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Higher Biology Exam Prep
Terms in this set (329)
What is mutagenesis?
Increasing the rate of mutations using a mutagenic agent.
Examples of mutagenic agents?
Ultraviolet light, X-Rays and Mustard gas
What are the problems with strains which have been improved by mutagenesis?
They are often genetically unstable so can undergo reverse mutations and revert back to original state.
What is a downside of breeding programmes?
Desired results are not always guaranteed
What is recombinant DNA technology?
Transfer of genetic material from one organism to another
Why might we want to insert genes to another organism?
Genes that amplify specific steps in a metabolic pathway = increased product yield ; Genes that remove inhibitory control of a metabolic pathway = increased product yield ; Genes that cause the organism to secrete the product into the surrounding environment - easy collection of product ; Genes which prevent the organism surviving in external environments = safety control mechanism
What is recombinant DNA?
DNA which contains host DNA and DNA from another source.
What is a restriction endonuclease?
An enzyme which cuts DNA into fragments at particular sequences.
What is a restriction site?
A genetic sequence which is recognised by a restriction endonuclease
When are restriction endonucleases used?
To remove the required DNA from the donor and to open the plasmids which will receive the DNA
What is meant by sticky ends?
When the cut ends of DNA overlap
What is DNA ligase?
The enzyme used to seal DNA fragments back together
What is a vector?
Something which is used to carry DNA from the genome of one organism to the genome of another (e.g. plasmid)
What are the same restriction endonucleases used to cut the gene and the plasmid?
So that the stick ends of the gene and the plasmid are complementary.
What must be present in a vector for it to be effective?
Restriction site, origin of replication and marker gene
What is the origin of replication
The genes which control the replication of the plasmid and the regulatory sequences which control gene expression
What is the function of marker genes?
To allow us to know if the recombinant gene has been taken up by the bacteria. E.g. only bacteria with the required gene will have a marker gene for antibiotic resistance so only bacteria which survive on that antibiotic have taken up the new gene.
What are the limitations of using prokaryotes to produce eukaryotic proteins in recombinant DNA technology?
They do not carry out splicing and they lack the ability to carry out post-translational modification
How do we overcome the limitations of prokaryotes in recombinant DNA technology?
Use eukaryotes like yeast although they all have more demanding culture conditions.
What is an ethical issue surrounding the use of microorganisms?
Pharmaceutical companies only spend time researching things that will make them money therefore treatments for common diseases are widely researched where as rare disorders are less likely to be cured. ; Companies want to patent their products but can a naturally occurring protein really be patented? ; Due to inability to patent genetic sequences companies keep them secret which some people argue hinders scientific progress.
What is meant by growth medium?
A mixture of chemicals which microorganisms are grown in / on.
What is found in a growth medium?
Energy source and supply of raw materials that can be used to make complex molecules needed for their growth.
What forms of growth media are there?
Broth (liquid) / Agar (solid)
What is a complex growth media?
Contains specific compounds like vitamins or fatty acids which are required by the microorganisms.
What is a simple growth media?
only contains simple chemicals as the organisms can make all of the amino acids required for protein synthesis
What is an example of a complex growth media ingredient?
Why are culture conditions kept sterile?
To avoid contamination by other microorganisms.
What is the name for the technique which allows us to keep conditions sterile?
Which abiotic factors must we control when working with microorganisms?
Temperature, oxygen concentration and pH
Which measure of growth can be used for unicellular organisms?
Measuring the increase in cell number over a period of time.
What is generation time / doubling time?
The time needed for a population to double in number.
What are the four phases of growth in microbes?
Lag phase, log/exponential phase, stationary phase, death phase.
What happens in the lag phase?
Little change in cell number as cells adjust to new growth medium and begin to induce enzymes required to metabolise their substrate.
What happens during the log / exponential growth phase?
The cells multiply at the maximum rate as long as there are no limiting factors.
What happens during the stationary growth phase?
The cells death rate equals the birth rate. Nutrients begin to run out and secondary metabolites start to build up.
What happens during the death phase?
Substrates and nutrients run out and / or toxic metabolites build up to a concentration which leads to the death of the cells. The death rate now exceeds the birth rate.
What is meant by a viable cell count?
Number of cells which are alive and capable of reproduction.
What is meant by total cell count?
Number of cells dead or alive.
What is primary metabolism?
Period of active growth where substrates are being broken down to produce primary metabolites (e.g. amino acids) which are necessary for growth.
What is secondary metabolism?
Phase where secondary metabolites which are not necessary for growth but may provide an ecological advantage to the organism are produced (e.g. antibiotics).
When does primary metabolism occur?
During lag phase and log phase
When does secondary metabolism occur?
During the stationary phase
How can wild strains of micro-organisms be improved?
Mutagenesis, selective breeding and recombinant DNA technology
Why may we want to improve a micro-organism?
Improved genetic stability, ability to grow on low-cost nutrients, ability to vastly overproduce target compounds and allow easy harvesting of target product
What do we call conditions which are beyond an organism's tolerable limits for its normal metabolic rate?
What is dormancy?
A period where organisms have a reduced metabolic rate.
What is predictive dormancy?
When organisms become dormant before the onset of adverse conditions.
What is consequential dormancy?
When organisms become dormant after the onset of adverse conditions.
Where is consequential dormancy more common?
In regions where conditions change suddenly and unpredictably.
What is hibernation?
A form of dormancy that helps an organism survive cold temperatures.
What happens to organisms during dormancy?
Rate of metabolism decreases, heart rate and breathing rate decreases and body temperature decreases
What is aestivation?
A form of dormancy that helps an organism survive hot temperatures / drought.
What happens to organisms during aestivation?
Rate of metabolism decreases, heart rate and breathing rate decreases and body temperature decreases Rate of metabolism decreases
Give an example of an organism that uses hibernation?
Give an example of an organism that uses aestivation?
What is daily torpor?
An organism's metabolic rate is greatly reduced for a period of time in every 24 hour cycle.
Give an example of an organism which uses daily torpor?
Birds - hummingbird
What is migration?
The regular movement by members of a species from one place to another.
Why do organisms migrate?
To avoid periods of metabolic adversity like food shortages or low temperatures.
Why do we study migration?
To find out: When organisms migrate, where they go, how long they stay, how long they live and when they return to their territory
Which specialised techniques can be used for studying migration?
Ringing / banding, electronic tagging, colour marking and using transmitters which send GPS signals
What is innate behaviour?
Behaviour which is inherited and inflexible.
What is learned behaviour?
Behaviour which is gained by experience and is flexible.
Which type of behaviour is thought to play a primary role in migration?
What is a conformer?
An organism which cannot control its metabolic rate and its internal environment is dependent on its external environment.
What are the disadvantages of being a conformer?
Narrow ecological niche and cannot tolerate change
What is an advantage of being a conformer?
Low metabolic costs.
What is a regulator?
An organism which can control its internal environment using physiological mechanisms.
What is an advantage of being a regulator?
Can exploit a wide range of ecological niches
What is a disadvantage of being a regulator?
High metabolic costs.
Give an example of a conformer?
Give an example of a regulator?
What is homeostasis?
Maintaining a stable internal environment.
What is negative feedback control?
A change from the optimum conditions is detected by receptors a corrective mechanism is switched on to bring the conditions back to the optimum.
What is a receptor?
Something which detects change in a condition.
What is an effector?
Something which brings about a change in response to messages from receptors.
How are messages sent between receptors and effectors?
Nerve impulses or hormones.
Why do organisms need to maintain stable body temperatures?
1. To ensure that enzymes have optimum conditions to maintain high metabolic rates. 2. To ensure high diffusion rates of substances. 3. Temperature affects the ability of nerves to send nerve impulses.
Which part of the brain detects changes in blood / body temperature?
What is a thermoreceptor and where are they found?
Detect changes in blood temperature, found in hypothalamus and skin.
How does the hypothalamus receive and send signals?
What are the effectors in thermoregulation?
Sweat glands, skin arterioles, hair erector muscles and skeletal muscles
Describe how sweat glands bring body temperature back to normal when it experiences high temperatures.
increase sweat production, heat energy is used to evaporate the water from the body lowering the body temperature
Describe how metabolic rate changes to bring body temperature back to normal when it experiences high temperatures.
Describe how skin arterioles bring body temperature back to normal when it experiences high temperatures.
arterioles widen increasing blood supply closer to surface of the skin so more heat is lost by radiation.
Describe how hair erector muscles bring body temperature back to normal when it experiences high temperatures.
Relax mean hairs are lowered so less insulating air trapped reducing body temperature
Describe how sweat glands bring body temperature back to normal when it experiences low temperatures.
Decrease sweat production, less heat energy is used to evaporate the water from the body increasing the body temperature
Describe how skin arterioles bring body temperature back to normal when it experiences low temperatures.
vasoconstriction- arterioles narrow decreasing blood supply closer to surface of the skin so less heat is lost by radiation
Describe how hair erector muscles bring body temperature back to normal when it experiences low temperatures.
contract mean hairs stand on end so more insulating air trapped increasing body temperature
Describe how skeletal muscles bring body temperature back to normal when it experiences low temperatures.
shivering which produces heat
Describe how metabolic rate changes to bring body temperature back to normal when it experiences lowtemperatures.
What is meant by metabolic rate?
The quantity of energy used per unit time.
How can metabolic rate be measured?
By measuring the oxygen uptake, heat production or carbon dioxide production.
Which pieces of equipment can be used to measure metabolic rate?
Respirometer or calorimeter.
Where does blood enter the heart?
Where does blood leave the heart?
What do we call the circulatory system of a fish?
Single circulatory system
What do we call the circulatory system of amphibians (and reptiles)?
What do we call the circulatory system of mammals and birds?
Why are incomplete double systems less efficient than complete double?
There is mixing of oxygenated and deoxygenated blood in incomplete so cells are not receiving the maximum quantity of oxygen.
How many chambers does a fish heart have?
How many chambers does an amphibian heart have?
3 - Two atriums, one ventricle
How many chambers do bird and mammal hearts have?
4 - Two atriums, two ventricles.
How do animals adapt to low oxygen niches e.g. high altitude?
Increased production of red blood cells
What is cellular respiration?
A series of enzyme controlled reaction which results in the release of energy from food and regenerates the supply of ATP.
What is aerobic respiration?
Respiration which occurs in the presence of oxygen.
What is fermentation?
Respiration which occurs without oxygen.
What is the summary equation for fermentation in animals (and some bacteria)?
Glucose -> Pyruvate -> Lactate
What is the summary equation for fermentation in plants and yeast?
Glucose -> Pyruvate -> Carbon dioxide + ethanol
What is ATP?
A high energy chemical compound with three phosphates.
What is ADP?
A low energy chemical compound with two phosphates.
How is ATP generated in the cell?
ADP is joined to Pi to create ATP which results in energy being stored.
What happens when ATP is broken down?
Energy is released.
How is it that organisms have a fixed quantity of ATP at all times in their bodies?
As ATP is broken down more ATP is regenerated.
What is phosphorylation?
The addition of phosphate to a molecule- acts as a transfer of energy and makes the molecule more reactive.
Where does the first stage of respiration take place?
What happens in the first stage of respiration?
Glucose -> Pyruvate; NAD -> NADH because DEHYDROGENASE releases electrons and hydrogen ions from the intermediates; 2 ATP used in energy investment phase; 4 ATP made in energy payoff phase
What is the second stage of aerobic respiration known as?
Citric acid cycle
Where does the second stage of aerobic respiration take place?
Matrix of the mitochondria
What happens in the second stage of aerobic respiration?
Pyruvate -> Acetyl group -> Acetyl Coenzyme A + Oxaloacetate -> Citrate
What is required for the second stage of aerobic respiration to occur?
What is the final stage of aerobic respiration which results in the generation of most of the ATP?
Electron transport chain
Where does the final stage of aerobic respiration take place?
The christae of the mitochondria, proteins which make up the electron transport chains are found in the inner membrane.
What is the role of NADH and FADH2 in the final stage of aerobic respiration?
They deliver high energy electrons and hydrogen ions to the electron transport chain.
What is the function of the high energy electrons in the final stage of aerobic respiration?
They provide the energy to pump hydrogen ions across the membrane.
What is the function of the hydrogen ions in the final stage of aerobic respiration?
The hydrogen ions flow back into the matrix of mitochondria causing ATP synthase to produce ATP from ADP + Pi.
What is the function of oxygen in the final stage of aerobic respiration?
Acts as the final hydrogen and electron acceptor. Combines with hydrogen and electrons to form water.
What is the main respiratory substrate?
Which stage of respiration can sugar molecules enter?
Which enzyme is responsible for the synthesis of ATP molecules?
Which enzyme removes hydrogen and electrons from molecules during respiration?
What is metabolism?
All of the enzyme controlled chemical reactions that take place within cells.
What is meant by an anabolic pathway?
Synthesis reaction that requires energy.
What is meant by a catabolic pathway?
Breakdown reaction that releases energy.
What is an example of an anabolic pathway?
Amino acids -> Proteins
What is an example of a catabolic pathway?
Glucose -> Carbon Dioxide and Water (in presence of oxygen)
Why are irreversible steps necessary in some metabolic pathways?
To commit the metabolic pathway to continuing.
Why are reversible steps necessary in some metabolic pathways?
To keep substrates at the required concentrations.
Why are alternative routes necessary in some metabolic pathways?
Allows reactions to proceed with different substrates and enzymes.
What are membranes made out of?
Phospholipids and proteins
Describe the structure of the membrane?
Phospholipid bilayer, flexible, fluid
What are the roles of proteins in the membranes?
Pumps, pores, enzymes, receptors and structural
Why are membranes important?
They increase the rate of reaction.
How are genes and metabolic pathways linked?
Genes need to be expressed to provide the enzymes for metabolic pathways.
What is an enzyme?
A biological catalyst that lowers the activation energy of reactions.
What is activation energy?
The energy required for the reactants to reach the transition state.
What is meant by the "induced fit model"?
When the substrate binds to the enzyme the active site changes shape slightly to fit more closely around the substrate.
What is meant by "affinity"?
Why are enzymes specific?
They only work on substrates which have a high affinity for the active site
Which factors can affect the rate of enzyme activity?
Temperature, pH, substrate concentration and presence of inhibitors
What is an inhibitor?
A substance which decreases the rate of an enzyme controlled reaction.
What is a competitive inhibitor?
An inhibitor which works by binding to the active site of the enzyme because it has a similar shape to the substrate.
How can the effects of a competitive inhibitor be overcome?
By increasing the substrate concentration.
What is a non-competitive inhibitor?
An inhibitor which works by binding to the enzyme at a site away from the active site which causes the active site to change shape.
What is end-product inhibition? (Sometimes known as feedback inhibition)
As the concentration of the end product builds up it can bind to the first enzyme in the pathway thus slowing down the pathway.
How is end-product inhibition useful?
It prevents the build up of end products and the wasteful breakdown of intermediates.
What are protein pores for?
Allow diffusion across membranes.
What are protein pumps for?
Active transport across membranes.
DNA is composed of repeating units called
A DNA nucleotide is made of
Deoxyribose sugar, phosphate, base
The DNA bases are
Adenine, Guanine, Thymine, Cytosine
The shape of a DNA molecule
The 5' end of DNA has what at the end?
The 3' end of DNA has what at the end?
These bonds hold the strands of DNA together and are found between complementary bases
These bonds hold adjacent nucleotides together
Covalent bonds / Strong Chemical bonds
How are adjacent nucleotides held together?
Bond between the phosphate of one nucleotide and the 3 carbon on the sugar of another nucleotide
Which DNA base pairs with Adenine
Which DNA base pairs with Guanine
What is a eukaryote?
Organism with membrane bound organelles and a true membrane bound nucleus.
What is a prokaryote?
Organism which does not have a nucleus and does not have membrane bound organelles.
Where is DNA found in eukaryotes and what form are they in?
Linear chromosomes in the nucleus and circular chromosomes in the mitochondria and chloroplast
Which organisms are eukaryotes?
Animals, plants, fungi (yeast)
Which organisms are prokaryotes?
Where is DNA found in prokaryotes and in what form?
Large circular chromosome, plasmids
What is a plasmid?
Small ring of DNA
Which eukaryotes contain plasmids?
How is DNA packaged in linear chromosomes?
Tightly wound around proteins
Why is DNA said to be antiparallel?
One strand runs in the 3'->5' direction, the other runs in the 5' -> 3' direction.
Which process occurs in the cells before mitosis to ensure each daughter cell gets identical copies of the genetic material?
Where on the DNA strand does DNA replication take place?
Which enzyme is needed for DNA replication?
What is a primer?
A small chain of DNA which provides a starting point for DNA polymerase.
Which direction does DNA polymerase work in?
5' -> 3' direction. (it adds nucleotides on to the 3' end)
What is the role of DNA polymerase?
To add free DNA nucleotides to the 3' end of a growing DNA strand.
Which enzyme joins fragments of DNA together?
Which strand of DNA is synthesised continuously?
Which strand of DNA is synthesised discontinuously?
What is meant by discontinuous replication?
Strand is synthesised in fragments
What is needed in the cell to allow DNA replication?
Template DNA, ATP, free DNA nucleotides, primers, DNA polymerase and ligase
Which process allows us to amplify DNA in vitro?
Polymerase Chain Reaction (PCR)
What are the stages of PCR?
1. Heating up to 92C-98C 2. Cooling to 50C -65C 3. Heating up to 70C-80C
What is required for PCR?
Primers, DNA (Taq) Polymerase, Free DNA nucleotides, Template DNA, buffer
Why is buffer required in PCR?
To keep a stable pH
What is an application of PCR?
Paternity testing, crime scene analysis and working out evolutionary relationships
Why is DNA heated to 92C-98C in PCR?
To separate the two DNA strands by breaking the hydrogen bonds between complimentary bases.
Why is DNA cooled to 50C -65C during PCR?
To allow the primers to anneal to their target sequences.
Why is DNA heated to 70C-80C during PCR?
To allow DNA polymerase / Taq Polymerase to build new strands by adding free DNA nucleotides.
Why are two primers needed in PCR?
One primer for each strand
What is meant by a positive control in PCR?
A control with a known sequence of DNA to show that all of the components are working.
What is meant by a negative control in PCR?
A control which lacks a DNA sequence to show that there is no contamination.
What is meant by genotype?
The sequence of DNA bases
What is meant by phenotype?
The physical and chemical state of the cell determined by the proteins that are synthesised.
What is gene expression?
A gene being transcribed and translated to make a protein.
What chemical elements are proteins made of?
Carbon, hydrogen, oxygen, nitrogen.
What subunits are proteins made of?
What is a polypeptide?
A chain of amino acids joined by peptide bonds.
Which type of bond joins two amino acids together?
What gives a protein its function?
The shape of the protein gives the protein its function.
What gives a protein its shape?
The order of the amino acids and the folding of the polypeptide chain.
What determines the order of amino acids in a polypeptide chain?
The order of DNA bases in the gene which codes for the protein.
Which process produces a primary mRNA transcript?
Which enzyme is required to make a molecule of mRNA?
What are the differences between RNA and DNA
RNA - single stranded, uracil, ribose sugar
What is the first stage in transcription?
RNA polymerase unwinds and unzips DNA strand.
What is the role of RNA polymerase in transcription?
Unwinds and unzips the DNA double helix. Adds RNA nucleotides to form a molecule of mRNA.
What is mRNA?
What is the function of mRNA?
To carry a complimentary copy of the DNA sequence from the chromosomes in the nucleus to the ribosome in the cytoplasm.
What is a ribosome made of?
rRNA and protein
What is the function of the ribosome?
The site of protein synthesis.
Which process allows the formation of a mature mRNA transcript?
What is an intron?
A non-coding section of mRNA
What is an exon?
A coding section of mRNA
What happens during splicing?
The introns are removed and the exons are joined together to make the mature mRNA transcript.
Where does transcription begin?
At a start codon
What is a codon?
Three bases on mRNA which codes for one amino acid
What is tRNA?
What is the function of tRNA?
Have an anti-codon which is complementary to a codon on mRNA. Carries specific amino acids to the ribosome.
What is an anticodon?
Three bases on a tRNA molecule which matches with a codon on mRNA.
What is the process which synthesises a protein using the information carried in mRNA?
Where does translation end?
Which process can allow many different proteins to be produced from one gene?
Alternative splicing and post translational modification
How many codons code for one amino acid?
How many bases are in a codon?
How many bases code for one amino acid?
What is cellular differentiation?
The process by which an unspecialised cell becomes a specialised cell.
How does differentiation occur?
Some genes are switched off and others on.
What is meant by a specialised cell?
A cell with a specific structure and function.
What makes a cell become specialised?
Expressing genes which make proteins specific to the cells.
What is a stem cell?
An unspecialised cell with the potential to self-renew by mitosis or differentiate into specialised cells.
What is a meristem?
A region of unspecialised cells in a plant capable of cell division.
What is an embryonic stem cell?
A stem cell with the potential to become any of the cells required in your body.
What word can be used to describe the potential of embryonic stem cells to become any of the body cells?
What is an Tissue (adult) stem cell?
A stem cell with the potential to become a narrow range of cells required in the body.
What word can be used to describe the narrow differentiation potential of tissue (adult) stem cells?
What is function of Tissue (adult) stem cells?
They provide a supply of differentiated cells needed for growth and repair in organisms.
How can stem cells be used therapeutically?
In bone marrow transplants to treat leukaemia, to treat damaged cornias and to grow skin grafts to treat burns.
How can stem cells be used in research?
To study cellular processes, to use as model cells in drug testing and to investigate causes of disease
What are the ethical implications of using stem cells in medicine or research?
Using embryonic stem cells leads to embryos being destroyed which some people believe is murder but they come from embryos which would have been destroyed any way so people believe they should be used for good
What is meant by "genome".
All of an organisms hereditary information encoded within its DNA.
What is the function of the coding regions of the genome?
Transcribed and translated to make proteins.
What are the functions of the non-coding regions of the genome?
Transcribed but not translated to make tRNA, rRNA and RNA fragments, regulate transcription and protect the ends of chromosomes from fraying
What is a mutation?
A change in an organisms DNA
What are gene/point mutations?
A change in one (or a few) bases in an organisms DNA sequence in one gene.
What are the three gene mutations?
Substitution, insertion and deletion
What happens in substitution?
One base is swapped with another base.
What happens in deletion?
One base is removed from the DNA sequence.
What happens in insertion?
One base is added to the DNA sequence.
Which mutations have a frameshift effect?
Insertion and deletion.
What is meant by a frameshift mutation?
A mutation which alters every amino acid after the mutation leading to a faulty protein being produced.
What is meant by a missense mutation?
Leads to a different amino acid being used so a different protein is produced.
What is meant by a nonsense mutation?
Premature stop codon inserted. Different / no protein produced.
What is meant by a neutral mutation?
A mutation which leads to the same amino acid being produced so no change in protein produced.
What is meant by a silent mutation?
A different but chemically similar amino acid is used to protein still functions correctly.
What is meant by the frequency of mutation?
How often the mutation occurs.
How often do mutations occur?
Randomly and rarely.
What is a mutagen / mutagenic agent?
Something which increases the frequency of mutations.
How can mutations alter gene expression?
If a mutation occurs DNA sequence that regulates transcription then this can lead to transcription being halted.
Which mutation can lead to introns being left in the mature mRNA transcript?
Splice site mutations.
How are mutations beneficial for evolution?
They provide new variation upon which natural selection can act.
What is a chromosome mutation?
A change in the number or sequence of genes on a chromosome.
What are the chromosome mutations called?
Translocation, inversion, deletion and duplication
What happens during translocation?
Genes from one chromosome become attached to the end of another non-homologous chromosome.
What happens in inversion?
The order of genes gets reversed around (ABC becomes CBA).
What happens in duplication?
a section of a chromosome is added from its homologous partner
What happens in deletion?
Some of the genes are removed from the chromosome.
How can duplication result in new characteristics?
The original information is still present so the genes can function. If mutations occur in the extra copies of the gene they can lead to new characteristics.
What is evolution?
The process of gradual change in the characteristics of a population that occurs over many generations.
What is vertical inheritance?
DNA is passed from parents down to offspring.
What is horizontal inheritance?
DNA passed from one cell to another,
Which organisms use vertical gene transfer?
Which organisms can use horizontal gene transfer?
Prokaryotes -> Prokaryotes/Eukaryotes and Viruses-->Prokaryotes/Eukaryotes
What are the benefits of horizontal gene transfer?
Can lead to rapid evolutionary change.
What is natural selection?
The non-random increase in frequency of genetic sequences which increase an organisms chances of survival.
Describe the process of natural selection?
Organisms which are better suited to their environment are more likely to survive and reproduce and are more likely to pass on their genes to the next generation.
What are the three ways that natural selection can affect the frequency of particular traits?
Stabilising, directional and disruptive selection
What is meant by directional selection?
The mean trait shifts towards one of the traits that was less common previously.
What is meant by stabilising selection?
The mean trait is maintained and more organisms sow the mean trait reducing genetic diversity.
What is meant by disruptive selection?
The extreme versions of the trait are favoured resulting in two new mean traits. The intermediate traits become less common.
How can you tell if two organisms are the same species?
If they can interbreed to form fertile offspring then they are the same species.
What is speciation?
The formation of new species.
Summarise the events in speciation.
Isolating barrier-->mutations-->natural selection-->many generations-->two new species are formed
What are the three types of isolating barriers?
Geographical, ecological, behavioural.
What is sympatric speciation?
Speciation which occurs as a result of a behavioural barrier.
What is allopatric speciation?
Speciation which occurs as a result of a geographical or ecological barrier.
What is a hybrid zone?
A region where populations can interbreed allowing genes to flow throughout the population.
What is genomics?
The study of genomes.
What is a restriction endonuclease?
An enzyme which cuts DNA at a specific sequence.
What is bioinformatics?
The use of computers and statistics to analyse DNA sequences.
Which types of organisms have had their genomes sequenced?
Model organisms, pest species, viruses and bacteria
How can you tell how closely related species are from the genomes?
The more similarities there are in the DNA sequences the more closely related the species are.
What is phylogenetics?
The study of evolutionary relatedness.
How can we produce phylogentic trees?
Using fossil records and sequence data .
What is a molecular clock?
A way of working out how long ago species diverged by looking at the number of mutations that have taken place. The rate of mutations is assumed to be constant.
What are the three domains of life?
Bacteria, Archaea, Eukaryotes.
What is the sequence of evolution of life on earth?
Prokaryotes -> Photosynthesis -> Eukaryotes -> Multicellular organisms -> Animals -> Vertebrates -> Land plants
What is the use of personal genomics?
Knowing the risk of developing diseases
What is pharmacogenetics?
Being able to prescribe medication that is personalised to a persons genome to make sure it is the correct drug and dosage.
What are the ethical issues associated with personal genomics?
Potential bias from employers, life insurance, and potential distress from knowing about risks of disorders.
What is food security?
Having access to a sufficient quantity and sufficient quality of food.
What is meant by sustainable food production?
Growing food without degrading natural resources on which agriculture depends.
How can we improve crop production with limited area for crop growing?
Growing higher yielding cultivars; Protecting crops from weeds and pests; Using fertilisers; Identifying and reducing the limiting factors of photosynthesis
Why is farming livestock less efficient than farming crops?
Energy is lost at each trophic level
What is an action spectrum?
Shows the rate of photosynthesis at different wavelengths of light.
What is an absorption spectrum?
Shows which wavelengths of light have been absorbed by plant.
Which wavelengths of light are absorbed by chlorophyll?
Which wavelengths of light are absorbed by the carotenoids?
What is the advantage of having the carotenoid pigments?
It extends the range of wavelengths of light that can be absorbed by plants.
What are the three fates of light when it strikes a leaf?
Absorbed, reflected, transmitted
Describe what happens in photolysis?
Light energy excites electrons which are passed into electron transport chains to generate ATP. Energy is used to split water into hydrogen which is picked up by NADP and oxygen which is evolved.
Describe what happens in the calvin cycle?
Carbon dioxide combines to RuBP to form intermediates. Intermediates are combined with hydrogen supplied by NADPH and ATP is used to form G3P. G3P molecules are either combined or used to regenerate RuBP.
Which enzyme is responsible for fixing Carbon Dioxide to RuBP?
Which coenzyme combines with hydrogen and takes it to the calvin cycle?
What happens to the glucose made by photosynthesis?
Either used in respiration, used to synthesise starch, used to synthesis cellulose or used in other biosynthetic pathways.
Citric Acid Cycle (Krebs Cycle)
Electron Transport Chain (ETC)
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