AQA A level Biology Unit 1 Notes

POPULATIONS AND ENVIRONMENTS Population: a group of interbreeding organisms of one species in a habitat Community: all Community:  all the populations of dierent organisms living and interacting in a particular place pl ace at the same time; group of dierent species form a community Habitat: where Habitat:  where a community of organisms live Ecosystem: Made up of all the interacting Biotic and biotic factors  !herefore two species which have dierent niches will provide a ma"imum yield as each each will e"ploit the environment more eectively# biotic $actors: non% living factors that aect an ecosystem and its organisms such as temperature and rainfall Biotic $actors: living $actors: living factors that aect an ecosystem and its organisms such as competition and predation Ecosystem: made Ecosystem:  made up of all the interacting biotic and biotic features in a speci&c area Ecological 'iche: the 'iche: the role of a species in an ecosystem; it is governed by the adaptation of the animal to biotic and abiotic factors# ('!E)*PEC($(C C+MPE!(!(+' !,E* !,E* P-CE .HE' !.+ *PEC(E* H H/E /E +/E)-PP('0 '(CHE* 1this is because no two species can coe"ist in the same habitat if they have the same niche2# !herefore if two species are observed to compete then they must have the same niche# *pecies: a *pecies:  a group of interbreeding individuals which do not normally breed with other species to produce fertile ospring $ood Chain: a Chain: a se3uence of organisms in an ecosystem in which each is the food f ood of the ne"t organism in the se3uence $ood .eb: all .eb: all the interconnected food chains in an ecosystem  !rophic  ! rophic -evel: -evel: a  a feeding level in a food wed4 it shows energy transfers away from the producer  !he primary consumer gains the most energy; energy; therefore herbivores herbivores gain more energy than carnivores Pyramid of energy energy:: a representation of energy at each trophic level4 it is a triangular shape as energy is lost BE!.EE' trophic levels .hy ecosystems rarely have more than &ve trophic levels: 'ot enough energy left as there are energy loses between trophic levels Producer: !he Producer:  !he &rst organism in a food chain4 it is an autotroph; capable of manufacturing food by photosynthesis How Producer converts energy to biomass: 52 6ses 6ses energy energy for for photos photosynt ynthes hesis is 72 Materials Materials are are synthesis synthesised ed to be be used for growth growth 82 !he chem chemica icall energy energy is stor stored ed .hy dry biomass of animals to dry biomass of plants is always a lot less than one: 52 Plants are produ producers cers and and animals animals are are consumer consumers s 72 Energy is lost between trophic trophic levels due to to loss of energy energy through through respiration4 heat4 etc# Primary Consumer: !he Consumer: !he second organism in a food chain4 obtains energy from the producer; herbivore *econdary Consumer: obtains Consumer: obtains energy from the primary consumer; carnivore 9ecomposers: +rganisms 9ecomposers:  +rganisms that brea down producers and consumers when they die and thus release minerals and elements which can be used by plants How 9ecomposers may wor on dead matter to mae the contents available to a plant: 52 *ecrete *ecrete enymes enymes for digestion digestion of of dead matter4 matter4 usually usually it is starch starch 72 9igestion 9igestion produces produces sugars and nitrog nitrogenous enous waste waste 82 !he nitrate nitrate 1nitroge 1nitrogenous nous waste2 waste2 is taen taen up up by plants plants <2 9ecomposers absorb the sugars 1glucose2 produced produced from digestion and use them for aerobic respiration 5) As decomposers decomposers respire they produce produce Cr!o" Dio#ide Dio#ide my my !e used !y the p$"t $e%es i" photosy"thesis &) 'o(e%er they $so use up O#ye" O#ye" s they respire* respire* there+ore reduci" reduci" di%ersity di%ersity o+ o#ye" depe"d"t or"isms ,) 9ecomposers will also change sub=ect to temperature and pH 9ierence between decomposers and detritivores: 52 9ecomposers 9ecomposers secret secret enymes enymes for e"tracellular e"tracellular breadown breadown of organic organic matter 72 9etritivor 9etritivores es ingest ingest organi organic c matter matter 9etritivores usually increase the activity of microbial decomposers by: 52 Breaing Breaing down down larger larger pieces pieces of organ organic ic matter matter 72 (ncrease (ncrease o"ygen o"ygen conten contentt for respiratio respiration n of decomposers decomposers Pyramid of 'umbers: )epresentation 'umbers: )epresentation of the number of organisms in each trophic level i n an ecosystem -imitations of Pyramid of 'umbers: 52 'umbers: 52 'o accounts is taen of sie

72 'umbers of certain organisms can be so great that they cannot be represented using the same scale as other species Pyramid of Biomass:  Biomass:  representation of the mass of each trophic level in an ecosystem > -. .?* ?* pyramid shaped 1e"cept one case where @ooplanton and Phytoplanton are involved2# Carrying Capacity: !he Capacity: !he ma"imum population that a particular environment can hold

biotic $actors: 52  !  !emperature emperature;; measured using a thermometer (n cold blooded animals: 52 animals: 52 !oo high temperature; enymes denature; growth stops# 72 !oo low temperature; enymes slow down; stop growth (n warm blooded animals: 52 !oo high temperature; more energy spent lowering body temperature to optimum 72 !oo low temperature; more energy spent raising body temperature to optimum (n plants4 when a plant is larger than another plant4 it not only taes away the outcompeted plantAs sunlight4 but also provides it with shade4 therefore eeping the temperature constant; this can be a good and a bad thing# 72 -ight -ight;; energy source for plants4 if it increases4 i ncreases4 then there is increase in rate of photosynthesis and therefore an increase in the population growth# (t is measured using a light meter or meter or light sensor# sensor# 82 .at ater er and and Humid Humidit ity y; if water is scarce4 then less organisms present# Humidity aects transpiration rate of plants and evaporation rate in animals# (t is measured using a hygrometer# hygrometer# <2 .in ind d *pe *peed ed;; (ncreases transpiration rate as it moves away the humidity bubbles at the stomata causing a more desirable diusion gradient for water vapour 2 pH; (nuences enyme activity# (t is measured using a pH meter# meter# D2 +"ygen; (t is an o"idiser which allows cellular cellul ar respiration which is to allow continued release of energy from food# +"ygen also aects photosynthesis# (t is measured using an o"ygen%sensitive electrode## electrode 2 .av ave e ct ctio ion n; (t may erode soil and rocs as well as moving any living organisms# (t is measured using an anemometer F2 Ca Carb rbon on 9i 9io o"i "ide de;; (t can be a limiting factor to photosynthesis# (t is used in forming permanent plant tissues# (t is measured using a gas analysis# analysis# G2 'it itrrog ogen en;; it is used by plants to mae PROTEIN ny abiotic measurement will be repeated several times at a site and then averaged# !he measurements may be repeated over a course of a year4 or day4 etc# *ome plants are more greatly aected by competition than others# $rom the above factors4 the following can be limiting factors of photosynthesis 1basically this is any factor that aects the rate of photosynthesis2: 52 !emperature% usually when this increases respiration and photosynthesis both increase 72 -ight 1believe it or not some plants plants grow better better when light intensity is -+.4 -+.4 they therefore therefore can survive latter stages of succession2 82 +"ygen <2 Carb Carbon on 9io 9io"ide "ide  plant which has a higher rate of photosynthesis will outcompete other plant species# )EMEMBE): Photosynthesis is the main route by which energy enters an ecosystem .ays in which larger plants aect smaller plants: 52 )educe light 72 )educe water 82 )educe mineral ions <2 )educe wind 2 (ncrease humidity D2 )educe temperature (t is best to carry out studies on animals ani mals in their natural habitats as this allows you to see the eect of  biotic and biotic factors# Measurement used in order to &nd rate of photosynthesis: +"ygen produce per unit time +ut of the above4 organisms would compete for light4 water4 carbon dio"ide4 nitrogen#

-REEN'OUSES .hy you should not increase temperature in a greenhouse on a dull day: 52 !emperature increases rate of respiration too4 therefore therefore the rate of photosynthesis photosynthesis will be be too low to replace respiratory losses

72 'ot cost eective How Carbon 9io"ide is enriched in a greenhouse: 52 9ry ice in the environment 72 Combustion 82 Manure Carbon 9io"ide is not enriched above #5I in the greenhouse because: 'ot cost eective as other factors could then limit photosynthesis .hy Carbon 9io"ide in a greenhouse is done in the winter: Cost of enrichment covered by e"tra cash gained from sale of crops as crops sell for more in the winter

.hy yield of crop grown in greenhouse in winter is lower than in summer when enhancing conditions not applied: 52 -ower light intensity limits photosynthesis 72 -ower light duration limits photosynthesis 82 -ower temperature limits photosynthesis How conditions are enhanced: 52 Carbon 9io"ide enhanced by burning oil 72 Heat enhanced by using heater 82 -ight enhanced by light left on for e"tra hours <2 $ertilisers 1contain nitrogen2 enhanced by regularly application $arming Practises which increase the productivity of crops: 52 $ertilisers added to soil 72 Pesticides applied 82 *elective breeding used <2 0enetic modi&cation 2 Ploughing aerates soil and allows nitri&cation D2 Crop rotation increases soil nutrients 2 (rrigation removes the limiting factor of water F2 Covers and netting protects against birds .hy arti&cial fertilisers are applied to crops: 52 (ncreases yields 72 )eplaces ions taen in by crop .hy e"tra arti&cial fertilisers are not applied: (ncreased application of fertiliser does not increase yields; uneconomical4 nown as the Jlaw of diminishing returnsA  high concentration of fertiliser in soil can reduce plant growth: 52 $ertiliser lowers soil water potential 72 9ecreases potential gradient between plant and soil therefore water cannot diuse from soil into plant via osmosis dvantages of (norganicKrti&cial fertilisers than +rganicK'atural fertilisers such as manure: 52 (ons in readily available form 72 Eects relatively rapid 82 Easy to apply 9isadvantages of (norganicKrti&cial fertilisers than +rganicK'atural fertilisers such as manure: 52 Luicly leached 72 More liely to cause pollution 82 )elatively e"pensive <2 Production is energy consuming 2 'atural fertilisers contain a wide range of elements D2 'atural fertilisers aerate the soil How features of a greenhouse control the physical environment: 52 0-**: allows light and heat through limits air movements 72 B-('9*: controls light and heat entering glass 82 /E'!(-!+): 52 llows entry of C+74 72 Prevents e"cess humidity and 82 -imits spread of disease .hy water is needed in soil for plants:  !o allow stomata to open which then allows C+7 absorption

PESTICIDES Parasites: +rganisms that live on or in4 host organisms#

C'EMICAL CONTROL .sometimes c$$ed i"secticide)/ dvantages: 52 (n pests such as weed4 removal of weed actually leads to less competition 72 (f it is very low to"icity4 it will not aect humans 82 cts 3uicly <2 Can be applied to speci&c area 2 ,ills greater variety of pests

9isadvantages: 52 'ot all plants may be sprayed 72 *ome spray may wash of plants 82 Pest may become resistant 1grow immune to pesticide2 <2 Bioaccumulation 2 ,ills bene&cial organisms D2 Enters food chain 2 )esidue is left on crop How a pest becomes resistant: 52  !here is variation in the pest population 72 Mutation occurs 82  !his produces the allele giving resistance <2  !here is a selection pressure for this gene 2  !herefore pests with this gene breed D2  !his leads to an increased fre3uency of surviving allele lthough pest plants are not wanted4 they do increase the diversity of the environment as they attract new species Plants with large surface area to volume ratio are easily aected by pesticides as there is a shorter diusion pathway *?*!EM(C ('*EC!(C(9E: (nsecticides absorbed by plants allowing plant tissues to ill insects feeding on them dvantages of *ystemic (nsecticide: 52 +nly aects an insect that eats plant 1speci&c2 72 (nsecticide is not diluted which reduces the amount needed 82 (nsecticide does not cause eutrophication *ome plants can be made as a pesticide by incorporating the pesticide into genome of plant to allow plant to produce to"in4 this called genetically modifying crops# dvantages of maing 0enetically Modi&ed Crops against pests: 52 More eective than other methods 72 Poisons may harm other 82 Prevent spread of disease <2 Economic bene&t to farmer 9isadvantages of maing 0enetically Modi&ed Crops against pests: 52 Plasmid may enter another species 72 May sterilise other species 82 9isruption of food chain .hy there may be Chemical Pesticides in bodies of other organisms other than the pest: 52 (nsect may eat a hih "um!er of pests which have been aected by the Chemical Pesticide 72 !he insect cannot brea down the chemical4 therefore it remains in the insectAs body .hy resistant pests increase in number:  !hey can survive the chemical; they then reproduce to allow the genes to be passed on 0IOLO-ICAL CONTROL .usi"  predtor to co"tro$ pest or"ism1 sometimes you c" re$ese steri$e m$es o+ the pest)/ dvantages: 52 (f well trained4 it will only attac the pests4 i#e# speci&c 72 +nly one application is re3uired and is therefore cheaper 82 *afer as it does leave chemical residue <2 Pests do not become resistant 2 pplication lined to life cycle of pest D2 Mi"ti"s  low level of pest 2 Can be used in organic farming

9isadvantages: 2)  3ou do "ot comp$ete$y remo%e pest 72 Can only be used for glasshouse crops 82  !here is a cost of researching 4) It my !ecome  pest itse$+  2 May attac non%target species &) It is s$o(er th" chemic$ co"tro$ 2 (t is more sub=ect to environmental factors F2 9iculty in maintaining population of predator G2 Cost of predator (n Biological Control you must: 52 -oo for predator of same origin as pest; predator can survive in similar climate 72 *tudy eect of predator on other organisms in laboratory; may outcompete native species or may attac them 82 )elease large number of predators; increases chance of successful introduction so that damage to crops is little <2 Ensure stable coe"istence of predator and pest at low population densities; no further introduction re3uired (n Biological Control4 the pests cannot be completely wiped out because: 52 Predator may die out 72 Predator may become a pest itself  -ethal Concentration: concentration which ills I Bene&ts of an (ntegrated Pest Management *cheme: 52 (f one method fails4 the other is still partially eective 72 )educed amounts of pesticides needed 82 (ncreases yield <2 -ess chance of resistance 2 -ess eect on food webs D2 Chemical controls initial surges in pest numbers whilst biological gives longer term control of pests How you would now that a pesticide was woring: Pest numbers decrease and )EM(' low

INVESTI-ATION I" $$ these i"%estitio"s* (e (i$$ !e mesuri" the 0IOTIC +ctors s !iotic +ctors re $i%i" or"isms .e can measure the biotic factors in  ways: 52 bundance of population: counting the number of organisms in the sample 72 )ichness of population: number of dierent species found in a sample 82 9iversity of population: *impson 9iversity inde" which taes into account the richness and abundance <2 0rowth of population: comparison of growth with between species 2 Biomass of population: used when studying productivity of an organism bundance of the population: 52 $re3uency: the lielihood of the species occurring in a 3uadrat 72 Percentage Cover: Estimate of the area within a 3uadrat that a species covers How Percentage Cover of an organism of an area may be measured: 52 6se of 3uadrats that are randomly placed 72 6se a large number of 3uadrats so as to reduce sampling error 82 Estimate percentage of area covered by organism 1by counting all the s3uares occupies by the species2 .hy Percentage Cover is better to use than $re3uency: 52 $re3uency is too large 72 Plants are too small *ometimes4 you may even lay 3uadrats every 5 metres rather than use random sampling4 this is because: 52 (t is systematic sampling 72 !o establish a pattern How to place 3uadrats at random: 52 *plit area into s3uares and number them 72 9raw numbers from a hat .hy 3uadrats must be placed at random:

 !o avoid bias4 generally whenever you collect animalsKplants4 whatever method it may be4 randomness is most important How you would decide the number of 3uadrats to use: 52 !ae enough to carry out a statistical test 72 !ae into consideration the amount of time you have to carry out the investigation 82 !ae a large enough number to mae results reliable <2 Ensure unnecessary e"tra 3uadrats are not placed .hat sie the 3uadrat should be: 52 9epends on sie of animal 72 (f a species occurs in a series of groups in an area4 then use a large number of small 3uadrats to give representative data  !wo methods of sampling a population: 52 *ystematic sampling 72 )andom *ampling *?*!EM!(C *MP-('0:

 !ransect: $i"es tht $$o( us to smp$e $o"  ch"i" h!itt 1usually used to measure distribution of a species from one habitat to another2 (nterrupted%Belt !ransect: 6udrts re p$ced t i"ter%$s $o" the $i"e Continuous%Belt !ransect: Luadrats are place along the entire line  Point !ransect:  ?ou record plants touching certain points along the line -ine !ransect:  ?ou record all plants touching the line Point !ransects and -ine !ransects are done without 3uadrats Characteristics of a -ine !ransect: it is 3uic but can be unrepresentative Characteristics of a Belt !ransect: it involves more wor but can generate more complete data  !ransects are usually used in environments such as down a rocy shore4 into a forest or down a mountain side# Purpose of a Chi%*3uared test:  !o compare dierent numbers collected from the two sites and show whether the dierences are signi&cant enough to con&rm or re=ect the null hypothesis )'9+M *MP-('0: 52 9ivide study area into grid of numbered line 72 6sing random numbers4 from a table or generated by computer4 obtain a series of coordinates 82 !ae samples at the intersection of each coordinates of number of individuals and number of species <2 )epeat many times and tae a mean )easons why sample may not represent of whole population: 52 *ampling Bias: investigators may mae unrepresentative choices 72 Chance: Even if sampling bias has been avoided you may still get a bias sample by chance How Mar%)elease%)ecapture can be used to estimate the number of a population that is M+B(-E: 52 Capture sample4 mar and release 72 !he harming must not harm the animal4 1mention method of maring2 82 !ae second sample and count mared organisms 4) Use the LINCOLN INDE7 (hich is .Num!er i" smp$e 2 # Num!er i" smp$e 8) 9 Num!er mr:ed i" smp$e 8  !hings to ensure when using Mar%)elease%)ecapture: 52 nimals are not harmed

72 nimals must not be made less mobile or more visible to predators due to the mar; one way to do this is to mar the animal using an ultra%violet maring pen which can only be seen under ultra%violet light 82 -eave enough time for the mared individuals to redistribute themselves and mi" with the population <2 Ensure it is not breeding season of the animal4 as breeding season increases the population sie 2 !he mar must not be rubbed of or lost during investigation D2 !he population has a de&nite boundary so there is no migration 2 !he proportion of mared to unmared in second sample is the same as the proportion of this in whole population F2 *ampling method is the same /E)? (MP+)!'!: sometimes4 instead of JmaringA the animal4 they tae the animalAs 9'4 this is &ne because &nding the animalAs base se3uence is lie maring the animal4 therefore &nding the same base se3uence again would show that the animal has been recorded before# long with measuring the population sie4 the scientists are also recommended to measure the biotic and abiotic factors# .hy population sie may change during a year: 52 Breeding 72 vailability of food source 82 Predator presence <2 /ariation in disease 2 !emperature variation D2 vailability of water

Precautions and ethical considerations when doing &eld wor: 52 +nly wor in places where ris of falling in water is small 72 +nly wor in places where ris of pollution is small 82 Ensure cuts and broen sin are covered <2 Ensure all participants wash hands afterwards 2 Ensure not to disrupt the food chain of the environment Population sie may vary as a result of: 52 !he eect of biotic factors 72 (nterspeci&c and (ntraspeci&c competition as well as predation (nterspeci&c Competition: competition between members of dierent species 1it taes place when two species have overlapping niches2  !herefore if two species have very dierent niches4 then they will have very little (nterspeci&c competition between themselves# (f species  has a predator called @4 and species B has a predator called ?4 and both species  and B eat from the same plants4 then if sie of predator @ decreases4 the sie of species B will also decrease4 why: 52 (f predator  decreases4 species  will increase 1survive more2 72 !herefore there will be more competition between species  and B for the plant 82 Competition will result in species B sie decreasing Predation can help other species: 52 Predator eats a speci&c species 72 !he other species has less competition and therefore can now increase percentage survival rate (ntraspeci&c Competition: competition between members of the same species (ntraspeci&c competition tends to have a stabilising inuence on population sie because it is density% dependent# lthough predators reduce population sie of prey4 they actually increase mean mass of prey: 52 Predators ill prey therefore reducing prey population sie 72 !herefore less competition between prey population 82 More food available <2 !herefore more food eaten by a single prey than would be eaten before presence of predator 2 !herefore preys may be small in number but each one will be fatter than usual )EMEMBE): species that are better camouaged will survive against predators; this is a form of 9irectional *election

nimals that use snow as a camouage against predators will be aected by global warming as global warming melts snow Population 0rowth: 52 -ag Phase; small number of individuals reproduce slowly 72 )apid 0rowth Phase; increasing number of individuals reproducing 82 *table Phase; population 0)+.!H declines and population sie remains stable <2 Carrying Capacity is established Population 0rowth: 1Births N (mmigration2%1deaths N emigration24 to wor out =ust 0)+.!H )!E4 you need birth rate and death rate4 (f a population stays the same sie4 then B N ( > 9 N E4 if a population is increasing in sie4 B N ( O 9 NE (f a population is decreasing in sie4 B N (  9 N E 1(mmigration increases genetic variability as migrants bring in new alleles4 therefore small populations have small genetic variability as their gene pool is small2 Percentage 0rowth )ate: 1Population change during period " 52 Q Population at start of period Birth )ate: 1'umber of births per year " 52 Q !otal population that year 9eath )ate: 1'umber of deaths per year " 52 Q !otal population that year (ncrease in population sie: 1Birth )ate R 9eath )ate2 " current population4 therefore overall population after increase will be: (ncrease in population N current population verage -ife E"pectancy: age at which I of the population in the sample used are still alive How to wor out average life e"pectancy from a graph of number of survivors against age as a I of ma"imum: 52 9ivide the ma"imum number of survivors by 7 72 0o across this value and see what age it produces on the "%a"is 82 9ivide the produced age by the ma"imum age4 then multiply by 5  womanAs life e"pectancy can be longer than a manAs because: 52 Men have a higher ris of cardiovascular disease 72 Men drin more and smoe more 82 Men are involved in war 9emographic !ransition: Change in the population structure E"amples of demographic transition: (ncrease in average life e"pectancy4 lower death rates4 higher birth rates

nalysing population pyramids: 52 !he wider the base of the pyramid4 the faster the population growth 72 (f the base of the pyramid is narrow4 this indicates a falling population 82 n age pyramid with a wide base that declines 3uicly and has a narrow tip indicates high infant mortality and short life e"pectancy *urvivorship Curves:  !ype ( curve: long life e"pectancy4 low infant mortality  !ype (( curve: intermediate life e"pectancy  !ype ((( curve: short life e"pectancy4 high infant mortality How a sample may be used as a control: *hows results without adding the element being e"perimented $actors which could to decrease in death rate: 52(mproved medical care 72(mproved nutrition and more food 82(mproved sanitation <2-ess disease 2(mproved living conditions D2(mproved economy 2 .ar ends verage -ife E"pectancy may increase: 52 (mproved medical care 72 (mproved nutrition 82 (mproved sanitation

<2 -ower infection rates 2 -ess disease D2 /accination and heath education

ENER-3  How and why the eciency of energy transfer is dierent at dierent stages in the energy transfer through an ecosystem: 52 +ver GI of the sunAs energy is reected into space by clouds and dust 72 'ot all wavelengths of light can be absorbed and used for photosynthesis 82 !he light might not fall on the chlorophyll molecule <2 Eciency of photosynthesis in plants is low R appro"imately 7I ecient 2 *ome of the energy is lost by the consumers through release of heat4 or by restoring heat depending on the environmental temperature D2 *ome of the energy is lost by the consumers through faeces 2 Consumers may not eat all of their foodKprey F2 $ood consumed may not be fully absorbed and digested G2 Eciency of energy transfer to consumers is greater than the eciency of energy transfer to the producers 52 Eciency of energy is lower in older animals 552 Carnivores use more of their food than herbivores Percentage Eciency of energy transfer: 1Energy given out Q Energy provided2 S 5

)EMEMBE): .hen producers that are single celled4 less energy will be lost between producers and primary consumers because: 52 *ingle%celled producers are more digestible4 therefore less energy lost in faeces 72 ll of the single%celled producer will be eaten How energy from the sun may ultimately end up in dead plant matter: 52 Photosynthesis will produce carbon containing substance 72 .hen plants die out4 these substances remain (ntensive )earing of livestoc: 52 $aster rate of growth 72 *laughtered while young so more energy transferred to biomass 82 $ed on concentrated diets so higher proportion of food absorbed from gut i#e# higher proportion of food digested <2 Heating so that no energy wasted maintaining body temperature 1mammals are Endotherms% have high body temp2 2 )educed movement4 therefore less respiratory losses D2 Plentiful food supply 2 High survival rate as no predators F2 *elective breeding However many of these methods re3uire energy input usually in the form of burning fossil fuels# )EMEMBE): nimals can lose energy 1have a high energy e"penditure2 maintaining their body temperature if the environmental temperature is too highKtoo low by increasing respirationKmetabolism 1to increase body temperature if environmental temperature too low2 or allowing heat to escape from the body 1to lower body temperature if environmental temperature too high2#  !his energy they have lost in maintaining temperature could leave them too wea to grow or breed# )esidual $ood (ntae 1)$(2: dierence between the amount of food an animal actually eats and its e"pected food intae Having animals with low )$( is better as it is more cost eective and allows more growth rate with the same amount of food ny animal that eats more than what is re3uired for it to ful&l its daily re3uirements will use the e"tra food for storage or growth# (ndirect energy input: Energy re3uired for producing things re3uired in crop production Energy Eciency: Energy in harvest crop Q total energy input4 energy eciency will be lower in well developed as they have more machines4 therefore higher energy input 0ross Production: !otal 3uantity of energy that the plants in a community convert to organic matter 'et Production 1Plant2: 0ross Production R )espiratory losses

ATP IN

P'OTOS3NT'ESIS

Photosynthesis: DC+7 N DH7+  CDH57+D N D+7; carbon dio"ide reduced 1gains electrons2 to form glucose )espiration: 0lucose N +"ygen  Carbon 9io"ide N water N energy; o"idation taes place4 electrons and energy lost !P: 52 Provides energy in small4 usable amounts for the wide variety of energy%re3uiring reactions 72 (s relatively small molecule that can diuse around the cell 3uicly 82 (t is soluble <2 Mainly found in mitochondria 2 (s e"tremely unstable and is constantly broen down and re%synthesised to and by 9P and Pi 1free organic phosphate2  !herefore it cannot be stored →

→

)easons why !P is a suitable source of energy: 52 Energy released in small amounts 72 *oluble 82 (nvolves a simple reaction <2 Maes energy available rapidly 2 -owers activation energy D2 (t is reformed .hy it is important to synthesise large amounts of !P: 52 !P is unstable 72 !P cannot be stored 82 !P is needed for processes such as active transport4 etc# <2 !P only releases small amounts of energy

 !he reaction for !P is: !P N H7+

 9P N Pi N Energy; this is a hydrolysis reaction

→

.hy organisms need !P: 52 Metabolism such as polysaccharide synthesis from monosaccahrides4 polypeptide synthesis from amino acids and 9' synthesis from nucleotides 72 Movement 82 ctive !ransport; provides the energy to change the shape of carrier proteins in a plasma membrane <2 Maintenance4 )epair and 9ivision 2 *ecretion; !P is needed to form the lysosomes necessary for the secretion of cell products D2 Production of substances such as enymes and hormones 2 Maintenance of body temperature F2 ctivation of molecules  !he -ight 9ependent )eaction: !aes place in Thy$:oids  1membranes within the chloroplast that contain chlorophyll2 -ight energy hits chlorophyll which then e"cites and emits 7 high energy electrons  !hese electrons pass down an electron transport system RELEASIN- ENER-3  that is used by phosphorylation to mae !P from 9P and used to reduce '9P to become '9PH • •

Energy is also used to split water via the process of PH+!+-?*(*4 which produces electrons to replace chlorophyll electrons# Photolysis also produces protons and +"ygen 17H 7+  
→

• • •

 !he -ight (ndependent )eaction: !aes place in the Strom o+ Ch$orop$st (t involves the )E96C!(+' of Carbon 9io"ide using !P and '9PH 9+E* depend on temperature as enymes involved4 therefore if temperature is too high4 enymes denature4 ending photosynthesis -ight (ndependent )eaction: *tages of Calvin Cycle: 52 C+7 combines with %carbon )uBP 1)ibulose Bisphosphate2 with the enyme )ubisco as a catalyst4 +"ygen acts a competitive inhibitor with C+ 7 for the active site of )ubisco 72 !his produces 7 M+-EC6-E* of 8 carbon compound 0P 10lycerate 8%Phosphate2 82 !P 1provides energy2 and '9PH used to reduce 0P into 8 carbon compound !P 1!riose Phosphate2 R this process will "ot (or:  in the dar4 this is because !P and '9PH cannot be made without light <2 *ome of the !P is used to mae carbohydrates lie 0-6C+*E4 !ut MOST o+ it is used to m:e more Ru0P +or the "e#t cyc$e  !herefore4 if the light dependent reaction ids stopped4 the Calvin Cycle will stop4 therefore less )uBP will be formed and thus there will be less C+ 7 uptae#  !he -ight (ndependent )eaction depends on the !P and '9PH made in the -ight 9ependent )eaction .hy more C+7 means higher rate of photosynthesis: 52 More C+7 to convert )uBP to 0P 72 !herefore more 0P available to use with !P and '9PH .hen plants are submerged in water the rate of photosynthesis would decrease because:  !he water would absorb light4 therefore less light absorbed by plants4 leading to a decreased rate of photosynthesis# How the concentration of C+7 would uctuate over 7< hours above ground level: 52 Higher C+7 concentration at night as photosynthesis in plants which removes C+ 7 only taes place in the light 72 )espiration taes place throughout the 7< hours4 therefore high C+7 at night 82 However4 even in the dar plants 9+ tae up C+74 but it is =ust signi&cantly less than the amount they tae up during the day <2 (n light4 the rate of photosynthesis will be higher than the rate of respiration 2 !he higher you go above ground level4 the lower the concentration of C+7 this is because the higher you go above ground level4 the more leaves there will be4 which will be carrying out photosynthesis which removes C+ 7 .hy it is important for plants to produce !P during respiration as well as photosynthesis: 52 (n the dar4 there is not !P production with photosynthesis4 therefore we need respiration as !P cannot be stored 72 *ome tissues are unable to photosynthesise 82 Plants use more !P than produce in photosynthesis <2 !P is needed for active transport • •

RESPIRATION erobic )espiration is 52 0lycolysis

• •

• • •

< processes:

one molecule of glucose o"idised to produce 7 molecules of Pyruvate 18 carbon ion2  !he reaction ?(E-9* two molecules of !P and two molecules of '9H T:es p$ce i" the C3TOPLASM o+ ce$$ s $ucose is too $re to e"ter the mitocho"dri  !he process does '+! re3uire +"ygen 0lycolysis is an o"idation reaction as it involves the removal of Hydrogen to form Pyruvate !P is necessary for 0lycolysis as it activates the glucose to become

phosphorylated glucose 72 -in )eaction lso called Pyruvate +"idation Pyruvate used to produce cetate and Carbon 9io"ide4 the cetate is piced up by co%enyme  forming cetyl Co%enyme  'o !P is produced in the -in )eaction but 7 '9H molecules are formed as well as C+ 7 and cetyl Co%enyme  T:es p$ce i" the Mtri# o+ MITOC'ONDRIA • •

•

82 ,rebs Cycle

•

• •

•

Electrons stripped from the cetate4 creating large amounts of electron carriers in the form of '9H and $9H 7 T:es p$ce i" the Mtri# o+ MITOC'ONDRIA Each cycle produces 5 !P4 8 '9H4 5 $9H 7 and 7 C+7  !he cycle turns !.(CE per molecule of glucose4 therefore it produces 7 !P4 D '9H4 7 $9H 7 and < C+7  !he ,rebs Cycle is a series of +"idation and )eduction reactions

<2 !he Electron !ransport Chain

• • • •

•

• •

•

•

 !aes place on the Cristae 1large surface area2 in the M(!+CH+'9)( Electrons released from '9H and $9H7 Electrons pass from one protein to another in o"idationKreduction reactions  !he energy from these reaction used to pump HN ions from the matri" into outer%membrane using ctive !ransport This cretes  di;usio" rdie"t o+ ' < io"s .c$$ed T'E PROTON -RADIENT)4 which diuse bac into the matri" through the centre of the !Pase enyme4 as they do4 the !Pase enyme synthesises a molecule of !P from 9P and Pi using some of the energy from the o"idationKreduction reactions By%products are low energy electrons and protons which combine with +"ygen to form .ater .e are breathing now due to Electron !ransport Chain4 we need to provide +"ygen to convert the electrons into water as +S?0E' (* !HE $('- E-EC!)+' CCEP!+) )ole of +"ygen in erobic )espiration: (t is the &nal acceptor for an electron and hydrogen to form water (mportance of the Proton 0)9(E'!:

.ithout it4 H N would not be able to move into the membrane4 therefore no !P produced4 the energy being made from the o"idationKreduction reactions would then be released as heat instead of being used to turn 9P and Pi into !P  !he mitochondria in musc$e ce$$s  contain many Cristae because: 52 Provides large surface area for the Electron !ransport Chain 72 !his allows for more !P to be made which is needed for muscle contraction

9ierence between how !P is produced in Electron !ransport Chain and Photosynthesis: 52 (n Electron !ransport Chain4 the energy comes from a chemical reaction whereas in Photosynthesis it comes from light 72 (n Electron !ransport Chain4 it is made in the dar as well as light whereas in Photosynthesis it is only made in the light (mportance of inner membrane 1middle membrane2 of mitochondria in the production of !P: 52 llows electrons to be transferred down electron transport chain by carrying out o"idationKreduction reactions with proteins 72 Provides energy to tae HN into space between the matri" and outer%membrane 82 llows HN bac into matri" through !Pase <2 Provides energy gained from the o"idationKreduction reactions to combine 9P and Pi to mae !P (n )espiration4 you will get '9 and '9H4 in Photosynthesis; you will get '9P and '9PH O%er$$ ech $ucose mo$ecu$e produces => mo$ecu$es o+ ATP +nly -in )eaction and ,rebs Cycle produce C+ 7  body cell will now it needs to respire more if the levels of 9P in it are very high as this shows that less !P is present  manometer which measures volume may be used to in an e"periment to measure respiration# *ubstances which would have a net movement into the M(!+CH+'9)(: 52 Pyruvate 72 9P 82 Phosphate 1Pi2 <2 +"ygen 2 '9H *ubstances which would have a net movement out of the M(!+CH+'9)(: 52 C+7 72 .ater 82 !P <2 '9 .hy !P is better than glucose for cell metabolism: 52 Energy available more rapidly 72 Energy released in small 3uantities dvantages of !P as an energy%storage molecule and why it is useful in many biological processes: 52 Cannot pass out of cell 72 Easily broen down as it taes place in one step: !P  9P N Pi4 this is why !P is called an Jimmediate source of energyA 82 )eleases energy in small amounts <2 -owers activation energy 2 (t is reformed OVERALL* 'O? ATP IS MADE IN T'E MITOC'ONDRIA .TRIC@ 6UESTION/ DONT MENTION -L3COL3SIS)/ 52 !P produced in rebs cycle 72 ,rebs cycle produces $9H and '9H 82 Electrons released from $9H and '9H <2 Electrons pass along proteins of the electron transport chain in a series of o"idationKreduction reactions 2 Energy is released which is used to allow HN 1protons2 to enter D2 s HN leave through !Pase4 energy is used to combine 9P with Pi to mae !P -.?* )EMEMBE): ll respiration reactions depend on temperature as they involve enymes4 therefore if temperatures are low4 respiration rates will be low as the enymes will have less inetic energy →

MEASURIN- AERO0IC RESPIRATION  !his e"periment is carried out by measuring +"ygen consumption P)+CE**:

52 +rganism respires4 it taes in +7 and gives out C+ 7 72 'ormally this will not change volume of gas in apparatus as C+7 made would replace +7 lost 82 But when we add *odium Hydro"ide4 *odium Hydro"ide absorbs C+7 1so itAs as though the organism is not maing C+ 72 <2 !herefore volume of air in apparatus decreases as the organism uses +7 2 !his change in volume causes a change in pressure which causes the coloured li3uid to move along the tube allowing the )!E +$ +S?0E' 6*E9 PE) 6'(! !(ME to be measured D2 6nits of rate of aerobic respiration: mm8+7g%5h%5

Measurements taen in this e"periment: 52 9istance the coloured li3uid moves and time 72 Mass of organism 82 9iameter of tube naerobic )espiration: it is simply 0lycolysis that does not go any further4 therefore net yield of !P is 7 molecules  !aes place when o"ygen is limited4 most organisms start with erobic )espiration4 then +"ygen runs out 1or cannot be taen in2 so they use naerobic )espiration Produces less !P 1724 therefore a lot less ecient4 therefore a lot more C+7 produced 1in plants and fungi2 as more anaerobic respiration must tae place to produce same amounts of !P as erobic )espiration  !aes place in the cytoplasm 1this means it does "ot tae place in an organelle lie Photosynthesis and erobic )espiration2 +nly taes a short time to complete nimals and bacteria convert Pyruvate into -actate Plants and fungi convert Pyruvate into Carbon 9io"ide and Ethanol4 therefore -actate and Ethanol production ('C)E*E* as +"ygen levels 9EC)E*E but eventually stop when glucose is used up completely# The co"%ersio" o+ Pyru%te to Eth"o$1Lctte is ssisted !y NAD' reduci" .!y pro%idi" '<) Pyru%te to Eth"o$1Lctte "d NAD < •

•

•

•

 !he conversion of Pyruvate to -actateKEthanol by giving Pyruvate a hydrogen from '9H is essential as it re%synthesises '9N from '9H4 therefore allowing '9N to accept a Hydrogen and allowing 0lycolysis to continue B+!H aerobic respiration and anaerobic respiration are aected by temperature as they B+!H involve enymes# .hy erobic )espiration yields more !P than naerobic )espiration: 52 +"ygen is the &nal electron acceptor and o"ygen is not present in anaerobic respiration 72 Electron !ransport Chain produces most !P which is not present in anaerobic respiration  !here is no +"ygen uptae in anaerobic respiration; therefore +"ygen levels remain constant whilst an organism respires anaerobically# BLOODIN- can also cause anaerobic conditions as water prevents +"ygen from being used# naerobic respiration has to start with glucose4 if it is not glucose4 then you will have to apply enymes to brea the substance down into glucose# *o overall4 there are only 8 reactions which P)+96CE !P: 52 -ight 9ependent )eaction in Photosynthesis4 1however the !P made in Photosynthesis is used up in the -ight (ndependent )eaction2 72 0lycolysis in )espiration 82 Electron !ransport Chain in )espiration 1H('!: !he !P JmadeA in ,rebs Cycle is the same !P originally made in 0lycolysis2 •

C3CLES Cr!o" Cyc$e/  (nvolved C+7 from atmosphere or HC+8% in water % being &"ed into organic molecules by photosynthesis and then released bac into the atmosphere by respiration and other systems# .hy global warming is taing place: Methane *ource: $ermentation of waste4 'atural gas4 B$tu$e"t co(s 4 Coal mining4 *torage of manure on farms4 naerobic soil  !hese are all anthropogenic sources 1caused by humans2; however DI of methane comes naturally# How producing and using biofuels results in a negative percentage change in C+ 7 production: 52 C+7 taen up in photosynthesis 72 More taen up than produced when using biofuels

Carbon *ource: Ecosystem that releases more carbon dio"ide than it accumulates in biomass over the long term4 e#g# deforestation Carbon 'eutral: Ecosystem is one where carbon &"ation and carbon release are balanced over the long term Carbon *in: Ecosystem is one that accumulates more carbon in biomass than it releases as carbon dio"ide over the long term Nitroe" Cyc$e/

52 Plants absorb 'itrate 1'+8%2 using active transport which )EL6()E* !P: *ome of the 'itrate is lost to the atmosphere as 'itrogen through denitrifying bacteria which are anaerobes and therefore thrive waterlogged soil4 *ome of the 'itrate has been gained from 'itrogen in the atmosphere using 'itrogen% &"ing bacteria which breas the triple bond in 'itrogen to convert it to MM+'( usi" the e"yme Nitroe"se s  ct$yst 4 1to do this nitrogen%&"ing bacteria use !P and organic compounds gained from soil2 lightning can also convert 'itrogen to MM+'(4 ammonia helps in amino acid production4 otherwise ammonia is gained through decay of organic material •

•

72 Plants combine 'itrate with carbohydrates to mae PROTEINS 82 Plants are eaten and 'itrogen is passed along food chain <2 .hen the 'itrogen%rich matter dies4 it is broen down by saprobionts using diusion41 as saprobionts respire aerobically4 they release C+7 which can also be used by the plant24 and converted to mmonium ions1'H
2 !his could lead to an increased nitrate in drining water which could cause human illness 'itrate concentrations in rivers and laes can be reduced by increase rainfall as it dilutes nitrate which in turn stops eutrophication# Eutrophication will be faster in warmer weathers as more heat means that bacteria will have higher inetic energy (n essence4 there are two ways in which nitrate can be lost from the soil: 52 -eeching 1eutrophication2 72 9enitri&cation

DEBORESTATION  CONSERVATION 9eforestation: 52 Creates C+7 as trees absorb C+ 7 which is released when burnt 72 Reduces di%ersity due to loss of habitats4 niches4 ecosystems4 food4 soil erosion and by changing the climate 82 Causes soil erosion as there are no trees to protect soil from rain <2 Causes changed rainfall patterns and droughts as there is less transpiration from leaves How deforestation increases C+7 concentration: 52 -ess trees means less photosynthesis 72 -ess photosynthesis means less C+ 7 absorbed from the atmosphere 82 Burning of the trees involves combustion which produces C+7 -ogging: )emoval of mature trees from a forest *ustainable -ogging: -ogging sectors of a forest in a se3uence4 ensures there is always tree to be cut# (t is the opposite of Jclear cuttingA dvantages of *ustainable -ogging: 52 )ecolonisation possible from ad=acent areas 72 !here is sucient time for recovery )easons for conservation of the forest ecosystem: 52 !rees available as a sustainable resource 72 Maintain habitats 82 Maintain diversity and protect endangered species <2 Maintain stability of ecosystem 2 Maintain food chains D2 )educed loss of soil 2 )educed ood F2 )educe greenhouse eect and therefore global warming G2 !he forest ecosystem is also a source for medicines Coppicing: Cutting down some trees in a wood to leave stumps4 new shoots grow from the stumps

SUCCESSION *uccession: Change in a community over time due to change in environment *uccession is of two types: 52 Primary *uccession: starts with bare roc usually after a volcanic eruption 72 *econdary *uccession: starts with soil usually after a forest clearing How *uccession occurs: 52 Colonisation by pioneer species 72 s pioneer species increase in number4 they die and are broen down by saprobionts which increase humus content 82 Change in environment as there is an increase in organic matter and nutrients4 the humus helps maintain moisture <2 !his enables other species to colonise 2 !his causes a change in biodiversity D2 !he environment becomes less hostile 2 'ew species better competitors and eventually one species outcompetes other species F2 !his species is called the clima" community .hat the pioneer species does: Change environment via nutrients to mae it less hostile .hy pioneer plants having seeds that grow in uctuating temperatures is an advantage: 52 t the start of succession4 there is only bare soil 72 !emperature in bare soil always uctuates

 !he environment before succession is e"tremely hostile; therefore very few species are able to tolerate the conditions# Clima" Community: *table community after which no more succession taes place  !rees that are usually the tallest and buliest will be the best as they will bloc light4 needed by other plants for photosynthesis4 therefore the clima" community usually reduces plant diversity as those plants survive which can photosynthesise with less light .hy species change during succession: 52 Pioneer species add humus to the soil maing the environment less hostile 72 !his allows a new species to develop which is a better competitor .hy nitrate in the soil increases during succession: 52 (ncrease in dead organisms 72 -eading to an increase in nitri&cation 82 lso nitrogen%&"ation could also be taing place maing ammonia4 which then turns into nitrate +n bare roc4 the pioneer species will usually be moss caused by the soil particles of a roc gathering in cracs as the roc weathers# Ecosystems develop by the process of colonisation and succession until the clima" community is reached# 0raing stops succession at the grassland stage# *ometimes4 the plantKforest is burnt4 and succession begins on the burnt land4 this is bene&cial because: 52 ?ounger plants have more shoots4 therefore provide more food 72 ?ounger plants provide more cover 82 6nproductive plants are removed .hy diversity of animals increases: 52 0reater variety of food 72 Higher variety of habitats 82 More detritus (n sand%dune ecosystem4 minerals enter the ecosystem by: 52 *hells 72 $looding by seawater 82 .eathering of underlying roc <2 'itrogen &"ation 2 E"cretory products (n a sand dune system4 the clima" community will be the furthest away from the sea and the pioneer species will be widespread# C+'*E)/!(+' +$ HB(!!* $)EL6E'!-? ('/+-/E* M'0EME'! +$ *6CCE**(+'#

IN'ERITANCE 0enotype: 0enetic constitution of an organismKcombination of alleles he individual posses4 E"ample of 0enotype: ((+ Phenotype: E"pression of the genotype and its interaction with the environment E"ample for Phenotype: if there is a genotype ((+ in which  is dominant4 then the phenotype is:  0ene:  length of 9' that codes for a particular protein 0ene Pool: ll the alleles in a population Chromosome: +ne long 9' molecules which contains genes -ocus: !he position of a gene on a chromosome llele: lternative version of a gene4 1there may be multiple alleles of a single gene2 9ominant llele: !he allele always e"pressed in the phenotype )ecessive llele: !he allele that is only e"pressed in the phenotype in the absence of the dominant allele Homoygous: .hen both the alleles are the same: BB or bb Heteroygous: .hen both alleles are dierent: Bb .hen seeing the possible genotype the children of two individuals may have4 we   draw a genetic cross4 separating the alleles of the parents: E#g# if the parents had    genotype: a and 4 then we do the following: a a a  !herefore there is a I chance the child has a and I chance the child has # Co%dominance: .hen both alleles are being e"pressed in the phenotype E"ample of Co%dominance: if the genotype is ( (B in which  and B are co%dominant4 then the phenotype will be: B Monohybrid (nheritance: (nheritance of a single gene with two alleles .hy Monohybrid Cross ratios may not tae place in reality: 52 fusion of gametes is random

72 Mating is related to chance 82 9ierential mortality Co%9ominance: when alleles are co%dominant4 so if they are present they are both e"pressed in the phenotype4 taes place usually when a gene has more than 7 alleles *e" -inage: concerns genes found on the se" chromosomes4 S and ?4 1S gene will contain the disease2 Males have only one S chromosome 1S?2 therefore can never be carriers# $emales have two S chromosomes 1SS2 therefore can be carriers# !he gametes will be each chromosome4 i#e# men have genotype S?4 separating them gives you two gametes4 S and ?# *e" -ined diseases that ill children will become e"tinct as children who are aected will not be able to pass on the disease# /E)? rarely there may be a gene that is e"istent on the ? chromosome4 however this would mean that all males would be aected and no females# Males are more liely to have a se"%lined disease that is recessive: 52 Males have only one alleles4 therefore it could be the recessive one 72 $emales need two recessive alleles to have the disease (n 3uestion where they as you to prove why a certain condition is recessiveKdominant4 =ust write E/E)?+'EA* genotypes and try to &gure out an answer# How to prove that a certain condition is on the recessive allele: 52 ected child produced from unaected parents 72 !herefore parents are heteroygous How to prove that a certain condition is on the dominant allele: 52 ected parents produce unaected child 72 !herefore parent are heteroygous 1and still aected4 therefore allele causing condition is dominant2 (f a certain condition was recessive4 but scientists wanted to JmaeA a person with the condition4 then this would be dicult because: 52 !he parents would have to heteroygous: Bb and Bb would mae bb 72 !here is no way of nowing which parents are heteroygous 1i#e# no way of dierentiating between Bb and BB2 How to prove a condition is not se"%lined: 52 !he condition is on the dominant allele 52 ected male 1S) ?2 and unaected female 1SrSr2 are producing an aected Sr Sr male 1S) ?2 which is not possible4 loo at diagram: S S) S) ) Sr Sr r r  ? S ? S ? How to prove a condition in on the "%chromosome: ected male children from unaected father *erious diseases caused by dominant alleles are uncommon compared with serious diseases caused by recessive alleles: 52 (f it is on the dominant allele4 then all individuals with allele of the disease develop the disease4 i#e# they become aware of the disease and therefore decided not to have children 72 (f the serious disease is on recessive allele4 it may not aect individual4 therefore individual will not be aware of the disease and may have children *ome diseases are fatal4 yet they are passed on4 this may be due to the fact that the disease taes eect in old age4 by which time ospring have already been produced#

(f a recessive allele is causing a hindrance to a speciesA ability to compete4 then the fre3uency of the recessive allele will decrease over time4 because: 52 9ue to directional selection 72 !he dominant allele has an advantage over the recessive allele4 therefore more liely to survive# 9ominant llele fre3uency N )ecessive llele fre3uency > 5; p N 3 > 5 1this is as long as the two alleles are for the same gene2 Homoygous )ecessive fre3uency N Heteroygous fre3uency N Homoygous 9ominant fre3uency > 5; p7 N 7p3 N 37 > 5 Hardy%.einberg principle: !he fre3uency of alleles will remain co"st"t  from one generation to the ne"t providing no mutation4 geographical isolation4 selection4 migration etc# taes place# 1!he Hardy%.einberg Principle is actually more of a P)E9(C!(+' than a principle2

.e cannot do an investigation on the fre3uency of certain alleles in a group of organisms if one of the organisms is deaf4 blind4 etc# !his is because this organism will not survive and therefore will not pass on allele ssumptions made when using the Hardy%.einberg e3uation: 52 'o selection 72 )andom mating 82 -arge gene pool <2 'o migration 2 'o mutation D2 E3ually fertile genotypes 2 0enerations do not overlap .hen studying genetic crosses4 you use an animal which: 52 0ives large number of ospring; low sampling error 72 *hort life cycle; results obtained 3uicly 82 Male and female easily distinguished for mating <2 *mall sie; easy to handle and less space re3uired How there is genetic variation in a se"ually reproducing animal: 52 (ndependent alignment of chromosomes which gives a new arrangement of alleles 72 )andom fertilisation which gives a chance combinations of gametes 82 Mutations create new alleles

SELECTION PRESSURE 'atural *election: process in which those organisms whose alleles give them a selective advantage are more liely to survive4 reproduce and pass on their alleles to the ne"t generation 1(ntraspeci&c competition is important for it2

*tabilising *election: +e( or"isms sur%i%e t e#tremes which means that is selects for the mean which remains unchanged4 it occurs in non%changing environment and i s repeated over many generations E"ample: /ery big animal is too slow but very small animal is too wea4 therefore middle pathway is best 9irectional *election: Or"isms (ith  prticu$r e#treme o+ phe"otype h%e  se$ecti%e d%"te E"ample: Bacteria which gain resistance 9isruptive *election: Se$ectio" i"st midd$e 4 selection for one e"treme E"ample: Bird species called J&nchesA4 smaller beas helped catching insect4 larger beas helped opening seed4 middle sied beas were useless nimals that are large have a small surface area to volume ratio4 therefore they lose less heat# I" the e#m* you (i$$ o"$y et uestio"s rerdi" directio"$ "d st!i$isi" se$ectio"

SPECIATION Process of *peciation: 52 (solation between two populations 1if the isolation has been due to separation of lands4 then write 0E+0)PH(C- (*+-!(+' between two populations2 72 'o gene ow i#e# interbreeding between populations 82 /ariation <2  !here are dierent environmental factors which allow a certain characteristic to survive 2 Mutation D2 *ome organisms have allele to adapt and therefore survive 4 for e"ample mutation allele may produce camouage 2 daptive organisms survive and reproduce F2  !here is an increase in the fre3uency of the surviving allele G2 0ene pool diers from original species4 therefore no interbreeding can occur 52  !his occurs over a long period of time )eproductive (solation: +rganisms cannot breed with another group .hen a species is isolated: 52 -ess competition 72 -ess predators *peciation is a lot less fre3uent these days: 52 *imilar biotic and biotic pressures 72 *imilar selection pressures 82 'o isolation )EMEMBE): !he larger a species4 the smaller the surface area to volume ratio4 therefore less heat is lost by these species#

I" -rph A"$ysis "d Dru Tri$s/ 52 .hen describing a graph4 mention pea points4 increase and decrease in graph and overall increaseKdecrease in graph 72 *ometimes the evidence from the graph may not be enough to draw a certain conclusion# .H?: ny correlation does not mean there is a causal relationship  !here may some other factor producing a riseKfall in both factors *ometimes4 there is no relation between both factors further along the graph lso if a control group was not used4 then eectiveness cannot be measured $luctuations in a graph are a clear sign that conclusions cannot be drawn from it (n graphs4 where conclusions are being drawn regarding a disease4 chec if it says Jreported casesA4 if it does you can mention about how we donAt now the full amount of disease cases as many were not reported and !HE)E$+)E we canAt draw conclusions# 82 +b=ective of a control: show eect of the thing you are investigating without the thing you are investigating it with <2 9ependent /ariable 1the variable that we measure2 must only be aected by the (ndependent /ariable 1the variable we change2 2 *ometimes4 data is given in a logarithmic form; this e"aggerates the numbers and allows the eect of low numbers to be seen4 therefore it increases the range of values# *ometimes4 data is given in a ratio; this allows comparison as it shows proportional change# D2 (n some graphs4 medical cases are presented for the prevalence of a certain disease; however4 the number presented may not be the actual number of people with that disease as many people do not go the doctors# 2 .hen an investigation involves metabolism4 scientists may e"periment on people of dierent ages as metabolism rate diers on age# F2 .hen it ass you to describe a graph4 be sure to mention a pea point if there is one4 if not4 describe the correlation4 i#e# whether it is negative or positive# G2 *ometimes data on a graph is given in a percentage4 the advantage of this is: 52 llows comparison 72 *hows proportional Change as sometimes the initial weightKsieKvolume etc# of substances is dierent# 52 E"periments are repeated for the following reasons: 52 llows anomalies to be identi&ed 72 Maes the average more reliable 82 llows more concordant results <2 llows the mean to be calculated 2 !o mae the line of best &t and intercept on a graph more precise 552 9ierence between accuracy and reliability: 52 ccurate: without error 72 )eliable: that &gure can be reproduced when measurement repeated 572 .hy it is important to chec the repeatability of measurements: 52 (ncreases reliability of measurements 72 (f measurements are repeatable4 then anomalies are unliely 582 (f you wanted to see if two results are similar: Plot scatter diagram of one set of results against the other and you should see a positive correlation 5<2 ny 3uestions in which data is regarding cancer4 it would be important to remember that cancer taes many years to develop; therefore this restricts conclusions drawn regarding it# 52 .hen ased to give an evaluation on a claim or statement4 mention all the points that indicate the claim or statement to be true4 and then mention how it could be false# 5D2 .hy it is best to have a large sample: reduces sampling error 52 dvantages of collecting large number of results: 52 llows anomalies to be identi&ed 72 llows use of statistical test 5F2 (f it ass you why a drug may not be perfect: 6nnown -ong%!erm side eects *tudy should be carried out on humans and the study should be repeated 5G2 Before carrying drug trials4 scientists should consider the following regarding the drug: 9ose to be given 'o serious side eects How eective • • • • • •

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.hen taing drug trial4 scientists should consider the following of volunteers: ge Health 0ender Ethnicity 0enetic $actors -ifestyle Body Mass 752 .hen scientists wish to use an animal in a test4 before deciding the number of animals to use they must consider: Ethical Consideration  !ae a large number to improve reliability Consider cost and space available 772 .hen e"periment involves volunteers4 they must be healthy as they will have JnormallyA functioning bodies# lso when dividing volunteers into groups4 it should be done randomly to avoid bias# 782 (f scientists use two drugsKvaccines and both combined have higher eect4 then both must be similar i#e# they must have the same antibodies4 etc# 7<2 How mean can be found from a graph: 9raw line of best &t  !hen &nd the gradient and divide it by the distance moved 72 ny e"periment wherein the words JwaterA and mention of the word Jpartially permeableA come together4 you should automatically realise that water potential will be involved somehow# 7D2 *ometimes4 in an e"periment4 they e"periment on people of all the same age: this is so that a comparison can be made# 72 .hen in an e"periment4 people are assigned to dierent groups )'9+M-?; it means everyone has an e3ual chance of being assigned to either group# !hey do this by using a random number generator# 7F2 lso remember your basics such as when you evaporate water from a substance4 it becomes more concentrated# 7G2 .hen scientists measure something per unit of another thing it is so as to a comparison between the two dierent things# 82 (f scientists wish to now the most common volume or concentration of a substance4 they tae a large random sample# 852 (n a medical study4 the information is useful to scientists because (t allows scientists to: 9etermine the most eective dose 9etermine the most length of treatment (nvestigate long%term eect $ind most cost%eective treatment 872 9ouble Blind trials are trials wherein neither the volunteers nor the doctors now which treatment a particular volunteer is receiving4 this improves reliability because: Prevents bias Prevents positiveKnegative psychological eects 882 .hen in a graph4 the points are =oined with straight lines rather than curves4 it is because: the intermediate values between points are unnown 8<2 .hen something is normally distributed4 it means median > mode4 this is nown as continuous variation and has a Jbell%shapedA graph 82 (n genetic research4 scientists need to ensure that the environment is the same 8D2 .hen it says the ratio of " to y was 4 it means  > " Q y 82 (n *pearmanAs )an Correlation test4 positive values mean positive correlation between " and y and negative values mean negative correlation between " and y 8F2 Even if an investigation was failure4 it is important for scientists to report their results because: 52 *aves money and time for others 72 Ensures same wor is not repeated • • • • • • •

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(' M+*! ('/E*!(0!(+'* ('/+-/('0 9!4 *C(E'!(*!* .(-- -*+ .+), +6! !HE *!'9)9 E))+) +$ !HE ME' .hen woring out percentage increase: 1big number%small number Q small number2 " 5 .hen woring out percentage decrease: 1small number%big number Q big number2 " 5 .hen woring out volume of a chemical after dilution: (nitial volume " concentration of chemical > volume of chemical that is in that initial volume4 the rest is basically water# Be wary of 3uestions in which the investigator recorded results of an investigation every couple of seconds4 then he displayed the investigation on a graph and the graph increases and then levels o# (f you thin about it4 after the graph has levelled o4 if the investigator recorded results4 he would begin to observe same results4 and therefore ero changes# E"aminers could as what did he observe when the graph levelled oT !he answer is nothing4 ero# *!'9)9 9E/(!(+': 9egree of variation from the mean#  !he smaller the *tandard 9eviation is the better# .hen *tandard 9eviations overlap4 conclusions cannot be made as e ectively as results may be due to CH'CE4 if standard deviations do not overlap4 we say the dierence is )E-# .hy at times *tandard 9eviation is better than the mean: 52 )ange only shows highest and lowest values 72 lso it is possible to have two very dierent data sets with the same range 82 lso range is aected by a single outlier <2 *tandard 9eviation shows spread about the mean and allows statistical use .hy a statistical test is necessary for analysis: 52  statistical test determines the probability of results being due to chance 72 !his enables us to re=ect or accept the null hypothesis Purpose of a Chi%*3uared !est: to compare dierent numbers collected from two sites and show whether dierences are signi&cant (f it says: e"plain the meaning of p  # using the words probability and chance4 you will write:  !here is a probability of less than I that the results are due to chance