Unit A 死记烂背 Flashcards
1
Q
A1.1
Properties of water that support life (6)
A
Cohesion and Surface Tension
Adhesion
Buoyancy
Viscosity
Thermal conductivity
High specific heat capacity/ latent heat of vaporisation
2
Q
A1.1
2 Examples of Cohesion/ Surface Tension
A
- Cohesion counteracts gravity to transport waterup the xylem in a continuous column.
- Water striders live on calm, unpolluted bodies of water. Ripples and pollutants interfere with surface tension, causing the water striders to sink.
3
Q
A1.1
Chemical bonding makes water a valuable coolant (4)
A
- There are hydrogen bonds between polar H2O
- Hydrogen bonds require energy to be broken
- Hydrogen bonds absorb heat and break to evaporate
- Water carries energy away by evaporation
4
Q
A1.1
Capillary Action in Soil and Cell Walls (3)
A
- Capillary action occurs when adhesion is greater than cohesion
- As water is absorbed from soil, it is replaced by capillary action, so soil does not dry out near the root.
- When water evaporates from leaf cells, it is replaced with xylem water by capillary action, so cells do not dry out.
5
Q
A1.1
4 Adaptations of ringed seals to water and land
A
- Streamlined shape reduces drag in viscous water
- Low-density blubber increases buoyant forces exerted by water
- Heat-insulating blubber reduces heat loss from body to heat-conducting water
- Seals build lairs under heat-insulating snow to stay warm from cold air on land
6
Q
A1.1
5 Adaptations of black-throated loon to water, air, and land
A
- Hydrodynamic body shape reduces drag in viscous water
- Aerodynamic body shape reduces drag in air
- Oiled exterior feathers reduce heat loss body to heat-conducting water
- Heat-insulating down feathers reduce heat loss from body to heat-conducting air
- Large wings generate lift in non-buoyant air
7
Q
A1.1
Extraplanetary origin of water (3)
A
- Bombardment by water-containing asteroids
- Water condensed as the Earth cooled, and gravity retained water on the Earth’s surface
- Earth is in the Goldilock’s zone, the orbital distance from a star that results in liquid water
8
Q
A1.2
Chargaff Experiment
A
- Paper chromatography of DNA from different organisms
- Adenine = Thymine; Guanine = Cytosine
- Finding supports double helix model, but contradicts tetranucleotide hypothesis
9
Q
A1.2
Hershey and Chase Experiment
A
- Infected bacteria with 144 T2 bacteriophages. 72 contained 35-S capsid, 72 contained 32-P DNA.
- Centrifugation.
- 32-P and bacteria stayed in pellet. 35-S and viruses rose to supernatant. NExt-generation bacteria were radioactive.
- 32-P was transferred to bacteria during infection. With knowledge of the lytic/lysogenic cycles, DNA must be the genetic material.
10
Q
A1.2
Watson and Crick
Franklin and Wilkins
A
- Tested ideas on the possible structures of DNA
- Used X-ray diffraction to discover the double helix structure of DNA
11
Q
A2.1
Conditions on Early Earth (5)
A
- Lack of oxygen/ozone
- High CO2, CH4, NH3
- High temperatures
- High UV penetration
- Frequent electrical storms
12
Q
A2.1
8 Processes of Life
A
- Metabolism
- Response
- Homeostasis
- Movement
- Growth
- Reproduction
- Excretion
- Nutrition
Viruses have no metabolism, cannot grow, reproduce nor obtain nutrition independently
13
Q
A2.1
Spontaneous Origin of Cells (5)
A
- Simple sugars and amino acids formed
- Chemical reactions are catalysed
- RNA can self-replicate
- RNA and phospholipids can self-assemble
- Compartmentalisation by a plasma membrane allows the cell to control pH and solute concentrations
14
Q
A2.1
RNA hypothesis (7)
A
- RNA formed from inorganic sources
- Ribozymes replicated RNA
- RNA catalysed protein synthesis
- Membrane compartmentalisation
- RNA produced both proteins and DNA
- DNA became the main genetic material due to its stability
- Proteins took over metabolic catalysis due to their chemical diversity
15
Q
A2.1
RNA hypothesis evidence (3)
A
- RNA molecules can duplicate other RNA molecules, so RNA must be able to self-replicate
- RNA has some catalytic activity
- Ribozymes are used to catalyse peptide bond formation in protein synthesis
16
Q
A2.1
Evidence of LUCA (3)
A
- DNA code is universal
- Existence of 355 conserved genes between bacteria and archaea domains found by genomic analysis
- Study of stromatolites show LUCA lived in warm ion-rich hydrothermal vents, was anaerobic and autotrophic.
17
Q
A2.1
Challenges in proving the spotaneous origin of cells (4)
A
- Evidence may be distorted or destroyed after such a long time
- The first protocells did not fossilise
- Cells originated in the deep ocean, which is hard to access
- Uncertainty surrounding pre-biotic conditions of Earth
18
Q
A2.1
Miller and Urey (3)
A
- CH4, NH3, H2, H2O run through electrical sparks and cooling jacket after heating in a closed system
- Collected fluid contained amino acids
- Evidence that primordial soup could form the spontaneous origin of cells
Note: Doesn’t mean this is exactly how cells actually formed!
19
Q
A2.2
4 Developments in Microscopy
A
- Electron microscopes have higher resolution
- Freeze-fracture microscopy to view internal structures
- Cryogenic electron microscopy for higher resolution and stability
- Immunofluorescence/ fluorescent dyes to visualise location of target molecules
20
Q
A2.2
Functions of Vacuoles in Animals, Plants, and Fungi
A
Animals: store waste
Plants: resist osmotic pressure
Fungi: degrade molecules
21
Q
A2.2
3 Principles of Cell Theory
A
- Living organisms are made up of cells.
- Cells are the basic structural/organizational unit of all organisms.
- All cells come from pre-existing cells.
22
Q
A2.2
4 Exceptions to Cell Theory
A
- Skeletal muscle cells – multinucleated because one cell is made from many fused myocytes
- Aseptate Fungal Hyphae - multinucleated because there are no septa
- Phloem Sieve Tube Elements – anucleate and have little cytoplasm or organelles to increase phloem fluid carrying capacity
- Erythrocytes – anucleate to increase oxygen carrying capacity
23
Q
A2.2
Evidence for Endosymbiosis (7)
A
- Mitochondria are similar size to prokaroytic cells
- Mitochondria have naked DNA as in prokaryotes
- Mitochondria have 70S ribosomes as in prokaryotes
- Mitochondria divide by binary fission like prokaryotes
- Mitochondria replicate independently of the host cell
- Mitochondria are susceptible to antibiotics
- Mitochondria have double membranes
24
Q
A2.2
3 Advantages of Cell Aggregation
A
- Specialisation leads to more efficient metabolism
- Specialisation leads to more complex functions possible (emergent properties)
- Death of one cell does not significantly impact organism survival
25
# A2.3
Examples of 4 Types of Viruses
Parvovirus - single-strand adenovirus
SARS-CoV-2/HIV/influenza - single-strand retrovirus
Bacteriophage lambda - double-strand adenovirus
Rotaviruses - doubel-strand retrovirus
26
# A2.3
6 Steps of Lytic Cycle
1. Viruses are obligate intracellular parasites
2. Virus attaches to surface of host
3. Virus injects DNA, or enters the cell by receptor-mediated fusion or endocytosis
4. DNA penetrates into the host, circularises, and is replicated to form new viral particles by biosynthesis, and the host's DNA is hydrolysed
5. Viral genes are expressed to form viral proteins, which self-assemble into viruses
6. The cell bursts and the new viruses are released
27
# A2.3
6 Steps of Lysogenic Cycle
1. Viruses are obligate intracellular parasites
2. Virus attaches to surface of host
3. Virus injects DNA, or enters the cell by receptor-mediated fusion or endocytosis
4. DNA integrates with host genome. The viral DNA is replicated when the host cell replicates.
5. Viral genes are expressed to form viral proteins, which self-assemble into viruses
6. The viral genome is integrated into the host genome
28
# A2.3
6 Differences in lytic and lysogenic cycles
- Viral genome integrated into host genome?
- Host DNA hydrolysed?
- Viral DNA replication depends on cell?
- Virulent/do not
- Virions released?
- Short/long time
29
# A2.3
4 ways viruses evolved in convergence
- Viruses infecting different cells have similar mechanisms in entering and exiting cells
- Viruses infecting different cells have similar mechanisms in evading immune responses
- Viruses infecting different cells have similar shape and size
- Viruses share the same genetic code of either RNA of DNA
30
# A2.3
Size of Viruses, Bacteria, and Eukaryotic Cells
* Viruses - 20 - 500 nm
* Bacteria - 1 - 10 μm
* Eukaryotic Cells - 10 - 100 μm
31
# A2.3
2 Explanations for Origin of Viruses
* Progressive Hypothesis - viruses form from modified cell components
* Regressive Hypothesis - viruses form from loss of cell components
32
# A2.3
4 Reasons for rapid virus mutation rates
- RNA polymerase and reverse transcriptase are error-prone
- Recombination
- Conjugation by lateral gene transfer
- Short life cycles
33
# A2.3
5 Reasons for Rapid Influenza Mutation Rate
- RNA polymerase and reverse transcriptase are error-prone
- Recombination
- Conjugation by lateral gene transfer
- Reassortment
- High mutation rates of haemaglutinin and neuraminidase antigens help evade identification by immune systems
34
# A2.3
3 Reasons for Rapid HIV Mutation Rate
- RNA polymerase and reverse transcriptase are error-prone
- Recombination
- Conjugation by lateral gene transfer
35
# A3.1
Challenges to the Morphological/Biological Species Concept (6/3)
Challenges to MSC
- Sexual dimorphism
- Organisms are microscopic
- Organisms are morphologically similar
- Some traits cannot be determined (eg. existence of a placenta)
- Organisms change morphologically throughout lifetime
- Dichotomous keys do not encompass all organisms
Challenges to BSC
- Ligers are fertile and can interbreed with lions and tigers
- Asexually reproducing organisms
- Conjugation by horizontal gene transfer
36
# A3.1
Evidence for the emergence of human chromosome 2 from the fusion of apes' chromosomes 12 and 13 (3)
- Human chromosome 2 contains similar genes to the proposed fused genes
- Telomeric DNA is found at the suggested fusion region of human chromosome 2
- There is a mutated dysfunctional second centromere on human chromosome 2
37
# A3.1
Evidence for and against the relationship between genome size and organism complexity (1/3)
For:
- Eukaryotes have larger genomes than prokaryotes
Against:
- Eukaryotes have many non-coding regions
- Prokaryotes only have exons
- Exceptions eg. amoeba have larger genome than humans
38
# A3.1
2 Applications of Genome Sequencing
- Reclassification of organisms
- Personalised medicine
39
# A3.1
4-step application of dichotomous keys
1. Series of questions with 2 answers
2. Answers identify contrasting morphological features
3. Progressively divide into smaller groups to narrow down on a species
4. Process is repeated until key indicates name of species
40
# A3.1
6 Steps of DNA Barcoding
1. Short section of DNA
2. Chosen genes have less intraspecific variation than interspecific variation
3. Amplification with PCR
4. Gel electrophoresis pattern is unique to an organism
5. Individuals have unique genetic profiles, but overall barcodes can represent the gene pool of a species
6. Environments can be sampled to investigate what species are present
41
# A3.2
3 Limitations of the Molecular Clock in estimating clade divergence
Mutation rates are dependent on:
- Length of generation time
- Size of population
- Intensity of selective pressure
42
# A3.2
Features of a Cladogram (4)
- Root -- most ancient common ancestor
- Node -- hypothetical common ancestor
- Terminal branch -- extant species
- Clade -- groups with common ancestry
43
# A4.2
4 Challenges to Identifying Species
- Poorly explored habitats (eg. deep sea, tropical forest soil)
- Mutualistic relationships
- Microorganisms
- Background extinction rate
44
# A3.2
7 Methods to Identify Members of the Same Species
- Fertility of offspring
- Phylogeny
- DNA barcoding
- Proteome bank
- Immunological Comparisons
- Fossil records
- Gause’s Law
45
# A3.2
Origin of the "Domain" taxonomic group (3-step explanation)
- 1977: rRNA sequences can be used to infer evolutionary relationships
- Eubacteria, archaea, and eukarya
- Demonstrates that molecular traits accurately represent evolutionary relationships
| This is not NOS. You need to know this.
46
# A4.1
3 requirements for natural selection
- Overproduction of offspring and competition create a fairly constant population size
- Individuals with genetic variations survive and reproduce to pass on the variations
- The genetic mutation is positive to the organism, and is selected for
47
# A4.1
Evidence for evolution (3)
- Conserved and varied DNA sequences
- Morphological variation between domesticated and wild species
- Homologous structures eg. pentadactyl limbs
48
# A4.1
Example of speciation by geographical isolation (4)
1. Chimpanzees and bonobos on 2 sides of the Congo river
2. Northern group competed aggainst aggressive gorillas for resources, and were selected for aggressive behaviour
3. Southern group had little competition for food
4. Separation of the two groups by the Congo river led to reproductive isolation
49
# A4.1
Types of Speciation
- Allopatric -- geographical isolation
- Sympatric -- temporal/behavioural isolation
50
# A4.1
Example of adaptive radiation (3)
1. Galapagos finches
2. Rapid evolution of seed-diet finch population to occupy new niches with new diets
3. Adaptive radiation increases biodiversity as the finches coexist without competition
51
# A4.1
4 Barriers to hybridisation of species
- Different courtship behaviour/ behavioural isolation
- Zygote is less viable
- Young offspring has high mortality rate
- Hybrid is less fertile
52
# A4.1
Example of polyploidy (4)
1. Knotweed produced 6+ allopolyploids
2. Non-disjunction causes polyploidy
3. Organism has more than 2 sets of chromosomes
4. Octoploid Japanese knotweed (88) can hybridise with tetraploid giant knotweed
53
# Miss Cheah covered this but it's not on spec.
5 Steps of DNA Hybridisation for Differentiating Species
1. Extract: cut genes using restrictive endonucleases
2. Label using a radioactive or a fluorescent tag
3. Heating: break hydrogen bonds between bases
4. Cooling: reform double helixes, some helixes are hybrids
5. Repetition: measure the degree to which the helixes attach, proportional to similarity of genes
54
# A4.2
4 Measures of Biodiversity
* Genetic Diversity
* Species Richness
* Species Evenness
* Ecosystem Diversity
55
# A4.2
4 Causes of anthropogenic mass extinction
- Overexploitation
- Habitat loss and degradation due to human activity
- Competition from invasive/alien species
- Climate change
56
# A4.2
3 Examples of anthropogenic mass extinction (3/4/4)
- North Island Moas
1. Polynesians colonised Aotearoa and hunted moas for food
2. Moas had not encountered terrestrial animals before, and could not protect themselves
3. Moas went extinct in 100 years due to overexploitation
- Carribean Monk Seals
1. Fishermen killed seals for blubber for oil lamps and machinery
2. Seals had not encountered such intense predation before, and could not protect themselves
3. Overfishing deprived seals of food
4. Monk seals went extinct in 600 years due to overexploitation
- Splendid Poison Frogs
1. Deforestation and expansion of urban areas led to habitat loss and degradation
2. Trafficking
3. Fungal disease outbreak
4. Splendid Poison Frogs went extinct in 2020 due to habitat loss and degradation, overexploitation, and pathogens
57
# A4.2
2 Examples of anthropogenic habitat loss
- Dipterocarps forests
1. Keystone species which supports epiphytic plants and makes up the canopy, also being a carbon sink
2. Slash-and-burn deforestation for timber and space for palm oil plantations
- Coreal reefs
1. Protect coasts from erosion, sustain marine food webs, provide medicines
2. Pollution, overfishing/explosives/cyanide, coastal reclamation, unsustainable tourism, climate change
58
# A4.2
4 Sources of evidence for biodiversity crisis
- IPBES Global Assessment Report on Biodiversity and Ecosystem Services
- IUCN Red List
- Horseshoe Count (citizen scientists)
- Biodiversity surveys
59
# A4.2
6 causes of biodiversity crisis
- Human population growth
- Overexploitation
- Urbanisation
- Deforestation and habitat fragmentation
- Pollution
- Spread of pathogens and alien species
60
# A4.2
6 Methods of Preserving Biodiversity
* In-Situ - conservation in natural habitat
* Ex-Situ - conservation outside natural habitat
* Captive Breeding - breeding and reintroduction
* Rewilding - restoring biotic conditions
* Reclamation - restoring abiotic conditions
* Storage of germplasm to conserve genome
61
# A4.2
2 Components of EDGE Scores
- Evolutionary Distinctiveness: higher score for species with few close relatives
- Global Endangerment: higher score for more threatened IUCN species
Higher score means species is more critically endangered.
