Unit D Scofield Reset Flashcards
(89 cards)
1
Q
D1.1
16 Step Process of DNA Replication
A
- Occurs in S stage of interphase
- Semi-conservative
- Each strand of parent DNA used as template for synthesis
- Helicase separates strands and unwinds helix at replication origin
- Hydrogen bonds between strands broken
- RNA primer synthesised on DNA by DNA primase
- DNA polymerase III adds nucleotides to 3’ end
- Synthesised in 5’ to 3’ direction
- Complementary base pairing
- Adenosine-Thymine, Cytosine-Guanine
- Continuous on leading strand
- Discontinuous Okazaki fragments on lagging strand
- DNA ligase joins Okazaki fragments by forming phosphodiester bonds
- DNA polymerase I removes primers and replaces them with DNA
- DNA polymerase III removes mismatched nucleotides from the 3’ terminal and replaces it with a correct nucleotide
- Energy obtained from the double hydrolysis of deoxynucleoside triphosphate
DNA pol III has multiple domains, but polymerisation and proofreading ar
2
Q
D1.1
7 Differences and 2 Similarities between Prokaryotic and Eukaryotic Genetic Material
A
Differences
- Associated with histones or not
- One vs many chromosomes
- Introns or not
- Replication points
- Circular vs Linear
- Plasmid or not
- In nucleoid vs in cytoplasm
Similarities
- Both are DNA
- Mitochondrial and chloroplast DNA similar to prokaryote DNA
Yes that has showed up in a markscheme before.
3
Q
D1.1
7 Step Process of Polymerase Chain Reaction
A
- Denaturation - DNA heated to 95’C using thermal cycler ⇒ Hydrogen bonds disrupted, DNA helix unwinds
- Annealing - Cooling to 54’C for primer binding
- Elongation - Heating to 72’C for addition of nucleotides by Taq-polymerase, Polymerase adds nucleotides to 3’ end
- Final Elongation - Temperature maintained to ensure complete elongation
- Final Hold - Cooling to below 20’C for temporary storage
- The start and end of the DNA sequence are amplified
- The sequence of Denaturation, Annealing, and Elongation is repeated to amplify DNA
PCR is good because of its efficiency but is prone to error, as Taq does
4
Q
D1.1
5 Step Process of Gel Electrophoresis
A
- Amplified DNA is fragmented using restriction endonucleases
- DNA sample is placed in well in agarose gel
- Negatively charged DNA is attracted to anode
- Fragments separate by charge and size
- Staining with ethidium bromide allows them to be seen under UV
5
Q
D1.1
8 Step Process of DNA Profiling
A
- Unique minisatellite = non-coding regions of DNA with tandem repeats
- Tandem repeats (at one locus) vary in number of times sequence repeats / represent different
alleles for one locus - DNA sample cut by restriction enzymes into fragments;
- DNA are amplified at specific genetic sites with PCR;
- Fragments are separated bygel electrophoresis;
- fluorescent/radioactive label attached to different tandem repeats
- Combinations of
alleles are specific to an individual; - Use comparisons/similarities between fragment patterns to determine paternity/evidence match to a
suspect’s profile / other example of comparison/similarity
6
Q
D1.1
Evidence of Semi-Conservative DNA Replication
A
Meselson and Stahl (1958)
* grow G1 bacteria in N-15 enviroment
* grow G2 bacteria in N-14 environment
* G1 is N-15 only
* G2 is N-15 + hybrid
* G3 is N-14 + hybrid
7
Q
D1.2
11 Step Process of Transcription
A
- Antisense strand is used as template
- Regulated by transcription factor, eg. promoters and enhancers
- RNA polymerase and helicase separates strands of DNA
- Unwinding of double helix exposes 10-20 bases for pairing with RNA nucleotides
- RNA nucleotides match to complementary bases
- 5’ to 3’ direction
- Adenine with Thymine and Cytosine with Guanine, but RNA has Uracil instead of Thymine
- Hydrogen bonds between RNA nucleotide and complementary DNA base
- Energy obtained from the double hydrolysis of deoxynucleoside triphosphate
- Terminator sequence signals end of transcription
- mRNA detaches from DNA
8
Q
D1.2
4 Types of Post-transcriptional Modification
A
- snRNP spliceosome splices introns and joins exons/ highly conserved sequences
- Alternative splicing produces different exon combinations from a single gene
- Terminal transferase binds to the 3’ of pre-mRNA and attaches the poly-A tail
- Modified guanine nucleotide attaches to 5’ (5’ cap)
Protects mRNA from enzymatic degradation and increases diversity
9
Q
D1.2
Example of Alternative Splicing
A
In babies, troponin is spliced to give higher sensitivity to Ca2+ and higher tolerance to acdiosis. Alternative splicing of the pre-mRNA several weeks later results in lower senstivity and lower tolerance.
Babies’ muscles are not very strong, which is why they need more sensiti
10
Q
D1.2
4 Functions of Telomeres
A
- Protect against enzymatic degradation
- Prevent the loss of genes from the 5’ end during replication
- Prevent ends of DNA from attaching to each other (the cell would be killed otherwise)
- Recognition sites for telomerase allows telomeres to length and to regenerate upon cell division
Since prokaryote DNA is circular, they do not need telomeres.
11
Q
D1.2
4 Examples of Non-Coding DNA
A
- Introns
- Telomeres
- Gene Regulators
- Genes for rRNA and tRNA
12
Q
D1.3
14 Step Process of Translation
A
- Initiation, Elongation, Termination
- mRNA binds to small subunit, tRNA binds to large subunit
- Ribosome slides along mRNA to start codon
- met-tRNA binds to AUG start codon
- tRNA anticodon pairs with mRNA codon
- Complementary base pairing of RNA bases between codon and anticodon
- Second tRNA codon moves from A site into P site to pair with next codon
- Peptide bond forms between amino acid of P site tRNA and existing chain
- P site holds the tRNA attached to the polypeptide chain
- Ribosome moves along mRNA by one codon
- Movement from 5’ to 3’ direction
- tRNA without amino acid detaches from E site
- tRNA activating enzymes link amino acids to specific tRNA
- Until stop codon reached
13
Q
D1.1
4 Types of Post-Translation Modification
A
- Removal of methionine
- Change of side chains
- Folding or cleaving
- Combination of domains and prosthetic groups to quaternary groups
14
Q
D1.2
3 Step Example of Post-Translational Modification
A
- Signal peptide is cleaved from pre-proinsulin
- C peptide is cleaved from proinsulin
- Insulin is made of A and B peptides bonded by disulfide bonds
15
Q
D1.2
3 Step Description of Proteasome
A
- Organisms maintain their proteome by diet
- Dysfunctional proteins can be recycled into amino acids by proteasome
- Proteasome hydrolyses peptide bonds between residues to supply ribosomes with amino acids
16
Q
D1.3
4 Types of Mutations
A
- Substitution/ SNP
- Insertion
- Deletion
- Inversion
17
Q
D1.3
7 Examples of Mutagens
A
- Mustard Gas
- Nitrous Acid
- Ethyl urethane
- Formaldehyde
- MMS and EMS
- UV radiation
- X-rays
18
Q
D1.3
Neutral vs Silent Mutations
A
- Neutral: mutation in non-coding region - sequence is not translated
- SIlent: degeneracy of genetic code - codes for same protein
19
Q
D1.3
5 Step Process of Gene Knockout
A
- Genetically engineers an organism wiht one dysfunctional gene so that its function can be observed
- Gene is replaced with non-homologous functional sequence
- The stem cell is fused with an embryo to create a chimera
- Adult organism is bred until a pure breeding offspring is produced
- Homozygous offspring are needed to study the gene’s function
20
Q
D1.3
Example of Gene Knockout
A
The p53 gene on chromosome 17 synthesises cell cycle-regulating proteins
21
Q
D1.3
5 Step Process of CRISPR Prime Editing
A
- CRISPR is a bacterial genomic record of viral attacks
- Single guide RNA identifies target sequence
- CRISPR RNA binds to viral sequence
- Cas9 makes a double cut in the sequence
- Reverse transcriptase transcribes a new sequence and replaces the target sequence
22
Q
D1.1
4 Differences between RNA and DNA
A
- Single strand vs double helix
- Ribose vs deoxyribose
- Thymine vs uracil
- One form of DNA, but multiple forms of RNA
23
Q
D1.3
4 Step Process: Cairn’s technique to measure the length of DNA
I used the exact 2022 May TZ2 P2 markscheme.
A
- Grow E. coli in radioactive thymidine in tritium
- Autoradiography and electron microscope
- Produced image of DNA and measured length of DNA
- All strands contained radioactive thymine
24
Q
D1.3
3 Reasons for Highly Conserved Genes
A
- Genes are needed for basic cellular function and survival, eg. for protein synthesis
- Slower mutations rates
- Higher frequency of transcription means the sequence is proofread more often
25
# D2.1
3 Steps of Animal Cell Cytokinesis
1. Actin and myosin pull on plasma membrane
2. cleavage furrow forms
3. cells separate when cleavage furrow forms to the centre of the cell
26
# D1.3
7 Differences and 3 Similarities between Unique and Repetitive Sequences in DNA
- variation between individuals
- sequence length
- proportion of genome
- whether translated or not
- genes or not
- exons vs introns
- number of times occurred
- satellite DNA is repetitive
- repetitive sequences are used for profiling
- prokaryotes do not usually have repetitive sequences
27
# D2.1
5 Steps of Plant Cell Cytokinesis
1. Microtubules assemble vesicle layer
2. Vesicles form cell plate
3. Vesicles build up on cell plate to form plasma membrane and plasmodesmatea
4. Pectins form lamellae
5. Cellulose deposited near lamellae to form cell wall
28
# D2.1
4 Stage, 10 Step Process of Mitosis
- Prophase
1. DNA condenses
2. Microtubules form from Microtubule Organizing Centres
3. Nuclear membrane dissolves
- Metaphase
1. Microtubules attach to kinetochore
2. Spindle fibre put under tension to test correct attachment to centromere
3. Chromosomes align at equator (metaphase plate)
- Anaphase
1. Cohesin loops cut
2. Spindle fibre contraction, pulling chromosomes towards opposite poles
- Telophase
1. Chromosomes are clustered and nuclear membrane reforms
2. DNA uncondenses
29
# D2.1
2 Processes Leading to Genetic Variation in Meiosis
* Crossing Over
* Independent Assortment
30
# D2.1
3 Genetic Diseases caused by Non-disjunction
* Down Syndrome - trisomy 21
* Klinefelter's Syndrome - XXY trisomy
* Turner's Syndrome - X only
31
# D2.1
6 Stages of Cell Cycle
* G0 - cell growth
* G1 - cytoplasm expansion, organelle replication, protein synthesis
* G1 Checkpoint - assess DNA damage
* S - DNA replication
* G2 - cell growth
* G2 Checkpoint - proofreading new DNA
32
# D2.1
2 Types of Genes in regulation of Cell Division
* Proto-oncogenes
* Tumour Suppression Genes
33
# D2.1
3 Purposes of cell proliferation (with examples)
* Plant meristems -- growth
* Early-stage embryos -- growth
* Skin -- routine cell replacement
34
# D2.2
Promoters, Enhancers, Transcription Factors
Promoters -- bind to RNA polymerase (genes with the same promoter is called an operon)
Enhancers -- bind to activating proteins, facilitating binding of RNA polymerase to a promoter
Repressor Proteins -- block the promoter
35
# D2.2
Epigenetic Inheritance (3-step)
1. Phenotypic changes without change to DNA nucleotide sequence
2. Epigenetic tags or histone modification remain in place during cell division
3. Gene expression in the offspring is affected
36
# D2.2
3 Factors affecting epigenesis
* Air pollution induces changes in inflammatory pathways, oxidative stress, and immune responses.
* High folic acid diet causes methylation of genes related to coat colour of mice
* Varying temperature influence flowering, hibernation, and species which sex is dependent on weather (eg. turtles)
37
# D2.2
Example of consequences of removing epigenetic tags from gametes (3)
| I'm serious.
1. Most epigenetic tags are removed from a gamete's genes, which allows for phenotypic variation in the population
2. Imprinted genes inherited from one particular parent retain their epigenetic tags
3. eg. Ligers inherit the imprinted gene for larger body size from the male lion parent, so are larger than tigons.
38
# D2.2
Example of biochemicals affecting epigenesis
1. In low lactose conditions, lac repressor binds to operator
2. Prevents lac promoter binding to RNA polymerase
3. Lactose binds to repressor, causing conformational change which detaches the repressor from the operator
4. Genes for lac operon are expressed only when lactose is present
39
# D2.2
Example of hormone affecting epigenesis
1. Oestradiol binds to intracellular receptor
2. Hormone-receptor complex is translocated into nucleus
3. Co-regulatory and co-activator proteins influence transcription
4. eg. Genes for FSH and LH
40
# D3.1
Ovarian Cycle (3 x 3)
1. Follicle Phase (Days 0-14)
- FSH + LH secreted from anterior pituitary
- FSH stimulates maturation of dominant ovum in follicle
- Ovum growth secretes oestrogen
2. Ovarian Phase (Days 12-17)
- Oestrogen stimulates LH (and FSH) secretion
- LH causes follicle to rupture
- Egg passes to uterus
3. Luteal Phase (Days 14-28)
- LH converts ruptured follicle to corpus luteum
- Corpus luteum secretes oestrogen and progesterone
- LH and FSH inhibited
41
# D3.1
Uterine Cycle (1+1+3)
1. Proliferative Phase (Days 0-14)
- Oestrogen from follicle maturation thickens endometrium (yolk only lasts 5 days, placenta only develops by week 8)
2. Secretory Phase (Days 14-28)
- Progesterone thickens endometrium, changing it into a secretory layer
3. Menstruation
- Low FSH and LH cause corpus luteum to break down
- Corpus luteum breakdown results in low oestrogen and progesterone
- Low oestrogen and progesterone cause endometrium to break down
42
# D3.1
Fertilisation (6)
1. Capacitation — receptors on acrosome guide it to ovum
2. Acrosome Reaction
3. Egg activation and Meiosis II
4. Cortical reaction
5. Sperm head enters egg yolk, but midpiece and tail are destroyed
6. Sperm nucleus changes into pronucleus. Pronuclei membranes dissolve for pronuclei fusion. Chromatin condenses into chromosomes
43
# D3.1
IVF (7)
1. Suppression of normal menstruation cycle (14 days)
2. FSH-containing fertility drugs induce superovulation
3. hCG injection causes follicles to mature
4. Eggs extracted by follicular aspiration
5. Egg and sperm place in dish for 16-18 hours
6. Fertilised eggs grow in a cultured medium
7. Healthy embryos implanted in uterus (often multiple)
44
# D3.1
GnRH in development of male characteristics (5)
1. Puberty induced by GnRH secretion from hypothalamus
2. GnRH stimulates FSH and LH secretion by anterior pituitary
3. FSH stimulates spermatogenesis by Sertoli cells
4. LH stimulates testosterone secretion by Leydig cells
5. Testosterone inhibits GnRH [negative feedback]
45
# D3.1
GnRH in development of female characteristics (5)
1. Puberty induced by GnRH secretion from hypothalamus
2. GnRH stimulates FSH and LH secretion by anterior pituitary
3. LH stimulates oestrogen and progesterone secretion by ovaries
4. FSH inhibits FSH and LH secretion [negative feedback]
5. Oestrogen and progesterone inhibits GnRH secretion
46
# D3.1
Spermatogenesis (4)
1. Multiplication: Spermatogonia divide by mitosis into Primary Spermatocytes
2. Growth: Primary Spermatocytes divide by meiosis into Secondary Spermatocytes
3. Maturation: Secondary Spermatocytes divide into Spermatids
4. Spermiogenesis: Spermatids mature into Spermatozoa (Sertoli cells involved)
47
# D3.1
Oogenesis (5)
1. Oogonia divide by mitosis into Primary Oocytes
2. Primary Oocytes divide by meiosis but are arrested at Prophase I (follicle cells form)
3. Meiosis I during puberty produces Secondary Oocytes and first polar body
4. Secondary Oocyte released during ovulation
5. Meiosis II during fertilisation produces Ovum and second polar body
48
# D3.1
Positive Feedback in Parturition (7)
1. Near parturition, foetal growth activates stretch receptors on uterine walls
2. Stretch causes cortisol secretion
3. Cortisol causes oestriol by placenta
4. Oestriol promotes oxytocin effect and inhibits progesterone effect
5. Oxytocin is secreted by posterior pituitary gland, increasing the rate and intensity of uterine contractions
6. Foetus releases prostaglandins
7. Prostaglandins stimulates oxytocin secretion until parturition [positive feedback]
49
# D3.1
Pollination (5)
1. Pollination
2. Pollen grain grows a pollen tube down the style to the ovule using hydrolytic enzymes
3. Pollen tube grows to micropyle
4. Pollen tube tip dissolves and pollen grain nucleus moves into ovule
5. Pollen grain fertilises ovum to form zygote.
50
# D3.1
3 adaptations to promote cross-pollination
- Different maturation times for pollen and stigma
- Different maturation times for anthers and pistils in hermaphrodites
- Male and female flowers are located on different plants
51
# D3.1
3 adaptations to inhibits self-pollination (self-incompatibility mechanisms)
- hermaphrodites cannot produces zygotes after self-pollination
- failure of pollen germination, pollen tube growth, fertilisation, embryo development
- incompatible anatomy determined by incompatibility genes
52
# D3.1
Acrosome Reaction (4) and Cortical Reaction (2)
- Acrosome Reaction
1. Sperm breaks through follicle cells
2. Sperm binds to zona pellucida
3. Hydrolytic enzymes from acrosome digest zona pellucida
4. Exposed area of membrane on sperm tip binds to proteins on egg membrane
- Cortical Reaction
1. Cortical granules released by exocytosis, digestion of binding proteins prevents further sperm binding
2. Enzymes harden glycoproteins in zona pellucida
53
# D3.2
Example of phenoplasticity (3)
1. Bicyclus anynana undergoes seasonal polyphenism
2. During cold, adults breed at the end of long life cycles, and have camouflage patterns.
3. During warmth, adults breed often througout thier short lifespan, and have eye patterns to scare predators.
54
# D3.2
Aetiology of PKU (3)
1. Mutation in phenylalanine hydroxylase gene on chromosome 12, recessive disease
2. Failure to convert phenylalanine into tyrosine
3. Eczema, seizures, tremors, hyperactivity, brain damage
55
# D3.2
Example of dual and intermediate phenotypes
- Codominance between blood groups
- Incomplete dominance between alleles for red and white petals in Marvel of Peru flower
56
# D3.2
4 Step Aetiology of Phenylketonuria
1. mutation in autosome 12
2. failure of phenylalanine hydroxylase
3. phenylalanine accumulation and tyrosine deficiency
4. cognitive impairment
57
# D3.2
7 Step Aetiology of Haemophilia
1. Mutation on X chromosome
2. More prevalent in males who only receive one X chromosome
3. Female is haemophilic if homozygous recessive homozygous recessive normally fatal
4. Insufficient clotting factors (IX or XIII)
5. Insufficient conversion of prothrombin to thrombin
6. Insufficient conversion of soluble fibrinogen to insoluble fibrin mesh
7. Clot does not form, bleeding continues
58
# D3.2
7 Step Aetiology of Sickle Cell Anaemia
1. SNP on haemoglobin-b gene on chromosome 11
2. Change to transcribed mRNA
3. Changed to translated polypeptide as a different tRNA with a different amino acid binds to the ribosome
4. Valine instead of glutamic acid
5. Abnormal polypeptides in haemoglobin
6. Abnormal shape of red blood cell
7. HBS allele is codominant, sickle cell anaemia requires hmozygous HBS
59
# C3.2
Why consanguineous marriages (incests) are bad for the gene pool (3)
- Increased prevalence of autosomal recessive disorders
- Congenital abnormalities
- Reduced genetic variation reduces ability of human population to adapt to sudden enviornmental changes (eg. epidemics)
60
# D3.2
Example of polygenic inheritance and environmental factors (7)
1. Many genes control skin colour
2. Genes control melanin concentration in skin
3. Combination of alleles decides phenotype
4. Diversity in combinations produced normally distributed continuous variation with many different skin colours
4. Phenotypes do not follow simple Mendelian ratios
5. Environment affects skin colour by phenoplasticity
6. The more recessive alleles, the lighter the skin
61
# D3.2
Genotype and phenotype ratios of Mendelian crosses
Monohybrid (het. and hom.r)
- 1:1
- 1:1
Dihybrid (het. and het.) [Mendel's 2nd Law: genes are far apart enough for recombination rate to reach 50%]
- 9:3:3:1
- 1:1:1:1
62
# D3.2
2 Reasons for non-independent assortment
- Formation of linkage groups between close-together genes on the same chromosome
- Recombination between homologous chromosomes
63
# D3.2
Sex determination by Y-chromosome
1. Y contains less genetic material than X
2. Y contains SRY gene, which releases Testes Determining Factor, causing embryonic gonads to develop into testes
64
# D3.3
Action of Insulin in controlling blood glucose (3)
1. Beta cells in Islets of Langerhans
1. Insulin promotes glycogenesis
1. As blood glucose decreases, secretion of insulin also decreases
65
# D4.1
Example of sexual selection as selection pressure (3)
1. Male birds of paradise have a specific mating ritual (courtship behaviour)
1. Female selects male with the best mating ritual
1. Female's behaviour dictates the behavioural evolution fo males
66
# D4.1
Endler's experiment
Pool A: Guppies
Pool B: Guppies with Rivulus (a weak predator)
Pool C: Guppies with pike cichlids (a strong predator)
Sexual selection favoured spots in A and B, but not in C
| wtf ikr
67
# D4.1
5 Conditions for Hardy-Weinberg's equation
* No mutations
* Random mating
* No natural selection
* The gene pool is closed
* Large population
68
# D4.2
4 Requirements for stability in ecosystems
* Supply of energy
* Nutrient recycling
* Genetic diversity
* Climate is within tolerance range
69
# D4.2
4 Requirements for the stability of the Amazon rainforest
* Large area for generation of water vapour
* Cooling
* Air flows
* Rainfall
70
# D4.2
Examples of plant and marine species as renewable resources
Teak tree
Atlantic cod
71
# D4.2
5 Methods of assessing sustainability of resources
* Population distribution
* Population age/sex structure
* Trends in distance required for hunting
* Harvest composition
* CPUE (Catch Per Unit Effort)
72
# D4.2
5 Factors affecting agricultural sustainability
* Soil erosion
* Nutrient leaching
* Fertilisers
* Pollution
* Carbon footprint
73
# D4.2
4 Impacts of plastic pollution
* Disruption of food webs
* Toxins
* Wildlife entanglement
* Habitat degradation
74
# D4.2
5 Strategies of rewilding + Example of rewilding
* Species reintroduction
* Habitat restoration
* Rewiliding urban areas
* Rewilding rivers and waterways
* Ecological management and natural processes
Hinewai Reserve in New Zealand: remove grazing livestock and halted herbicide use
75
# D4.2
Example of cyclical succession (4)
1. Coastal chaparral ecosystems in California
2. Annual grasses regrow where fires have occurred
3. Wind dispersion of seeds expands the range of plant life
4. Grasses are replaced with shrubs and trees
76
# D4.2
2 Examples of anthropogenic arrested succession
* Grazing of livestock in grasslands
* Drainage of wetlands for agriculture
77
# D4.2
4 Measures of Ecological Stability
* Resistance - ability of an ecosystem to withstand negative impacts of disturbances
* Latitude - maximum disturbance a system can tolerate before tipping point
* Resilience - ability of an ecosystem to recover from negative impacts of disturbances
* Precariousness - how close the ecosystem is to tipping point
78
# D4.2
5 Types of Succession
- Hydrosere = in a body of freshwater
- Halosere = in salt water marshes
- Psammosere = in sand dunes
- Xerosere = in dry regions (usually with arid climate)
- Lithosere = from bare rock
79
# D4.2
4 Impacts of Succession
- Improved soil depth, mineral ion content, water retention
- More ecological niches
- Complex feeding relationships
- Ecological stability
80
# D4.2
5 Steps of Eutrophication
1. Nutrient enrichment of water bodies (agricultural runoff, sewage and wastewater discharge, and industrial activities)
2. Algal bloom blocks light.
3. Smaller plants which cannot access light and photosynthesize die. Accumulation of organic matter (positive feedback)
4. Increased decomposition leads to higher bacterial reproduction. Aerobic respiration causes oxygen depletion.
5. Collapse of aquatic ecosystem as other organisms cannot respire.
81
# D4.3
8 Points for Enhanced Greenhouse Effect
1. Greenhouse gases occur naturally
2. Human activity produces greenhouse gases
3. Incoming UV from Sun
4. Reflection produces IR
5. Greenhouse gases absorb and reemit radiation as heat
6. Increased greenhouse gases causes abnormal rate of heat emission
7. Global temperature increase threatens ecosystems
8. There are natural fluctuations in temperature
82
# D4.3
5 Positive feedback loops in global warming
* Release of CO2 from deep ocean
* Increase in absorption of solar radiation due to reduce snow
* Accelerating peat and permafrost decomposition
* Permafrost decomposition releases methane
* Increased droughts and forest fires due to temperature increase
83
# D4.3
Example of ecological tipping point (3)
1. Boreal forests originally accumulated carbon, but now has a net loss
2. Warming temperature and reduced rainfall leads to drought and reduced primary production
3. Forest browning and forest fires lead to legacy carbon combusion
Tipping point = critical threshold where a small change can cause severe and irreversible consequences
84
# D4.3
2 Examples of polar habitat change (3 + 3)
1. Emperor penguins
2. Premature breaking of landfast ice reduces protection for breeding and for protecting young
3. Disrupted breeding cycle leads to population decline
1. Walruses
2. Melting ice reduces resting platforms for migration
3. Walruses adapt to sub-optimal habitats
85
# D4.3
Examples of poleward and upslope range shifts (3 + 3)
Poleward
1. Range contraction and northward spread of North American trees
2. Rising temperatures make southern climate unsuitable
3. Shifting distribution impacts forest composition, ecological stability, and carbon sequestration
Upslope
1. Tropical zone montane bird species in New Guinea move to higher altitudes
2. Rising temperatures make mountain climate more suitable
3. Shifting distribution impacts local biodiversity
86
# D4.3
3 Strategies to carbon sequestration
* Afforestation
* Forest regeneration
* Restoration of peat-forming wetalnds
87
# D4.3
2 Examples of disruption to synchrony of phenological events by climate change (3 + 3)
Example 1
1. Reindeer and Arctic mouse-ear chickweed
2. Rising temperature causes chickweeds to initiate growth earlier
3. Migrating reindeer have less chickweed to feed on
Example 2
1. Great tit and caterpillars
2. Rising temperature causes caterpillars to emerge earlier
3. Parent great tits have less caterpillars to feed newborns
88
# D4.3
Example of climate change increasing insect life cycles (3)
1. Spruce bark beetle
2. Rising temperatures increase metabolism and maturation
3. Increased infestation of spruce trees compromises local food webs, habitats and carbon sequestration
89
# D4.3
Example of climate change impacting evolution (3)
1. Tawny owl
2. Rising temperatures reduce snow cover, and reduce viability of grey colour
3. Increased brown colour to camouflage against foliage
