BIOLOGY AQA AS UNIT 2
- Created by: dom
- Created on: 21-05-14 11:06
CAUSES OF VARIATION
VARIATION - DIFFERENCES THAT EXIST BETWEEN INDIVIDUALS
INTERSPECIFIC - VARIATION BETWEEN DIFFERENT SPECIES
INTRASPECIFIC - VARIATION WITHIN A SPECIES
INTRASPECIFIC
NO 2 MEMBERS OF A SPECIES ARE EXACTLY A LIKE
CAUSES OF VARIATION in INTRASPECIFIC....
GENETIC FACTOR - all species have same gene, however different versions of gene called ALLELES, alleles make up genotype, genotype determines phenotype, genetic variation inherited
PHYSICAL FACTOR - affected by enviroment, e.g. plants in more salts and minerals grow more, or identical twins same alleles, grew up in different areas of womb
variation is often a combination of both e.g. someone could grow 6ft by their genes but need enviro factors e.g. diet
STUDYING VARIATION
YOU HAVE TO TAKE A SAMPLE POPULATION - time cosuming to take whole thing, models for whole population
SAMPLE HAS TO BE RANDOM - to make sure it isnt biased, not due to chance
WHEN ANALYSING AND INTERPRETING DATA RELATING TO VARIATION...
- DESCRIBE DATA - give figures
- DRAW CONCLUSIONS
- SUGGEST A REASON - give reasons why??
STANDARD DEVIATION
MEAN - AVAERAGE OF VALUES IN SAMPLE - can be used to tell variation between samples
MOST SAMPLES GIVE YOU A NORMAL DISTRIBUTION CURVE (bell like shape)
STANDARD DEVIATION - how much the values vary around the mean
A large standard deviation means the value in sample vary alot
DNA STRUCTURE
POLYNUCLEOTIDE - made up of lots of nucleotides joined together
NUCLEOTIDE - MADE UP OF A SUGAR (DEOXYRIBOSE), PHOSPHATE AND AN ORGANIC BASE
FOUR BASES - A T G C
SUGAR AND PHOSPHATE STAYS THE SAME ORGANIC BASE CHANGES
DOUBLE HELIX
NUCLEOTIDES JOIN TO FORM POLYNUCLEOTIDE STRANDS
SUGAR AND PHOSPHATE GROUP JOIN THROUGH COVALENT BOND TO FORM A SUGAR PHOSPHATE BACKBONE
TWO POLYNUCLEOTIDES JOIN TOGETHER BY HYDROGEN BONDS BETWEEN THE BASES
ONE OF STRANDS IS CALLED CODING STRAND - THE OTHER NON CODING STRAND
EACH BASE CAN ONLY JOIN TO THERE COMPLEMENTARY BASE
WIND UPTO FORM DOUBLE HELIX
DNA FUNCTION
CONTAINS GENETIC INFO NEEDED TO GROW AND DEVELOP
LONG AND COILED, PACKED UP IN SMALL SPACE IN NUCLEUS - HOLDS ALOT OF GENETIC INFO
DNA HAVE PAIRED STRUCTURE - EASIER TO COPY ITSELF - CALLED SELF REPLICATION - GOOD FOR PASSING GENETIC INFO FROM GENERATION TO GENERATION
DOUBLE HELIX STRUCTURE MEANS IT IS STABLE
EUKARYOTIC CELL DNA
EUKARYOTIC CELLS - contain DNA molecules that exist as chromosomes
DNA MOLECULE is really long so it has to be wound up so it can be fit into the NUCLEUS.
IT GETS WOUND UP IN TO PROTEINS CALLED HISTONES - THEY SUPPORT IT
LINEAR DNA MOLECULES
COILED AND PACKED TIGHTLY INTO CHROMOSOME
PROKARYOTIC CELL DNA
CARRY DNA AS CHROMSOMES - DNA MOLECULES ARE SHORTER AND CIRCULAR
DNA ISNT WOUND IN PROTEINS - IT CONDENSES TO FIT IN THE CELL BY SUPERCOILING
GENES
GENES - section of dna found on chromosomes, they code for proteins- contain instructions to make them
PROTEINS - made from amino acids, proteins have differed number/order of amino acids, order of bases determines order of amino acids - 3 bases - triplet code e.g. GTC codes for a specific amino acid which will make up a protein
NON CODING DNA
GENES IN DNA THAT DONT ACTUALLY CODE FOR AMINO ACIDS
CALLED INTRONS - EXONS DO CODE FOR AMINOS
INTRONS DURING PROTEIN SYNTHESIS ARE REMOVED
MULTIPLE REPEATS OF DNA ALSO DONT CODE FOR AMINO ACIDS E.G. CCTCCTCCTCCT
THESE ARE CALLED MINISATELIITES
DNA GENES AND DEVELOPMENT
order of bases in GENE DETERMINES AMINO ACID SEQUENCE to make proteins
ENZYMES ARE PROTEINS - enzymes speed up our metabolic pathways - these determine how we grow and develop - phenotype
ALLELES
DIFFERENT VERSIONS OF THE SAME GENE
ORDER OF BASES IN EACH GENE IS SLIGHTLY DIFFERENT - code for slightly different versions of the same group
e.g. EYE COLOUR IS THE GENE THE ALLELES WILL BE WHETHER ITS GREEN OR BLUE
GAMETES
SPERM AND EGG CELLS (gametes) - fertilise to form a zygote - divides and develops into new organism
GAMETES ARE HAPLOID - HALF THE NUMBER OF CHROMOSOMES
WHEN IT FUSES TO FORM ZYGOTE IT BECOMES DIPLOID AGAIN
MEOSIS
TYPE OF CELL DIVISION - DIPLOID TO START - CELLS FORMED HAPLOID, happens in sexual reproduction
DNA REPLICATES - each chromosome becomes doubled, forms 2 identical strands of DNA
2 DIVISIONS;
MEOSIS 1 - HALVES THE NUMBER OF CHROMSOMES after being arranged in homologus pairs, CHROMATIDS CROSS OVER AND BITS OF CHROMATIDS SWAP - DIFFERENT COMBINATION OF ALLELES
MEOSIS 2 - THE PAIRS OF SISTER CHROMATIDS THAT MAKE UP EACH CHROMOSOME ARE SEPERATED
FOUR HAPLOID GAMETES WHICH ARE GENETICALLY DIFFERENT FORM
HOW MEIOSIS PRODUCES GENETICALLY DIFFERENT CELLS
1) CROSSING OVER - crossing over in meoisis 1 - 4 daughter cells have different alleles
2) INDEPENDENT SEGREGATION OF CHROMOSOMES - different combinations of maternal and paternal chromosomes go into each cell - 4 daughter cells have different combinations of chromosomes
GENETIC DIVERSITY
WITHIN A SPECIES - DNA VARIES A LITTLE (99.5% SAME) SAME GENES DIFFERENT ALLELES
DIFFERENT SPECIES - DNA VARIES ALOT - DIFFERENT GENES
THE MORE ALLELES IN A POPULATION, THE MORE DIVERSE IT IS
GENETIC DIVERSITY INCREASED BY;
- MUTATIONS - FORMS NEW ALLELES
- DIFFFERENT ALLELES BEING INTRODUCED - individuals from another porulation migrate in and reproduce - called GENE FLOW
GENETIC BOTTLENECKS
AN EVENT THAT CAUSES A BIG REDUCTION IN A POPULATION E.G. HUNTING OF SEALS
REDUCED ALLELES IN POPULATION
WHEN THE SURVIVORS START TO REPRODUCE AGAIN THERE WILL BE A LARGER POPULATION CREATED FROM A FEW INDIVIDUALS
FOUNDER EFFECT
WHAT HAPPENS WHEN A FEW INDIVIUDALS FROM A POPULATION START A NEW COLONY
ONLY A SMALL NUMBER OF ORGANISMAS HAVE CONTRIBUTED ALLELES TO NEW GENE POOL - MORE INBREEDING
E.G. AMISH PEOPLE SEPERATED THEMSELVES BECAUSE OF RELIGION
SELECTIVE BREEDING
HUMANS SELECTING WHICH DOMESTICATED ANIMALS OR PLANTS REPRODUCE TOGETHER TO PRODUCE HIGH-YIELDING BREEDS
LEADS TO REDUCTION IN GENETIC DIVERSITY - ONCE THE ORGANISM WITH DESIRED CHARACTERISTICS PRODUCED - IT WILL CONTINU TO BE BRED
REDUCES ALLELES IN GENE POOL
ARGUMENTS OF SELECTIVE BREEDING
FOR ;
IT CAN PRODUCE HIGH YEILDING ANIMALS AND PLANTS
IT HELPS PRODUCE ANIMALS AND PLANTS THAT HAVE INCREASED RESISTANCE TO DISEASE - buy less drugs and pesticides
BRED TO INCREASE TOLERANCE TO BAD CONDITIONS E.G. DROUGHT
AGAINST ;
HEALTH PROBLEMS - dairy cows, short life expectancy - strain whilst carrying vast amounts of milk
REDUCES GENETIC DIVERISTY - LESS ALLELES - MORE SUCEPTIBLE TO NEW DISEASES
HAEMOGLOBIN
PROTEIN WITH QUATERNARY STRUCTURE - RED BLOOD CELLS CONTAIN HAEMOGLOBIN
BINDS TO OXGEN TO FORM OXYHAEMOGLOBIN IN THE LUNGS - OXYGEN THEN LEAVES THE HAEMOGLOBIN NEAR THE BODY CELLS - DISSACCOCIATES
EACH POLYPEPTIDE CHAIN HAS A HAEM GROUP WHICH GIVES IT ITS RED COLOUR
HIGH AFFINITY FOR OXYGEN - IT CAN CARRY 4 OXYGEN MOLECULES
HAEMOGLOBIN SATURATION AND PARTIAL PRESSURE
PARTIAL PRESSURE OF OXYGEN - measure of oxygen concentration, the more o2 the higher the partial pressure
OXYGEN LOADS ON TO HAEMOGLOBIN WHERE THERES HIGH PARTAL PRESSURE OF O2
OXYGEN UNLOADS ITS OXYGEN WHERE THERES A LOWER PARTIAL PRESSURE OF O2
ALVEOLI HAVE A HIGH PARTIAL PRESSURE IN THE LUNGS, SO OXYGEN BINDS HERE TO HAEMOGLOBIN
WHERE CELLS RESPIRE - THEY USE UP OXYGEN - LOWERING PARTIAL PRESSURE - RED BLOOD CELLS DELIVER OXYHAEMOGLOBIN TO RESPIRING TISSUE WHERE THE OXGEN DISSOCIAES
HAEMOGLOBIN RETURNS TO LUNGS
DISSOCIATION CURVES
DISSOCIATION CURVES
SHOWS HOW SATURATED HAEMOGLOBIN IS WITH OXYGEN AT A GIVEN PARTIAL PRESSURE
WHEN PO2 IS HIGH - haemoglobin has a high affinity for oxygen, so it has a high stauration of oxygen
WHEN PO2 IS LOW - haemoglobin has a low affinity for oxygen, low saturation of oxygen
SATURATION OF OXYGEN MEANS THE AMOUNT OF O2 MOLECULES IT HAS ON IT - E.G. 100% SATURATION WOULD MEAN IT WOULD HAVE THE MAXIUM OF 4 MOLECULES BINDED
DISSOCIATION CURVES AND CO2
HAEMOGLOBIN GIVE UP MORE OXYGEN AT HIGHER PARTIAL PRESSURES OF CO2
WHEN CELLS RESPIRE THEY PRODUCE C02 WHICH RAISES PP
INCREAES RATE OF UNLOADING
THIS IS CALLED BOHR AFFECT
DISSOCIATION CURVES IN DIFFERENT ORGANISMS
ORGANISMS THAT LIVE IN ENVIROMENTS WITH LOW CONCENTRATION OF OXYGEN HAVE HAEMOGLOBIN WITH A HIGHER AFFINITY THAN HUMAN (TO THE LEFT)
ORGANISMS THAT ARE VERY ACTIVE AND HAVE A HIGH OXYGEN DEMAND HAVE HAEMOGLOBIN WITH LOWER AFFINTY FOR OXYGEN THAN HUMAN (TO THE RIGHT)
POLYSACHARIDES
3 TYPES
STARCH
GLYCOGEN
CELLULOSE
STARCH
MAIN ENERGY STORAGE IN PLANTS
CELLS GET ENERGY FROM GLUCOSE - PLANTS STORE GLUCOSE AS STARCH (when it needs more energy it breaks down starch to get glucose)
STARCH IS A MIXTURE OF 2 POLYSACHARIDES -
- AMYLOSE - a long unbranched chain of a glucose, cylinder shape, compact good for storage and can fit into small spaces
- AMYLOPECTIN - a long branched chain of a glucose, side branches allow enzymes to get to glycosidic bonds easier - glucose can get relasesd quicker
STARCH INSOLUBLE - GOOD FOR STORAGE
GLYCOGEN
MAIN ENERGY STORAGE IN ANIMALS
ANIMAL CELLS GET ENERGY FROM GLUCOSE - STORE IT IN GLYCOGEN
LOTS OF BRANCHES COMING OFF OF IT - STORED GLUCOSE CAN GET RELEASED QUICKER
COMPACT SO GOOD FOR STORAGE
CELLULOSE
MAJOR COMPONENT OF CELL WALLS IN PLANTS
LONG UNBRANCHED CHAINS OF BETA GLUCOSE - STRAIGHT
LINKED TOGETHER BY HYDROGEN BONDS TO FROM STRONG FIBRES CALLED MICROFIBRILS.
THE STRONG FIBRES MEANS IT PROVIDES STRUCTURAL SUPPORT FOR CELL
DIFFERENCE BETWEEN ANIMAL AND PLANT CELLS
ANIMALS - PLASMA MEMBRANE, CYTOPLASM, NUCLEUS, MITOCHONDRIA, RIBOSOMES
PLANTS - ALL THE SAME AND EXTRA
- RIDGID CELL WALL - MADE OF CELLULOSE - SUPPORTS AND SRENGTHENS
- VACOULE - CELL SAP A WEAK SOLUTION OF SUGAR AND SALTS
- CHLOROPLASTS - WHERE PHOTOSYNTHESIS OCCURS - MAKES FOOD FOR PLANT - CONTAIN CHLORPHYLL
CELL CYCLE
PROCESS OF CELL GROWTH AND DIVISION - IN MULTICELLULAR ORGANISMS
G1 PHASE - CELL GROWS, NEW PROTEINS AND ORGANELLES ARE FORMED
SYNTHESIS - CELL REPLICATES DNA
G2 - CELL KEEPS GROWING AND SPINDLE PROTEINS ARE MADE FOR CELL DIVISON
THESE 3 PHASES ARE PART OF INTERPHASE.
DNA REPLICATION
ENZYME DNA HELICASE BREAKS HYDROGEN BONDS BETWEEN HYDROGEN BONDS
HELIX UNZIPS TO FORM 2 SINGLE STRANDS
ORIGINAL STRANDS ACT AS A TEMPLATE, FOR A NEW STRAND, FREE FLOATING DNA NUCLEOTIDES JOIN TO EXPOSED COMPLEMENTARY BASES
ENZYME DNA POLYMERASE JOINS THE TEO TOGETHER
HYDROGEN BONDS FORM BETWEEN THEM
SEMI - CONSERVATIVE BECAUSE HALF THE NEW STRANDS OF DNA ARE FROM THE ORIGINAL PIECE OF DNA
MITOSIS
CELL DIVISION, PRODUCES GENETICALLY IDENTICAL
PARENT CELL DIVIDES TO PRODUCE 2 IDENTICAL DAUGHTER CELLS
NEEDED FOR GROWTH OF MULTICELLULAR ORGANISMS AND FOR REPAIRING DAMAGED TISSUE
STAGES OF MITOSIS
INTERPHASE - prepares to divide, dna unravelled and replicated (to double genetic content) organelles are replicated and ATP content increases (energy needed for cell division)
PROPHASE - chromosomes condense and becomes visible as 2 chromatids held together by a centromere, nuclear envelope starts to break down
METAPHASE - spindle forms, centromeres attatch chromatids to spindle and line up in the middle of the cell
ANAPHASE - centomeres divide, spindle fibres pull sister chromatids to opposite poles of the cell
TELOPHASE - spindle fibres break down, nuclear envelope forms around each chromsome at eaither end, chromsomes uncoil
CYTOKENISIS - where the two identical cells form.
CANCER
CELL GROWTH AND DIVISION CONTROLLED BY GENES
THEY STOP WHEN THEYVE DIVIDED ENOUGH TIMES - HOWEVER IF THERES A MUTATION IN A GENE THAT CONTROLS CELL DIVISION, THE CELLS CAN GROW OUT OF CONTROL
IF CELLS CARRY ON DIVIDING THEY CAN FORM A TUMOUR
CANCER IS A TUMOUR THAT INVADES SURROUNDING TISSUE
CANCER TREATMENT
DESIGNED TO DISRUPT CELL CYCLE - dont distinguish normal cells to tumour cells and kill them both - doesnt matter because tumour cells divide much quikcer so our more likely to kill tumour cells
TREATMENTS INCLUDE; CHEMOTHERAPY - prevents synthesis of enzymes needed for dna replication - cant enter synthesis so kills itslef
RADIATION AND DRUGS - damage dna so when cell in synthesis it detcts damaged dna so it kills itself
TO REDUCE IMPACT ON NORMAL CELLS - tumour removed using surgery, this removes a lot of tumour cells and increases the access of any left to nutrients and ocygen which trigger them to enter the cell cycle making them more suceptible to treatment.
CELL DIFFERENTIATION
ALL CELLS ARE SPECIALISED TO SPECIFIC FUNCTIONS
STRUCTURE ADAPTED TO ITS PARTICULAR JOB THE PROCESS OF BECOMING SPECIALISED IS DIFFERENTIATION
2 EXAMPLES - SQUAMOUS EPITHELIUM CELLS - thin,in the lungs and allow gases to pass through them easily - lining alveoli
PALISADE MESPHYLL CELLS - in leaves where photosynthesis occurs - contain lots of chloroplasts , so they can absorb a lot of sunlight
TISSUE IS A GROUP OF SIMILAR CELS THAT PERFORM THE SAME FUNCTION
ORGANS STRUCTURES WITHIN AN ORGANISM THAT ARE MADE UP OF SEVERAL TISSUES ALL WITH A DIFFERENT FUNCTION WHICH CONTRIBUTE TO THE OVERALL FUNCTION OF THE ORGAN
EXCHANGING SUBSTANCES
CELLS NEED TO TAKE IN OXYGEN AND NUTRIENTS BY EXCHANGING WITH THE ENVIROMENT
THEY ALSO NEED TO EXCRETE WASTE PRODUCTS LIKE CO2 AND UREA
MOST ORGANIMS NEEED TO STAY AT THE SAME TEMP SO HEAT NEEDS TO BE EXCHANGED
SURFACE AREA TO VOLUME RATIO
DETERMINES HOW EASY THE EXCAHGE OF SUBSTANCES IS
SMALLER ANIMALS HAVE A LARGER SURFACE AREA TO VOLUME RATIO THEN BIGGER ANIMALS
DIFFERENT EXCHANGE SYSTEMS
SINGLE CELLED ORGANISMS - substances diffuse diretcly in/out of cell acroos membrane - diffusion rate is quick becaue small distance to travel
MULTICELLUAR ORGANISMS - diffusion across membrane is too slow because some cells to deep in body, and large and animals have a small surface area to volume ratio
SO MULTICELLULAR ORGANIMS NEED SPECIALISED EXCHANGE ORGANS
IT ALSO NEEDS A EFFICENT SUBSTANCE TO CARRY SUBSTANCES TO AND FROM CELLS - MASS TRANSPORT - CIRCULATORY SYSTEM
BODY SHAPE AND SIZE ; HEAT
THE RATE OF HEAT LOSS DEPENDS ON ITS SURFACE AREA - A BIGGER ANIMAL WITH A SMALL SURFACE AREA WILL LOSE LESS HEAT
IF ORGANISM SMALL AND HAS A LARGE SA TO VLUME RATIO THEN IT LOSES HEAT QUICKER
SHAPE - IF ITS MORE COMPACT AND ROUND THEN IT WILL MAINTAIN BODY HEAT BECAUSE THERES LESS SURFACE AREA IF ITS LESS COMPACT AND HAS STICKY OUT BITS LARGER SURFACE AREA MEANS MORE HEAT ESCAPES
ADAPTIONS TO AID EXCHANGE
ANIMALS WITH HGIH SA TO V RATIO - LOSE MORE WATER AS IT EVAPORATES FROM SURFACE - some small desert mamals have kidney structure adaptions so they produce less urine
SMALL ANIMALS IN COLDER AREAS - higher metabolic rate to compensate for high sa to v - this helps them keep warm by creating heat - eat lots of high energy food e.g. nuts
SMALLER MAMMALS - thick hair or hibernate when it gets cold
LARGER ORGANISMS IN HOT REGIONS - find it hard to keep cool - elephants developed large flat ears which increase surface area alowing them to lose more heat - hippos spend alot of time in water
FISH GAS EXCHANGE
WATER CONTAING O2 ENTERS FISHES MOUTH AND PASSES THROUGH THE GILLS
GILLS ARE MADE UP OF GILL FILAMENTS WHICH GIVE A BIG BIG SURFACE AREA FOR EXCHANGE OF GASES - filaments covered in llamale which increase surface area further
LLAMALE HAVE LOTS OF CAPPILARIES AND THIN SURFACE AREA TO INCREASE DIFFUSION
COUNTERCUREENT (blood flows in one direction and water in the opposite) MAINTAINS A LARGE CONCENTRATION GRADIENT - as much oxygen can be passed on
INSECTS GAS EXCHANGE
THEY USE TRACHAE - AIR ENTERS THESE THROUGH PORES ON SURFACE CALLED SPIRICALES
OXYGEN TRAVELS DOWN CONCENTRATION GRADIENT TOWARDS CELLS, CO2 MOVES DOWNS ITS OWN CONCENTRATION GRADIENT TO SPIRICALES
TRACHAE BRANCH OFF INTO TRACHEOLES WHICH HAVE THIN PERMEABLE WALLS AND GO TO INDIVIDUAL CELLS
INSECTS USE ABDOMINAL MUSCLES TO MOVE AIR IN AND OUT OF SPIRICLALES
PLANT EXCHANGE
NEED CO2 FOR PHOTOSYNTHESIS - O2 WASTE GAS
NEED 02 FOR REPSIRING CO2 WASTE GAS
GAS EXCHANGE SURGFACE IS A SPONG MESOPHYLL CELLS IN LEAF - LARGE SURFACE AREA
THE MESPHOPHYLL CELLS ARE IN THE LEAF - GAS MOVES IN THROUGH PORES CALLED STOMATA
STOMA CAN OPEN AND CLOSE TO ALLOW GASES IN OR OUT DEPENDING IF PLANTS LOSING TO MUCH WATER - GUARD CELLS CONTROL THIS
INSECTS AND PLANTS AND WATER LOSS
IF INSECTS ARE LSOING WATER THEY CLOSE THEIR SPIRACLES USING MUSCLES, THEY HAVE WATERPROOF WAXY CUTICLE ALL OVER THEM AND TINY HAIRS AROUND SPIRACLES TO REDUCE EVAPORATION
PLANTS - STOMATA KEPT OPEN DURING DAY TO ALLOW GAS EXCHANGE - water will flow in and make guard cells trugid -if dehydrated it will become flacid and stoma will close
CURLED LEAVES WITH STOMATA INSIDE PROTECTING FROM DRY WIND
REDUCED AMOUNT OF STOMATA SO LESS WATER CAN ESCAPE
WAXY WATERPROOF CUTICLES SO LESS WATER CAN ESCAPE
CIRCULATORY SYSTEM
MASS TRANSPORT SYSTEM - large mamals have a small surface area to volume ratio so need specialised gas exchange system
MADE UP OF HEART AND VESSELS - heart pumps blood through veins atreries and cappilaries to diffeent parts of the body
BLOOD TRANSPORTS - RESPIRATORY GASES, PRODUCTS OF DIGESTION AND HORMONES IN IT
2 CIRCUITS - ONE TAKES BLOOD FORM HEART TO LUNGS WHILST THE OTHER - TO THE REST OF THE BODY
BLOOD VESSELS AND ORGANS
HEART - AORTA AND VENA CARVA
LUNGS PULMONARY ARTERY/VEIN
GUT - HEPATIC PORTA VEIN
LIVER - HEPATIC VEIN AND ARTERY
KIDNEY - RENAL ARTERY AND VEIN
ARTERIES
CARRY BLOOD FROM THE HEART TO THE REST OF THE BODY, THICK MUSCULAR WALLS - ELASTIC TISSUE TO COPE WITH HUGH BLOOD PRESSURE
ALL CARRY OXYGENATED BLOOD - APPART FROM PULMONARY
THEY DIVID INTO SMALLER ARTERIOLES - FORM A NETWORK THROUGOUT THE BODY
VEINS
VEINS TAKE DEOXGENTAED BLOOD BACK TO THE HEARTUNDER LOW PRESSURE
WIDER LUMEN AND LITTLE ELASTIC IN TISSUE
VEINS CONTAIN VALVES TO STOP BACKFLOW
PULMONARY VEIN CARRIES OXGENATED BLOOD FROM HEART TO THE LUNGS
CAPILLARIES
ARTERIOLES BRANCH INTO CAPILLARIES - SUBSTANCES ARE EXCHNAGED BETWEEN CAPPILARIES AND CELLS E.G. OXYGEN AND GLUCOSE
ADAPTED FOR DIFFUSION
NEAR CELL - SHORT DIFFUSION PATHWAY
WALLS ONLY ONE CELL THICK
LARGE NUMBER OF THEM - INCREASES SURFACE AREA
TISSUE FLUID
FLUID THAT SURROUNDS CELLS IN TISSUES - made from substances that leave the blood e.g. oxygen water and nutrients - cells take these in from the tissue fluid - and release metabolic waste into it
SUBSTANCES MOVE OUT OF CAPILLARIES INTO TISSUE FLUID BY PRESSURE FILTRATION
AT THE START OF THE CAPPILARY WHIC HAS COME FROM THE ARTERY - pressure is higher in cappilary than tissue fluid so some of it comes out into tissue fluid
this means less pressure in cappilaries - nearer the end going to the vein
due to fluid loss - water potential is high out side of cappilary so it moves in through osomosis
TISSUE FLUID DOESNT CONTAIN REDBLOOD CELLS AND PROTEINS BECAUS THEY ARE TO BIG TO BE PUSHED OUT
ANY EXCESS TISSUE FLUID IS DRAINED INTO LYMPHATIC SYSTEM
WATER TRANSPORT IN PLANTS
WATER ENTERS A PLANT THROUGH ITS ROOT CELLS - HIGH TO LOW WATER POTENTIAL - covered in root hairs - increases surface area so more water is take in
ONCE WATER IS ABSORBED IT GOES THROUGH THE CORTEX BEFORE IT GETS INTO THE XYLEM
LEAVES EVAPORATE WATER - CREATES A CONSTENT WATER POTENITIAL GRADIENT THAT KEEPS WATER MOVING FROM ROOTS TO LEAVES
ROUTES THROUGH THE ROOT
SYMPLASTIC PATHWAY - goes through living parts of the cell - the cytoplasm - cytoplasm of neighbouring are linked by plasomodesmata (small channels in cell walls)
APOPLASTIC PATHWAY - goes through non living - cell walls - water diffuses through them
APOPLASTIC PATHWAY GETS BLOCKED BY CASPARIAN ***** - FORCES IT TO USE SYMPLASTIC PATHWAY - MADE OF SUBERIN WHICH IS IMPERMEABLE TO WATER
IT THEN MOVES TI XYLEM
HOW WATER MOVES UP A PLANT
COHESION AND TENSION -
- water evaporates from leaves at top of xylem
- creates a tension/suction which pulls more water into the leaf
- water molecules are cohesive (bond together) forcing them upwards
ROOT PRESSURE -
- when water is transported into the xylem it creates a pressure and forces water already in the xylem further upwards
TRANSPIRATION - water evaporates from moist cell walls and out of the stomata when it opens
FACTORS THAT AFFECT TRANSPIRATION
LIGHT - lighter it is the faster - stomata open in daytime
TEMPERATURE - higher the temp fatser - warmer water molecules have more energy - evaporate faster - makes water diffuse out faster
HuMIDITY - lower the humidity the fasster the transpiration - if air around the plant is dry - concentration gradient between leaf and air is increased- increasing transpiration
WIND - windier it is the faster - air movement blws water molecules from around the stoma - increasing concentration gradient
CLASSIFICATION
TAXONOMY - naming and organising organisms into groups based on similarities and differences
SIMILAR ORGANISMS ARE SORTED IN TO LARGE GROUP DUE TO SIMILARITIESAND PLACED IN A KINGDOM AND THEN GOES DOWN IN ORDER OF ;
KINGOM, PHLUM, CLASS, ORDER, FAMILY, GENUS, SPECIES
SPECIES ARE A GROUP OF SIMILAR ORGANISMS THAT ARE ABLE TO REPRODUCE TO GIVE FERTILE OFFSPRING
PHYLOGENETICS TELL US ABOUT AN ORGANIMS EVOLUTIONARY HISTORY - ALL ORGANISMS HAVE EVOLVED FROM RELATIVES AND COMMON ANCESTORS.
WHY DEFINING AN ORGANIM AS A DISTINCT SPECIES COUL
YOU CANT ALWAYS SEE THERE REPRODUCTVE BEHAVIOUR :
- MAY BE EXTINCT
- REPRODUCT ASEXUALLY
- PRACTICAL AND ETHICAL ISSUES - E.G. CHIMPS AND HUMANS ARE CLASSED AS A SEPERATE SPECIES - BUT HAS ANYONE TRIED MATING THEM
SO SCIENTISTS COMPARE DNA INSTEAD TO SEE HOW RELATED
CLASSYFING SPECIES
SPECIES CAN BE CLASSIFIED BY PROTEINS OR DNA/SIMILARTIES IN GENES ]
COMPARE DNA BASE SEQUENCE OR LOOKING AT THEIR PROTEINS
ORGANISMS THAT ARE MORE CLOSELY RELATED WILL HAVE MORE SIMILAR DNA THAN DISTANTLY RELEATED ORGANIMS
COMPARING DNA
DNA SEQUENCING - directly compared by looking at the order of the bases, closely related species will have a high percentage of similarity in their DNA base order
DNA HYBRIDISATION - DNA from 2 different species is collected, seperated and into single strands and mixed together - where base sequence of DNA are complementary a hydrogen bond will form - the more bonds the more alike - dna is then heated to seperate strands - similar dna will have more bonds connecting so a higher temp would mean more energy would be required to break all the bonds
COURTSHIP BEHAVIOUR
CARRIED OUT TO ATTRACT A MATE OF THE RIGHT SPECIES
SPECIES SPECIFIC - PREVENTS INTERBREEDING
IT CAN BE USED TO CLASSIFY ORGANISMS
THE MORE CLOSELY RELATED THE MORE SIMILAR COURTSHIP BEHAVIOUR
ANTIBIOTICS
CHEMICALS THAT KILL/ INHIBIT GROWTH OF BACTERIA
DIFFERENT TYPES OF ANTIBIOTICS - an example some prevent growth of a cell wall (which provides structural support) this can lead to osmotic lysis (water moves into cell and bursts it!)
IF A MUTATION OCCURS IN THE BASE SEQUENCE OF AN ORGANISMS DNA IT CAN CAUSE A DIFFERENT CHARACTERISTIC
SO MUTATION IN A BACTERIAL CELL - COULD MEAN ITS NOT AFFECTED BY ANTIBIOTICS ANYMORE
E.G. METHECILLIN IS AN EXAMPLE - bacteria have developed resistance to it because of mutation - methecillin inhibits a enzyme for cell wall formation - a mutated gene will produce a mutated enzyme which methecillin no longer ecognises
PASSING ON ANTIBIOTIC RESISTANCE
VERTICAL GENE TRANSMISSION - bacteria reproduce asexually (exact copy) - this meand each daughter cell has the same genesincluding antibiotic resistance - found in plasmids
HOROZONTAL GENE TRANSMISSION - two bacteria join together (conjugation) and a copy of plasmid is passed on
ANTIBIOTIC RESISTANCE AND NATURAL SELECTION
INDIVIDUALS IN A POPULATION SHOW VARIATION IN CHARACTERISTICS
PREDATION, DISEASE AND COMPETITION CREATE STRUGGLE FOR SURVIVAL
INDIVIDUALS WITH BETTER ADAPTIONS ARE MORE LIKELY TO SURVIVE E.G BACTERIA WITH ANTIBIOTIC RESISTANCE ARE MORE LIKELY TO SURVIVE WHEN EXPOSED TO ANTIBIOTIC RESISTANCE
OVER TIME NUMBER OF ORGANISMS WITH ADVANTAGEOUS VHARACTERISTICS INCREASE
ANTIBOTIC RESISTANCE AND DISEASES
ANTIBACTERIAL RESISTANCE MAKES IT MORE DIFFICULT TO TREAT SOME BACTERIAL INFECTION;
TUBERCULOSIS - lung disease, natural selection has caused resistance to bacteria mycrobacterium tuberculosis, multidrug resistance,
MRSA - methecillin resistance, resistance to nearly all antibiotics on offer, take along time for doctors to decide which one will kill the bacteria
SPECIES DIVERISTY
SPECIES DIVERISTYIS THE NUMBER OF DIFFERENT SPECIES AND ABUNDANCE OF EACH SPECIES IN A COMMUNITY
THE HIGHER THE AMOUNT OF TREES AND PLANTS THE MORE THE ANIMALS - PROVIDES HABITATS
DEFORESTATION AND AGRICULTRUE
DEFORESTATION - decreases species diveristy, reduces species of trees, destroys habitats, this means other animals wont have a home and migrate,
AGRICULTURE -
- woodland clearence for room
- monculture - growing one plant
- pesticides - chemicals that kill pests that feed on crops
- herbecides - chemicals that kill unwanted plants
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