1
Q
What is the structure and function of a plant cell wall?
A
Composed of cellulose
Provides cell with structural support
2
Q
What is the structure and function of the middle lamella?
A
Outermost layer of cell, produced between adjacent new cells
Holds cell walls together by acting like a sticky glue
3
Q
What is the structure and function of the plasmodesmata?
A
Narrow threads of cytoplasm connecting cytoplasm of neighbouring cells (cytoplasmic connection)
Allows efficient exchange of signalling molecules between neighbouring cells (allows transport/communication)
4
Q
What is the structure and function of a pit?
A
Thin region of the cell wall arranged in pairs
Facilitates the transport of substances
5
Q
What is the structure and function of a chloroplast?
A
Double membrane with thylakoids containing chlorophyll in stacks called grana
Site of photosynthesis
6
Q
What is the structure and function of an amyloplast?
A
Small membrane bound organelles containing starch granules
Store starch and synthesise it
7
Q
What is the structure and function of the vacuole and tonoplast?
A
Vacuole - cell sap filled sac, tonoplast is the membrane that surrounds it
Vacuole keeps cell turgid, tonoplast regulates ion movements around cell
8
Q
What 3 basic principles do plant cells use to build structures?
A
Strong cell walls from cellulose
Columns and tubes made from specialised cells
Stiffen some of these cells with lignin
9
Q
What is cellulose?
A
A polysaccharide made up of beta glucose units
10
Q
How do 2 beta glucose molecules join?
A
Via a condensation reaction
B glucose molecules are rotated alternately through 180 degrees, creating a 1-4 glycosidic bond
11
Q
What is a cellulose microfibril?
A
A bundle of around 60-70 cellulose molecules
12
Q
What is the structure of a cellulose microfibril?
A
Parallel chains of cellulose polymers
H bonds form between the neighbouring molecules due to hydroxyl groups
13
Q
What holds cellulose microfibrils together?
A
Hemicellulose and pectins (short polysaccharides) which bind to the cellulose and each other
14
Q
What is the xylem and how is it adapted for it’s function?
A
Long tube like structure formed from dead cells placed end to end for the transport of water and mineral ions
Adaptations: hollow lumen, no end walls (allows mass flow), thickened with lignin (strength to withstand hydrostatic pressure), pits allow lateral movement of water (in case of air bubbles)
transportation and support
15
Q
What are mature lignified xylem cells?
A
They are dead
16
Q
What is the phloem and how is it adapted to it’s function?
A
A transport tissue (not support) made of sieve tube elements joined together for the transport of organic solutes (mainly sugars like sucrose)
Adaptations: sieve tube elements have no nucleus and few organelles (maximises space for translocation), they have a companion cell which provide the energy for active transport of solutes (lots of mitochondria), sieve pores allow continuous movement, plasmodesmata links sieve tubes to companion cells
17
Q
What is the difference between mature phloem and xylem cells?
A
Mature phloem contain living cells, unlike mature xylem which are dead
Xylem cells are used for transportation and structure while phloem cells only for transportation
Translocation vs tranpiration stream
18
Q
What is the sclerenchyma and how is it adapted to it’s function?
A
Support fibres made of bundles of dead cells thickened with lignin - provides mechanical support
Adaptations: lignification of cell wall, hollow inside, dead cell
19
Q
Why are plant fibres so strong?
A
Due to factors affecting the cell wall:
- the arrangement of microfibrils in a mesh like pattern
- secondary thickening (development of a secondary cell wall which contains lignin)
20
Q
How is water transported in the xylem?
A
Transpiration stream: water is pulled up as it evaporates out of the stomata due to the tension of the H bonds and cohesive forces
21
Q
How are inorganic ions transported by the xylem?
A
The movement of water through the xylem provides a mass flow system for transport
22
Q
Suggest how the structure of sclerenchyma fibres makes them useful for making rope
A
Thick walls/lignin for strength
Lignin making fibres waterproof
Flexible so doesn’t break easily
Light because they are hollow
23
Q
Why are plant fibres sustainable?
A
Less fossil fuels used
Can be replanted for next generation (resources made available for future generations)
Plant fibres are biodegradable
Cheaper and easier to grow and process
24
Q
How can starch contribute to sustainability?
A
Can be used to make bioplastics, which are more sustainable as starch is a renewable resource
crops can be regrown and there are no fossil fuels
Can make fuel from starch
25
How can the use of starch (over plastic) contribute to sustainability?
Bioplastic/starch comes from plants
plants/starch is renewable
oil based plastic is derived from oil which is a non renewable resource
26
What is the importance of water to plants?
Solvent properties (can transport dissolved substances)
Thermal properties (cools and heats slowly to avoid rapid changes in internal temp)
Density/freezing (ice is less dense than water as water expands as it freezes)
Cohesion and surface tension (H bonds keep water molecules in a column in xylem vessels)
27
What is the importance of water and different inorganic ions to plants?
Water - photosynthesis, transport medium, turgidity, temp regulation
Mg ions - production of chlorophyll (yellow leaves, plants smaller)
Nitrate ions - plant growth, DNA and protein synthesis (stunted growth)
Ca ions - cell wall growth (component of middle lamella/primary cell wall/calcium pectate/pectin) - leaves cannot grow fully without)
28
What are the conditions required for bacterial growth?
-nutrients (materials to grow and respire)
-oxygen (if respiring aerobically)
-optimum temp/pH to allow correct enzyme function
29
What 2 things must new drugs be tested for?
Efficacy
Side effects
30
Why are healthy volunteers in a drug trial given different doses of the drug or placebo?
Check for side effects, different doses to determine safe dose, placebo to ensure side effects were due to drug
31
Explain what is meant by a double blind trial and suggest why it is important
Some people receive the new drug, some people receive the placebo dummy drug
Doctors and patients both dont know who is on the new drug and who has the placebo
To see if the new drug works better
Reduces bias
32
What did William Withering do with foxglove?
Used it to treat dropsy - contains drug digitalis. However foxglove can be poisonous so he tried out different doses on his dropsy patients to find a ‘safe’ dose
33
What are the stage of drug testing today?
Pre-clinical - animal and lab studies
PHASE I - small group of healthy volunteers in low concentrations to monitor safety
PHASE II - small group of volunteer patients who need the drug to monitor effectiveness of treatment
PHASE III - large number of patients split into 2 groups (double blind). If successful, becomes licensed
Post licensing - begin development of new drug
34
What is a double blind trial?
One set of patients receives real drug, other set = placebo
Neither doctors or patients know whether they have received placebo or real drug to reduce the bias from results
35
What is a placebo?
A dummy pill to ensure there is no psychological ‘placebo’ effect
Used as a control/comparison with the actual drug
36
How is contemporary drug testing protocol an improvement on the trial used by William Withering?
SAFER - pure drug rather than extract, pre testing on cells/animals rather than people, legislated by regulations
MORE VALID - placebo, double blind, controlling factors in cohort
MORE RELIABLE - more people tested, analysed statistically
37
what do antimicrobial properties do
kill or inhibit growth of organisms - useful components of drugs
38
what are aseptic techniques used for
prevent bacterial cultures on agar plates from being contaminated by other micro organisms or human pathogens
39
steps of aseptic techniques
1. all work should be carried out in front of a bunsen burner
2. hot agar jelly is poured into a sterilised petri dish and agar is left to cool and set
3. an inoculating loop is passed through a hot flame before it is used to transfer bacteria to the culture medium
4. petri dishes should only be opened as little as possible at the side facing the bunsen burner
5. the lid of the petri dish should be secured with tape at intervals around the dish and stored upside down
6. the cultures should not be incubated above 25 degrees celsuus in a school lab
40
What is a 'niche'
The role of a species within its habitat - no two species have the same niche as every species has its own specific niche
41
What does the niche a species have depend on
its interactions with living organisms (biotic) and the nonliving environment (abiotic)
42
What happens if two species try occupy the same niche
They will compete with one another for the same limited resources
43
What are the two different types of niche
Structural and feeding
44
What are adaptations
Special features or characteristics that help the organsim survive
45
What are the 3 different types of adaptations
Behavioural
Physiological
Anatomical
46
What are some examples of behavioural adaptations?
Possums playing dead if threatened by predator
Plants turning leaves to sun to maximise photosynthesis
47
What are physiological adaptations
A feature of the internal workings of organisms that help them to survive of reproduce
48
What are behavioural adaptations
these are actions by the organism which help them survive or reproduce
49
What is a species?
A group of organisms with similar morphology, physiology and behaviour, which can interbreed to produce fertile offspring and which are reproductively isolated from other species
50
What is a habitat?
The area inhabited by a particular organism/species
51
What is a population?
A group of interbreeding individuals within an area
52
What is a community?
All the various populations within a habitat
53
What is an ecological niche?
The way an organism uses/exploits it’s environment
54
What are some examples of physiological adaptations?
Brown bears hibernate and lower rate of metabolism to conserve energy
Bacteria produce antibiotics to kill threatening bacteria
55
What is biodiversity?
The variety of species in an ecosystem/community/habitat
The variety of alleles in a gene pool
56
What are the 3 levels to assess biodiversity?
1. number and range of different ecosystems/habitats
2. number of species and their relative abundance
3. genetic variation within each species
57
What is a structural adaptation
Structural features of organisms for survival/reproduction
58
What are some examples of structural adaptations?
Otters have a streamlined shape to glide through water
Whales have a layer of blubber for insulation
59
What is evolution?
A change in allele frequency over time
60
How does natural selection occur?
1. A population has a naturally occurring genetic variation, with new alleles created through mutation
2. A selection pressure occurs in the environment
3. Survival of the fittest - advantageous allele
4. Organisms with the allele are more likely to survive, reproduce and so produce offspring
5. Their offspring are more likely to have the allele, so it becomes more common in the population
61
Index of diversity
D = N(N-1)/Σn(n-1)
where N = number of organisms in the habitat
n = number of organisms of each species
High D value = greater biodiversity
Takes into account richness and evenness
Count the number of different species and the number of individuals in each species
62
What does a bigger index of diversity mean
The more biodiverse an ecosystem is
There are many species and fairly evenly distributed so the ecosystem is more stable
63
Calculating genetic diversity
number of heterozygotes divided by total population
a closer proportion (closer to 1) means higher genetic diversity (same as 100%)
64
Why is heterozygosity important?
Heterozygosity indicates more individuals carrying different alleles
A low heterozygosity suggests a population. is genetically uniform, which can make it more vulnerable to diseases and environmental changes as a result of inbreeding
65
What is endemism?
a species only found in one geographical location
66
What is species richness?
The number of a species present in a given habitat
67
What is species evenness?
The relative abundances of different species within a community
68
What does the Heterozygosity Index measure?
Genetic diversity within a species
69
What can you look at to measure genetic diversity?
Genotype - genetic makeup of an organism
Phenotype - observable characteristics of an organism
70
What information should you collect for studies of biodiversity?
-presence of endemic/rare species
-use of a diversity index
-genetic diversity of populations
-species richness
71
Where does genetic diversity come from
Mate selection, random fertilisation, chromosome mutations, meiosis
72
What is classification, and why do we classify organisms?
The process by which scientists group living organisms
Allows us to look at evolutionary relationships
73
What is the order of the hierarchy of classification?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
74
What is phylogeny?
The study of the evolutionary history of groups of organisms
75
What is molecular phylogeny?
Molecular phylogeny looks at molecules (DNA and proteins) to see how closely related
organisms are, e.g. more closely related organisms have more similar molecules.
Looking for molecular similarities/differences
In DNA/RNA
in proteins/proteomics
evolutionary relationships are determined
76
What are phylogenetic trees?
Representation of evolutionary relationships based on molecular differences accumulated over time
77
What were the 5 traditional kingdoms?
Plantae
Fungi
Animalia
Protoctista
Prokaryotae
78
What are the 3 newer domains?
Archaea
Bacteria
Eukaryota
79
Why were the 3 domains created?
To create 2 separate bacteria categories - molecular phylogeny had determined that archaea and bacteria were more distantly related than initially thought
80
What is conservation?
The wise use of natural resources and planning and carrying out action to preserve and protect living and non-living resources
81
What are the 2 approaches to conservation?
In-situ - conserving species in it’s natural environment
Ex-situ - conserving a species by taking it out of it’s natural environment
82
What happens when a species goes extinct?
There is an overall decrease in biodiversity
83
What is an endangered species?
One that is threatened with extinction
84
What is a seed bank?
A facility that conserves plant diversity by drying and storing seeds in a temperature controlled environment
85
Explain how seed banks can help to conserve the genetic diversity of plant species
Large number of seeds collected / seeds collected from many different plants
Ensures large gene pool/variety of alleles in seeds collected
86
What are the stages of seed bank storage?
Seed collected, transferred to seed bank and unpacked and checked.
Seed cleaned and identification checked
Seeds are dried and packed
Seeds stored at -20 degrees C
Periodic germination trials to check seed viability
87
What are the advantages of seed banks?
Less labour intensive, more cost effective, makes seeds less vulnerable
Ensures future food security, conserves genetic diversity, protects from natural disasters/mismanagement
88
What are the disadvantages of seed banks?
Testing seeds is time consuming and expensive, some seeds are difficult to collect
89
How are seeds selected for storage in the seed bank?
From different plants to provide genetic variation, X rayed to ensure/check viability
90
What conditions are seeds stored at in seed banks and why?
Cool and dry
- reduce enzyme activity
- prevent germination/keep seed dormant
- reduce growth of microbes
- decrease rate of decomposition
91
Why is it better to store seeds than fully grown plants?
-seeds are smaller so more can be stored
-seeds can be stored for a longer time (dormancy)
-do not require maintenance in the same way as growing plants
-reduced cost
92
How can zoos help conservation?
-scientific research
-captive breeding to increase number in the wild
-reintroduction programmes
-education
93
What are the disadvantages of zoos?
Ethical concerns, captive breeding can lead to genetic drift and loss of genetic diversity, scientific data unreliable due to captivity conditions, certain animals may not breed in captivity
94
What are the advantages of reintroduction programmes?
Prevents extinction, rebalance ecosystems, restore habitats
95
What are the disadvantages of reintroduction programmes?
New organisms may carry disease, a struggle to readjust to the wild and therefore may die.
96
How does the scientific community critically evaluate new theories?
theories communicated to scientific community
peer review
checking of evidence to ensure its validity
97
Why would you use systematic sampling instead of random sampling?
Due to presence of environmental gradient
98
How can differences in primary structure of a protein be used to produce phylogenetic trees?
-determine sequence of amino acids
-determine number of similarities/differences in amino acid sequence
-greater number of differences = less related species are
99
How do zoos play a role in animal conservation?
-research (improving health, developing genetic database)
-education (conservation)
-repopulation (captive breeding and reintroduction programmes)
-protection (from poachers)
100
How do captive breeding programmes in zoos maintain genetic diversity of captive populations?
-selection of unrelated/genetically different mates
-use of stud books contain records of mating and DNA profiling to identify those not related
-exchange of animals between zoos
-exchange of gametes between zoos
-IVF
101
What is the Hardy Weinberg equation
p2 + 2pq + q2 = 1
102
What is the Hardy Weinberg principle
The Hardy-Weinberg principle states that if certain conditions are met, the allele frequencies of a gene within a population will not change from one generation to the next
103
What are the conditions needed to be met for Hardy Weinberg to be true
Mating must be random between individuals
The population is infinitely large
There is no migration, mutation or natural selection
104
Characteristics and features of the 3 domain table
105
Aseptic techniques explanation 1-3
106
Aseptic technique explanations 3-6
107
Suggest why a drug can be tested on rats before testing on humans
1. laboratory rats of reduced genetic variability
2. Rats have a similar/well known metabolism
3. No harm to humans
4. Looking for potential toxicity/adverse effect
5. ethical issues if test directly on humans
108
State what is done during Phase 1 and Phase 2 of drug testing on humans
Phase 1: Drug is given to small group of healthy volunteers in low concentration to monitor safety
Phase 2: Drug is given to small group of patients to monitor effectiveness of treatment
109
Explain how organisms can be classified into taxonomic groups
Organisms with specific/similar characteristics are placed in a group
These characteristics are assessed via molecular phylogeny, observable characteristics, behavioural similarities, similarities in DNA
110
How does critical evaluation of research occur
1. scientific findings published in a journal
2. presented at a scientific conference
3. peer review
4. other scientists repeat experiments to confirm findings/test reliability of data
111
In an investigation, all seedlings were grown from seeds from the same wheat plant. Suggest why this would improve the validity of results
There would be less genetic variation
Seeds are the same age/produced under the same conditions
112
Suggest two factors other than time for growth and source of seeds that should been kept constant for this investigation
Light
Temperature
Volume of solution
Concentration of other mineral ions
pH
Initial status of seedlings
113
Suggest how inbreeding could have led to genetic defects in these lions
Closely related lions mating with each other / small gene pool
Inbreeding depression
Increased chance of homozygous recessive genotypes for genetic defects
Increased likelihood of offspring inheriting two copies of the same harmful recessive gene
114
Suggest why bioplastic is described as more sustainable than oil based plastics
Bioplastic is made from starch
Starch is a renewable resource
Oil based plastic is from a non renewable resource
115
Suggest one environmental advantage of using biodegradable packaging
It will not accumulate/contribute to landfill
It can be decomposed
116
What does uniformity of seedlings in an experiment refer to
All from the same parent plant
Same age
Same original root length
117
Describe an experiment to find optimum nitrate ion concentration for the growth of wheat seedling roots
Sensible range of nitrate ion concentrations
Repeats at each concentration
Seedlings same age, come from same parent plant
Solution should contain other mineral ions
Keep temperature, light intensity and volume of mineral solution constant
Mechanism of judging root growth
118
Suggest how the use of starch rather than plastic may contribute to sustainability
Starch is renewable
Plastic comes from oil
Oil is a non-renewable resource
119
variables that should be controlled when investigating tensile strength of fibres of different diameters
Length/mass of fibres
Age of fibres
Source of fibres (taken from same leaf)
Temperature
humidity
120
Describe and explain the procedures that must be followed before these drugs can be tested on patients
Testing on non-humans e.g. animals or tissue culture
To test for toxicity
Then testing on healthy volunteers
To test for side effects
121
Explain how a double blind trial is used to test a new drug
Patients who require the drug are split in two groups
One group receives the real drug and one group receives a placebo drug
A dummy pill used as a control to prevent psychological 'placebo' effect taking place
Neither patients nor doctors know if whose treatment contains the placebo or real drug
This reduces bias
Testing to find out if the drug is effective
122
Suggest the effects of habitat loss on the biodiversity of a tropical forest could be measured
Measure species richness
Before and after habitat loss
123
Suggest why cells in this parenchyma tissue depend on the functions of xylem vessels
supplies water for photosynthesis/keeps cells turgid
Supplies magnesium ions for the synthesis of chlorophyll
Supplies nitrate for the synthesis of amino acids
Supplies calcium for the cell wall structure
Supplies phosphate for synthesis of ATP / DNA
Supports the leaves so they are exposed to the sunlight
