much less less as they are are completing completing cycles rapidly A 2ey factor that a3ects cancer is age. Also Al so chemotherapy only 2ills some cancer cells$ hence the others continue to divide. 4n cancer, medical screening is advised so that cancer can be diagnosed early. early. ancerous tumours result in a mass of cells with an inade;uate blood supply and therefore a low l ow '#ygen environment. "ome cancer treatments reduce blood Jow to cancer cells, this helps because 8ess '#ygenB&lucose to cancer cells Therefore less carcinogens carcinogens Therefore reduction reduction in spread of cancer cells 4mportance of
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This is how it is done done >* DNA has two strands )polynucleotides*, which are joined through bases via Hydrogen (onding (onding /* H0(onding is wea2, therefore therefore DNA HE84A"E )en@yme* )en@yme* brea2s bond and separates separates strands !* These strands act as template and other free N78E'T4DE" N78E'T4DE" )see )see above* attach attach themselves to their complimentary bases * Adenine Adenine joins with Thymine Thymine and ytosin ytosine e joins with with &uanine &uanine * 'nce activated DNA %'89* DNA DNA stran strand d separ separat ates es /* New molecules molecules formed have one one old strand strand and one new strand strand > > How DNA labelled N could be separated from DNA containing N >* DNA centrifu centrifuged ged in solution solution of aesium aesium hloride hloride /* DNA sepa separat rate e depend depending ing on its its mass mass !* 4t is then then compare compared d with positio position n of band formed formed by >N * DNA wit with h >N further down the tube hy speci=c base0pairing is important in DNA replication >* 4dentical 4dentical copies copies of DNA made made with same same base se;uence se;uence as origina originall DNA /* ('TH ('TH stra strands nds act act as a templa template te %rocess of * hromo hromosom somes es thic2 thic2en en /* hromosome hromosomes s form form two identical identical hroma hromatids tids !* hromo hromosom somes es more more to e;uator e;uator of cell cell * Attac Attach h to indiv individu idual al =bre =bres s * "pindl "pindle e 5ibr 5ibres es contr contract act ?* hromatids hromatids move to to opposite opposite poles poles of of "pindle "pindle I* each pole receives receives genetic genetic information informationBident Bidentical ical copies of each chromosom chromosome e K* Nuclear Nuclear envelope envelope forms forms around around each group group of chromoso chromosomes mes IN OUR BO'Y( T)E BO'Y CELLS GO T)ROUG) * P)ASES: >* 4nterphase 4nterphase >* >* &> &rowth %hase hen proteins are produced /* " "ynthesis %hase hen DNA is replicated$ )&ene
!* & / "econd &rowth %hase hen organelles grow and divide and energy stores are increased /* Nuclear Division N78E7" divides either into two pieces )* hange in DNA base se;uence changes se;uence of amino acids made /* Therefore a change in Hydrogen bonds ta2es place changing the shape of the active site of the soon to be en@yme !* Now the substrate shape is no longer complimentary to shape of active site, therefore no en@yme0substrate comple#es Hence if no en@yme0substrate comple#es are ta2ing place, then the reaction catalysed by this en@yme will no longer be ta2ing place. How a mutation can lead to cancer >* * %revent %revent (acteria (acteria from from forming forming a cell cell wall /* 4nhibit 4nhibit productio production n of speci=c speci=c peptide peptide cross cross lin2ages lin2ages ea2en cell wall so as to allow water to enter from high water potential to low water potential, therefore cell wall is not strong enough to resist outward pressure, causing 'smotic 8ysis. !* (inds to ribosome ribosomes, s, therefor therefore e inhibits inhibits translation and protein synthesis * 4nhibits 4nhibits nucleic nucleic acid, therefore therefore prevents prevents transcription Antibiotics do not wor2 against viruses as they have a di3erent covering from bacteria. Antibiotics do not harm
<+"A * %atie %atients nts have have wea2 wea2 immune immune system system /* * 4solat 4solation ionB6u B6uara aranti ntine ne /* "creening "creening of patient patients, s, d doctor octors, s, etc. !* "teril "terilisa isatio tion n of of war wards ds (acteria usually becomes resistant to antibiotics when lots of antibiotics are given, this is because >* * All antib antibiot iotics ics may may not be absor absorbed bed /* Antibi Antibiotic otics s may be be metabol metabolise ised d !* "ome bacteria bacteria may be be resistant resistant to antibioti antibiotics cs "ometimes a harmful bacteria may not a3ect you because it is outcompeted by another harmless bacteria, however when antibiotics are used, the harmless bacteria may be reduced, thus allowing the harmful bacteria to now harm you. A lot of antibiotics stop en@ymes$ they do this by having a complimentary shape to the active site and thus behaving as a competitive inhibitor. inhibitor. How (acteria travels from one species to another >* Hori@ontal Hori@ontal &ene Transmission ransmission /* Cia conj conjug ugat ation ion !* %lasmid %lasmid is replicat replicated ed and then then plasmid plasmid is transfer transferred red How &ene Transmission Transmission and selection have increased diculty of treating bacteria with antibiotics >* Antibiotic Antibiotic resistant resistant gene is produ produced ced /* Therefore vertical transmission transmission ta2es ta2es place and resistant resistant bacteria reproduce !* This increases increases fre;uency fre;uency of resistan resistantt gene * Thus hori@onta hori@ontall gene transmission transmission ta2es ta2es place wherein wherein the resistant resistant plasmid plasmid is passed to another species of bacteria * This This is done done via via conju conjugat gation ion
/ ays in which (acteria becomes resistant to antibiotics >* * * 4t 2eeps 2eeps changi changing ng shap shape e /* Therefore Therefore en@yme en@yme of bacteria bacteria no longer complimen complimentary tary to new shape shape of %enicillin %enicillin !* Therefore Therefore %enicillin %enicillin not bro2 bro2en en down down "ome farmers add antibiotics into food of cattle, this is illegal, but it is bene=cial for farmers because >* Antibiotics 2ill pathogenic bacteria /* This reduces spread spread of infection !* Therefore faster growth growth of animal as less energy wasted =ghting disease hy this action is illegal >* 4t favours antibiotic resistance /* Therefore resistant resistant bacteria may be formed !* This may cause harm to humans OVERALL SUMMARY OF STRUCTURE OF 'NA AN' )O+ SE,UENCE OF 'NA IS REPLICATE': >* There are nucleotides present, which contain Deo#yribose, Deo#yribose, %hosphate and a Nitrogenous (ase (ase /* There are nitrogenous nitrogenous bases Adenine, Thymine, Thymine, ytosine, &uanine !* Hence DNA has a Msugar0phosphate bac2boneL and contains two polynucleotide strands each connected with speci=c base pairing * (etween base pairs there are Hydrogen0(onds which can easily be bro2en * 4n DNA +eplication there are MuncoilingL of these strands via the en@yme DNA Helicase
?* The replication is semi0conservative semi0conservative as original DNA strands can act as a template for new complimentary strands, together they form speci=c base pairing I* Nucleotides of new strand joined together by DNA %olymerase K* There are now two molecules molecules of DNA, each containing a parent parent strand and a new stand O* DNA is then inserted into NucleusB%lasmids, which in the case of plasmids are self0replicating
ell Di3erentiation %rocess by which cells become specialisedB cells become adapted for di3erent functions E:A<%8E "perm ell$ 5unction * "elective (reeding This (reeding This is also 2nown as arti=cial arti=cial selection, o3spring with particular alleles are are selected and others rejected, this reduces the variety of alleles al leles as only certain individuals are selected to breed, therefore the character that is re;uired is based on an allele. Hence non0selected alleles are eliminated whilst selected alleles increase in fre;uency. fre;uency. Ensure not to confuse selective breeding with naturalBdirectional selection wherein nature selects against one e#treme /* 5ounder E3ect New E3ect New colonies formed by a small number of individuals )individuals becoming isolated*, and founders have a small gene pool, or this could happen if a species become isolated and then mutation occurs !* &enetic (ottlenec2s hen (ottlenec2s hen a chance event ma2es the population si@e very low, this reduces variation of alleles and therefore &enetic Cariation Cariation Haemoglobin %rotein Haemoglobin %rotein with 67ATE+NA+9 67ATE+NA+9 "T+7T7+E that has haem groups which can carry molecules of o#ygen. 4t is found in +ED (8''D E88" )not the blood plasma*. e can prove that Haemoglobin has a ;uaternary structure as it has <'+E THAN 'NE %'89%E%T4DE. %'89%E%T4DE. Haemoglobin has di3erent chemical structures in di3erent organisms as it can have a di3erent %+4* %artial %ressure of o#ygen is high in lungs /* '/ binds to Haemoglobin !* 5orms '#yhaemoglobin * 4n red blood cells, Haemoglobin has a high anity to '#ygen * Dissociation occurs when partial pressure of ' / is low ?* Dissociation is increased by high ' / pressure I* %artial %ressure of '#ygen is low in respiring tissue K* Therefore Haemoglobin has low anity to '#ygen O* Dissociation curve shifts to the right Throughout our whole body this graph will be moving from from left to right shift constantly constantly.. An easy way to remember this is 8E5T08'AD4N&087N&", +4&HT0+E8EA"4N&0+E"%4+AT4'N 'nce all the Haemoglobin groups are attached to '#ygen, increasing the partial pressure of '#ygen will have no e3ect. During respiration urve moves to right as concentration of ' / is high whilst ' / concentration is low Advantage of having curve to the left in people who live at high altitudes >* &reater &reater anity anity of Haemoglobin Haemoglobin to '#ygen '#ygen at lower partial partial pressure pressure of '#ygen '#ygen /* Higher saturation of Haemoglobin with '#ygen as high altitudes have low partial partial pressure pressure of '#ygen in lungs %eople who live at high altitudes have more red blood cells, the advantage of this is i s
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>* 5oetus 5oetus has higher higher o#ygen o#ygen anity anity at lower partial partial pressur pressure e of '#ygen /* At partial partial pressures pressures when when adult haemoglobin dissociates dissociates from '#ygen, foetus haemoglobin ta2es up '#ygen from motherLs blood Disadvantage of having graph too much to the left >* Dicul Dicultt to dis dissoc sociat iate e /* There Therefor fore e cells cells su3er su3er Advantage of having curve to the right during e#er e#ercise cise >* Haemoglobin Haemoglobin has a lower anity anity for '#ygen '#ygen /* Ther Therefo efore re mor more '/ for respiration
How having a lot of Haemoglobin can help an athlete >* * %artial %artial pressur pressure e of '#ygen '#ygen very very low in muscle muscle cells cells /*
The %alisade plant cell as show is adapted so as as to allow ma#imum photosynthesis to ta2e place >* Q* &aps &aps betwe between en adjac adjacent ent cells cells >>* They They are are elonga elongated ted cells cells tto o allow allow ma#im ma#imum um light light absorp absorptio tion n The hloroplast is the the site of photosynthesis. hloroplast A("'+(" 84&HT 5'+ %H'T'"9NTHE"4", this is because when light energy hits a chloroplast, it e#cites hlorophyll and thus releases electrons. hloroplast produces A+('H9D+ATE". A+('H9D+ATE". Here is a loo2 at a hloroplast in more detail The following shows the 8ight Dependent "tage, the 8ight 4ndependent stage ta2es place in the "troma. The functions of the ell all all of the %alisade %alisade plant cell are %rovide mechanical strength against cell bursting from osmotic entry and strength to the plant as a whole To To allow water to pass along it and so contribute to movement of water through through plant 4n plants, during the day %hotosynthesis ta2es place '/ di3uses from e#ternal air into leaf through the "T'. Thin Jat shape to provide provide large large surface surface area area /. * arbon arbon Dio#ide Dio#ide enters via stomata stomata which which are opened opened by guard guard cells /* arbon arbon Dio#ide Dio#ide moves via di3usion di3usion through through stomata stomata down the concentratio concentration n gradient "ome plants have other adaptations that help in the following ways >* "horter "horter stem$ stem$ less energy energy used used in stem stem growth growth /* Thic2 Thic2er er root$ root$ storag storage e !* 8arger 8arger leaves leaves$$ %hotosy %hotosynth nthesi esis s •
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4f a plant grows ;uic2er, then this is bene=cial for a farmer as it will wi ll produce its fruits ;uic2er. ;uic2er.
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5unction Has "piral "hape This ma2es it '<%AT, therefore can be "T'+ED R0glucose molecules can be used in aerobic respiration 4nsoluble therefore does not a3ect water potential or osmosis and 8arge
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5unction "torage molecule
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E8878'"E
(onds provide strength as they are in large numbers 4t is insoluble
5unction 4n %8ANT E88 A88 >* ellulo ellulose se is long long,, straig straight ht unbranched of glucose joint by Hydrogen bonds, /* This This forms forms
THE 5'88'4N& 4" A β0glucose 'verall "tructure of ellulose >* lin2 /* Alt Altern ernate ate molec molecule ules s MJip over overLL Any time scientists wish to see if a cell has any of the above in it, they will cut a thin section of a tissue. 4t has to be a TH4N "ET4'N because >* because >* 'nly a single single layer of of cells is needed /* 8ight must be able able to pass through ays in which ellulose is similar to "tarch >* (oth are polymers$ made of monomers /* (oth have monomers joined by condensation !* (oth have >0 lin2s * (oth contain arbon, Hydrogen and '#ygen
* (oth are made up of &lucose ?* (oth are insoluble I* (oth contain &lycosidic (onds ays in which ellulose is di3erent to "tarch >* "tar "tarch ch mad made e up up of of α0glucose molecules, whereas ellulose made of β0glucose molecules /* "tarch "tarch is heli#Bcompac heli#Bcompact, t, whereas whereas ellulose ellulose is straight straight !* "tarch "tarch forms no micro micro =brils, =brils, whereas whereas ellulose ellulose does form form micro =brils =brils
'ne way by which di3erent species may be distinguished 4nter0breed 4nter0breed to produce infertile o3spring Every species has a (4N'<4A8 NA* Fingdom Fingdom /* %hylum %hylum !* lass * 'rder 'rder * 5amily ?* &enusB&ene &enusB&enera ra I* "pecies "pecies +emember it li2e this )F*eep )%*luc2ing )*hic2ens )'*r )5*ear )&*etting )"*ac2ed "pecies 'rganisms "pecies 'rganisms which have similar features and can breed to produce fertile o3spring An e#ample of a F4N&D'< is the %ro2aryote Fingdom$ it is di3erent from all other Fingdoms as %ro2aryotes have no nucleus, no mitochondria, etc. losely +elated * * Number Number of hromo hromosom somes es /* Hierar Hierarchic chical al with with no over overlap lap !* 5eatu eature res s in com common mon * Evolutionary relationships by loo2ing at their ancestors, this is called %H98'&EN9 %H98'&EN9 * An Anat atom omic ical al featu feature res s ?* Embr Embry yolog ology y I* DNA K* Homolo Homologous gous "truct "tructure ures s O* 5ossi ossill record ecord >Q* (ioch ochemical di3er i3ere encesB( esB(iinomial ial No Nomenc enclature How biological classi=cation supports the idea that animals animal s in di3erent groups have some genes in common >* lassi=cation is phylogenetic$ phylogenetic$ based on evolutionary %H98'&ENET4 grouped %H98'&ENET4 grouped according to evolutionary lin2s )4<%'+T )4<%'+TANT DE54N4T4'N* /* Hierarchy start with close common ancestry )&enus, "pecies*, then into larger groups and more distant common ancestry )5amily, 'rder, lass, %hylum* in same 2 ingdom H4E+A+H9 groups within groups with wi th no overlap between the groups )4<%'+TANT )4<%'+TANT DE54N4T4'N* !* Hence they must be related Another way that scientists compare two species is through &ENET4 '<%A+4"'N '<%A+4"'N.. %rocess >* "cientists "cientists ta2e ta2e DNA DNA from from similar similar genes of of two species species /* They heat both both DNA molecules, molecules, brea2ing brea2ing all the Hydrogen Hydrogen (onds in between strands strands of both molecules !* All strands strands are now separate, separate, two are mar2ed mar2ed as from one species whilst whilst other two strands strands are from other species * All four strands are left to to cool, this allows strands from from one species to to form Hydrogen Hydrogen (onds with complimentary N78E'T4DE" from strands of other species * The more more Hydrogen Hydrogen (onds formed formed between between the bases of the H9(+4D H9(+4D )the combinat combination ion of two strands, one from each species*, the more related the two species are and the longer it will ta2e for the strands to separate when heated hen scientists ta2e DNA, they ta2e DNA from same gene from each species, this is because (ase se;uence will be similar (ases will therefore bind together Another way that scientists compare two species is through A<4N' A4D "E67ENEB%+'TE4N '<%A+4"'N.. This is because se;uence of amino acids in proteins is determined by DNA, therefore '<%A+4"'N the more similar the amino acid se;uence in "A
4t is still better to compare the base se;uences of &ENE" rather than comparing structure of proteinsBamino acid se;uence, this is because DE&ENE+A because DE&ENE+A9 9 '5 T+4%8ET 'DE in each species can be compared. Another way that scientists compare two species is through 4<<7N'8'&4A8 '<%A+4"'N '<%A+4"'N..
%rocess >* "erum injected injected from species species A into random random species species /* "pecies "pecies produces produces antibodi antibodies es speci=c speci=c for "pecies "pecies A serum !* These antibo antibodies dies from from "pecies "pecies removed removed and and put in in tube * "erum "erum from from speci species es ( added added to tube tube * hec2 to see how much much precipitat precipitate e forms, i.e. i.e. how much of the antibodies antibodies actually actually a3ect a3ect the serum from "pecies ( ?* The more the precipit precipitate ate forms, the the higher the relationsh relationship ip between "pecies "pecies A and "pecies ( 'CE+A88 ompare DNA >* "e;uence "e;uence of bases bases compared compared via via DNA Hybrid Hybridisatio isation n /* DNA "trands "trands are separate separated d and mi#ed mi#ed together together !* Heat re;uired re;uired to separate separate hybrid strands strands indicates indicates relation relationship, ship, if a lot of heat re;uired, re;uired, species more closely related as more complimentary bases, therefore more H0(onds formed ompare %rotein >* "e;uence "e;uence of amino acids i.e. the primary primary structure structure compared, compared, this reJects reJects DNA base base se;uence 4mmunological Evidence >* 4nject 4nject serum serum into into animal animal /* 'bta 'btain in ant antib ibod odies ies !* Add serum serum from from other other spec species ies * Amount of precipita precipitate te indicates indicates relations relationship hip •
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ourtship (ehaviour "ignals to communicate with a potential mate +eason why ourtship (ehaviour is necessary and how it increases probability of successful mating +ecognition of same species +ecognition of opposite gender 4ndication of se#ual maturity 5orm %air (ond "timulates release of gametes "ynchronises mating +eleases %heromones 4f a male and female mate to produce 5E+T48E '55"%+4N&, '55"%+4N&, then the male and female are from the same species. Also usually when hybrids )o3spring of two di3erent species* are born, they cannot display proper courtship behaviour which the females are attracted to and they will not produce fertile o3spring as they have a di3erent chromosome number, gene pool, etc. Also two animals will not mate if they loo2 di3erent to each other in colour, si@e, etc. • • • • • • •
"pecies that are more closely related will have a higher chance of mating as they will have compatible genitalia$ also !0#tshi% is s%eies-s%ei1 s%eies-s%ei1 and can be used by scientists to chec2 relationship between two species as same species have similar simi lar calls. The probability of fertilisation is increased if it ta2es ta2es place in a limited area. '3spring '3spring that are born born in burrows and hidden places have a high chance of survival as they are protected from predators. "mall 'rganisms )such as most single0celled organisms* >* Have a large surface area volume ratio, i.e. their surface area area is ;uite ;uite large compared to their volume. /* Therefore substances substances di3use di3use into their their body over over the s2in s2in surface, usually usually their s2in s2in will beBhave Thin$ to allow short di3usion pathway Hairs$ greater surface area for gas e#change !* Therefore they lose more heat per gram of tissue, they therefore therefore respire 5A"TE+, and therefore therefore their '#ygen Dissociation urve is displaced to the right as they need more '#ygen. This is also the reason they are a3ected more by substances such as pesticides because the pesticide di3uses into their body very ;uic2ly. 8arge animals • •
>* Have a small surface surface area volume volume ratio, i.e. their surface surface area is ;uite ;uite small compared compared to their volume. /* Therefore Therefore they they have specially specially adapted adapted gas e#ch e#change ange surfaces surfaces !* Also, the the di3usion di3usion is slow slow as di3usion di3usion depends depends on surface surface area area * The cells of a large large organism organism are far away, away, therefore therefore they must must be supplied supplied to by a transport transport system * 8arge animals that that are more more active have high high metabolic rate, therefore therefore they +espire +espire <'+E as respiration provides the heat to maintain body temperature. ?* 8arge 8arge animals also also however, lose lose less heat per per gram of tissue as they they have fat, fat, etc. for insulation I* Di3erent Di3erent organisms organisms absorb absorb things things by di3er di3erent ent amounts amounts as each organism has a di3erent metabolism. The relationship between the si@e si@e of a mammal and its surface area volume ratio is The is The larger the mammal, the smaller the surface area volume ratio Energy 8ost 4n +espiration Energy Attained Through 5ood P Energy 8ost 4n 5aeces - Energy 8ost 4n New (ody
5eatures 5eatur es of "pecialised E#change "urface 8arge "urface Area Colume ratio$ increases rate of e#change Cery thin so that the di3usion distance is i s short %artially permeable to allow selected materials to cross * aterproof aterproof coatings coatings over over their their body surfaces surfaces /* "mall surface surface area to Colume Colume ratio ratio to minimise area area over which water water is los &as E#change in insects The level of o#ygen o#ygen inside insect will decrease due to to respiration. This means that the level of ' / will increase in the insect. There is a concentration gradient of '#ygen from '7T"4DE 4N"ET )high* to 4N"4DE 4N"ET )low*, there is another concentration gradient of ' / )created from respiration* from '7T"4DE 4N"ET )low* to 4N"4DE 4N"ET )high*, therefore when the spiracles open '#ygen comes in and AT THE "A* Air enter enters s throug through h open spir spiracl acles es /* Then through through trachea trachea where where there there is a di3usion di3usion gradient gradient !* The trachea trachea is closely closely assoc associated iated with with cells cells * '#ygen '#ygen di3uses di3uses into cells of muscle muscle =bre =bre * Centilation entilation replaces replaces air air in trachea trachea ATE+ 7"7A889 E"A%E" HEN THE "%4+A8E" '%EN T' +E8EA"E ' / "piracles in an insect open hen concentration of '/ increases oncentration of '#ygen falls in tracheaBtracheoles because '#ygen is used in respiration, therefore it di3uses from trachea into tissues How an insect limits water loss >* (ody covered covered with with waterproo waterprooff wa#y layer /* "piracles "piracles are able to close, close, they will will close in dry condition conditions s to maintain maintain water and prevent prevent dehydration !* "un2e "un2en n spirac spiracles les to trap trap moist moist air air * Trachea cuticle cuticle lined lined so as to only lose water water through through tracheoles tracheoles The many small branching tracheoles provide provide a 8A+&E "7+5AE "7+5AE A+EA. During this process you also have muscles which reate large movement of gases in and out of trachea This speed up e#change e#change of respiratory gases Also, the gas e#change system has a large surface area as well as the tracheoles are (+ANHED, inside the muscle =bre. 5eatures 5eatur es of an insectLs gas e#change system that allows ecient o#ygen supply >* 8ots 8ots of tracheoles tracheoles give large large surface area, area, loss of water from from tracheoles tracheoles also helps helps '/ di3use from tracheoles /* "hort distance distance between between tracheoles tracheoles gives gives short di3usion di3usion pathway pathway !* Di3usion Di3usion through through <7"8E <7"8E is slow, slow, therefo therefore re •
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'ur lung alveoli have a moist surface$ this is because Alveolar epithelium is permeable to small molecules such as water. water. The diagram shows how there there is '7NTE+07++ENT '7NTE+07++ENT 58' system in gas e#change e#change in =sh. =sh. The structure of gills allows allows ecient '#ygen upta2e upta2e because >*
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Advantage for =shes of having a one0way Jow of water over its gills >* less energy needed /* continuous Jow of water How a =sh maintains a 58' '5 ATE+ over its gills >* * ater too too dense dense to move move in and and out of lungs lungs /* 8ow o#ygen o#ygen concentratio concentration n in water !* High metabo metabolic lic rate rate in terms terms of of activity activity in mammals How a oncentration gradient is maintained between a =sh gill and surrounding water >* irculatory irculatory system system brings brings in blood blood with low concentration of '#ygen due to respiration etc. /* There There is also also a counter counter0curr 0current ent system system !* Also the the water water surro surroundin unding g the =sh is is highly o#ygenated * Also the the =sh =sh has a ventilati ventilation on system system to replace water How gills of a =sh are adapted for ecient gas e#change Adaptation How it helps 8arge surface area provided by 4ncreases di3usion lamella Thin epithelium between water and "horter di3usion pathway blood ater and blood Jow in opposite
"ome =shes have lungs and gills$ this means that if they perform gas e#change through lungs a lot as well, then it is li2ely that they can survive even after water dries up$ this is because gills do not function as eciently in air as they do in water. 5eatures of Transport "ystem >* A su suita itable ble tran transpo sport rt medi medium um /* 5orm 5orm of mass transport transport in in which transpo transport rt medium is moved moved !* losed system system of tubular tubular vessel vessels s that contain contain transpor transportt medium * * 'nly single single layer layer of epithelia epitheliall cells lining lining alveolu alveolus s /* ell ells s are are Jatt Jatten ened ed !* apillaries apillaries surr surrounded ounded by single single layer layer of cells * apill apillarie aries s and alveo alveoli li are are close close * ell ell membran membrane e permea permeable ble to gase gases s ?* alls of capillary capillary and alveoli alveoli are thin thin to provide provide a short di3usion di3usion pathway pathway
Type Type of vessel
How its structure is related to its function
>* No valves$ constant high pressure therefore no bac2 Jow /* Thic2er muscle compared to veins$ enables withstand blood at high pressure !* Thic2 !* Thic2 elastic =bres$ =bres$ elastic +ecoil Action maintains pressure as it allows wall to e#pand under high pressure when blood leaves the heart via the ventricle A+TE+9BA'+ contracting and spring bac2 under low pressure when ventricle rela#es, therefore therefore TA TA evens out pressure * A lot of muscle$ m uscle$ maintains pressure * Endothelium consists of Jat cells which reduce friction fri ction with blood "ubstances di3use into the aorta through its wall via a blood vessel. The changes in the pressure pressure of the aorta would tell tell you the heart rate as each pressure surge surge caused by one contraction of the heart. >* Thin alls$ because it does not have to withstand high pressure as there is little di3erence in a vein between the ma#imum pressure and minimum pressure /* Calves throughout$ throughout$ prevent bac2Jow when muscle contract and increase pressure, CE4N valves close when pressure at one side of the valve is higher than pressure at the other side of the valve !* * * Thin wall$ allows "H'+T D4557"4'N %ATHA9 /* Numerous and highly branched$ provides large surface area for di3usion !* Narrow lumen$ reduces di3usion distance A%488A+9 * 'nly endothelium present$ short di3usion pathway
* Narrow diameter$ permeate tissues, i.e. ensures that no cell is far from capillary ?* (lood Jow in capillaries is slow because &ives substances time to pass through wall of capillary The rate of blood Jow •
decreases from Aorta to apillaries, this is because 8arge increase in total cross0sectional area. +emember Arteries will contain '#ygen, &lucose, Amino Acids, 8ipids, etc. Ceins will not. (oth capillaries and arteries are similar in the way that they both have an endothelium. / di3erences between veins and arteries >* Arterie Arteries s have have thic2e thic2err muscula muscularr wall /* Arterie Arteries s have have more more elastic elastic tissu tissue e !* Cein have have relatively relatively larger larger lumen lumen * Ceins eins hav have e valv valves es hy total number of Arterioles is more than total number of main arteries Arteries divide to form arterioles hy the total number of main Arteries is same as total number of ain veins (lood goes to an organ along an artery and leaves by a vein The more active a muscle, the more blood Jow there there is to the capillaries of that muscle, muscle, this helps because >* * &as e#change e#change surfaces surfaces are are permea permeable ble /* Higher concentrati concentration on of water water inside inside animal animal than than out !* ater ater will di3us di3use e outward outwards s How blood in a vein is returned to the heart >*
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The above picture shows how tissue Juid at the Arterial end containing ' / and ater is passed along the capillary at the Cenule end, where it now contains ' / and waste material. The reason of net loss of ater ater from the capillary at the arterial end Hydrostatic %ressureB(lood %ressure %ressure greater than pressure of water potential gradient The reason as to why there is a high Hydrostatic %ressureB(lood %ressure at the arterial end ontraction of left ventricle in heart hy Hydrostatic %ressur %ressure e decreases as blood moves along capillary 5rictional force from contact with wall 8oss of Juid Total T otal volume of Juid going from from capillary is greater than volume volume coming bac2 in, this is because because "ome Juid is removed by the 8ymphatic Node, which returns the Juid to the blood The blood Jow in capillaries is slow, this is because To To allow more time for di3usion of substances substances Tissue Juid Juid accumulates in the tissues of people people who do not eat enough protein, protein, this is because 4n an unhealthy person, less protein in blood Therefore water potential gradient lower at venule venule end 8ess water reabsorbed into capillaries via osmosis How tissue Juid is formed >* High hydros hydrostatic tatic pressur pressure e at Aortic end pushes pushes Juid out out /* 8arge 8arge proteins proteins however, however, remain in blood as they cannot cannot pass through through capillary capillary wall How tissue Juid is i s returned to capillary >* Hydrostat Hydrostatic ic pressur pressure e lower in capillary capillary at venule venule end /* ater returns returns via via osmosis osmosis from high water water potential potential to low water potential potential !* 8ow water potential in capillary caused by proteins in blood, i.e. proteins proteins more concentrated due to less or no water * Tissue Tissue Juid also also returns returns to the circulat circulatory ory system system via lymph lymph vessels vessels Also remember that (lood %lasma AND Tissue 5luid contain glucose and sodium ions$ however Tissue 5luid contains less '#ygen as '#ygen is used by respiring cells. hy water potential is of (lood %lasma is lower than (lood %lasma at venule end >* %lasma proteins proteins too large large to leave leave capilla capillary ry /* ater lost, lost, i.e. plasma plasma proteins proteins more more concentrat concentrated ed The lymph vessel has valves$ valves$ these valves assist assist the return of lymph to blood plasma >* "top "top bac2 bac2Jo Jow w /* No pump pumpin ing g act action ion The function of the 8ymphatic 8ymphatic vessels >* Drai Drains ns e#c e#ces ess s Juid Juid /* %reve %revents nts accu accumula mulatio tion n of Juid !* Transpor ransports ts fats fats •
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'smosis Di3usion through a partially permeable from less
negative water potential
to a more negative water potential :ylem T :ylem Transports ransports water and ions up the root, and then up the stem, it has ligni=ed walls to provide support %hloem T %hloem Transports ransports soluble food molecules up the plant such as sucrose$ sucrose$ it does this using Active Transport Transport and therefore re;uires AT%
How an increase in rate of transpiration a3ects water potential of leaves >* Transpiration ranspiration involves involves evaporation evaporation of water through through the stomata /* +educed water content content lowers lowers water water potential potential How a decrease in water content of soil a3ects the rate of transpiration +educes transpiration as less water upta2e, therefore water potential gradient across leaves and atmosphere reduced How water enters root hair cells >* Active Active transport transport of mineral mineral ions by the root root hair cells reduce reduce water water potential potential gradient gradient /* Therefore Therefore water water enters down down the water potential potential gradient gradient via osmosis osmosis H' ATE+ &ET" T' THE :98E< ells of orte# contain mineral ions and amino acids, therefore lowering water potential ater moves from soil into the =rst cortical cell from high water potential to low water potential via osmosis This continues from cortical cortical cells to cortical cell Apoplastic %athway )movement of water through cell walls* >* ater moves through intra0cellular intra0cellular cellulose of E88 A88 A88 =bres =bres of ortical ells /* 4t is caused caused by transpiratio transpiration n pull and water moves moves down a concentrat concentration ion gradient gradient !* ater movement movement is by cohesive cohesive proper properties ties of water water * ater moves in continu continuous ous column column until it reaches reaches endoderma endodermall layer * Endodermal Endodermal cells contain contain caparian caparian strip, strip, which is a water proof substance substance,, at this point water cannot pass ?* ater Jips to the "9<%8A"T4 %A %ATHA9 THA9 and then by osmosis moves into cytoplasm of the END'DE+* hole process process ta2es ta2es place through through cytoplasm cytoplasm )N'T CA7' CA7'8E* 8E* of cells /* ater passes passes from cell to cell through through plasmodesmat plasmodesmata a from high water potential potential to low water potential via osmosis !* Therefore Therefore a continuous continuous column column of cytoplasm cytoplasm present present from from root hair cell to #ylem #ylem hy all water passes through the END'DE+<4" by the same pathway >* aspar asparian ian stri strip p is pre presen sentt /* Therefore Therefore water <7"T go through through cytopl cytoplasm asm ater ENTE+" #ylem by >* :yl :ylem em is non0li non0livin ving g tissue tissue /* Active Active Transpo Transport rt of salts from endoderma endodermall cells into the #ylem vessel vessel !* This is why '#ygen is necessary necessary as '#ygen '#ygen is used in respiration to produce AT% AT% which causes active transport * ater potenti potential al is lower lowered ed in #ylem #ylem vessel vessel * ater moves by osmosis from high water potential to to low water potential which is a passive process ?* This This creat creates es root root press pressur ure e How structure of #ylem is related to its function f unction Adaptation How it helps Thic2 ell alls alls ithstand negative negative pressure 8ignin in ell alls ithstand negative pressure :ylem ells have no end walls
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+ole of Endodermis in entry of water and mineral m ineral ions into the :ylem
>* Endodermis has waterproof strip so water must must cross cell membrane go via "ymplastic %athway /* * +oot oot %re %ress ssur ure e /* ohesi ohesion on Tens Tension ion Theory Theory !* apillarity apillarity )not needed for this this unit* ause of +oot %ressure >* Active Active Transpo Transport rt by endodermis endodermis of saltsBions saltsBions into #ylem #ylem /* This lowers water potential potential in in #ylem #ylem !* There Therefor fore e water enter enters s via osmosi osmosis s * Colume of water water in #ylem increases increases * Therefore Therefore pressur pressure e in #ylem increa increases ses and pushes pushes water upwards How water moves up the stem )ohesion Tension Tension Theory* >* "olar "olar Ene Energ rgy y sour source ce /* Therefore Therefore evaporat evaporationBtr ionBtranspi anspiration ration of water water ta2es ta2es place !* A water potent potential ial gradient gradient is created created across across the the leaf mesophyll cells * Thus when water potential potential is low in leaf leaf cells water moves out of the #ylem into surrounding tissues by osmosis thus transpiration e#erts force creating tension in water columns * Hence water pulled pulled up, however however the the polarity polarity of water causes H0(onds between water molecules, therefore cohesion ?* This maintains maintains a continuou continuous s column as cohesio cohesion n holds water columns columns together together I* The column column does not brea2 brea2 as there there is also adhesion adhesion between between the water and the the walls of #ylem vessel K* This decreas decreases es diameter diameter of #ylem vessels vessels and therefor therefore e tree trun2 O* 4f an air bubble bubble is present, present, the column column is bro2en bro2en and the movement movement of water is bloc2ed bloc2ed Evidence that supports ohesion Tension Theory >* * ater ater evaporates via osmosis from high water w ater potential in leaves to low water potential in low /* The stomata are open "ometimes, when leaves are sprayed with grease or thic2 substance, transpiration rate decreases >* The stomata are covered /* The thic2 substance gives longer di3usion pathway !* Therefore less transpiration How rate of Jow of water in #ylem is i s highest at midday >* "tomata are open /* Transpiration Transpiration highest around midday as middle of day is lighter and warmer !* This increases the tension as more water is pulled up * Therefore, there is cohesion between water molecules hy :ylem diameter is least during midday >* ater ater pull pulled ed up up trun trun2 2 /* ater ater column column under under tensio tension n !* Adhesion Adhesion between between water water molecules molecules and #ylem #ylem * :y :yle lem m pul pulle led d in The values of pressure pressure in :ylem are negative negative because >* %ressur %ressure e inside :ylem :ylem lower than than atmospheric atmospheric pressur pressure e /* ater ater is under under tens tension ion •
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How the plant uses water reate turgor 7se as solvent for transport 7se as a medium for chemical reactions 'CE+A88, H' ATE+ ENTE+" 5+'< +''T T' :98E<, THEN 5+'< :98E< T' 8EACE" )if as2ed in e#am* >* ater enters #ylem through through "ymplastic pathway as casparian strip bloc2s apoplastic pathway /* Active Active transport transport by endodermis endodermis of saltsBions saltsBions into #ylem #ylem which lowers the water water potential potential of #ylem !* ater enters enters #ylem #ylem down potentia potentiall gradient via via osmosis osmosis * Evaporation Evaporation from leaves leaves causes H0(ondin H0(onding g between water moleculesBco moleculesBcohesio hesion n * This causes causes water water molecules molecules to bind bind to the the #ylem #ylem vessel vessel ?* This creates creates continu continuous ous water column hen root tips are e#amined, they are cut o3, stained and put on a slide, a cover slip is i s then placed on top and used to s;uash the root tip. hy the root should be stained "o that chromosomes can be seen hy the root should be s;uashed To To allow light to pass through through 4n plants, scientists always try to cross plant between species, this is because >* %reserve %reserve variety variety of alleles )cross )cross plants plants are still fertile, fertile, unli2e unli2e in mammals* /* * Throug Through h the the open open stoma stomata ta /* Down Down the water water pote potenti ntial al gradie gradient nt !* (y D4557"4 D4557"4'N 'N )do )do not mention osmosis osmosis here* here* "ometimes, the "tomatal openings are remaining constant, however, the rate of transpiration increases, this is due to 4N+EA"E 4N TE* Di3usion Di3usion gradient gradient not as steep steep as diameter diameter in stomata stomata increa increases ses /* "maller stomata stomata have have more more MedgeL MedgeL of of area area • • •
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The diameter of a trun2 decreases as rate of Jow of water increases because because >* 4ncre 4ncreasi asing ng trans transpira piratio tion n /* Transpiration ranspiration creates creates tension tension !* ater molecules molecules are cohesive, cohesive, therefor therefore e adhesive forces forces between between #ylem and water * %rodu %roduces ces water water column column A %otometer measures rate of ATE+ 7%TAFE )cm ! per minute* via the following apparatus How the air bubble is i s returned to start of capillary tube 'pen tap and add water from reservoir %recautions to be ta2en to obtain reliable results >* "eal eal join jointts /* ut shoot shoot under water and cut cut shoot shoot at at slant !* Dry Dry o3 o3 lea leave ves s * 4nsert 4nsert into into appara apparatus tus under under wate waterr * Note Note where where bubble bubble is at at the start start ?* Ensure Ensure no no other other air air bubbles bubbles present present •
* 8ight /* Humidity !* Air * ater ater used used for for suppo support rt /* ater ater used for for photosy photosynth nthesi esis s !* ater produced produced in respiratio respiration n The fewer the leaves a plant has, the lower the rate of water upta2e, this is because >* 8ess ess sur surfac face e area area /* 5ewer ewer sto stoma mata ta !* There Therefor fore e less tran transpi spirati ration on * There Therefor fore e less less cohesi cohesion on The shoot should be cut and put into the photometer under water water because >* %reve %reventi nting ng air enterin entering g /* * 8oss 8oss is mass mass as as water loss is is not replaced replaced /* 4nitially 4nitially the stomata stomata are are open as there there is a high water potential potential in leaf cells cells compared compared with atmosphere !* Therefore Therefore di3usio di3usion n of water ta2es ta2es place and leafLs leafLs mass decreas decreases es * Eventually water potential of leaf reduced, therefore therefore di3usion di3usion gradient reduced reduced and therefore therefore loss of water reduced +E
5actor A3ecting How 4t A3ects Transpiration 4f any of the above ta2es place, the Apoplastic %athway will decrease as less water will have been lost Transpiration T ranspiration by the leaves, therefore, decreasing the water potential gradient. :erophytic :eroph ytic %lants %lants %lants %lants %hotosynthesis that do not have onlyplentiful occurs in water light,therefore thereforehave majority adaptations of stomata to limit are open water0 8ighttranspiration loss through for '/ The best #erophytic #erophytic plant that will survive survive is light the one with the seases hallowest roots, i.e. 4DE spread of Therefore increase incr ease in intensity incrshallowest increases transpiration roots for rapid absorption. Temperature Temperature As temperature increases, 2inetic energy increases %opulation T %opulation Total otal number of organisms a species in increases ancreases area Therefore rate ofoftranspiration in (io Diversity Cariety Diversity Cariety of living organisms, the range of variety of genes, species, and habitat within a hen atmosphere is humid, there is similar amount of water in the leaf, leaf , particular region Humidity therefore(iodiversity there is little or no concentration gr adient gradient reducing rate of Ethical argument for preserving (iodiversity %revents e#tinction and loss of thus habitats )
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"pecies Diversity Diversity Number of di3erent species and number of individuals of each species within one community &enetic Diversity Di3erences Diversity Di3erences in DNA se;uence Ecosystem Diversity C Diversity Cariety ariety of habitats within a particular area hat we need to wor2 out 4nde# of Diversity Diversity Total Total number of organisms of all species species Number of organisms of each species How you would =nd the number of individuals of one species in a habitat >* "uitab "uitable le metho method d of capt captur ure e /*
>* /* !* *
4ncre 4ncrease ase in in variet variety y of plan plants ts 4ncrease 4ncrease in variety variety of plants plants allows allows more more habits &reat &reater er variety variety of food food sourc sources es 4nsect 4nsect diversity diversity will usually usually be proportio proportional nal to plant diversity diversity
hy using inde# of diversity is a better measure me asure of biodiversity than counting the di3erent number of species >* * 5ew species species able able to withstand withstand harsh harsh weather weather /* %rodu %roducin cing g unstabl unstable e ecosyste ecosystem m !* There There are are very very few alter alternat native ives s * hanges hanges in number number of one species species will a3ect a3ect those those that feed on on it Economic reasons for maintain (iodiversity >* * ontributed by humans /* "pecies are selectively chosen which have high ;ualities 4mpact of Agriculture !* +esulting in less species, and therefore less variety of alleles * 8ess space available for other species, other species are outcompeted * The overall e3ect is that it reduces species diversity >* Deliberately done by humans 4mpact of /* %ermanent clearing of forests, then the space used for agriculture, DeforestationB8ogging housing !* * +ate of species e#tension >QQ0>QQQ times fasterBgreater Human Activity - 8oss of /* * Di3ere Di3erent nt adapta adaptatio tions ns /* "ome survive survive to reprod reproduce uce and and pass on gene gene !* This allows for changing changing environment environment auses of Cariation Ge"eti 'ie#e"es: >*
"ampling Ta2ing "ampling T a2ing measurements of individual species from a selected population of organisms being investigated +easons why sample may not represent of whole population >* "ampling "ampling (ias investigato investigators rs may ma2e unrepre unrepresentat sentative ive choices /* hance hance Even if sampling sampling bias has been been avoided avoided you may still get a bias bias sample by chance chance
+andom "ampling >* Divide Divide study study area area into grid of of numbered numbered line line /* 7sing random random numbers, numbers, from from a table or generated generated by computer, computer, obtain obtain a series of coordinat coordinates es !* Ta2e samples at the intersection of each coordinates of number of individuals individuals and number of species * +epeat epeat many times times and and ta2e ta2e a mean "ometimes, you may even lay ;uadrants every >Q metres rather than use random sampling, this is because >* 4t is is sys system tematic atic sampli sampling ng /* To establ establish ish a patt pattern ern 4ncreasing +eliability 8arger sample si@e$ produces more reliable mean and ensures representative sample +andom number generator$ removes bias that 4sotonic "olutions can be used to dilute solutions because >* They They have have the same same water water potent potential ial /* There Therefor fore e no osmosi osmosis s !* Therefore Therefore cells in s solutio olution n will not burst burst • • •
"tandard Deviation
ALL NOTES +ERE MA'E FROM EXAM PAST PAPERS BET+EEN 3ANUARY 2442 AN' 3UNE 245* TRY TR Y TO MEMORISE ALL ANS+ERS AS T)EY ARE A,A ANS+ERS6
4n &raph Analysis and Drug Trials >* hen describing a graph, mention pea2 points, increase and decrease in graph and overall increaseBdecrease in graph /* "ometimes the evidence from from the graph may not be enough to to draw a certain conclusion. conclusion. H9 H9 Any correlation does not mean there is a causal relationship There may some other factor producing producing a riseBfall in both factors "ometimes, there is no relation between both factors further along the graph Also if a control group was not used, then e3ectiveness cannot be measured 5luctuations in a graph are a clear sign that conclusions cannot be drawn from it 4n graphs, where conclusions are being drawn regarding a disease, chec2 if it says Mreported casesL, if it does you can mention about how we donLt 2now the full amount of disease cases as many were not reported and THE+E5'+E we canLt draw conclusions. !* "ometimes, data is given in a logarithmic form$ this e#aggerates the numbers and allows the e3ect of low numbers to be seen, therefore it increases the range of values. "ometimes, "ome times, data is given in a ratio$ this allows comparison as it shows proportional change. * 4n some graphs, medical cases are presented for the prevalence of a certain disease$ however, the number presented may not be the actual number of people with that disease as many people do not go the doctors. * hen an investigation involves metabolism, scientists may e#periment on people of di3erent ages as metabolism rate di3ers on age. ?* hen it as2s you to describe a graph, be sure to mention a pea2 point if there is one, if not, describe the correlation, i.e. whether it is negative or positive. I* "omet "ometimes imes data on on a graph is given given in a percenta percentage, ge, the advanta advantage ge of this is is >* Allow Allows sc com ompa paris rison on /* "hows proportio proportional nal hange as sometimes sometimes the initial weightBsi@eBv weightBsi@eBvolume olume etc. of substances substances is di3erent. K* E#per E#periments iments are repeate repeated d for the following following reas reasons ons >* Allows Allows anoma anomalies lies to to be identi identi=ed =ed /* Q* hen as2ed to give an evaluation on a claim or statement, mention all the points that indicate the claim or statement to be true, and then mention how it could be false. >>* 4f it as2s you why a drug may not be perfect 7n2nown 8ong0Term side e3ects "tudy should be carried out on humans and the study should be repeated >/** >/ (efor (ef ore e car carry rying ing dr drug ug tr trial ials, s, sc scie ient ntis ists ts sh shou ould ld co cons nsid ider er th the e fol follow lowin ing g rega regard rdin ing g the the dr drug ug Dose to be given No serious side e3ects How e3ective ost of drug >!** >! hen h en ta2 ta2in ing g drug drug tr tria ial, l, sc scie ient ntis ists ts sh shou ould ld con consi side derr the the fol follo lowi wing ng of vol volun unte teer ers s Age Health &ender Ethnicity &enetic 5actors 8ifestyle (ody
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>** > hen h en sc scien ienti tist sts s wis wish h to to use use an an anima imall in in a te test st,, befo before re de deci cidi ding ng th the e num number ber of an anim imal als s to to use they must consider Ethical onsideration Ta2e Ta2e a large number to improve reliability onsider cost and space available >* hen e#periment involves volunteers, they must be healthy as they will have MnormallyL functioning bodies. Also when dividing volunteers into groups, it should be done randomly to avoid bias. >?* 4f scientists use two drugsBvaccines and both combined have higher e3ect, then both must be similar i.e. they must have the same antibodies, etc. >I** >I Any An y tim time e doc docto tors rs wi wish sh to se see e how how we well ll th the e lung lungs s wor wor2, 2, the they y wil willl use use th the e gas gas a arb rbon on
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>K* (lood Jow is given per gram of tissue as organs di3er in si@e, therefore it allows comparison >O* How mean can be found from a graph Draw line of best =t Then =nd the gradient and divide divide it by the distance moved moved /Q* Any e#periment wherein the words MwaterL and mention of the word Mpartially permeableL come together, you should automatically realise that water potential will be involved somehow. />* "ometimes, in an e#periment, they e#periment on people of all the same age this is so that a comparison can be made. //* hen in an e#periment, people are assigned to di3erent groups +AND'<8 +AND'<89$ 9$ it means everyone has an e;ual chance of being assigned to either group. They do this by using a random number generator. generator. /!* Also remember your basics such as when you evaporate water from a substance, it becomes more concentrated. /* hen scientists measure something per unit of another thing it is so as to a comparison between the two di3erent things. /* 4f scientists wish to 2now the most common volume or concentration of a substance, they ta2e a large random sample. /?** /? 4n a med medic ical al st stud udy, y, th the e inf infor orma mati tion on is us usefu efull to to sci scien enti tist sts s bec becau ause se 4t al allo lows ws sc scien ienti tist sts s to to Determine the most e3ective dose Determine the most length of treatment 4nvestigate long0term e3ect 5ind most cost0e3ective treatment /I** /I Doubl Dou ble e (lin (lind d tria trials ls ar are e tria trials ls wh wher erei ein n neit neither her th the e vol volun unte teers ers no norr the the do doct ctor ors s 2no 2now w whi which ch treatment a particular volunteer is receiving, this improves reliability because %revents bias %revents positiveBnegative psychological e3ects /K* hen in a graph, the points are joined with straight lines rather than curves, it is because the intermediate values between points are un2nown /O* hen something is normally distributed, it means median mode, this is 2nown as continuous variation and has a Mbell0shapedL graph !Q* 4n genetic research, scientists need to ensure that the environment is the same • •
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4N <'"T 4NCE"T4&AT4'N" 4NC'8C4N& DATA, "4ENT4"T" 488 A8"' '+F '7T THE "TANDA+D E++'+ '5 THE QQ hen wor2ing out percentage decrease decrease )small )small number0big number S big number* # >QQ hen wor2ing out volume of a chemical after dilution 4nitial volume # concentration of chemical volume of chemical that is in that initial volume, the rest is basically water. water. Although not always true, but just as a tip, in e#periments regarding the heart, females tend to su3er less from heart attac2 than males. (e wary of ;uestions in which the investigator recorded results of an investigation every couple of seconds, then he displayed the investigation on a graph and the graph increases and then levels le vels o3. 4f you thin2 about it, after the graph has levelled o3, if the investigator recorded results, he would
begin to observe same results, and therefore @ero @ero changes. changes. E#aminers could as2 what did he observe when the graph levelled o3 The answer is nothing, @ero. Also be wary of cases c ases where they present data regarding chic2enpo#, chic2enpo#, mumps and rubella as children were made to catch these diseases by their parents as the symptoms of these diseases at childhood are much less severe than they are after puberty, and these diseases ta2e place only on ce usually during oneLs lifetime. "TANDA+D DEC4AT4'N Degree of variation from the mean. +he" Sta".a#. 'e$iati!"s !$e#&a%( !"&0si!"s a""!t 7e ma.e as eeti$e&/ as #es0&ts ma/ 7e .0e t! C)ANCE, if standard deviations do not overlap, we say the di3erence is +EA8. hy at times "tandard Deviation is better than the mean >* +ange +ange only shows highest highest and lowest lowest values values /* Also it is possib possible le to have two two very di3eren di3erentt data sets sets with the the same range range !* Also range is a3ected a3ected by a single single outlier outlier * "tandard "tandard Deviation Deviation shows shows spread spread about the mean mean and allows statist statistical ical use
