Biology mock (unit2 chapters 7 till 13.2)

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what is dna made of?
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what are nucleotides made from?
A sugar ( deoxyribose) a phosphate and a base ( a c g or t)
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what is formed when nucleotides join together?
polynucleotide strands
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Where do the nucleotides join up to make a polynucleotide? and what does it form?
between the phosphate group of one nucleotide and the sugar of another, making a sugar-phosphate back bone
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What bond joins two polynucleotide strands together?
Hydrogen bonds between bases
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what is specific base pairing?
one base can only join with one particular partner.
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what does adenine pair with?
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what does guanine pair with ?
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what is formed when 2 polynucleotides wind up?
dna double helix
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how many hydrogen bonds form between Cytosine and guanine?
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how many hydrogen bonds form between adenine and thymine?
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what does dna contain?
your genetic information
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what is genetic information?
the instructions needed to grow and develop from an egg to a fully grown adult
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What is good about DNA being very long and coiled up very tightly?
You can fit a lot of genetic information in a small place
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what is good about dna having a paired structure?
It makes it easier for it to self replicate ( copy its self) which is important for cell devision and passing on genetic information.
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What makes dna a very stable cell?
the double helix
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what is a difference between eukaryotic dna and prokaryotic dna?
Eukaryotic dna is linear and wound around proteins ( histones) where are Prokaryotic dna molecules are shorter and circular, it condenses into the cell by super coiling.
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what is the protein that dna is wound around to make chromosomes?
a histone
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What are genes?
instructions for proteins ( they code for proteins)
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where are genes found?
on chromosomes
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what are proteins made from?
amino acids
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what determines the order of amino acids in a particular protein?
the order of nucleotide baces
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What is a 'triplet'?
each amino acid is coded for by a sequence of 3 bases
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what are introns?
sections of dna that do not code for aminoacids
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what are exons?
the sections of dna that do code from aminoacids
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How do genes help to determine our nature, development and phenotype?
Because they produce all our proteins and enzymes which enable metabolic pathways, which help determine nature and development
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What is an allele?
and different form of gene that codes for characteristics, eg a gene codes for a blood group and the allele could code for type 0 , type A and type B
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what are gene mutations?
changes in the base sequence of an organisms dna ( they can produce new alleles of genes)
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What is a problem caused by gene mutations?
As genes code for a particular protein, if the base sequence changes, and non functional protein could be produces. Also could cause the active site of enzymes to change so they no longer are specific.
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What passes DNA from one generation to another?
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What is formed when 2 gametes form together at fertilisation ?
A zygote
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what is a diploid number?
each cell contains 2 of each chromosome ( one from mum one from dad) 46 in humans
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what is the haploid number?
only one copy of each chromosome ( half the diploid number) in humans it would be 23
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how many cell devisions are there in meiosis?
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how many cells does meiosis produce?
four haploid cells that are genetically different
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Describe the first devision of meiosis... ( meiosis one)
1) DNA unravels and replicates so there are 2 copies of each chromosome ( chromatids) 2) dna condeses and forms double armed chromosomes 3) (first devision) chromosomes arrange them selves in homologous pairs
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Describe what happens after the first devision of meiosis...(meiosis two)
The homologous pairs are then separated halving the chromosome number. Then there is a second devision, the pairs of sister chromatids that make up each chromosome are seperated. For haploid cells ( gametes) that are genetically different are made
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what is a chromatid?
two copies of each chromosome
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How does 'crossing over' lead to genetic variation?
Crossing over of chromatids in meiosis one means that each of the four daughter cells formed from meiosis contain chromatids with different alleles.
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How does independent segregation of chromosomes lead to genetic variation?
When the gametes are produced different combinations of the maternal and paternal chromosomes go in to each cell.
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what is oxygen carried round the body by?
haemoglobin in the red blood cells
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Describe the structure of haemoglobin...
A large protein with a quaternary structure; made up of 4 polypeptide chains. each with a haem group (iron).
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how many molecules of oxygen can each haemoglobin carry?
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what is formed when oxygen joins haemoglobin?
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Where in the body would you find a low partial pressure of oxygen?
Muscles ( where tissues respire)
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Where in the body would you find a high partial pressure of oxygen?
Alveoli in lungs
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Why are oxygen dissociation curves S-shaped?
because when haemoglobin combines with the first oxygen molecule, its shape alters in a way that makes it easier for other molecules to join too
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What happens as haemoglobin becomes more saturated with oxygen?
its harder for my oxygen molecules to join.
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What does a dissociation curve show?
How saturated the haemoglobin is when oxygen at any given partial pressure
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What is partial pressure?
a measure of oxygen concentration
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What is the affinity for oxygen when there is a high partial pressure
it has a high affinity ( more readily associates)
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What is the affinity for oxygen when there is a low partial pressure?
it has a low affinity ( more readily dissociates)
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What is the Bohr effect?
An effect by which an increase of carbon dioxide in the blood and a decrease in pH results in a reduction of the affinity of haemoglobin for oxygen.
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What are carbohydrates made from?
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Glucose is a monosaccharide.. what are its two forms?
Beta Glucose and Alpha Glucose
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What reaction joins two monosaccharides?
Condensation reaction
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What are the bonds that join sugars together?
Glycosidic bonds
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What are polysaccharides?
loads of sugars joined together
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What is the main energy storage material in plants?
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What does a plant do when it needs more energy ( glucose)?
It breaks down the starch
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what form of glucose is in starch?
alpha glucose
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Describe the structure of starch...
chains of alpha glucose that wind in to a coil, no branches.
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How is starch adapted to being an energy store?
insoluble, so doesnt cause water to enter cells by osmosis ( which would make them well) compact and can be easily hydrolysed back to glucose for respiration due amylopectin being branched.W
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What is the main energy storage material in animals?
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Where is glycogen found?
Liver and muscles
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How is glycogen adapted to storing energy?
its insoluble so will not be effect osmosis, highly branched so enzymes and hydrolyse glucose quickly, which is also enhanced by its shorter chains
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Where is cellulose found?
The cell walls of plant cells
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What form of glucose is cellulose made from?
Beta glucose
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Describe the structure of cellulose...
Long unbranched chains of beta glucose, in which the bonds between the sugars are straight. Cellulose chains are also linked by hydrogen bonds to form microfibrils.
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What about cellulose provides plants their strength?
They have hydrogen bonds linking chains together , this makes microfibrils, which provide support for the cells.
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Give three structures found in plant cells but not in animal cells..
Cell wall, permanent vacuole, chloroplasts.
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What membrane surrounds chloroplasts?
a double membrane and a thylakoid membrane
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thylakoid membrane are stacked up in the chloroplast to form what?
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What links grana together?
lamellae ( thin flat pieces of lamellae)
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Where does photosynthesis happen in the chloroplast?
In the grana and some parts in the stroma.
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What are the two main stages of cell devision?
Nuclear devision and cell devision
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What are the 4 requirements for semi conservative replication?
1)4 types of nucleotide, each with bases of adenine,guanine,thymine and cytosine 2)both strands of dna must act as a template for attachment of these nucleotides 3)enzyme dna polymerase must catalyse reaction 4)source chemical energy(driveprocess)
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Describe semi-conservative replication..
DNA helicase break the hydrogen bonds linking base pairs of DNA. Double helix seperates and unwinds. Each polynucleotide strand acts as a template for complementary nucleotides. Energy activates nucleotides. DNApolymerase joins nucleotides together
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If an inhibitor or DNA polymerase were introduced into a cell, explain what the effect would be on dna replication
The linking together of the new nucleotides could not take place. While nucleotides would match up to their complementary nucleotides on the original DNA strand they would not join together to form a new strand
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Which part of DNA contains nitrogen?
The bases
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What does mitosis produce?
two daughter nuclei that have the same number of chromosomes as the parent cell and eachother
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What are the four stages of mitosis?
1) prophase 2) metaphase 3) anaphase 4) telophase
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What happens in prophase during mitosis?
the chromosomes become viable and the nuclear envelope disappears
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What happens during metaphase during mitosis?
chromosomes arrange themselves at the centre of the cell and spindle forms
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what happens during anaphase?
each of the two threads of a chromosome migrates to an opposite pole as they are being pulled but spindle fibres
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What happens during telophase?
( cell devides) chromatids reach the poles and become indistinct. nuclear envelope reforms and organelles disintergrate
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What is happening during interphase?
the cell is actively synthesising proteins and dna replicated prior to mitosis
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What are three main reasons for mitosis making genetically identical daughter cells to parent cells?
1) growth 2)differentiation 3) repair
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What are the three stages of a cell cycle?
1) interphase 2) nuclear devision 3) cell devision
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what are the three sections interphase is devided in to?
G1(first growth)proteins to make organelles are synthesised S (synthesis) dna is replicated G2 (second growth stage) organelles grow and divide and energy stores increased
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What can a mutation during mitosis cause? and how do the drugs used to treat it disrupt the cell cycle?
Cancer, they prevent DNA from replicated and inhibit the metaphase stage of mitosis by interfering with spindle formations
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What is a tissue?
a collection of similar cells aggregated together to preform a specific function
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Give an example ( one for animals one for plants ) of a tissue
For animals: epithelial tissues ( or the skin) For plants: the xylem
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Describe the tissues that are in the organ the stomach
muscle to churn and mix contents. epithelium to protect stomach wall and produce secretions and connective tissue to hold together other tissues
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What is an organ?
a combination of tissues that are co-ordinated to preform a variety of functions
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Describe the tissues that are in an organ of a plant (the leaf)
Palaside mesophyll- carries out photosyntheses, spongy mesophyll- adapted for gaseous diffusion, phloem - to transport organic materials away from leaf xylem - transport water and ions to leaf
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name three organ systems in the human body
1) digestive system 2) respiratory system 3) circulatory system
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Name four general things that need to be exchaged between organisms and their enviroment
1) respiratory gases(02 or CO2) 2) nutrients (glucose, fatty acids, amino acids, vitamins, minerals) 3) excretory products 4) heat
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what has a larger surface area to volume ratio, big animals or small animals?
small animals
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Name some features specialised for exchange surfaces
1) large surface area to volume ratio-2)very thing so that diffusion distance is short 3)partially permeable membrane to allow selected materials cross 4)movement of environmental(air) and internal(blood) medium to maintain diffusion gradient
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name two things are likely to increase genetic diversity
1)increasing variety of alleles within a population 2)mutation of an allele
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name something that is likely to decrease genetic diversity
1) selective breeding
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What process causes plants to constantly lose water?
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what is transpirtation?
evaporation of water through leaves
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How are root hair cells effiecent exchange surfaces?
1) provide a large surface area as they are very long extensions and occur in thousands on each of the branches of a root 2) they have a thin surface layer so materials can move across easily
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why does water move from the soil in to the root hair cell?
because the root hair cell has a lower water potential than the soil , so by osmosis water moves across the water potential gradient
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what is the apoplastic pathway?
water is drawn ( by cohesion tension) along the cell walls of the cells of the root cortex
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what is the symplastic pathway?
Takes place across the cytoplasm of cells in the root cortex as a result of osmosis
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how does water move from one cells cytoplasm to another?
through the plasmodesma ( they are a small opening filled with a strand of cytoplasm)
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How does the symplastic pathway transport water across the root cortex and to xylem?
by setting up a water potential gradient across all of the cells in the cortex
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How is water transported in to the xylem?
Through the active transport of salts in to the xylem to decrease its waterpotential so by osmosis water moves from the endodermal cells and in to the xylem across a water potential gradient
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why does water leave the apoplastic pathway and enters the symplastic pathway at the endodermis? why is this important
because of the casparian strip ( waxy waterproof substance) its important as carrier proteins for active transport are in the living protoplast of the cell, and these decrease the W.P of xylem
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what is the evidence for root pressure?
1) pressure increases with a rise in temperature and decreases at low temps 2)metabolic inhibitors(cyanide) prevent most energy release by respiration and causes rootpressure to stop 3) decrease in 02 causes reduction in root pressure
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what causes root pressure?
active transport of salts into xylem, creating a water potential gradient
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what are the two main factors responsible for movement of water up the xylem?
root pressure and cohesion tension
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Explain cohesion tension
water molecules form hydrogen bonds between one another and stick together (cohesion) water forms a continuous unbroken pathway across the mesophyll cells and down the xylem
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Explain how water is pulled up the xylem because of the transpiration pull?
because on cohesion tension , water forms a continuous pathway across mesophyll cells and down the xylem so when water evaporates from mesophyll cells in the leaf into the air more molecules are drawn up
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state two differences between the apoplastic pathway and the symplastic pathway
1) apoplastic pathway is through cell walls and symplastic pathway is through cytoplasm 2) apoplastic pathway is by cohesion tension and symplastic pathway is by osmosis
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why is the movement of water from an endodermal cell into the xylem passive?
Because only the movement of ions is active, water moves by osmosis as a result of the ions creating a water potential gradient
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Suggest 3 pieces of evidence to support the cohesion-tension theory
1) change in diameter of tree trunks (during day-transpiration is greatest=tension is greatest=more negative pressure so would shrink) 2)if a xylem vessel is broken air enters it so can no longer draw up water (column broken)3)if broken no h20 leaks
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Why is transpiration a necessary evil?
because with out it water would not be so plentiful and the transport of materials would not be so rapid
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Why is transpiration not efficient?
because it loses a lot of water through evaporation through stomata during photosynthesis
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How does light affect transpiration?
stomata open in light and close in dark, so higher light intensity= increase rate of transpiration lower light intensity= decreased transpiration
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How does temperature affect transpiration?
alters kinetic energy of water molecules and relative humidity of air , high temps = increased rate low temps = decrease rate
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how does humidity affect transpiration?
affect the water potential gradient between the air spaces in the lead and atmosphere, low humidity = higher rate high humidity = lower rate
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how does air movement affect transpiration?
changes the water potential gradient by altering the rate at which moist air is removed from around leaf, more air movement = higher rate less air movement = decrease rate
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how can you measure water uptake?
by using a potometer
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what are xerophytes?
plants that are adapted to living in areas where water losses due to transpiration may exceed their water uptake
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What modifications may a plant ( xerophyte) have to reduce the rate at which water is lost through transpiration?
1) a thick cuticle 2) rolling up leaves traps still air 3) hairy leaves to trap moist air
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why might a sample not be representative to a population as a whole?
1) sampling bias 2)chance
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How can you minimise chance in sampling
1)using a larger sample size 2) analysing data collected
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what 3 things can genetic variation arrise from?
1) mutations 2) mixing up of genetic material in meiosis 3) fusion of gametes
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Other cards in this set

Card 2


what are nucleotides made from?


A sugar ( deoxyribose) a phosphate and a base ( a c g or t)

Card 3


what is formed when nucleotides join together?


Preview of the front of card 3

Card 4


Where do the nucleotides join up to make a polynucleotide? and what does it form?


Preview of the front of card 4

Card 5


What bond joins two polynucleotide strands together?


Preview of the front of card 5
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