Biology AS


Biological Molecules- Carbohydrates 1.1

Monosaccharides- A single sugar monomer e.g Glucose, Fructose, Galactose

  • Triose Sugars- 3 Carbons --> C5H6O3
  • Pentose Sugars- 5 Carbons --> C5H10O5
  • Hexose Sugars- 6 Carbons--> C6H12O6

Disaccharides- Sugar made up of 2 monosacaride units joined by a glycosidic bond, formed in a condensation reaction e.g

  • Sucrose,- stored in plants - made from A Glucose + Fructose
  • Lactose, - in milk  -  made from AGlucose + B Glucose
  • Maltose- found in germinating seeds e.g barley -  made from A Glucose + A Glucose
  • ALL D are made through a Condensation Reaction between the 2 molecules creating a Glycosidic Bond.

Condensation Reaction- Molecule of H20 is removed from the reacting molecules and a bond is formed between them

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Carbohydrates 1.1

Polysaccharides- Polymer made up of long chains of monosaccharide units joined ny glycosidic bonds (molecules containing 11 or more monosaccharides) e.g Glycogen, Starch formed from amylopectin, amylose

  • Amylose- Unbranched polymer of G, lengthens= spirals = compact (releases G slowly, keep going for longer) 1-,4- GB
  • Amylopectin- Branched polymer of G. Branches mean G broken off rapidly when energy needed (release g rapidly for cellular R) 1,4 + 1,6 GB
  • Compact= storage
  • Glycosidic bond = easily broken = rapid release of monosaccharide units for cellular respiration
  • NOT soluble in H20 = little effect on H20 potential within a cell = no osmotic H20 movements
  • G.B broken by Hydrolosis Reaction <--  Bonds broken by the addition of H20 (occurs in digestion in gut, muscle nd liver)

Glycogen- Made of A/G 1,4 + 1,6  GB = more side branches = broken down very rapidly. Good for muscle for C/R

Cellulose- Insouble made of  B G 1,4 GB Hydtroxyl groups stick out both sides - H bonds join between Delta H of -OH groups = cross linking = chains firm = strength = good as in cell wall nd need strength/support

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Lipids 1.2

(Only contain C/O/H)

Lipid- Organic molecule, important in cell membranes and energy store in organisms

Saturated fatty acid- C atom joined to another C atom in HC chain by a CB bond

Unsaturated fatty acid- C atoms in HC chain have1 or more double CB bonds in them


  • Waterproofing- Hydrophobic nature. Oil WP fur/feathers plants use wax.
  • Insulation- 1. Fatty sheah insulates nerves so electrical impulses travel faster. 2. Insulate animals through heat loss e.g whale blubber

Ester Bond- Formed in a condensation reaction between Carboxyl Group of  a Fatty Acid and 1 Hydroxyl Groups of Glycerol (This type of C/R is called Esterification)

Triglyceride- ester bond is formed in condensation reaction (3 h20) 

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Proteins 1.3

Peptide Bond- Formed by condensation reactions between amino acids

Formation of protein

  • Condensation reaction between 2 amino acids = peptide bond
  • Dipeptide is now the result
  • More amino acids join = polypeptide chains
  • Polypeptide folds or coils OR associates with another P/C = Protein
  • Hydrogen Bonds- In -COOH the o = delta - and H atoms are delta + in AA when the groups close = charges attract = H bond
  • Disulfide Bond- when 2 Cysteine molecules close in polypeptide. Oxidation reaction occurs in 2 sulfur containing groups = strong C/B bond = D/B (Stronger than H bonds hold folded PPC in place)
  • Ionic Bonds- Between the strong + and - amino a chains withn protein molecules

E.G- Hair = Keratin. Styling hair change bonds within the protein. Heat = break H bond and reform with hair curling in different way temp until H refom to orignal. Perming = break disulfide bonds reform = different = effect permenant. Stay until cut

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Proteins 1.3

  • Primary Stucture- Sequence of amino acids that make up polypeptide chaain held by peptide bonds
  • Secondary- the repeating pattern in the structure of the peptide chains such as A helix or B pleated sheets
  • e.g Fibrous Proteins( COLLAGEN) - Insoluble in H2O = Tough = Gives strength to tendons. Due to C being made of 3 PolyP chains.
  • Tertiary- 3D folding of the secondary structure. H, DS and I bonds hold the 3D shapes in place.
  • e.g Globular Proteins- In H2O form colloid. Maintain structure of cytoplasm, important in immune system( antibodies) also form enzymes. 
  • Quaternary- the 3D arrangement of more than one tertiary polypeptide
  • e.g Hb- Conjugated protein, each PolyP chain is arraged around iron containing haem group.  This iron enables Hb to bind and release O2 molecules 

Bonds which hold 3D shapes of proteins together are affected by condtion changes e.g temp/Ph. Result in bonds breaking, loss 3D shape = denatured. Can cause proteins such as enzymes- stop working efficently. 

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DNA 1.4

Nucleotides-  5- Carbon Pentose sugar , nitrogen containing base and phosphate group( -PO4 3) All joined in a Condensation Reaction removing 2 H20 molecules 

  • Purine base- 2 nitrogen containing rings e.g Adenine(A) and Guanine(G) <-- Both in DNA and RNA
  • Pyrimidine base- 1 Nitrogen ring E.g Cyostine (C) Thymine(T) and Uracil (U) <-- C = DNA and RNA. T= DNA U= RNA 
  • Purines will only join with pyrinmidines as purines have a double ring structure meaning they have to join with a smaller base so that the polynucleotide strands are equally spaced apart

DNA (Deoxyribonucleic Acid) 

  • 2 polynucleotide strands with the nitrogenous bases projecting inwards 
  • The antiparrel strands twist in complete DNA structure forming a double helix 
  • Strands held together by H bonds between the complemntary bases that are opposite eachother (A-T and G-C)
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DNA Replication 1.4

DNA Replication- dna needs to be copied when cells divide called R occurs during interpase 

Semi-Conservative Replication

  • 2 Strands unzip along line the line of H bonds and unravel due to enzyme DNA Helicase 
  • Strands act as templates for the new strands
  • Exposed DNA bases attract free DNA nucleotides and new H bonds form between base pairs 
  • DNA Polymerase lines up, catalysing linking of nucleotides along strand 
  • DNA Ligase catalyses formation of phosphodiester bonds between 2 strands of DNA 
  • Result= 2 new strands of DNA identical to original -> auto coil 

gene-  sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain. 

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Genetic Code 1.4

Codon- Sequence of 3 bases in DNA or mRNA

  • The genetic code in the DNA making up the chromosomes acts as a code for protein synthesis.
  •      It dictates the amino acids required to make the protein and the order in which they should be bonded together.
  • 3 bases code for 1 amino acid and these base triplets are non-overlapping.
  • The code is degenerate: there is more than 1 triplet for each amino acid. 
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Types of RNA 1.4

mRNA-  The RNA formed in the nucleus that carries the genetic code out into the cytoplasm

tRNA- Small units of RNA that pick up particular amino acids from the cytoplasm and transport them to the surface of the ribosome to align with the mRNA 

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Protein Synthesis 1.4

Protein Synethesis(2)

  • 1. Transcription
  • Takes place in nucleus
  •  A complementary copy of the gene is made using RNA
  •  Gene opens up. Hydrogen bonds break between bases.
  • RNA nucleotides attracted to complementary bases and form hydrogen bonds.
  • RNA nucleotides joined together by RNA Polymerase.
  • Complementary RNA copy of gene now made. It is called mRNA (messenger RNA).
  • mRNA molecule leaves nucleus through nuclear pore
  • 2. Translation 
  • Occurs on the ribosomes of the rough endoplasmic reticulum
  • The beginning of the sequence is always marked with the start codon AUG which codes for the amino acid methionine
  • A transfer RNA molecule (tRNA) with 3 bases exposed (an anticodon) pairs with a specific codon on the mRNA
  • Attached to the tRNA molecule is a specific amino acid
  • The amino acids, arranged in the order dictated by the mRNA codons, are joined with peptide bonds to form a polypeptide
  • A stop codon signals the last amino acid in the polypeptide chains 
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Mutations 1.4

Mutation can be good or bad such as 

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Enzymes 1.5

Enzyme has a globular protein structure. Prodcuced during protein synthesis transcribed from DNA molecule thats translated  

Enzymes are biological catalysts which control the rate of reactions that take place in individual cells and whole organisms. (They reduce the activation energy)

  • Changes that affect enzyme activity:
  • Temp and PH- affect the intramolecular bonds within the protein that are responsible for the shape of the molecule 
  • substrate and enzyme conc- 
  • Lock and key hypothesis 
  • active site specific shape, fits only 1 type of substrate = enzyme specificity 
  • enzyme + substrate = slot = enzyme substrate complex
  • Induced fit hypothesis 
  • Active site distinctive shape BUT flexible 
  • when substrate enters, shape site modified to form the active complex 
  • once p left complez reverts to its inactive form 
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Enzymes 1.5

Intial rate of enzyme activity (only one varaiable changes rest same)

  •  important to have excess substrate in ezyme experiments
  • intial rate of reaction is when reaction proceeds at its fastest 
  • = max reaction rate for an enzyme under particular conditions e.g ph,temp, sub conc
  • Competitive inhibitation 
  • inhibitator molecule similar shape to shape to substrate = competes for binding active site = enzyme inhibitator complex
  • inhibitator amount fixed can be reduced by increasing the substrate conc
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inorganic ions 1.6

 role in plants of:

  • ●  nitrate ions – to make DNA and amino acids

  • ●  calcium ions – to form calcium pectate for the middle lamellae

  • ●  magnesium ions – to produce chlorophyll

  • ●  phosphate ions – to make ADP and ATP. 

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water 1.7

  • High specific heat capacity- caused by H bods so temp water bodies = constant 
  • high surface tension (h bonds cause) = skin on water organisms can move on/aids plant transport 
  • lipid cant be compressed = important for hydraulic system in organisms
  • reaches max density 4 degrees allowing ice to float, insulate water bwlow = helps living to survive in the cold temperatures 
  • water = POLAR due to oxygen = delta neg and H = delta pos creates polarity = h2o cohesive and adhesive properties 
  • water is solvent- able to dissolve charged molecules = polar nature of the H20 = ions pulled apart 
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eukaryotic struc and function 2.1

Eukaryotic- ANIMAL (cell surface membrane containing cyto and organelles) 

  • membrane + cyto = protoplasm
  • the nucleus
  • mitochondria 
  • centrioles 
  • vaculoes 
  • 80s and 70s ribsomes
  • endoplasmic reticulum
  • lysosomes
  • golgi apparatus and proteins 

Eukaryotic- PLANT 

  • Plant cell walls
  • plasmodesmata 
  • plant cell wall layers 
  • vaculoes 
  • chloroplasts 
  • amyloplasts 
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eukaryotic struc and function 2.1

Eukaryotic- ANIMAL (cell surface membrane containing cyto and organelles) 

  • membrane + cyto = protoplasm
  • the nucleus
  • mitochondria 
  • centrioles 
  • vaculoes 
  • 80s and 70s ribsomes
  • endoplasmic reticulum
  • lysosomes
  • golgi apparatus and proteins 

Eukaryotic- PLANT 

  • Plant cell walls
  • plasmodesmata 
  • plant cell wall layers 
  • vaculoes 
  • chloroplasts 
  • amyloplasts 
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E Cells- cell organisation

E.C can be uni or multi cellular 

  • organ- collection of tissues grouped to carry out a particular body function 
  • organ system- many organs that work, carry out a function
  • multi require organistion to improve function 
  • cell tissure --> tissue --> organ --> system 
  • tissues- group of specialised cells that carry out a particular functions in the body 
  • epithelial tissue --> connective tissue --> muscle tissue --> nervous tissue 


  • damaged cells can self destruct- release enzymes to destroy the contents of the cell
  • cause problems 
  • can play role in death from cancer 
  • danaged hearts from heart attack = death white blood cells in HIV 
  • may play role in arthritis and osteoporois 
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prokaryotic cells 2.1

  • Features-
  • capsule 
  • cell wall
  • cell membrane 
  • cytoplasm
  • nucleoid 
  • palsmid 
  • 70s ribsomes (smaller than 80s, involved in protein synthesis) 
  • glycogen grandules/lipid 
  • droplets 
  • flagella
  • mesosome 
  • photosynthetic membranes 
  • GRAM STAINING (add iodine complex, add alcohol, add red safarnin counterstain)
  • GRAM POS- Thick layer of peptidoglycan = trap purple due to P cant decolourise by alchhol = purple
  • GRAM NEG- thin layer P, no technoic acid, outer membrane = lipopolysaccharides =declourised by the ethanol = red 
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Viruses 2.2

  • viruses- invade living cells and take over biochemsitry. 
  • capsid- protein coat made up of repeating units = caspomeres 
  • lipid envolope- some = extra outer layer = derived from host cell membranes = easier for viruses to pass from cell to cell
  • Virus attachment- particles attach to host cells = target proteins receptors in host cell surface membrane 
  • Bacteriophages- infect bacteria, inject genetic material into host cell but bulk of viral remains outside the bacterium 
  • to infect ANIMAL CELLS- lipid envolope fuses with host cell membrane 
  • to infect PLANT CELLS- use vector to pierce the cellulose wall. 
  • LYSOGENIC- doesnt case harm to host cell, non virulent, provirus produces repressor protein meaning no other viral proteins synthesied 
  • LYTIC-  new viruses made in host cells = damaged, virulent, provirus directs synthesis of new viral proteins, host cell bursts releasing assembled viruses 
  • DISEASE- occur when HC damaged = if undergo lysis, release own lysosome = digest themselves from inside, produce toxins that inhbibt cell membranes 
  • SPREAD = FOOT AND MOUTH - spread by animals infected milk, can pick it up by contaminated objects or meat, MAJOR outbreak in 2001 = animals destroyed.                             EBOLA (ssRNA V) = animal spread, passed by direct contact of skin, body secretions. Z-Mapp experimented in 2014 = saved someones life 
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viruses 2.2

DNA viruses- Viral DNA acts as a template for the cell to make mRNA then viral proteins.

RNA Viruses- 

  • RNA viruses do not produce DNA as part of their life cycle.
  • Most viruses contain single stranded RNA known as ssRNA.
  • Positive ssRNA- Viruses that contain a single strand of RNA that is a sense strand. It acts directly as mRNA and can be translated at the ribosomes. 
  • Negative ssRNA- The single strand of RNA In these viruses is an antisense strand. It must be transcribed into a sense strand before its translated.( E.g. Ebola)

RNA Retrovirus-

  • use their strand of viral RNA to make an enzyme called reverse transcriptase.
  • This goes on to use the RNA template to make DNA
  • The  DNA is then used as a template mRNA synthesis then viral protein synthesis.
  • The viral DNA is then incorporated into the host DNA and can then be transcribed and translated to make new viral proteins.
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Eukaryotic cell division and cycle 2.3

Cell cycle- regulated process in which cell divides into 2 daughter cells. 3 stages Interphase, Mitosis, cytokineisis 

  • INTERPHASE (3)- 
  • G1- Cells absorb material, grows, inactively divides cells 
  • S- DNA replication 
  • G2- More growth and DNA rep, checkpoint for damgage to DNA 
  • MITOSIS (4)
  • 1. PROPHASE- Chromosomes coil and codense = 2 chromatids joined at centromere. Centrioles move to opposite ends of polls 
  • 2. METAPHASE- nuc memb breaks down = chrom align at equator attached to spindle fibres at centromere 
  • 3. ANAPHASE- centreomeres split = sister chromatids pulled towards opposite polls = now chromosomes 
  • 4. TELOPHASE- nuc memb reforms  = cyto divides between cells 
  • CYTOKINESIS- Cyto fully divided between 2 daughter cells = nucleolus fully reformed 
  • M contribtes to Growth- PLANTS= increase cell number and size.  MAMMALS= Continous growth INSECTS- Discontinous- shed exoskeleton while new = soft = expand by taking in air/water. when new skeleton hardened air and water = released = room for tissues increase in size. 
  • M contributes to Asexual repro- ANIMALS- replace body parts by regeneration.  MICROBES- binary fission = microbe split 2 daughter cells. OTHER MICROBES= Budding difference = bud produced = different size parent.  PLANTS = vegatative repro.   PARTHENOGENESIS = virgin births in komodo dragons 
  • M contributes Repair- ANIMALS- M rapid = regenerate wounds.    PLANTS = produce scar tissue to seal
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meiosis 2.3

MEIOSIS- (1 and 2. One cell divides into 2 then 4)

  • Before meiosis 1 during interphase DNA replicated 
  • during meiosis 1- diploid parent cell divides give rise to 2 haploid daughter cells with 1 set of chromosomes each 
  • before meiosis 2 each chromo replicates 2 seperate chromatids during interphase 
  • during meiosis 2 second division carried out where chomatids seperate = 4 haploid gametes
  • Recombination 
  • crossing over- during meiosis 1 homologous chromo = paired and sections chromo = cut off and joined to homologous pair 
  • Independent Assortment- maternal and paternal chromosomes of diploid parent cell = randomly distributed into new haploid gametes
  • Chromosomal Mutations 
  • NON- disjunction = when chromo = fall to seperate during anaphase 1 or when sister chromatids fall to seperate during anaphase 2. RESULT in gametes being EITHER 
  • MONOSOMY- gametes no copies of chromo fuse with normal gamete during fertilisation = individual having 1 copy of chromo instead homologous pair 
  • POLYSOMY- gametes extra chromo fuse with normal gamete in fert = individual have 3 copies of particular chromo
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repo in mammals 2.4


  • Primary oocyte formed in the foetus (is a 2n diploid cell formed by MITOSIS)
  • Secondary oocyte formed (in ovulation) during the FIRST MEIOTIC DIVISION. It is a  1n haploid cell therefore a 1n polar body is also formed (only one cell receives all food stores)
  • The ovum is formed at fertilisation when THE SECOND MEIOTIC DIVISION is completed.
  • Again a 1n polar body is also formed (along with two more if the first 1n polar body initially divides  


  • primary spermatocyte formed during puberty (2n in diploid formed by MITOSIS) 
  • Secondary spermatocytes formed during 1st MEIOTIC DIVISON = 1n haploid cells 
  • chromatids formed during SECOND MEIOTIC DIVISON = develop into spermatozoa 


  • Many sperm cluster round the oocyte.
  • Once the head of one sperm cell touches the surface the acrosome, a reaction is activated.
  • Enzymes are released by many sperm cells which digest the follicle cells and jelly layer.
  • The head of one sperm fuses with the oocyte membrane and enters the cell (the tail is left behind).
  • The head absorbs water and bursts releasing its chromosomes to fuse with those of the ovum.
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Repo in mammals 2.4 (GT)

POLYSPERMY  (Egg ferilized by more than one S)

  • Sperm cell fuses with the egg cell membrane
  • Cortical granules from the egg cell move towards the egg cell membrane and fuse with it.
  • Exocytosis of the cortical granules occurs and the enzymes they contain move into the jelly layer of the egg cell.
  • The protease enzymes cause the jelly layer to thicken or harden forming a fertilisation membrane.
  • At the same time ion channels in the membrane open and close to change the charge across the cell membrane.

INTERNAL F- Transfer of male gametes directly to the female. 

EXTERNAL F- occurs outside thr body with gametes shed directly into the environ  (aquatic s)

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Repo in plants 2.5


  • Meiosis occurs in pollen grain = male gametes. Each anther = 4 pollen sacs = pollen grain develops
  • pollen sac = diploid mother cell = divide by meiosis = haploid microspores
  • microS = mitosis. 1 cell envelopes another = pollen grain = 2 haplod nuclei, tube nucleus(produce pollen tube goes through ovary down the ovule), generatuve nucleus(divide by mitosis on stigma of plant- 1 fuses with nucleus of ovule to form offspring)


  • Meiosis = ova produced
  • diplod megasore cells divide meiosis = 4 haploid megaspore 3 degenerate
  • megaS undergo 3 miotic divisions = each enveloped by other
  • embryo sac contains egg cell


  • Pollen grain = surface of stigma = interaction. When recongise pollen grain = grow
  • P.T grows from tube cell of poll grain --> stigma --> hallow style
  • tube = grow down --> ovary. Generative cell = generative nuc travels down it
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repo in plants 2.5


  • Poll Tube --> microspyle. 2 male nuclei --> ovule
  • flowering plants = double fertil
  • 1 male nuc fuse with nuclei of 2 polar bodies in egg = endosprm nucleus
  • other male nuc fuse with egg = diploid zygote
  • development of seed + embryo begin
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Classification 3.1

Taxononmy- classification split into different groups (3 main)

  • 1 kingdom- archaebacteria, ancient bacteria, only found extreme envrionments 
  • Kingdom- Eubacteria, true bacteria, useful roles some = pathogenic 
  • 4 kingdoms- Protista- heterotrph, autotroph. Fungi- heterotroph/saphrophytic. Plantae- all autotroph. Animalia- heterotroph 

SPECIES- Group of closely related organisms are potentially capable of interbreeding to produce fertile offspring 

  • MORPHOLOGICAL SPECIES CONCEPT- Based apperance of organsims, easy identify organisms, sexual dimorphism = confusing when male and females look different 
  • REPRODUCTIVE SPECIES CONCEPT- Based interbreeding to produce fertile offspring, overcomes sexual dimorphism, some org = not same species produce fertile offspring e.g tiger/lion not always right 

DNA BARCODING- Use short section DNA from standarised region of geonome all animals.   Gene region = effective identifying animal groups- short enough = sequenced quickly but still identify various species 

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Biochemical Relationships 3.1

GEL ELECTROPHORESIS- Movement of small particles through gel application of electricity. 

  • particles can be DNA, RNA or proteins 
  • GE seperates molecules depending on size, molecule shape and charge = influenced 
  • BIOCHEMICAL RELATIONSHIPS- scientists analyse structure of different chemicals organsims to identity relationships between them = molecular phylogeny.                       African, American porcupines look similar but biochemical analysis implies they are distantly related.   By analysing sequence of amino acids in proteins = see relationships within group e.g phylum 
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Natural Selection 3.2

EVOLUTION- Change in genetic compostion of population of organsims over several generations as a result of natural selection acting upon variation 

  • organisms reproduce sexually = variation 
  • organsims produce offspring in excess 
  • organisms that inherit advantageous characteristics most likely to surive pass on advantagous characteristic to offspring 
  • org inherit charcteristics put them at disadvantage = more likely to die out before reproduce 

Neo- Darwinism- Developed due to growth =  human knowledge of genetics presenting more modern way evo 

Change in Genotype -> change in phenotype -> advantageous alleles 

  • Niches- role of an organism in its community e.g food niche 
  • industral melanism- evolution of dark coulored individuals in a habitat thats been made darker or lighter by industrial pollution (antipollution leg 1960s)
  • directional selction- change from dominant phenotype to another in response to change in environment 
  • competition = 2 organisms require same resources = similar niches = intense 
  • BEHAVIOURAL- change in organsims behaviour 
  • PHYSIOLOGICAL- Internal workings e.g mammalian diving response 
  • ANATOMICAL- structures in organism = dissected (dead)
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Speciation 3.2

S- Formation is formation of a new species 

  • Allopatric Speciation- occurs pop = physically(natural)/geographically(human) isolated = seperately evolve separately diff envriron 
  • Sympatric S- S that occurs in same geographical region/habitat but species cannot reproduce = repro isolated 
  • Endemic Species- s only found in one area of the world
  • geograohical- physical barrier 
  • ecological- same region preference for different parts of the habitat 
  • seasonal- 2 groups reproduce different parts of month 
  • behavioural- dont recongise eachother as potential mates 
  • mechanical- reprodutive organs dont function only mate with some members 
  • adaptative radiation- 
  • species evolves rapidly forming number of different species which all fill different ecolog niches 
  • WHY DIFFERENT- food = selection pressure,  similar beaks = advan charc passed on,  different species = look different, DNA analysis = same 
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3.2 Evo of bacteria

  • path = evolve= more complex methods of defeating 
  • no med 1940s= death
  • production PENICLLIIN = though permenant cure for bacterial diseases 
  • P only affects GRAM POS Bac as PEPTIDOGLYCAN layer
  • range antibiotics created = prescribed freely 
  • Within 1 year reports of STAPHLYOCOCUSS AUREUS = resistant to antibiotic 
  • % created mutation = enzyme PENICILLINASE = breaks down P 
  • B = advantage, result of natural selection 
  • METHICILLIN = developed. People = ahead path = NOT resistant as new 
  • soon resistant pathogens = MRSA = B ahead 
  • growing num of B resistant to MORE than one antibiotic 
  • 1. AntiB = too widely used
  • 2. full course not completed 
  • 3. lack basic hygine in hospitals = spread resistant strains
  • 1. Reduce use AntiB
  • 2. educate people -> dont always need
  • 3. reduce use of AntiB in farming 
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3.3 Biodiversity

  • BioD- variety of living organisms in the world 
  • species D- number of diff species and individuals of each species within a community 
  • genetic D- variety genes possessed by individuals of one species 
  • ecosystem D- range habitats within particular area 


  • species richness- number of different species in area (more diverse less risk of S loss)
  • relative abundance- of organisms of the different S
  • Mutations- changes in DNA structure (alllows variation = speciation),  no affect on the phenotype,  some = severe affect  = increase gene pool population,   ADVAN = allele freq = increase,   DISAD= remove itself from GP
  • Species- same geonome -> different alleles -> different phenotype
  • Genetic variety- measure biological health -> less variety -> more vunerable population (less chance survive environ change) 
  • RICH BioD but LOW genetic D = ENDEMIC population = Vunerable disease.  Only FEW founders = LACK variation
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3.3 biodiversity


  • Provisioning Services-  provide food, fibres for clothes,  materials for building, greater BioD = more avaliable to us 
  • Regulating Services- Help maintain environ = water purification,  sewage treatment 
  • Supporting Services-  Provide support for other ecosystems-> soil formation and nutrient cycling = services NEEDED for growing food 
  • Cultural Services- biodiverse, healthy ecoS used in recreation/education, dependent on people visting wildlife e.g SouthA

Conservation- keeping/protecing a living environ

  • Ex- Situ-preservation of compounds BioD, outside natural habitats 
  • 1. allows gen material = conserved 
  • 2. breeding pop returned nat environ 
  • 3. complementary approach to insitu 
  • IN-SITU- Conservations of ecosystems and natural habitats and maintenance/recovery of viable populations 
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4.1 Surface area to volume ratio

  • as the size of an organism increases the surface area to volume ratio decreases
  • VOLUME- Determines the amounrt of substance which needs exchanging 
  • SURFACE AREA- determines how much can be exchanged 
  • UNICELLULAR ORGANISMS-  readily diffuse in/out of the membrane due to short diffusion pathway 
  • LARGER organsims have adaptations to cope with the large demand for exchange 
  • INSECTS- System of tubules which distribute air in the body to be able to reach all parts of bod 
  • MAMMALS- Lungs and blood vessels which are aimed at making it possible to exchange substances e.g O2, nutrients and heat between organism and evnviron
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4.2 cell transport mechanisms

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4.3 gas exchange

  • GE in Mammals
  • EXCHANGE-    site of GE = alveoli = lungs = adapted as = 1 cell thick = short diffusion p = larege SA, surrounded by capilliaries = deoxygenated blood = high conc gradient 
  • CO2 diffuses blood -> alveoli -> bronchiole and EXhaled 
  • O2 diffuses alevoli -> blood -> heart = circulation
  • INHALATION-  Volume inside chest = DECREASE,   Pressure= DECREASE below atmospheric P = draws IN air DOWN pressure gradient = ACTIVE process 
  • EXHALATION- Volume inside ches = DECREASE,  Pressure = INCREASE above atomospheric pressure = air OUT DOWN pressure gradient = PASSIVE process due to elastic recoil of the lungs 


  • Most CO2 = transport as part of hydrogen carbonate ion in red blood cells 
  • O2 dissolves from Hb when low levels of O2 in tissues = more CO2 transport in blood as CO2 molecules must compete with O2 for Hb 
  • O2 dissociates -> respiring tissues, CO2 from tissue -> attach to the Hb as H carbonate ion = transport around blood = change over respiring tissues = change over at O2 rich Lungs 
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4.3 Gas exchange in Fish and Insects

  • FISH 
  • Gills- composed of lamellae = stacked filaments = high surface area. Thin = short diffusion pathway 
  • counter current system across llamellae = maintain high conc gradient 
  • bony fish- ventaliate their gills using their mouth/operculum.  Buccal chamber expands while operculum closed = draws H2O into mouth.  Mouth closes = buccal chamber contracts = forces H2O out over gills through operculum 
  • Tracheoles spread through body = recieve air from environ VIA spiracles on exoskeleton -> trachea -> tracheoles 
  • Tracheoles are adapted to GE as- lots tiny branches which cover a large surface area.   Thin = short DP  

The Bohr effect 

  • CO2  rich environ = more O2 dissociates from Hb = O2 dissociation curve to shift to the RIGHT. 
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