PAPER 2 Flashcards
(693 cards)
1
Q
What is a mutation?
A
A random change to the genetic material.
2
Q
What is a gene mutation?
A
A random change to base sequence of a gene.
3
Q
What is a mutagen?
A
A substance or radiation that can cause a mutation.
4
Q
What is a triplet?
A
A set of the 3 bases in DNA.
5
Q
What is a point mutation?
A
A substitution of one DNA nucleotide for another, changing the triplet.
6
Q
What are the 3 types of point mutation?
A
Silent, missense, nonsense
7
Q
What is a silent point mutation?
A
A change to the DNA base triplet sequence that has no effect on the amino acid sequence in a protein.
8
Q
What is a missense point mutation?
A
A change to the DNA base triplet sequence that leads to a change in the amino acid sequence in a protein.
9
Q
What is a nonsense point mutation?
A
A change to the DNA base triplet sequence resulting in a termination triplet that leads to a truncated protein.
10
Q
What is an indel mutation?
A
Insertion or deletion of one DNA nucleotide causing a frameshift.
11
Q
What is a frameshift?
A
A change to every DNA base triplet downstream of an indel mutation.
12
Q
Give an example of chromosome mutations.
A
Deletion / duplication / translocation / inversion
13
Q
What is translocation in chromosome mutations?
A
A section of a chromosome breaks off and joins another non-homologous chromosome
14
Q
What is inversion in chromosome mutations?
A
A section of a chromosome breaks off and is reversed before joining back onto the chromosome
15
Q
What is the main example of gene expression control in prokaryotic cells?
A
lac operon
16
Q
What is the function of the enzyme lactose permease?
A
Allows lactose to enter a bacterial cell.
17
Q
What is the function of the enzyme beta-galactosidase?
A
Hydrolyses lactose into glucose and galactose.
18
Q
What are the 4 components of the lac operon?
A
promoter, operator, lacZ structural gene, lacY structural gene
19
Q
What is a structural gene?
A
A gene that codes for a functional protein.
20
Q
What is a regulatory gene?
A
A gene that codes for a transcription factor which initiates/inhibits transcription of structural genes
21
Q
What does the gene lacI code for?
A
Repressor protein
22
Q
What does the gene lacZ code for?
A
Beta-galactosidase
23
Q
What does the gene lacY code for?
A
Lactose permease
24
Q
Where does the repressor protein bind in the lac operon?
A
Operator
25
Where does RNA polymerase bind in the lac operon?
Promoter
26
What is the inducer for the lac operon?
Lactose
27
What is the effect of lactose on the repressor protein?
Binds to the repressor protein, altering its shape and preventing it from binding to the operator region of the lac operon.
28
What conditions are necessary for the lac operon to be switched off?
Glucose present, lactose absent
29
What conditions are necessary for the lac operon to be switched on?
Glucose absent, lactose present
30
How can the action of RNA polymerase in lac operon be up-regulated?
Binding of the CRP-cAMP complex to RNA polymerase
31
How does cAMP levels within the cell affect the rate of lactose metabolism? Explain with reference to the lac operon.
Move glucose into cell decreases cAMP levels --> less transcription of lac operon --> less lactose metabolised
32
Give one way of transcriptional control in eukaryotic cells.
Converting heterochromatin to euchromatin
33
What is heterochromatin?
Tightly wound DNA around histones during cell division, visible under light microscope
34
What is euchromatin?
Loosely wound DNA during interphase, invisible under light microscope
35
At which state would the DNA be during cell division - heterochromatin or euchromatin?
Heterochromatin
36
At which stage of cell division would gene expression occur?
Interphase (G1 + G2)
37
Why can gene expression only occur with euchromatin?
Loosely wound DNA, therefore RNA polymerase can access/bind to genes
38
Explain how heterochromatin is converted to euchromatin.
Aceylation or phosphorylation of histones --> decrease its positive charge so negatively charged DNA is less attracted to it
39
Explain how euchromatin is converted to heterochromatin.
Methylation of histones --> make histones more hydrophobic to bind to each other more, wounding up the DNA more tightly
40
Give one way of transcriptional gene regulation.
Transcription factors
41
What are transcription factors?
Proteins or non-coding RNA that regulate the transcription of genes.
42
What 2 areas do transcription factors bind to?
Promoters, enhancers
43
What has happened if a transcription factor has repressed a gene?
The TF has attached to the promoter, preventing the attachment of RNA polymerase and expression of the gene.
44
What has happened if a transcription factor has up-regulated a gene?
The TF has attached to the enhancer, aiding the attachment of RNA polymerase to the promoter and expression of the gene.
45
Give one way of post-transcriptional gene regulation.
Maturing of mRNA through removal of introns.
46
What is an intron?
A non-coding region of DNA / RNA.
47
What is an exon?
A coding region of DNA / RNA.
48
What is pre-mRNA?
mRNA containing both introns and exons.
49
What is mature mRNA?
mRNA containing only exons (introns have been removed).
50
What is alternative splicing?
The joining of exons in a region of mRNA in different combinations resulting in one gene encoding more than one protein.
51
Give one way of translational gene regulation that up-regulates translation.
Activating initiation factors (through phosphorylation by kinases) to help mature mRNA to bind to ribosomes
52
Give one way of translational gene regulation that inihibits translation.
Degrade mRNA / Inhibition proteins bind to mRNA to prevent it from binding to ribosomes
53
Give one way of post-translational gene regulation.
Cyclic AMP to activate CRP or kinases / protein modification or further folding
54
What enzyme catalyses the formation of cyclic AMP from ATP?
Adenyl cyclase
55
What activates protein kinase A (PKA)?
Cyclic AMP
56
What is the function of protein kinase A (PKA)?
Activate enzymes / transcription factor proteins by phosphorylation.
57
What is a homeobox gene?
A gene controlling the anatomical development of an animal, plant or fungus.
58
Why are homeobox genes highly conserved in plants, animals and fungi?
Highly conserved anatomical structure ensures survival and reproduction
59
What is the homeobox sequence?
A sequence of 180 DNA base pairs found in all homeotic / homeobox genes --> codes for the homeodomain of regulatory proteins
60
What is the homeodomain sequence?
A sequence of 60 amino acids encoded by the homeobox sequence.
61
What is a Hox gene?
A homeobox / homeotic gene found only in animals.
62
What type of genes are homeotic / homeobox / Hox genes?
Regulatory
63
How many Hox gene clusters are found in humans?
4
64
What is apoptosis?
Programmed cell death
65
How is apoptosis different to cell death due to trauma?
Apoptosis does not involve hydrolytic enzymes.
66
What is a bleb in terms of apoptosis?
A protusion from a cell early on in apoptosis.
67
What are 4 cell signals that can induce apoptosis?
Cytokines, hormones, growth factors, nitric oxide
68
What are 4 uses of apoptosis in plant and animal tissue development?
Separation of limbs and digits in embryonic development, removal of anti-self T/B lymphocytes, immune response to viral infection, prevent tumour growth
69
What is a genotype?
An individual's unique genome / collection of alleles.
70
What is a phenotype?
The visible characteristics of an individual as a result of their genotype interacting with the environment.
71
What is an allele?
A version of a gene (as a result of mutation).
72
What are the 3 causes of genetic variation in a population?
Mutation, meiosis, random fertilisation
73
What are the 3 causes of genetic variation that occur during meiosis?
Crossing over / chiasmata / allele shuffling, independent assortment in meiosis I, independent assortment in meiosis II
74
When does allele shuffling due to crossing over occur during meiosis?
Prophase I
75
When does independent assortment of chromosomes occur during meiosis?
Metaphase I
76
When does independent assortment of chromatids occur during meiosis?
Metaphase II
77
What are the 4 chromosomal mutations that can occur during meiosis?
Deletion, inversion, translocation, duplication
78
What are the 3 features of discontinuous genetic variation?
Qualitative differences in phenotype, no intermediate phenotypes, usually monogenic
79
What are the 3 features of continuous genetic variation?
Quantitative difference in phenotypes, a range of phenotypes, polygenic
80
Name 2 examples of environmental variation.
Dialect / accent, scar
81
What is a gene locus?
The position of a gene on a chromosome.
82
How many alleles are inherited for a single gene?
2
83
How many dominant alleles are needed for its phenotype to be expressed?
1
84
How many recessive alleles are needed for its phenotype to be expressed?
2
85
What is meant if an individual is homozygous at a gene locus?
Alleles are identical.
86
What is meant if an individual is heterozygous at a gene locus?
Alleles are different
87
What is meant by a true-breeding individual?
An individual homozygous for a particular trait.
88
What does it mean if a characteristic is monogenic?
It is controlled by one gene.
89
What is the expected phenotypic ratio for monogenic inheritance in offspring from heterozygous parents?
0.12569444444444455
90
What is a test cross?
A cross between an individual from the F2 generation and a true-breeding recessive individual in order to determine the F2 individual's genotype.
91
What is the expected outcome for a test cross if the F2 individual is homozygous?
100% dominant phenotype.
92
What is the expected outcome for a test cross if the F2 individual is heterozygous?
50% dominant, 50% recessive phenotype.
93
What is meant by codominance?
Both alleles contribute to the phenotype in a heterozygous individual.
94
What is meant if a gene has multiple alleles?
There are 3 or more possible alleles within the gene pool.
95
What is the human male combination for the sex chromosomes?
XY
96
What is the human female combination for the sex chromosomes?
XX
97
What is meant by the homogametic sex?
Sex chromosomes that are fully homologous and so result in only one type of gamete e.g. XX
98
What is meant by the heterogametic sex?
Sex chromosomes that are not fully homologous and so result in 2 types of gamete e.g. XY
99
What is a sex-linked characteristic?
Characteristic with a gene locus on a sex chromosome.
100
What is an X-linked characteristic?
Characteristic with a gene locus on the X chromosome.
101
How many alleles do males have for an X-linked characteristic?
1
102
How many alleles do females have for an X-linked characteristic?
2
103
Haemophilia is an example of which type of inheritance?
Sex Linkage
104
Calculate the probability of the offspring being a female carrier if the father was a haemophiliac male and the mother carried no alleles for haemophilia.
0.5
105
Fur colour in cats is partly controlled by a gene on the X chromosome. The gene has two alleles, one coding for balck fur and one coding for ginger fur. The two alleles are codominant, so a heterozygous cat has pathces of black and patches of ginger fur, a pattern called tortoiseshell. When a black cat was mated with a ginger male, the F1 generation consisted of black males and tortoiseshell females. What phenotypic ratio would be expected in the F2 generation?
1 black female: 1 tortoiseshell female: 1 black male: 1 ginger male
106
What is dihybrid inheritance?
Inheritance involving 2 genes with loci on different chromosomes.
107
What is the expected phenotypic ratio for dihybrid inheritance in offspring from heterozygous parents?
9:3:3:1
108
What are autosomes?
Chromosome (pairs) that are non-sex chromosomes
109
What is autosomal linkage?
Multiple gene loci located on the same non-sex chromosome and inherited together.
110
What is the expected phenotypic ratio for the inheritance of 2 autosomally linked genes in offspring from heterozygous parents?
0.12569444444444455
111
What is a recombinant genotype?
A genotype only possible due to meiotic crossing over.
112
What is epistasis?
Where one gene masks or suppresses the expression of another gene.
113
What is antagonistic epistasis?
Where one gene suppresses the expression of another gene.
114
What is an epistatic gene?
Gene that prevents the expression of another gene.
115
What is a hypostatic gene?
A gene whose expression is prevented by another gene.
116
What is recessive epistasis?
Where the epistatic gene locus must be homozygous recessive in order to prevent the expression of the hypostatic gene.
117
What phenotypic ratio in offspring from heterozygous parents may suggest recessive epistasis?
0.3771296296296296
118
What is dominant epistasis?
Where the epistatic gene locus must have at least 1 dominant allele in order to prevent the expression of the hypostatic gene.
119
What 2 phenotypic ratios in offspring from heterozygous parents may suggest dominant epistasis?
13:3, 12:3:1
120
Epistasis is shown in the inheritance of corn colour, with gene P that codes for a purple (P) or red (p) pigment and gene C (dominant) allows the expression of gene P. If gene P is not expressed, then the corn remains yellow. If two sweetcorn plants were crossed which were heterozygous for both genes P and C, what would the probability be of the offspring being yellow?
0.25
121
What is complementary gene action?
Where 2 genes contribute to a final phenotype.
122
What 3 phenotypic ratios in offspring from heterozygous parents may suggest complementary gene action?
9:7, 9:3:4, 9:3:3:1
123
What statistical test can be used to determine whether the observed phenotypic ratio is significantly different from the expected ratio?
Chi-squared
124
What form should the null hypothesis for a chi-squared test take?
There is no significant difference between the observed and expected data. Any difference is due to chance.
125
What is the Hardy-Weinberg principle?
In a stable population with no disturbing factors, the allel frequencies will remain constant from one generation to the next, and there will be no evolution
126
What are the 2 Hardy-Weinberg equations?
p + q = 1, p2 + 2pq + q2 = 1
127
What are the 5 assumptions made if the Hardy-Weinberg principle applies to a population?
No mutation, random mating, no migration, large population size, no selection (natural of genetic drift)
128
The deer in a captive population vary in colour. 53 deer are brown and 14 are white. The coat colour of is determined by the gene R/r, where the dominant allele R codes for brown and recessive allele r codes for white. Calculate the frequency of the allele R in the population using the Hardy-Weinberg principle.
0.54
129
What is genetic drift?
Changes in allele frequencies caused by chance events.
130
What are the 2 causes of genetic drift?
Genetic bottleneck, founder effect
131
What is a genetic bottleneck?
When a population dramatically shrinks in size and then increases again.
132
What is the effect of a genetic bottleneck on genetic diversity?
Decrease
133
What is the founder effect?
Establishment of a new, small population of a species derived from a larger, parent population.
134
What is the effect of the founder effect on genetic diversity?
Decrease
135
Selection pressure can affect homozygous individuals. The effect can be investigated using a model gene pool. Why is a large gene pool neccessary?
So the effect of chance variation in gene frequencies are minimised.
136
What is natural selection?
Changes in allele frequencies caused by environmental selection pressures favouring the survival of some individuals over others.
137
What is stabilising selection?
Natural selection that favours normal phenotypes due to unchanged environmental selection pressure
138
What is directional selection?
Natural selection that favours one extreme phenotype due to a change in environmental selection pressure
139
What is disruptive selection?
Natural selection that favours both extremes of a given phenotype due to a change in environmental selection pressures
140
What is speciation?
Splitting of a population into 2 or more reproductively isolated populations.
141
What is meant by geographical isolation?
A population that is separated and reproductively isolated by geographical barriers such as rivers, lakes, mountains.
142
What type of speciation is a result of geographical isolation?
Allopatric
143
What is reproductive isolation?
A population that is separated due to biological and behavioural changes.
144
What type of speciation results in reproductive isolation?
Sympatric
145
What is sympatric speciation?
Speciation that occurs within populations in the same habitat
146
What can lead to sympatric speciation?
Members of two different species interbreed and form fertile offspring (more common in plants), forming a hybrid that usually is infertile/reproductively isolated
147
What is artificial selection?
Selective breeding of a species by humans resulting in a change in allele frequency.
148
What is inbreeding?
Breeding of closely related individuals
149
Describe a problem with inbreeding.
Reducing the gene pool and hence genetic diversity --> reduces their chance to evolve and adapt to environmental changes / Higher chance of inheriting recessive alleles that may cause genetic disorders
150
What is the effect of artificial selection on genetic diversity?
Decrease
151
What is a gene bank?
Storage of genomes within organisms so as to provide possible new alleles for future artificial selection.
152
What are the 2 main ethical objections to artificial selection?
Loss of a species' natural characteristics / behaviour, inbreeding depression
153
What is a DNA probe?
Single stranded piece of DNA that is complementary to a gene of interest. It is attached to a marker (tag) to identify the presence of specific genes
154
Which part(s) of the genome are compared in DNA profiling for forensics
Non-coding regions (introns, STRs, VNTRs, minisatellites, microsatellites)
155
Put these steps for creating a DNA profile in the correct order: Amplification, Visualisation, Extraction, Digestion, Separation
Extraction, Amplification, Digestion, Separation, Visualisation
156
Give 2 uses of DNA profiles.
Paternity testing, forensic investigations, determining how closely related organisms/species are, genetic screening for disease risk
157
State three potential sources of DNA at a crime scene
Hair, blood, skin cells, semen, saliva etc.
158
Two primers are needed in PCR. What is a primer?
Short, single-stranded DNA fragment (used to 'tell' the DNA polymerase the part of DNA to copy)
159
The first step of a PCR cycle is to heat to 95oC. What happens in this step?
Double stranded DNA is searated into two single strands (hydrogen bonds break)
160
What is special about Taq polymerase compared to other DNA polymerases?
Very stable at high temperatures so does not denature
161
The second stage of PCR (after heating to 95oC) is to cool to around 55oC. What is the purpose of this step?
Allow primers to anneal (bind)
162
A PCR mixture must contain DNA polymerase, free nucleotides, buffer, primers and what?
The target DNA sequence to be amplified
163
If the number of DNA fragments doubles in each PCR cycle, how many fragments will there be if one piece of DNA goes through 15 cycles of PCR?
32768
164
What does PCR stand for?
Polymerase chain reaction
165
In gel electrophoresis, is DNA attracted to the anode (+ve) or cathode (-ve)
Anode (DNA is negatively charged)
166
Decribe the movement of small fragments compared to larger fragments in gel electrophoresis
Smaller fragments move further/faster
167
In gel electrophoresis, what are DNA markers?
Mixtures of DNA molecules of known size. They are run in one lane and are used to estimate the sizes of the other DNA samples
168
In gel electrophoresis, what is the gel made of?
Agarose
169
What is the purpose of gel electrophoresis?
Separate DNA fragments in order of size
170
What is a genome?
genes or genetic material present in a cell or organism
171
Give two reasons why new DNA sequencing techniques have improved upon old methods
Quicker, cheaper
172
In order to use the Sanger sequencing method, apart from the DNA sample to be sequenced, what are the four other chemicals needed?
Taq DNA polymerase, a primer, normal nucleotides, chain terminator nucleotides (ddNTPs)
173
How is a terminator base different from a normal nucleotide?
Has a hydrogen instead of hydroxyl group on C3 of the deoxyribose sugar
174
How are the terminator bases altered in order for the sequence of nucleotide to be seen or detected?
Has a coloured fluorescent tag - 4 different colours for different bases
175
Why would the addition of the terminator base stop further extension of the DNA strand in DNA sequencing?
Terminator bases do not have hydroxyl group on C3 of deoxyribose, therefore cannot form phosphodiester bonds with the next nucleotide
176
What is the first step in sequencing a whole genome?
Cut the genome into smaller fragments (and clone into BACs to make a clone library)
177
How are the DNA fragments separated and read in DNA sequencing?
Gel electrophoresis in minute capillary tubes --> separate DNA fragments by size --> They can be read when passing through a laser that reads the colour as they pass through
178
Briefly describe how next-generation sequencing works.
Automated, high-throughput sequencing process: millions of DNA fragments are attached onto a surface and sequenced as clusters at the same time
179
Explpain how genome sequencing can help identify evolutionary relationships.
Closer % match of genome sequence means less time since the two speices diverged from a common ancestor.
180
Bioinformatics is transforming epidemiology. What is epidemiology?
The incidence, distribution, and possible control of diseases (and other factors relating to health)
181
What’s the difference between Bioinformatics and Computational Biology?
Bioinformatics – development of software to process large amount of data produced from sequencing etc. Computational Biology – using that data to create computer models and test theories
182
Name one benefit to sequencing pathogens' genomes.
Find out the source of an infection / Identify antibiotic-resistant bacteria strains to evaluate the use of antibiotics / monitor a disease outbreak / find useful targets in genome when developing new drugs
183
What is proteomics?
Study and amino acid sequencing of an organism's entire protein complement
184
The amino acid sequence is not always what would be predicted from the genome sequence itself. Suggest two reasons why.
1.) Genomes have exons and introns --> introns are removed + spliceosomes join different exons together in different ways to make different proteins; 2.) Protein modification by Golgi apparatus
185
What is DNA barcoding?
Identifying particular DNA sections that are common to all species but vary between them --> useful as comparison for evidence for evolution
186
Once scientists have sequenced a gene they can work out the amino acid sequence of the protein it codes for. How?
Triplet code has been worked out (i.e. all 64 combinations of three bases are known and decoded)
187
What is synthetic biology?
Creating biological molecules from scratch (e.g. "printing" a sequence of DNA)
188
What is recombinant DNA?
DNA molecule artificially generated from different origins (often different species)
189
What is a restriction endonuclease?
Enzyme that cuts a double stranded DNA fragment at a specfic place (its restriction site)
190
What is meant when a restriction enzyme recognition site is said to be 'palindromic'?
It has the same sequence on both strands (reading from 5' to 3')
191
What are 'sticky ends' in genetic engineering?
Complementary single stranded 'overhangs' of DNA which can be used to stick two DNA fragments together.
192
Do restriction enzymes catalyse condensation or hydrolysis reactions?
Hydrolysis
193
What is another method of getting the desired gene apart from using restriction endonucleases?
Use reverse transcriptases
194
What is a reverse transcriptase?
Enzyme that makes a complementary DNA (cDNA) from the isolated mRNA made from the desired gene
195
What does it mean when we say that two DNA fragments are 'annealed'?
Joined together (compatable sticky ends)
196
What process could you describe as the reverse of restriction digestion?
DNA Ligation
197
Name a common vector used in genetic engineering.
Plasmids (also cosmids, viruses, artificial chromosomes such as BACS, liposomes)
198
What is the role of DNA Ligase?
Joins DNA backbone/sugar phosphate backbone (makes phosphodiester bonds) of two DNA fragments together
199
How are restriction enzymes used in genetic modification?
Cut plasmid, isolate gene, producing sticky ends
200
What is electroporation?
Using an electrical current to make cell membranes more porous (to allow plasmids to enter)
201
What is electofusion?
Pass tiny electric currents to the membranes of two different cells to fuse them together, forming a hybrid/polyploid cell
202
What is a transgenic organism?
One that has been genetically altered to include genetic material from another organism
203
Suggest a reason for genetically modifying a plant.
Insect resistance, drought tolerance, pesticide resistance, faster growth, better flavour, slower ripening etc.
204
State a negative aspect of genetically modifying plants.
Create monocultures (susceptible to extinction), chance of gene transfer to create superweeds, expensive to buy
205
What is 'pharming'?
Making medicinal drugs (pharmaceuticals) from genetically modified organisms
206
Give an ethical positive and negative to “pharming”.
Positive– easier/cheaper production of medicine. Negative – long term effects to health of organism unknown, patenting issues.
207
Give a positive and negative ethical issue of geneticially engineering pathogens
Positive - may be able to engineer them to attack cancer cells. Negaive - Risk of mutation/revertion and therefore cause major outbreak of disease, intentialal biowarfare
208
What is gene therapy?
Altering alleles to treat genetic diseases
209
What’s the difference between somatic cell therapy and germ line cell therapy?
Somatic - altering genes in body cells. Germ Line – altering genes in gametes or zygote
210
State a negative feature of somatic cell gene therapy.
Effects are often short-lived, multipple treatments may be needed, hard to target some body cells, allele could go to wrong place and cause a problem, expensive, where do we draw the line? (e.g. should we 'fix' shortsightedness, baldness, hair colour etc.)
211
State a negative feature of germline gene therapy.
Offspring will also carry altered genes - may be unknown long term effects.
212
Why is it harder to treat genetic disorders caused by dominant alleles than disorders caused by recessive alleles?
Recessive allele treatment just needs addition of the "correct" allele anywhere in genome. Treatment of a dominant condition requires that specific gene to be disrupted/silenced. This requires more sppecific placement of inserted DNA.
213
State whether each type of gene therepy (somatic and germline) is legal or illegal.
Somatic = legal. Germline = illegal.
214
State 3 ways in which plants clone themselves.
Sending out runners, making suckers, producing bulbs, producing corms, producing immature plants on the leaves (e.g. kalanchoe), producing tubers,
215
Define micropropagation
Growing large numbers of plants from meristem tissue taken from a sample plant
216
Define tissue culture.
Growing new tissues, organs or plants from certain tissues cut from sample plants
217
In what circumstances would micropropagation be used?
If the plant doesn't produce many seeds, doesn't respond well to natural cloning, is rare, needs to be pathogen free, is GM or selectively bred
218
Outline the steps involved in micropropagation.
Cells removed from the shoot > cells /explants are sterilied before being placed onto the sterile nutrient medium > explants divide to form a callus, small clumps of undifferentiated cells > callus transferred to a new agar medium > plantlets transferred to compost
219
State 3 advantages of cloning plants.
Can produce lots of plants quickly, if aseptic technique is followed the new plants will be disease free, plants can be chosen with desirable traits (high-yielding, pest-resistant, disease-resistant, frost-resistant), infertile plants can be grown, harvesting is easier as all plants have the same genotype,
220
State 3 disadvantages of cloning plants.
Expensive, can fail due to microbial contamination, all cloned offspring are susceptible to the same pest or disease (monoculture), reduces genetic variation in a species.
221
Describe the difference between micropropagation and tissue culture.
Micropropagation produces a large number of plants from a small sample of plant material whereas tissue culture is growing plant cells in an artificial medium, forming large numbers of plantlets (i.e. the first step in micropropagation).
222
Describe how to take cuttings.
Cut a 10cm section from a non-flowering stem of the plant > remove the top leaves > dip the cut end into a rooting powder > push the plant into the compost > add water to the compost and cover the plant with a plastic bag
223
What are explants?
Small pieces of plants cuttings taken
224
How are explants processed before cultured for cloning, and why?
Sterilised using bleach/ethanol/sodium dichloroisocyanurate --> avoid growth of pathogens or microorganisms that may compete with explants for resources during growth (aseptic reasons)
225
What chemicals need to be added to the nutrient agar plates to induce plant development during micropropagation? Give two examples.
Plant hormones: Auxins for shoot growth, cytokinins for root growth
226
State the term given to a ball of unspecialised plant cells produced during micropropagation.
Callus
227
What do we call natural human clones?
Twins.
228
Outline how twins / natural animal clones are formed.
One sperm fertilises one egg > mitosis produces a ball of cells called an early enbryo > the embryo splits and implants in the uterus lining where mitosis continues.
229
Outline how embryo twinning works.
One sperm fertilises one egg > zygote divides to form an embryo > the embryo is split into separate cells > the cells divide by mitosis to form genetically identical embryos > each embryo is planted into a surrogate > offspring are born which are genetically identical to each other.
230
In artificial twinning, explain why the cow needs to be treated with hormones as the first step.
So it super-ovulates to release mature eggs (for collection)
231
In artificial twinning,the offspring are genetically identical to whom?
To each other (all offpsring are clones of each other)
232
Which method is a type of reproductive cloning - Artificial twinning or somatic cell nuclear transfer?
Somatic cell nuclear transfer (SCNT)
233
Outline how somatic cell nuclear transfer cloning works.
A somatic cell is obtained and the nucleus is removed > a donor egg is obtained and enucleated > the somatic cell nucleus is inserted into the enucleated oocyte > electrofusion of the host cell and new nucleus > the transformed egg divides in vitro > the embryo is transferred into a surrogate uterus > the clone is born.
234
In SCNT, which cell becomes enucleated?
Mature egg cell/ovum from a female animal
235
How is the enucleated egg cell fused with the somatic cell nucleus?
Electrofusion
236
Explain why the offspring in SCNT is not an exact clone of the nucleus donor.
Different mitochondrial DNA as mitochondria are inherited from the egg cell donor
237
State 3 advantages of cloning animals.
Desirable traits are selected for and guaranteed to be passed on, infertile animals can be reproduced, do not need to wait for breeding season, increase populations of endangered species,
238
State 3 disadvantages of cloning animals.
Difficult time-consuming and expensive, all are susceptible to the same disease, undesirable characteristics also always passed on, clones tend not to live as long as natural offspring
239
Give one use of animal cloning.
Farming / Pharming / Restore endangered animal populations
240
Name the microorganism used in baking.
Yeast (often Saccharomyces sp.)
241
Explain why bread rises.
Yeast respires, releasing carbon dioxide which gets trapped between crosslinked gluten molecules. As the temperature rises, the carbon dioxide bubbles expand.
242
Name the microorganism used in brewing.
Yeast (often Saccharomyces sp.)
243
Name the type of respiration used by microorganisms during brewing and state the products of this.
Anaerobic respiration (fermentation), producing carbon dioxide and ethanol.
244
Give the balanced symbol equation for fermentation of glucose.
C6H12O6 --> 2C2H5OH + 2CO2
245
Name the type of organism used in making cheese.
Bacteria (e.g. Lactococci and Lactobacilli sp)
246
Which enzyme is used in cheese making and what is the source of this?
Chymosin (from rennet), from the stomach of a calf
247
Describe the steps involved in making vegetarian chymosin (by genetic engineering).
Use genetic engineering - isolate the gene for chymosin from a cow > cut the gene using restriction endonucleases > remove a plasmid from a prokaryotic cell > cut the plasmid using the same restricton enzyme > insert the gene into the plasmid, with H bonds holding the complementary base pairs in place > use DNA ligase to form phosphodiester bonds between the gene and the plasmid > insert the transformed plasmid into a prokaryotic cell > provide aseptic conditions with plentiful nutrients > the prokaryote will express the gene as it divides by binary fission.
248
Name the type of organism used in making yogurt.
Bacteria (e.g. Lactobacillus or Streptococcus)
249
Name the type of organism involved in producing penicillin.
Fungus (Penicillium sp.)
250
Which microorganism is used to make single cell protein / mycoprotein?
Fungus (Fusarium sp.)
251
State the reactants and conditions in the fermenter when mycoprotein is made and explain why each is needed.
Fusrium fungus - to produce the mycoprotein; glucose - respiratory substrate; ammonia - to provide a nitrogen source; sterile oxygen - to ensure aerobic respiration without contaminating the mixture; pH and temperature at an optimum - to ensure maximum growth; water cooling jacket - to remove thermal energy released in respiration; stirring paddles - to ensure thorough mixing of reactants;
252
State 3 advantages of producing and consuming SCP.
Suitable for vegetarians; high protein, low fat; lots can be produced in a short space of time; does not require a lot of land as fermenters are built vertically; can be transformed into different flavours and textures
253
State 3 disadvantages of producing and consuming SCP.
Risk of contamination if fermenter/ reactants are not sterile; have to extract, purify and flavour the mycoprotein; some people may not want to eat fungal protein
254
Is penicillin produced in batch fermentation or continuous fermentation?
Batch
255
Where did insulin historically come from?
Animal pancreases (e.g. pigs)
256
What was the problem with using insulin from animals?
Not very effective as not the same structure to human insulin, difficult to extract in large quantities, ethical concerns about the use of animals to provide insulin, not suitable for use by people with particular beliefs
257
Describe the steps involved in making synthetic insulin.
Use genetic engineering - isolate the gene for insulin from a human pancreas > cut the gene using restriction endonucleases > remove a plasmid from a prokaryotic cell > cut the plasmid using the same restricton enzyme > insert the gene into the plasmid, with H bonds holding the complementary base pairs in place > use DNA ligase to form phosphodiester bonds between the gene and the plasmid > insert the transformed plasmid into a prokaryotic cell > provide aseptic conditions with plentiful nutrients > the prokaryote will express the gene as it divides by binary fission.
258
Is insulin produced in batch fermentation or continuous fermentation?
Continuous
259
Define bioremediation.
The use of microorganisms to clean the soil and underground water on polluted sites.
260
Describe how bioremediation works.
Microorganisms covert toxic substances to less harmful substances.
261
What is the difference between in situ and ex situ bioremediation?
Contaminants are broken down on-site during in situ and taken elsewhere during ex situ.
262
Why is a source of carbon needed when growing microorganisms?
To provide a respiratory substrate
263
Why is a source of nitrogen needed when growing microorganisms?
To allow protein synthesis to occur
264
What is the jelly-like substance called on which microorganisms are often grown?
Agar
265
What is meant by a closed culture?
A culture which has no exchange of nutrients or gases with the external environment.
266
Sketch and label the growth curve for a population of microorganisms in a closed culture.
Correct curve sketched, time x axis, population size y axis, lag phase, exponential phase, stationary phase, death/ decline phase all labelled
267
Describe the lag phase of the bacterial growth curve.
The population does not grow quickly. Reproduction rate = death rate.
268
Explain the lag phase of the bacterial growth curve.
Population is small and is adjusting to new conditions - taking up water / cell growth / synthesising proteins
269
Describe the log / exponential phase of the bacterial growth curve.
The population grows quickly. Reproduction rate > death rate.
270
Explain the log / exponential phase of the bacterial growth curve.
Population has adjusted; microorganisms have enzymes they need; sufficient space and nutrients
271
Describe the stationary phase of the bacterial growth curve.
The population becomes static / no population growth. Reproduction rate = death rate
272
Explain the stationary phase of the bacterial growth curve.
Nutrients and space are running out; waste is accumulating
273
Describe the death / decline phase of the bacterial growth curve.
Population begins to fall. Reproduction rate < death rate.
274
Explain the death / decline phase of the bacterial growth curve.
Nutrients run out; concentration of waste products becomes toxic.
275
Give 1 / 2 / 3 steps you'd take to work aseptically.
Wash your hands, disinfect the working area, work near a Bunsen burner, flame the neck of any bottles upon opening and closing, only open the lid of the Petri dish enough to inoculate the plate, flame any glassware or metal equipment before use
276
Explain why you'd work near a Bunsen burner when working aseptically.
The air warms and rises, preventing any air-borne microorganisms from settling / creates an area of sterile air in which the microbiologist can work
277
How is the nutrient agar medium sterilised when preparing to grow microorganisms?
Heating in an autoclave
278
How is the equipment sterilised when preparing to grow microorganisms?
Heating in an autoclave
279
Describe the conditions when something is placed in an autoclave.
121oC, 15 minutes
280
Explain the conditions in an autoclave.
All living organisms are killed, including bacterial or fungal spores.
281
What is meant by inoculation?
The deliberate introduction of microorganisms to a sterile medium.
282
Name 1 / 2 / 3 / 4 ways of inoculating a medium.
Streaking / seeding / spreading / using a sterile cotton swab to collect microorgansisms and wipe them over the medium
283
Describe the plate streaking technique.
A drop is transfered to the medium using an inoculating loop and drawn into a streak
284
Describe the plate seeding technique.
A sterile pipette transfers a small drop of liquid medium to the agar surface or to the Petri dish before the agar is poured
285
Describe the plate spreading technique.
A sterile glass spreader spreads the inoculating drop over the surface of the agar
286
How is the agar plate stored after inoculation?
Taped at 4 points, incubated at 25oC, placed upside down,
287
Explain the reasons for not sealing the lid to the agar plate using sticky tape after inoculation.
Allows oxygen to enter - preventing the growth of anaerobic pathogens
288
Explain the reasons for incubating at 25oC after inoculation.
Incubating at 25oC prevents growth of pathogens
289
Explain the reasons for storing the agar plate upside down after inoculation.
This prevents drops of condensation falling onto the agar; also prevents the agar drying out too quickly
290
When looking at your plate, how would you distinguish bacterial colonies from fungi?
Bacterial colonies are shiny or smooth whereas fungi look like cotton wool with fluffy hyphae
291
Why would serial dilutions be used in microbiology?
To determine the population size and growth rate of a population of microorganisms
292
Describe how you'd make a serial dilution that has a dilution factor of 10.
Use 1cm3 of broth and 9cm3 of distilled water.
293
Once you have made your dilution series, describe what can be done with it.
Place 1 drop of each dilution onto a sterile agar plate. Allow colonies to form. Count the number of colonies on the plate which is easiest to count. Then multiply by the dilution factor.
294
Describe the difference between primary and secondary metabolites.
Primary metabolites are produced during the normal activities of the microorganism during the log phase whereas secondary metabolites are produced during the stationary phase.
295
Batch or continuous culture: carried out in a closed fermenter, with nothing added or removed?
Batch
296
Batch or continuous culture: microorganisms are left for a set period of time?
Batch
297
Batch or continuous culture: carried out in an open fermenter, with nutrients added and products removed?
Continuous
298
Batch or continuous culture: no idle time and greater product yields?
Continuous
299
Give an advantage of batch culture over continuous culture.
The fermenter can be used for different reactions with each separate use
300
Give a disadvantage of batch culture over continuous culture.
There is lots of idle time between use therefore higher costs
301
Give a disadvantage of continuous culture over batch culture.
Higher risk of contamination due to constant additions and adjustments
302
How is penicillin produced - batch culture or continuous culture?
Batch (fermentation)
303
How are bioreactors cooled?
Using a water jacket
304
Why is it necessary to cool bioreactors?
Reactions are exothermic - heat generated can denature enzymes
305
Which gas is added to aerobic fermenters?
Oxygen
306
Describe and explain the condition of all reactants added to a fermenter.
Sterile - to avoid contamination of the product / to avoid competition from other microorganisms for reactants
307
How are substrates and organisms mixed in a fermenter?
Motor with stirrers / mixing blades (impellers)
308
How is the pH monitored in a fermenter?
Using an electronic pH probe
309
Why is it necessary to monitor and adjust the pH in bioreactors?
Enzyme activity (and therefore growth) is affected by extremes of pH
310
How are fermenters sterilised?
With superheated steam
311
Define immobolised enzyme
An enzyme that is held in place and not free to diffuse through the solution
312
Give 1 / 2 / 3 advantages of using immobilised enzymes.
Extraction costs are lower as enzymes do not mix with the product / the enzymes can be easily reused / a continuous process is made easier as there are no cells requiring nutrients and releasing waste products / the enzymes are protected from extreme conditions so don't get easily denatured.
313
Give 1 / 2 disadvantages of using immobilised enzymes.
Setting up the immobilised enzymes is more expensive / immobilised enzymes are less active so the reaction is slower
314
Name the method described: enzyme molecules are bound to a supporting surface by hydrophobic interactions and ionic links.
Adsorption
315
Name the method described: enzyme molecules are separated from the reaction mixture by a partially permeable membrane
Membrane separation
316
Name the method described: enzyme molecules are bonded to a supporting surface by strong covalent bonds
Covalent bonding
317
Name the method described: enzyme molecules are trapped in a matrix that does not allow free movement
Entrapment
318
What materials can be used as a supporting surface when using adsorption as a technique to immobilise enzymes?
Unreactive material - eg. Clay, porous carbon, glass beads, resins.
319
Give one disadvantage of using adsorption as a method of immobilising enzymes.
Active site may be distorted so enzyme activity may reduce / enzymes can become detached and leak into reaction mixture so need separating or replacing
320
Give one disadvantage of using covalent bonding as a method of immobilising enzymes.
Can be expensive / can distort the active site
321
Give one disadvantage of using entrapment as a method of immobilising enzymes.
Substrate needs to diffuse in to the matrix / product needs to diffuse out so only suitable for processes where substrate and product are small
322
Why is it an advantage to convert glucose to fructose?
Used to produce high fructose corn syrup - much sweeter than sucrose
323
What is the role of lactase?
Converts lactose to glucose and galactose to produce lactose-free milk
324
Define the term 'abiotic factor'
any non-living factor e.g. sunlight
325
Define the term 'biotic factor'
any living factor e.g. predators
326
Give 3 examples of abiotic factors
temperature, light, pH, water, humidity, oxygen availability, edaphic(soil) factors
327
Give 3 examples of biotic factors
Competition, food, territory, breeding partners, predators
328
Describe the importance of soil for plants
Soil provides minerals for growth, water for photosynthesis, anchorage for roots
329
Explain how particle size affects the air content and permeability of soils
small particles - few air spaces, retains water and floods easily eg. clay. large particles - lots of air spaces, does not retain water eg. sand
330
Define the term ecosystem
Made up of all the living organims that interact with one another in a defined area and also the physical factors presetn in that region eg. rock pool
331
Define the term producer
Producer - makes its' own food, usually by photosynthesis to produce biomass ( inlcudes algae and plankton)
332
Define the term carnivore
eats only other animals
333
Define the term herbivore
Eats only plants
334
Define the term Omnivore
Eats both plants and animals
335
Define the term primary consumer
Eats producers, usually a herbivore
336
Define the term secondary consumer
Eats primary consumers, usually an omnivore
337
Define the term tertiary consumer
Eats a secondary consumer
338
Define the term trophic level
Trophic level - position or stage that something occupies in a food chain
339
Define the term biomass
The mass of living material present in a particular place or in particular organisms
340
How do you find the dry mass of an organism?
Organism has to be killed and put in an oven to evaporate the water
341
How do you calculate the net production of biomass made by a primary producer?
Net production = gross production – respiratory losses
342
A group of scientists measured the gross production of a grassland area as 60gm-2yr-1. if respiration loss was 20gm-2yr-1, calculate the net production of this area of grassland
60-20 =40gm-2yr-1
343
Why can't plants use all of the sunlight that hits them?
some parts of a plant do not photosynthesis, some light passes through, some is the wrong wavelength
344
Why isn't all energy transferred to the next trophic level?
some parts of an organism are not digested, some parts are not eaten eg. bones, some is used up for energy for movement/ respiration (respiratory losses)
345
approximately what % of energy is passed to the next trophic level
0.1
346
How do you calculate % efficiency of energy transfer?
net productivity of energy transfer of trophic level/ next productivity of previous trophic level x 100
347
What is the role of a herbicide?
kills weeds that compete with crops - reduces competition
348
What is the role of a fungicide?
kills fungal infections that damage crops
349
What is the role of an insecticide?
kills insect pests that damage and eat crops
350
What is the role of fertiliser?
a chemical that provides crops with the minerals required for growth
351
Why is intensive farming beneficial?
controls living conditions for organisms so that more energy is put in to growing e.g. animals are kept warm and move around less
352
Define the term ecosystem
Self contained unit in ecology made up of biotic and abiotic factors
353
Define the term Community
All the populations of different species living and interacting with eachother in a particular area
354
What is meant by 'nitrogen fixation'?
When nitrogen gas is converted to nitrogen containing compounds
355
Give examples of two types of bacteria that are involved in nitrogen fixation
Azotobacter and Rhizobium
356
Explain why Rhizobium bacteria can be described as mutualistic
Rhizobium live in root nodules in peas and beans and they get carbohydrates from the plant, the plant gets amino acids from the bacteria
357
What is meant by ammonification?
production of ammonia from organic compounds e.g. urea, proteins and nucleic acids
358
Describe the process of nitrification
Ammonium ions --> nitrite ions --> nitrate ions
359
Give the role of nitrosomonas bacteria in the nitrogne cycle
ammonium ions --> nitrite ions
360
Give the role of nitrobacter bacteria in the nitrogen cycle
nitrite ions --> nitrate ions
361
What is denitrification and how does it occur?
when soil nitrates are converted to nitrogen gas. Occurs when sol becomes waterlogged, short of oxygen and carried out by anaerobic bacteria - means that less nitrogen compounds are available to plants.
362
List 3 processes that return carbon dioxide to the atmosphere
respiration, decomposition and combustion
363
name a process that removes carbon dioxide from the atmosphere
photosynthesis
364
Give reasons for the levels of carbon dioxide increasing over the past 100 years
combustion of fossil fuels, deforestation
365
Define the term global warming
the increase in average temperature over the last century
366
Give 3 consequences of global warming
changes in temperature, precipitation, failure of crops, timings of the seasons may change, melting ice caps, flooding of low lying land, increasing extreme weather, alter niches available - loss of species we don't know
367
Give reasons for the levels of methane increasing
increased extraction of fossil fuels, increased decaying waste in landfill, more cattle producing methane, frozen stores are thawing
368
Define the term succession
The process of ecosystem change over time
369
State features of a pioneer species
produce large quantities of easy to disperse seeds/spores, rapid germination of seeds, ability to photosynthesise, ability to fix nitrogen, withstand extreme conditions
370
Define the term deflected succession
A community that remains stable only because human activity prevents succession from running its course
371
Where does primary succession occur?
on land that has been newly formed
372
What is meant by the term 'climax community'?
when the soil is rich enough to support large trees the climax community is formed (may not be large trees if in the Arctic for example)
373
When does secondary succession occur?
on land that has been cleared but where soil remains
374
Give the calculation for estimating population size using 'capture, mark, release and recapture'
population size = (number in first sample x number in second sample) / number in second sample previously marked
375
Define the term abundance
the number of individuals of one species in a particular area
376
Define the term distribution
where a particular species is within the area you are investigating
377
How could you ensure that your sampling method is random?
use a random number generator for coordinates
378
What is a transect?
A transect is a line across an area of land
379
Name 2 types of quadrat
frame quadrat and point quadrat
380
How could you capture fish?
use a net
381
How could you capture insects?
use a sweepnet
382
How could you capture butterflies?
make a pitfall trap
383
Name 2 pieces of apparatus needed for calculating percentage cover of plant species
frame quadrat and measuring tape(transect) (could have species index)
384
How can distribution of organisms be measured?
Using line or belt transect - non-random, systematic sampling
385
Should measuring distribution be random or non-random?
Non-random
386
Give the equation to calculate the estimated plant abundance within an area of 1m2.
(number of individual in sample) ÷ (area of sample in m2)
387
What method is used to find the animal abundance in an area?
Capture-mark-release-recapture technique
388
Name an assumption you make when you use the mark-release-recapture method
marking the organism does not impact its survival / no migration / organisms randomly distribute after first release
389
What is the term to describe the maximum population size that an ecosystem can maintain?
Carrying capacity
390
Why can't populations cannot reach an infinite size?
Limiting factors - Resources are limited.
391
True or false: exponential growth always takes place in real ecosystems.
392
State the term for non living factors.
Abiotic factors
393
What will happen to the population size when abiotic conditions are favourable?
Increase
394
What is a limiting factor?
A factor in a habitat limits the further growth of a population.
395
Are limiting factors abiotic or biotic?
Both abiotic and biotic.
396
What is happening at the lag phase of a populations growth?
Indivuduals are aclimitising to a habitat, low reproduction rate.
397
What is happening at the log phase of a populations growth?
Plenty of resources available in good conditions, population increasing rapidly.
398
What ia happening at the stationary phase of popuation growth?
Rate of reproduction equals mortality, stable population size.
399
What are the names given to the different stages of a population growth curve?
lag, log (or exponential), stationary
400
What does it mean by 'density independent factors'?
They act irrespective of the size of the population.
401
Suggest an example of a denstiy independent factor.
Weather or climate
402
Give 3 examples of limiting factors that are density dependent to birds?
List 2 from: Availablity of food, water, light, oxygen, nesting sites
403
Name the type of competition between individuals of different species.
Interspecific
404
Name the type of competition between individuals of the same species.
Intraspecific
405
In interspecifc competition, what biotic factors could be involved?
Food source, habitat
406
Fill in the gaps: There is a limited supply of resources in ecosystems. Species have .....?.... that allow them to gain resources faster than other species are more likely to survive and therefore ....?....
adaptations / reproduce
407
What is a predator?
Animals that hunt other animals for food
408
What are prey?
Animals that are hunted by other animal (predators) for food
409
What is the relationship between the numbers of a predator and a prey?
When the predator population increases more prey are eaten and the numbers of prey fall. When the prey population decreases there is less food for predator and so their numbers fall.
410
What mechanism controls the predator and prey populations?
Negative feedback
411
Define Preservation.
Keeping a species or habitat as they are now, minimising any human impact.
412
Define Conservation.
A active management process of a species, habitat or ecosystem involving human intervention.
413
Which strategy focuses on improving biodiversity, preservation or conservation?
Conservation strategies.
414
What is biodiversity?
The range and number of different living species in an ecosystem.
415
How is the human population threatening biodiversity?
Over-exploitation of wild populations for food/ disruption and fragmentation of habitats/ introduction of new species to an ecosystem outcompeting native species.
416
What is an important factor of a successful conservation strategy?
Effective education and liason with the local community.
417
Give 2 examples of the strategies that could be used for conservation?
Any 2 from: providing extra food raising the carrying capacity/ restricting dispersal of individuals using fencing/ vaccination of animals against disease/ controling predators or poachers/ preserving habitats by preventing pollution/ moving individuals to enlarge populations.
418
What ethics are involved in a conservation strategy?
All species have value and humans have an ethical reponsibility to look after them.
419
What economic or social reasons might influence the conservation of a species or habitat?
A valuable food source or potential food source/ potential drug sources or potential biological control agent for pests.
420
Cutting down trees in a way in which lets them grow back is known as
Coppicing
421
Without management, grassland would quickly turn into shrubs and then woodland by...
Succession
422
What is sustainable management mean?
Management of an ecosystem to provide resources in a sustainable way avoiding depletion of natual resources.
423
Why have humans had to use more intensive methods of agriculture?
Increasing population
424
What problems has the increasing world population caused to ecosystems?
More intensive land use/ disruption or destruction of ecosystems, reducing biodiversity.
425
How does coppicing provide sustainable timber production?
Woodland is divided in sections, with only one section harvested each year in rotation.
426
What is pollarding of trees?
Branches of a tree are cut back to a point higher up the mainstem from the ground.
427
What is the difference between coppicing and pollarding?
Coppicing cut branches at ground level while in pollarding they are cut above ground level.
428
Why is rotational coppicing good for biodiversity?
Different areas of the woodland will be at different stages of development providing a variety of habitats.
429
Why is large scale clear felling of woodland not good for biodiversity?
Habitats are destroyed on a large scale and the soil is left susceptible to erosion.
430
What land management problems could result from clear felling a large forest?
Erosion of the soil and reduction of soil mineral content.
431
Why is there an optimal distance for planting trees in woodland?
Too close - too much competition for light, producing tall and thin trees, poor quality timber.
432
What are the principles of modern sustainable forestry?
Replace any tree that's harvested/ maintain the ecological function of a forest/ local people should be able to benefit from the forest.
433
What is selective cutting or harvesting in forests?
Removing the largest or most valuable trees.
434
How is selective cutting good for biodiversity?
Only a few trees are removed which leaves the habitat broadly unaffected.
435
How do foresters manage the trees in sustainable woodland to maximise yields?
Control pest and diseases/ only plant tree species that will grow well/ position trees the optimum distance apart.
436
Name two ways of managing fish stocks.
Fishing quotas/ mesh sizes
437
List the prinicples of fish sustainability proposed by the Marine Stewardship Council.
Fish at a level that ensures continuing fish stocks/ fish to maintain diversity of ecosystem/ follow local and national regulations.
438
To allow sustainablity of fish populations, what must happen if there is over fishing?
The fish population must be allow to build back up.
439
What would be the optimum strategy for managing fish populations?
Maintain the fish population at the carrying capacity for that environment, while fishing continues to harvest fish in excess of that capacity.
440
How can human activities affect populations of plant and animals?
Habitat destruction/ competition for natural resources/ hunting/ pollution.
441
What protection areas have humans set up to protect plant and animal species around the world?
Setting up mational parks and reserves/ green belt land/ world heritage sites/ marine protected areas/ areas of outstanding natural beauty.
442
Why has the human population on the Galapagos islands increased?
Increased demand for marine products and increased tourism.
443
How has more building development and increased use of land for agriculture affected the Galapagos islands?
Destruction and fragmentation of habitats.
444
Why has it been difficult to foster a culture of conservation and education on the Galapagos Islands?
Because most residents were not born on the islands.
445
Large areas of the coastal zones have been designated 'No Take' zones. What are they?
No extraction of any resources are allowed, leaving communities undisturbed.
446
What are financial incentives given to farmers for in national parks?
To reduce chemical use/ safeguard hedges/ care for natural habitats.
447
How do they manage cliffs, rock and scree habitats in the Lake District?
Seasonal restrictions on walkers during nesting/ education of visitors/ good maintenance of paths.
448
What is a light microscope used for? Observing living and dead specimins
449
What are the pros and cons of a light microscope? Pros: Cheap
portable
450
What is a laser scanning confocal microscope used for? Creating a high resolution
high contrast image
451
What is a transmission electron microscope be used for? Observing the internal ultrastructure of cells under high magnification and resolution
452
What is a scanning electron microscope used for? Viewing the surface of objets under high magnification and resolution
453
What are the pros and cons of an electron microscope? Pros: Very high magnification and excellent resolution. Cons: specimen has to be dead
very expensive
454
What is the difference between a transmission and an scanning electron microscope? TEM sends a beam of electrons through the specimen
the SEM bounces electrons off the surface.
455
What is the difference between light and electron microscopes? Light uses lenses to focus a beam of light. Electron uses a beam of electrons
focused by magnets.
456
What is an eye piece graticule? A small ruler fitted to a light microscope's eyepiece. It must be calibrated using a stage micrometer before being used to measure specimens.
457
What is a stage micrometer? A millimeter long ruler etched onto a slide. it has 100 divisions
each of 0.01mm or 10 micrometers. It is used to calibrate the eyepiece graticule
458
Why do we stain specimens? To provide more contrast
and make it easier to distinguish certain parts.
459
What is differential staining? Using a stain to distinguish between either 2 different orgaisms
or between organelles of a specimin due to preferential absorbtion of stain.
460
What is the formula to calculate magnification? Magnification = Image size / Actual size
461
What is classification?
The process of putting living things into groups
462
Why do scientists classify organisms?
It makes identification of organisms simpler. It predicts characteristics, comparing one species with others from the group. It identifies evolutionary links.
463
What is taxonomy?
A hierarchical grouping system, where each group is subdivided into smaller groups.
464
What are the eight taxonomic groups in order of largest to smallest?
Domain; Kingdom; Phyllum; Class; Order; Family; Genus; Species.
465
What is the binomial naming system?
A naming system devised by Karl Linnaeus. It uses two (bi) names. The genus and species. The genus has a capitalised first letter.
466
Why is the binomial naming system important?
A species may have many different common names, but the scientific name will be universal.
467
What are the 5 kingdoms in classification?
Prokaryotae, protoctista, fungi, plantae, animalia
468
What are the general features of prokaryotae?
- Unicellular
- No nucleus or membrane bound organelles
- A ring of naked DNA
- No feeding mechanism (nutrients absorbed or created through photosynthesis)
469
What are the general features of protoctista?
- Mainly unicellular
- Nucleus and membrane bound organelles
- Some have chloroplasts
- Some sessile, others have cilia or flagella or move through amoeboid mechanisms
- Nutrients aquired either by photosynthesis, ingesting of other organisms or both. Some are parasitic
470
What are the general features of fungi?
- Unicellular or multicellular
- A nucleus and membrane bound organelles
- A cell wall made of chitin
- No chloroplasts of chlorophyll
- No mechanisms for locomotion
- Body or mycelium made of threads or hyphae
- Saprotrophic (absorb nutrients mainly from decaying material) Some are parasitic
- Most store food as glycogen
471
What are the general features of plantae?
- Multicellular
- A nucleus and membrane bound organelles
- Cell wall made from cellulose
- All contain chlorophyll
- Do not move (some gametes have cilia or flagella)
- Autotrophic (nutrients created through photosynthesis)
- Store food as starch
472
What are the general features of animalia
- Multicellular
- A nucleus and membrane bound organelles
- No cell wall
- No chloroplasts
- Move using cilia, flagella or contractile proteins (sometimes in the form of muscular organs)
- Heterotrophic (nutrients aquired by ingestion)
- Store food as glycogen
473
What are the 3 domains of classification?
Bacteria, archaea, eukarya
474
Why are 3 domains preferred to 5 kingdoms?
1 Fits better with phylogeny
2 There are key differences between prokaryotes and the eucaryotes (other 4 kingdoms)
3 All of the 4 eucaryotic kingdoms have a nucleus
4 There are key differences between bacteria and archaea
475
What is the difference between eukarya, bacteria and archaea in terms of ribosomes?
Eukarya have 80s
Bacteria have 70s
Archaea have 70s
476
What is the difference between eukarya, bacteria and archaea in terms of RNA polymerase?
Eukarya have 12 proteins
Bacteria have between 8 and 10, very similar to eukaryotic ribosome
Archaea have 5 proteins
477
In the new system of classification, what are the 6 kingdoms?
Eubacteria, archaebacteria, protoctista, fungi, plantae, animalia
478
Which group has been divided to form eubacteria and archaebacteria?
Prokaryotae
479
What is the difference between the habitats of archaebacteria and eubacteria?
Archaebacteria - ancient bacteria, live in extreme conditions, such as hydrothermal vents or anaerobic conditions, they can make methane.
Eubacteria - true bacteria found in all environments, bust bacteria are in this kingdom.
480
What is phylogeny?
The name given to the evolutionary relationships between organisms.
481
What are phylogenetics?
The study of the evolutionary history of groups of organisms. How closesly related they are to one another.
482
What is a phylogenetic tree?
A diagram showing the evolutionary history of groups of organisms. They are branched, showing which groups have evolved from a common ancestor.
483
What are the advantages of phylogenetic classification over hierarchical / Linnean classification?
Phylogenetic classification conneects groups based on their relationships rather than thair characteristics; Phylogeny produces a continuum rather than discrete groups; Phylogony gives a better discription of the variety present within groups, rather than giving the impression all groups are equal in age and differentiation.
484
What is evolution?
The theory that describes how organisms change over many years through natural selection.
485
What did Darwin observe to support his thory of evolution through natural selection?
He realised that organisms best suited to the environment were more likely to survive and to reproduceand therefore pass on their characteristics to their offspring. Therefore a species over time will become more adapted to it's environment by having a more advantageous phenotype.
486
What did Darwin notice about the finches of the Galapagos?
He noticed that different islands had different finches, that although they were very similar, and therefore related, that their beaks and claws were different shapes and sizes.
487
What did Darwin determine about the shape of the Galapagos finchs' beaks and their environment?
He linked the shape of the finchs' beaks to the food that they ate. He concluded that the birds with beaks most suited to the available food would survive longer and be more likely to reproduce and pass on characteristics to their offspring.
488
Who was Alfred Wallace?
A contemporary of Darwin who independently developed a theory of evolution.
489
When Darwin published "On the Origin of Species" describing the theory of evolution through natural selection, why was it originally extremely controversial?
He read that fossils were evidence of animals from millions of years ago. He also read about the principle of uniformitarianism. That the Earth is shaped by processes still occuring today, erosion, weathering etc. This gave Darwin the idea that evolution was a very slow process.
490
What are the 3 main sources of evidence for evolution?
Paleontology; comparative anatomy; comparative biochemistry.
491
What is paleontology?
The study of fossils and what they can tell us about the Earth's past.
492
What evidence for evolution is shown in the fossil record?
- Fossils of simple organisms in oldest rocks, more complex organisms in youngest rocks.
- Ecological sequencing is consistent. I.E. fossil plants appear before fossil animals (animals need plant to survive)
- Studying the similarity in fossil anatomy, we can see the links between organisms and the evolution from a common ancestor.
- The link between living and extinct organisms can be investigated.
493
Why is the fossil record not complete?
- Many organisms are soft bodied and therefore decompose
- The conditions aren't right for fossilisation
- Fossils may be destroyed by the Earth's movement
494
What is comparative anatomy?
The study of similarities and differences in the anatomy of living species.
495
What is a homologous structure?
A structure which appears differently in different organisms, but has the same underlying structure, eg the pentadactyl limb of vertebrates.
496
What do homologous structures provide evidence for?
Divergent evolution
497
What is divergent evolution?
The description of different organisms evolving from a common ancestor.
498
What is comparative biochemistry?
The study of similarities and differences in the proteins and other molecules that control life proceses.
499
How are molecules used in comparative biochemistry?
Some molecules are important for all life and remain highly conserved (don't change much). Slight changes in these molecules over time and between species can be used to identify relationships. The greater the similarity, the closer the relationship.
500
Which molecules can be used in comparative molecular biochemistry?
Cytochrome C (used in respiration)
Ribosomal RNA.
501
What are the two types of variation between organisms?
Interspecific and intraspecific
502
What is interspecific variation
Variation between organisms of different species
503
What is intraspecific variation?
Variation between organisms of the same species
504
What are the causes of variation?
1 - Genetic
2 - Environmental
505
What are the causes of genetic variation?
1 - Alleles
2 - Mutations
3 - Meiosis
4 - Sexual reproduction (2 partners)
5 - Chance
506
How do alleles cause genetic variation?
Alleles are varient forms of a gene. Different alleles produce different affects and different characteristics. Individuals of a species may inherit different alleles.
507
How do mutations cause genetic variation?
Mutations are changes to the DNA sequence, and therefore the proteins the genes code for. this can affect the physical and metabolic characteristics.
508
How does meiosis cause genetic variation?
Meiosis is the formation of gametes. During this process the independent assortment of chromosomes and the crossing over (creating chiasmata) occurs. This leads to genetically unique sex cells.
509
How does sexual reproduction (2 partners) cause genetic variation?
During sexual reproduction, the offspring inherits genetics from both parents, therefore being their own different organism.
510
How does chance cause genetic variation?
During sexual reproduction, any 2 of the many gametes are produced could end up combining. This is random fertilisation, it is why siblings differ from one another.
511
Why is there much more variation in sexually reproductive organisms than those which reproduce asexually?
Meiosis, sexual reproduction (2 partners) and chance are all aspects of sexual reproduction. There is therefore more likelyhood of variation through this process.
Asexual reproduction results in the creation of clones.
512
Are animals or plants more likely to be affected by the environment and cause variation? Why
Plants, as they lack mobility.
513
Give an example of a purely environmental variation.
The presence or absence of scars. these can not be inherited.
514
In most cases, what causes variation within a population?
Both genetic and environmental causes.
515
Give an example of a charachteristic that can be affected by both genetic and environmental factors.
Height - you can inherit the genes to allow you to grow, but if your diet is poor, you may not be able to reach your potential height.
Skin colour - your skin colour is determined by genes, though exposure to sunlight and UV rays will darken the skin.
516
It is hard to separate genetic and environmental factors from causing variation. What investigations are done to allow better understanding between nature and nurture?
Twin studies, especially twins who have been separated and brought up in different environments.
517
Into which 2 groups can data on characteristic variation be sorted?
Discontinuous and continuous variation.
518
What is another term for discontinuous variation?
Discrete variation
519
What is discontinuous variation?
Variation that can only be put into particular categories, or results in certain values.
520
Give an example of discontinuous variation.
- An animals sex,
- The shape of a bacteria
- Human blood group
521
What causes discrete variation?
A characteristic purely determined by genetics, typically a single gene.
522
How is discontinuous variation displayed graphically?
Using a bar chart.
523
What is continuous variation?
A characteristic that can take any value within a range. Thare is a gradual change from one extreme to another.
524
What is an example of continuous variation?
- Height
- Mass
525
What causes continuous variation?
- Multiple genes determining that characteristic (polygenes) also influenced by the environment.
526
How is continuous variation displayed graphically?
- Collected on a frequency table
- Histogram drawn
- Curve drawn onto graph
527
Continuous variation typically show what distribution?
Normal distribution.
528
What is normal distribution?
Data that creates a bell curve when plotted.
529
What are the characteristics of normal distribution?
- Mean, median and mode are the same
- Distribution is a bell curve, symetrical about the mean
- 50% of values are less than the mean, and 50% greater
- Most values are close to the mean, the values at the extremems are low.
530
What is standard deviation?
A measure of how spread out the data is.
531
What does the variation look like if there is a high standard deviation?
A large amount of variation.
532
What does the variation look like if there is a low standard deviation?
A small amount of variation.
533
In normal distribution, what are the typical values for the first 3 standard deviations?
1 SD - 68% of values
2 SD - 95% of values
3 SD - 99.7% of values
534
What What do the symbols in the standard deviation formula stand for?
σ - Standard Deviation
∑ - Sum of (add all the numbers together)
x - measured value
x ̅- mean value
n - total number of values
535
What is the Student's t test used for?
Comparing the averages of data values between two populations. (Are two populations statistically similar or different?)
536
What is Spearman's rank correlation coefficient used for?
Considering the relationship between two sets of data. (is there a correlation or not, if so is it positive or negative?)
537
What are the purpose of statistical tests?
To determine wether any relationship or outcome is due to chance, or an outside factor effecting the organisms. It determines the significance of the data.
538
What is a null hypothesis in a Student's t test?
The prediction that there is no significant difference between the populations. Any observed difference is due to chance.
539
What is a null hypothesis in a Spearman's rank?
The prediction that there is no significant relationship between the data. Any observed relationship is due to chance.
540
What are the degree of freedom in a Student's t test?
It describes how much data was collected. It is calculated by (n1 + n2) -2
541
How do you determine significance in a Studen't t test?
The value of "t" is looked up in the Student's t test significance tables comparing the probability value to the degrees of freedom. For the data to be significantly different to chance alone, the value of "t" must be lower that a probability 5% or 0.05.
542
What do the probability values in the significance tables mean?
how likely the effect observed is down to chance. We use the 5% (0.05) probability value.
543
How do you determine significance in a Spearman's rank?
The value of the correlation coefficient is looked up in the Spearman's rank significance tables comparing the probability value to the number of values, "n". For the data to be significantly different to chance alone, the value of "t" must be lower that a probability 5% or 0.05.
544
What are adaptations?
Characteristics that allow an organism to survive and reproduce in it's environment.
545
What are the 3 types of adaptation?
Anatomical; behavioural; physiological.
546
What is an anatomical adaptation?
A physical feature, internal or external.
547
What is a behavioural adaptation?
The way an organism acts, either inherited or learned from parents.
548
What is a physiological adaptation?
A process that goes on inside an organism.
549
Give an example of an anatomical adaptation.
Body coverings - such as a shell, hair or feathers
Camouflage - to blend in with the environment so as not to be seen
Teeth - the shape and type allows different food to be eaten
Mimicry - copying another organisms appearance or sound to fool predators
550
How is Marram grass adapted to stop transpiration?
Curled leaves - minimise exposed area of leaves
Hairs on inside - trap moist air increasing humidity
Sunken stomata - less likely to loose water
Thick waxy cuticle - reduces water loss through evaporation
551
Give an example of a behavioural adaptation.
Survival - eg playing dead
Courtship - eg mating dances
Seasonal - eg migration or hibernation
552
What are the two main types of behavioural adaptation?
Innate; learned
553
What is an innate behaviour?
Instinctive, it is inherited through genes, e.g. avoiding light, building webs.
554
What is a learned behaviour
Developed through experience and observation, e.g. use of tools, language.
555
Give an example of physiological adaptations.
Poison production
Antibiotic production
Water storing
Reflexes
Homeostasis
556
What is convergent evolution?
Where two unrelated species develop traits or characteristics. Same function, but different genetic origin.
557
Why does convergent evolution occur?
The unrelated organisms live in similar environments and are experiencing similar selection pressures
558
What is natural selection?
THe process by which organisms best suited to their environment survive and reproduce, passing on their characteristics to their offspring through their genes.
559
What are the steps involved in natural selection?
1 - Organisms within a species show variation;
2 - Organisms best adapted to a selection pressure are more likely to survive and reproduce;
3 - Successful organisms pass the allele encoding the advantageous characteristic to their offspring;
4 - This proccess is repeated each generation, and the frequency of the advantageous allele increases;
5 - Over a very long time period, this process may lead to the evolution of a new species.
560
What is a selection pressure?
Factors which affect an organisms chance of survival mor reproductive success.
561
What are examples of selection pressures?
Predation;
Competition (mates / resources);
Disease;
Etc.
562
What are modern examples of evolution?
Anti-biotic resistant bacteria;
Peppered moths;
Sheep blowflies;
Flavobacterium.
563
How does anti-biotic resistant bacteria show modern evolution?
Methicillin-resistant Staphylococcus aureus has become resistant to many anti-biotics. As the bacteria were exposed to them, some which were resistant, survived and reproduced. They passed on the allele for resistance.
564
How do peppered moths show modern evolution?
Changes to the environment changed the allele frequency in the peppered moths.
Before the industrial revolution pale moths were camoulfaged against pale trees.
During the revolution, the trees were black with soot. Dark moths were better adapted and their frequency incresed.
After the clean air act, the trees are now clean again, and the pale moths have increased in frequency.
565
How do sheep blowflies show modern evolution?
A pesticide was used to kill off the blowflies.
A resistance quickly appeared, this was passed though generations allowing a resistant population to evolve.
When studied it was revealed that blowflies had a resistance to a previous pesticide.
The mutation of the old allele allowed much more rapid evolution to occur.
566
How do Flavobacterium show modern evolution?
An example of a positive selection pressure.
The bacteria are found in the waste water of nylon producing factories.
A mutation has allowed them to use the waste as an energy source.
The bacteria can now be used in bioremediation.
567
What is biodiversity?
The variety of living organisms in an area.
568
Why is biodiversity important?
Biodiversity allows a balanced ecosystem. Many organisms rely on one another, they are interconnected.
569
Why do humans rely on balanced ecosystems?
They supply us with oxygen, food, and other materials for survival.
570
How can human activities lead to a reduction in biodiversity?
Farming, clearing land for housing can remove biodiversity.
571
What are the 3 ways of measuring biodiversity?
1 - Habitat biodiversity;
2 - Species biodiversity;
3 - Genetic biodiversity.
572
Why is it important to measure biodiversity?
Supports conservation, giving a baseline for scientists to monitor changes.
573
What is habitat biodiversity?
This refers to the number of habitats found within an area. In general the greater the habitat biodiveristy, the greater the species biodiversity.
574
What is species biodiversity?
A measure of the species present within an area. Made of 2 components:
1 - Species richness;
2 - Species evenness.
575
What is species richness?
The number of different species living within an area.
576
What is species evenness?
A comparison of the numbers of individuals of each species in a community.
577
What is a community?
All of the populations of living organisms in a particular habitat.
578
What is genetic biodiversity?
This refers to the variety of genes making up an organism. It also takes into account the different alleles that exist for those genes. This is what created variation within a species.
579
Why is genetic variation important?
Greater genetic variation within a species allows for better adaptation to a changing environment.
580
What is sampling?
Taking measurements of a limited number of organisms of an area.
581
Why is sampling important?
It is often impossible to count / measure all of the organisms in a particular area.
582
What is sampling used for?
It can be used to:
1 - estimate the number of organisms of an area;
2 - estimate a particular characteristic of an organism.
583
What are the 2 ways sampling can be carried out?
Random and non-random.
584
What is random sampling?
Selecting individuals by chance, each individual has an equal likelihood of being selected.
585
How is random sampling carried out?
A random number generator is used, The scientist is not involved in choosing at all. Often 2 tape measures are laid out as a grid, random numbers generate coordinates. Samples are taken here.
586
What is non-random sampling?
This is where the sample is chosen, or selected.
587
What are the 3 main types of non-random sampling?
1 - Opportunistic;
2 - Stratified;
3 - Sytematic.
588
What is opportunistic sampling?
Weakest form of sampling. May not be representative of the population. Measures the organisms conveniently available.
589
What is stratified sampling?
Separating populations into strata (sub-groups). e.g. male / female. Random sampling is done on these proportional to their size.
590
What is systematic sampling?
Different areas within a habitat are defined, and then sampled separately. e.g. the change in organisms as you move inland from the sea.
591
What are two techniques that could be used in systematic sampling?
Line transect and belt transect.
592
What is a line transect?
A line is marked between two points. Samples are taken at specified points. Everything touching the line is counted.
593
What is a belt transect?
2 parallel lines are marked, and samples are taken in the area between the lines. More information gathered than with a line transect.
594
What is an interupted belt transect?
A line transect is drawn. A quadrat is placed at regular intervals. A sample is taken from within the quadrat.
595
What is reliability?
A measure of how representative of the organisms present in the habitat the sampling is. How accurate the sampling is.
596
What can decrease the reliability of the sampling being done?
1 - Sampling bias
2 - Chance
597
What is sampling bias?
Accidental or deliberatly choosing a particular area to sample. This effect is reduced by random sampling.
598
What is chance?
The organisms selected may not be representative of the whole population. Chance can not be removed, but its effect can be reduced by having a large sample size.
599
What are the techniques used in collecting live animal samples?
1 - Pooter;
2 - Sweep nets;
3 - Pitfall traps;
4 - Tree beating;
5 - Kick sampling.
600
How is a pooter used?
It collects small insects by drawing them into a holding chanber by sucking on a mouthpiece.
601
How are sweep nets used?
By sweeping long grass, they collect insects.
602
How are pitfall traps used?
They collect small crawing invertebrates. A hole is dug in the ground which they fall into and can't climb out of.
603
How is tree beating used?
A large white cloth is laid under a tree or bush. This collects invertebrates knocked off as the tree is shaken.
604
How is kick sampling used?
The riverbed is gently kicked to disturb substrate. A net is held just downstream to collect organisms released into the water.
605
How are plants generally sampled?
Using a quadrat. Either frame quadrat or point quadrat.
606
What is a point quadrat and how is it used?
A frame with a horizontal bar. Down which long pins can be dropped. Any plant touching the pin will be recorded.
607
What is a frame quadrat?
A square frame, divided into smaller equal sections. The type and number of each species within a section is recorded.
608
What is the most valid way of sampling an area?
Random sampling using quadrats.
609
What is the most valid way of sampling the change in distribution of species across an area of land?
Laying quadrats along a line or belt transect.
610
How is species richness measured?
A variety of sampling techniques is used to identify all species present in a habitat. A list is created and the total number calculated. An identification key may be used to accurately identify organisms.
611
How is species evenness measured?
A variety of sampling techniques is used to identify both the species, and number of idividuals in those species present in a given habitat. They are then number of individuals per species is compared to identify how evenly distributed they are.
612
What are the different types of data that can be collected using frame quadrats?
1 - Density;
2 - Frequency;
3 - Percentage cover.
613
How and when is density measured using a frame quadrat?
This is an absolute measure of individual plants in a specific area. E.G. count the number of dandelions in 1m2 gives density per square meter.
614
How and when is frequency measured using a frame quadrat?
If the plants are too small to count. Count the number of squares in which they are present. Give this as a percentage of the total number of squares in the quadrat.
615
How and when is percentage cover measured using a frame quadrat?
Used for speed when there is abundant plants which are difficult to count. An estimation of the cover is done by eye, using the quadrat and its squares as a guide.
616
How is the use of quadrats made more reliable?
Multiple samples are taken from an area. The mean is then calculated. To calculate the total cover for that area, the mean value per m2 is multiplied by the total area.
617
How is a mean calculated?
Add the individual results, then divide by the number of repeats.
618
How is animal population size estimated?
Using capture - mark - release - recapture.
619
Why is measuring animal population size difficult?
The animals move about, they may be hidden, they go through different stages of development, so may be hard to identify.
620
What are abiotic factors?
Non-living conditions in a habitat.
621
What are common abiotic factors?
- Wind speed
- Light intensity
- Humidity
- pH
- Temperature
- Oxygen content in water.
622
What formula is used to calculate biodiversity?
Simpson's index of biodiversity.
623
In Simpson's index of diversity, what do D, n and N stand for?
D - Is the measure of diversity
n - is the sum of organisms of a particular species
N - is the total number of organisms of all species
624
When D is calculated in the Simpson's index of diversity, what does it mean?
The value falls between 0 and 1. 0 is no diversity, 1 is infinite diversity. A higher value means a more diverse habitat.
625
What are the characteristics of a low biodiversity habitat?
1 - Few successful species
2 - stressful / extreme. Few ecological niches
3 - Species have very specific adaptations
4 - Simple food webs
5 - Environmental change has a major effect on the ecosystem
626
What are the characteristics of a high biodiversity habitat?
1 - Many successful species
2 - Benign environment, many ecological niches
3 - Species have few specific adaptations
4 - Complex food webs
5 - Environmental change has a relatively minor effect on the ecosystem
627
What is genetic biodiversity?
This refers to the variety of genes making up an organism. It also takes into account the different alleles that exist for those genes. This is what created variation within a species.
628
Why is genetic biodiversity important?
Species with greater genetic biodiversity are more likely to survive changes to their environments. They will be more likely to reproduce, and then allow the species to survive.
629
What are the factors that affect genetic biodiversity?
1 - Mutations
2 - Interbreeding (gene flow)
3 - Selective breeding (artificial selection)
4 - Captive breeding
5 - Rare breeds
6 - Artificial cloning
7 - Natural selection
8 - Genetic bottlenecks
9 - The founder effect
10 - Genetic drift
630
How do mutations affect the genetic biodiversity?
They change the DNA, and can create new alleles. Increases genetic biodiversity.
631
How does interbreeding (gene flow) change the genetic biodiversity?
Individuals moving from one population to another and breeding, will cause alleles to transfer between populations. Increases genetic biodiversity.
632
How does selective breeding (artificial selection) change the genetic biodiversity?
Only a few individuals are selected from a population to breed due to their advantageous characteristics. Decreases genetic biodiversity.
633
How does captive breeding change genetic biodiversity?
Only a few individuals are present in zoos or conservation centers, the gene pool is relatively small. Wild population is often endangered or exdtinct. Decreases genetic biodiversity.
634
How do rare breeds change genetic biodiversity?
Selective breeding has produced a breed of domestic animal/plant which is no longer popular. Therefore the population number is small, and as it has been selected for particular traits, the gene pool is very low. Decreases genetic biodiversity.
635
How does artificial cloning change genetic biodiversity?
Cloning animals and plants produces genetically identical organisms. Decreases genetic biodiversity.
636
How does natural selection change genetic biodiversity?
Species evolve to contain the alleles which code for advantageous characteristics. Over time the alleles for less advantageous characteristics become removed. Decreases genetic biodiversity.
637
How do genetic bottlenecks change genetic biodiversity?
Few individuals from a population survive a catastorphic event. Therefore the gene pool is reduced. Only the alleles of the survivinig members are available to be passed on to their offspring. Decreases genetic biodiversity.
638
How does the founder affect change genetic biodiversity?
A small number of individuals start a new population. They are genetically isolated. The gene pool is small, and gene flow does not happen. Decreases genetic biodiversity.
639
How does genetic drift affect genetic biodiversity?
Due to the random nature of alleles being passed on to subsequent generations, the frequency of a particular allele can vary from generation to generation. In some cases it may even disappear. This effect is more pronounced in populations with a low genetic biodiversity. Decreases genetic biodiversity.
640
What are polymorphic genes?
Genes which have more than one allele.
641
Why are most genes not polymorphic?
By having a single allele for most genes, the basic structure of an individual within a species remains consistent.
642
How can we measure genetic biodiversity?
By measureing the proportion of genes that are polymorphic.
Proportion of polymorphic gene loci = (number of polymorphic gene loci / total number of loci)
643
What is the locus of a gene?
The position of the gene on a chromosome.
644
How does the proportion of polymorphic gene loci relate to genetic biodiversity?
The greater the proportion of polymorphic gene loci, the greater the genetic biodiversity within the population.
645
Describe one way of how deforestation can affect biodiversity.
Trees' species diversity decreases; Habitats destroyed, leading to decline in animal species population/diversity; Forced migration, increasing biodiversity in other areas
646
Describe one way of how agriculture can affect biodiversity.
Deforestation; Hedgerow removals, destroying habitats of small animals; Use of pesticides and herbicides; Monoculture
647
Describe on way of how climate change can affect biodiversity.
Global warming leading to habitats or food sources destroyed
648
Give three reasons for maintaining biodiversity.
Asthetic reasons (for people to enjoy, provide inspirations etc.); Economic reasons (Deforestation leads to soil erosion and desertification, fail to grow crops, potential loss of useful species in research and medicine); Ecological reasons (affect keystone species which then has a knock-on effect on other species and the environment)
649
Define 'keystone species'.
Species that are essential for maintaining biodiversity, have a disproportionately large effect on their environment relative to their abundance
650
What is the difference between 'in situ' and 'ex situ' conservation? Give an example for each.
in situ = within natural habitat (eg. wildlife reserves, marine conservation zones); ex situ = out of natural habitat (eg. zoos, botanic gardens, seed banks)
651
What is the IUCN?
The IUCN updates conservation status of threatened species and also established CITES
652
What is the CITES?
A treaty that regulates the international trade of wild species and their products to prevent over-exploitation
653
What is the Rio Convention?
Made up of 3 parts - sustainable development, stabilise greenhouse gas conc to tackle climate change, combat desertification
654
What is the Countryside stewardship scheme?
UK conservation scheme to make conservation a part of normal faming and land management practice
655
State the kingdom of organism that causes each of the following diseases: tuberculosis, Black Sigatoka, Athlete's foot, malaria
Bacteria, fungi, fungi, protoctists
656
State the kingdom of organism that causes each of the following diseases: blight, ringworm, ring rot, bacterial meningitis
Protoctists, fungi, bacteria, bacteria
657
Give one plant disease caused by each of the following: viruses, bacteria and fungi
Tobacco mosaic virus, ring rot, black sigatoka
658
State three factors that would affect the speed of disease transmission in plants
Overcrowding; poor mineral nutrition; damp, warm, humid conditions; climate change
659
State how the influenza virus is most likely to be transmitted between different humans
Respiratory droplets (inhalation)
660
State four different types of vector that can be used to transmit a communicable disease
Water (e.g. diarrhoeal diseases); animals (e.g. mosquito transmits Plasmodium); wind (carries spores); humans (hands, clothing etc.)
661
State three passive physical defences that prevent plants being infected by a pathogen
Bark, waxy cuticle, thorns, spines, lignified cell walls, cellulose etc.
662
State three active physical defences a plant would employ against an invading pathogen
Callose synthesised and deposited between plasma membrane and cell wall; callose blocks sieve plates in phloem; callose deposited in plasmodesmata between infected cells and their neighbours; lignin added to cell walls; tyloses block xylem vessels
663
State three chemical defences a plant would employ against an invading pathogen
Antibacterial compounds like phenols, alkaloids; terpenes; hydrolytic enzymes like glucanases and chitinases; caffeine; tannins etc.
664
Describe the role of the skin as a primary non-specific defence
Dead outer layer of keratin prevents pathogen entry; skin flora outcompete pathogens for space; oil secretions inhibit pathogenic growth
665
Describe the role of mucous membranes as a primary non-specific defence
Mucus traps pathogens and contains lysozymes; phagocytes engulf and digest pathogens in mucus
666
Which enzyme catalyses the conversion of prothrombin to thrombin
Thromboplastin (thrombokinase)
667
Describe the role of thrombin in the clotting process
Causes the conversion of soluble fibrinogen into insoluble fibrin fibres
668
Describe the process of inflammation as a secondary non-specific response
Mast cells release histamines;
histamines increase permeability of capillaries meaning plasma leaks into tissue fluid (pain and swelling);
vasodilation of arterioles so more blood reaches infected area (heat and redness);
neutrophils attracted to area for enhanced phagocytosis
669
Describe the process of phagocytosis
Phagocyte engulfs pathogen into a phagosome; lysosomes fuse with phagosome to form a phagolysosome; enzymes, hydrogen peroxide and nitric acid break down the pathogen
670
Describe how macrophages process antigens for presentation on their cell surface membrane
Antigen fragments combined with MHC (special glycoproteins in cytoplasm)
671
What name is given to small protein molecules that act as cell-signalling compounds?
Cytokines
672
Describe how neutrophils are specialised for their role
Plasma membrane contains receptors for opsonins, well developed cytoskeleton for phagocytosis, many mitochondria for respiration, many ribosomes to make enzymes, many lysosomes.
673
Opsonins are non-specific. Explain why
Opsonins can attach to many types of pathogen and help the process of phagocytosis, by giving the phagocyte something to bind to. They must be non-specific, so they can attach to many different pathogens.
674
Where do B lymphocytes and T lymphocytes mature?
Bone marrow and thymus respectively
675
What is meant by the term 'autoimmunity' and give two examples of autoimmune diseases
Destruction of self-tissue; rheumatoid arthritis, lupus, type I diabetes
676
What is the role of T regulatory cells?
Dampen down the immune response; prevents destruction of self tissue (autoimmunity)
677
Describe how an antigen presenting cell leads to large numbers of T helper cells
APC binds specifically to a Th cell (clonal selection). This selected Th cell then proliferates by mitosis (clonal expansion)
678
Describe how B lymphocytes are activated and the role of activated B lymphocytes
Th cell binds specifically to B lymphocyte; B lymphocyte differentiates into a plasma cell. Plasma cells release antibodies specific to the particular antigen
679
Describe how T killer cells destroy a virally infected cell
Release perforins which punch holes in the membrane of the cell; Tk cell inserts channels through which it floods hydrogen peroxide/nitric acid/hydrolytic enzymes
680
Dinstinguish clearly between an antigen and an antibody
An antigen is a cell-surface molecule that is specific to the cell (and a particular antibody); an antibody is an immunoglobulin manufactured by the plasma cells (which binds specifically to an antigen).
681
Antibodies are made by plasma cells. Explain how plasma cells are specialised for their role
Plasma cells have a lot of ribosomes, rough endoplasmic reticulum, Golgi apparatus and mitochondria.
682
Describe how opsonins function
Opsonins bind specifically to an antigen on a pathogen (via the variable region), clearly marking the pathogen for destruction by a neutrophil. A neutrophil will bind to the constant region of the opsonin and destroy the pathogen by phagocytosis
683
Describe how agglutinins function
Agglutinins cross link pathogens by binding specifically via their variable regions. Pathogens are clumped together (agglutinated), meaning they cannot enter host cells and are easier to phagocytose
684
Describe how antitoxins function
Neutralise toxin molecules released by a pathogen through direct binding
685
Describe how the structure of an antibody enables it to perform its function
The variable region is specific to the antigen – it has a shape that is complementary to the shape of the antigen; the disulfide bridges hold the four polypeptide chains together; the hinge region allows some flexibility so that the molecule can bind to more than one antigen; the constant region may have a shape that can be recognised by the neutrophils.
686
Explain why it may take several days for the primary immune response to become effective
After infection, the pathogen must be detected and attacked by macrophages; antigen presentation occurs to select the correct B and T cells (clonal selection); these cells must reproduce in clonal expansion; then they must differentiate to form plasma cells; the plasma cells must start to produce the antibodies – each step takes time.
687
Explain why a secondary immune response is so much faster than a primary immune response
B memory and T memory cells are circulating in the blood. On second encounter with a pathogen, the correct B/T memory cell is clonally selected and can very quickly differentiate into correct specific Th/Tk/plasma cell. Plasma cells can produce antibodies faster, sooner and in much greater quantity. Pathogens are wiped out before symptoms are experienced; level of antibody stays higher for longer
688
Give an example of both natural active immunity and natural passive immunity
Natural active - antibodies made by immune system in response to infection; natural passive - antibodies provided via placenta/breast milk (useful in developing immune system)
689
Explain why passive immunity only provides short-term immunity
Passive immunity is provided by an external supply of antibodies – these are proteins and will not last long in the body. They may even act as antigens and be attacked by antibodies from our immune system.
690
Give an example of artificial active immunity
Immunity provided by antibodies made in response to vaccination (dead/inactive pathogens injected)
691
Define the term epidemic
A rapid spread of disease through a high proportion of a population (usually within a country)
692
Describe the difference between herd vaccination and ring vaccination
Herd vaccination is where everyone, or almost everyone, is vaccinated. Ring vaccination is vaccinating people around the site of the outbreak, so that the pathogen will not be transmitted across that ring to the whole population.
693
Describe how a microorganism can become resistant to an antibiotic
Bacteria that survive a treatment will be slightly resistant to the antibiotic and the antibiotic acts as a selective force which selects the resistant individuals. When they reproduce, some of their offspring may be more resistant, thus resistance evolves.
