Biology Revision Unit 2 Apr 26Th

Front 1

in chloroplast, other than double membrane, it also has?

Back 1

thylakoid membranes

Front 2

thylakoid membranes are stacked up in some parts of the chloroplast to form?

Back 2

grana

Front 3

grana are linked together by?

Back 3

lamellae, thin, flat pieces of thylakoid membrane

Front 4

what is stroma?

Back 4

a thick fluid found in chloroplasts

Front 5

what's the disadvantage to keep two animals together all the time?

Back 5

increase inbreeding and reduce genetic diversity

Front 6

nucleus?

Back 6

DES: a large organelle surrounded by a nuclear envelope (double membrane), which contains many pores. the nucleus contains chromatin and often a structure called the nucleolus.

FUNC: chromatin is made from proteins and DNA. the pores alllow substances (eg. RNA) to move between the nucleus and the cytoplasm. the nucleolus makes ribosomes.

Front 7

lysosome?

Back 7

DES: a round organelle surrounded by a membrane, with no clear internal structure.

FUNC: contain digestive enzymes. these are kept separate from the cytoplasm by the surrounding membrane, but can be used to digest invading cells or to break down worn out components of the cell.

Front 8

vesicle?

Back 8

a small fluid-filled sac in the cytoplasm, surrounded by a membrane.

FUNC: transports substances in and out of the cell (via the cell membrane) and between organelles. some are formed by the Golgi apparatus or the endoplasmic reticulum, while others are formed at the cell surface.

Front 9

ribosome?

Back 9

a very small organelle that floats free in the cytoplasm or is attached to the rough endoplasmic reticulum.

FUNC: the site where proteins are made.

Front 10

endoplasmic reticulum?

Back 10

there are two types of endoplasmic reticulum: the smooth ER is a system of membranes enclosing a fluid-filled space. the rough ER is similar, but is covered in ribosomes.

FUNC: the smooth ER synthesises and processes lipids. the rough ER folds and processes proteins that have been made at the ribosomes.

Front 11

golgi apparatus

Back 11

a group of fluid-filled flattened sacs. vesicles are often seen at the edges of the sacs.

FUNC: it processes and packages new lipids and proteins. it also makes lysosomes.

Front 12

centriole

Back 12

hollow cylinders, containing a ring of microtubules (tiny protein cylinders)

FUNC: involved with the separation of chromosomes during cell division.

Front 13

mitochondrion

Back 13

they are usually oval-shaped. they have a double membrane - the inner one is folded to form structures called cristae. inside is the matrix, which contains enzymes involved in respiration.

FUNC: the site of aerobic respiration, where ATP is produced, they are found in large numbers in cells that are very active and require a lot of energy.

Front 14

explain the meaning of tissue?

Back 14

similar cell types working together for the same function

Front 15

proteins in a cell can be made radioactive by supplying the cell with radioactive amino acids. the movement of the radioactive protein within the cell can be traced over time.

in an investigation, it was found that the quantity of radioactivity in the protein that entered the Golgi apparatus was less than that supplied to the cell.

suggest reasons for the difference?

Back 15

1. some amino acids do not enter the cell ;
2. some amino acids are not used in protein synthesis ;
3. some protein is elsewhere in the cell / on ribosome / in
RER / in cytoplasm / in mitochondria / in vesicles / in
nucleus ;
4. not modified;
5. some metabolised;
6. some has been ejected from cell ;
7. radioactive decay / decrease ;

Front 16

name structures that may be found in a leaf cell that identifies it as both a eukaryotic cell and a plant cell

Back 16

chloroplast / vacuole / vacuole
membrane / tonoplast / cellulose cell wall ;

Front 17

describe anaphase of mitosis

Back 17

1. spindle fibres contract ;
2. chromatids pull apart / separate
3. kinetochore / centromere leads ;
4. move to opposite poles of cell ;

Front 18

during anaphase, the cell from the root tip did not have a nucleus but was still considered to be eukaryotic. suggest two reasons why this cell was still considered to be eukaryotic

Back 18

1. membrane bound organelles present e.g. mitochondrion ;
2. has large ribosomes ;
3. nucleus will reform;
4. presence of cellulose cell wall ;

Front 19

suggest why "which stage of the cell cycle takes the longest" may be unreliable?

Back 19

not enough data / samples / cells / slides observed / data only taken from one point in time ;

Front 20

suggest why calculating the difference between final mass and initial mass of each seedling may be an even better indicator of growth than measuring length

Back 20

plants grow in other dimensions / idea of more likely to be an error in measuring length ;

Front 21

suggest variables that the student would need to keep constant to ensure the reliability of her data. in the plant growth experiment.

Back 21

1. temperature ;
2. volume of solution ;
3. light ;
4. measuring technique ;
5. stage of development e.g. same number of leaves ;
6. seedlings raised in same environment / named
environmental condition ;
7. seedlings being genetically similar to start with e.g.
same parent plant ;

Front 22

whats the main role of calcium pectate in a plant?

Back 22

component of middle lamella, holding adjacent plant cells together ;

Front 23

explain how differential gene expression can enable cells which have the same genetic material to have very different structures and functions?

Back 23

1. different genes active in different cells / different genes
active at different times / some genes active / inactive
2. active genes make mRNA
3. active genes make proteins;
4. proteins control cell processes
5. permanent change to cell

Front 24

what's the term for the sperm tail?

Back 24

flagellum

Front 25

explain why it is important that the sperm has a nucleus that is haploid?

Back 25

1. has 23 / half the required chromosome complement ;
2. so at fertilisation full complement / 46 of chromosomes is restored / diploid number restored ;
3. allowing mixing of alleles / allowing for genetic variation

Front 26

describe the changes in the female gamete from the point when a sperm releases its digestive enzymes to the point when the two nuclei fuse?

Back 26

1. idea of jelly layer hydrolysed ;
2. sperm nucleus enters the egg cell;
3. meiosis completes;
4. cortical granules in egg fuse with egg cell surface membrane ;
5. release enzymes
6. zona pellucida hardens ;
7. to prevent polyspermy ;
8. egg nucleus envelope breaks down;
9. spindle forms;

Front 27

compare the effect of temperature on the mean length of pollen tubes in variety A with variety B, between 15c and 30c

Back 27

1. mean pollen tube length increases as temperature increases from 15°C to 30°C for both ;
2. variety B has a greater mean pollen tube length than A up
to 30°C;
3. both have longest length /maximum length at 30°C ;
4. correct comparative manipulation of the data e.g. mean pollen tube length is 50% more for cotton variety B at 30°C ;

Front 28

suggest an explanation for the change in the mean length of pollen tubes when the temperature increased from 35c to 40c

Back 28

pollen tube dies / enzyme denature

Front 29

suggest how this use of starch to clear window, rather than plastic, may contribute to sustainability.

Back 29

1. starch from a renewable resource ;
2. plastic from oil
3. oil is a non-renewable resource;

Front 30

similarity and difference between xylem vessels and sclerenchyma fibres?

Back 30

Similarity
1, both for support
2, both contain lignin
3, both associated with vascular bundles
4, both dead ;

Differences
1, only xylem vessels transport water and mineral ions
2, position within vascular bundle
3, only xylem has open ends
4, type of lignin deposition ;

Front 31

suggest two features of the mayfly nymph, shown in the diagram above, that makes it well-adapted to survival in fast-flowing streams. explain how each feature helps it to survive.

Back 31

1. flattened body reduces drag

2. hooked feet to hold onto rocks

3. wide spread legs to grab rocks

Front 32

the rat-tailed maggot lives in water which has a low concentration of dissolved oxygen. suggest how the tail structure helps it to survive in this environment

Back 32

1. tube breaks water surface / reaches into the air
2. acts as a snorkel
3. atmospheric air / oxygen obtained ;

Front 33

adaptation can occur within the same species. leopards and panthers are members of t same species found in Africa. leopards have spotted fur and hunt in open grasslands, whiltst panthers have black fur and hunt in forests.

suggest how natural selection has led to the evolution of these two different forms of the same species.

Back 33

1. its unique features of the fur helped it to camouflage in its environment ;
2. thus they are more likely to catch prey, they have a selective advantage
3. therefore they are more likely to survive to adulthood
4. to breed ;
5. pass on coat colour allele and genetic information ;
6. to offspring;
7. change in allele frequency over generations ;
8. disruptive selection ;
9. genetic variation present in ancestral population ;

Front 34

explain what is meant by the term species.

Back 34

1. the species is reproductively isolated ;
2. produce offspring that are sexually viable /fertile ;
3. many features in common / homologous ;

Front 35

explain the meaning of the term genetic diversity within a species

Back 35

1. the number of different alleles and allele frequency ;
2. in a population / gene pool ;

Front 36

describe how zoos maintain the genetic diversity of endangered species.

Back 36

1. breeding programme ;
2. careful selection of mate ;
3. allowing only to mate with a different individual to previous
mating;
4. only allowing those with different genes to mate ;
5. use of genetic testing ;
6. record keeping studbooks ;
7. reason for outbreeding ;
8. reintroduction to the wild ;

Front 37

features of prokaryotes

Back 37

1, extremely small cells
2, DNA is circular
3, no nucleus, DNA free in cytoplasm
4, cell wall made of a polysaccharide, but not cellulose or chitin
5, few organelles, no mitochondria
6, smaller ribosomes

Front 38

which the following features of mitochondria is in chloroplasts as well?
surrounded by a double membrane, crista present, circular DNA, matrix, glycogen granule, stalked particles

Back 38

1, surrounded by a double membrane
2, circular DNA

Front 39

Give one difference between an organ and a tissue.

Back 39

organ has many functions, tissue has one / fewer.

organ has many cell types, tissue has one / fewer.

Front 40

Suggest one way in which tissues and organs are similar.

Back 40

both have cells working together for the same function.

Front 41

In the space below, draw a fully labelled diagram of a nucleus, as seen using an
electron microscope.

Back 41

Drawing (max 2):
1. double membrane / nuclear envelope ;
2. nuclear pores ;
3. (1 or more) nucleoli present ;

Labels (max 2):
4. (nuclear) envelope / double membrane / {inner / outer} (nuclear) membrane ;
5. (nuclear) pore ;
6. nucleolus ;
7. correct reference to chromatin / nucleoplasm ;

Front 42

formation of a sun tan when human skin is exposed to sunlight. what kind of adaptation is this?

Back 42

physiological

Front 43

the human egg cell is adapted for its function. describe and explain two adaptations of the human egg cell.

Back 43

1D haploid / 23 chromosomes / nucleus ;
1E so that diploid number / full
complement / 46 chromosomes restored
at fertilisation ;
2D lipid droplets / food store;
2E supplies energy / nutrients for division;
3D large cell size / surface area;
3E increased chance of fertilisation;
4D cortical granules / lysosomes / zona pellucida in cytoplasm;
4E to prevent polyspermy ;
5D release of a chemical ;
5E to attract sperm ;
6D membrane with ‘sperm receptors’ on surface ;
6E to allow sperm to bind ;
7D much mRNA present ;
7E to allow early translation of transcription factors;

Front 44

suggest how you could investigate the antimicrobial properties of pine needles.

Back 44

1. pine needles /extract / filter paper soaked in extract and placed on agar plate
2. with bacterial lawn ;
3. sterile/aseptic approach e.g. appropriate reference to sealing ;
4. an appropriate time for incubation e.g. 24 hours, 1 week ;
5. incubate at a sensible temperature suggested e.g. 25°C
6. looking for clear area / inhibition zone / loss of cloudiness /reduced cell number around pine needles, extract / filter paper ;
7. clear area shows no bacteria ;
8. suitable control ;

Front 45

which of the four statements about cell division is that meiosis is involved?
1, required for both sexual and asexual reproduction
2, produces gametes
3, crossing over can occur
4, occurs in mammals but not flowering plants

Back 45

2,3

Front 46

Suggest why the tip of the onion root is used.

Back 46

site of cell division / mitosis / actively dividing cells

Front 47

Suggest why acid is used in stage 2.

Back 47

to soften the material / break middle lamella

Front 48

Name a suitable stain for the root tip squash.

Back 48

acetic orcein / lacto-propionic orcein / toluidine (blue) / Schiffs

Front 49

There are various risks associated with the production of a root tip squash.
Suggest two risks and the precautions you would take to minimise each risk.

Back 49

1. cut and appropriate precaution ;
2. acid and appropriate precaution ;
3. heat and appropriate precaution ;
4. stain and appropriate precaution ;
5. coverslip and appropriate precaution ;

Front 50

The pollen tube grows from the pollen grain to the micropyle. Suggest one
stimulus, other than water, that causes the pollen tube to grow towards the
micropyle.

Back 50

chemical / air / gravity / light

Front 51

The tip of the growing pollen tube releases digestive enzymes into the style.
Suggest the role of these digestive enzymes in the growth of the pollen tube.

Back 51

1. breakdown / digestion of style ;
2. breaks down protein / pectin / middle lamella ;
3. hydrolysis ;
4. easier for pollen tube to grow / reduced resistance
5. supplies nutrients / named nutrient / energy for pollen tube growth;

Front 52

Give three roles of water in a plant other than for pollen tube growth.

Back 52

1. photosynthesis ;
2. component of cytoplasm / sap ;
3. water as a solvent ;
4. water as a transport medium ;
5. involved in thermoregulation ;
6. role in structural support ;
7. involvement in hydrolysis ;
8. turgor changes ;

Front 53

Suggest which of the graphs, A, B, C or D shown below, would represent the
height distribution in this plant population and give an explanation for this
height distribution.

Back 53

1. A ;

2. height controlled by many genes / polygenic inheritance;
3. continuous variation ;
4. normal distribution;

Front 54

Suggest two environmental conditions that were controlled in this investigation.

Back 54

1. water / humidity ;
2. light ;
3. minerals / soil type / pH ;
4. CO2 ;
5. temperature ;
6. altitude ;

Front 55

Describe the effect of increasing altitude on the mean height of yarrow plants.

Back 55

1. height (of yarrow plant) decreases (as altitude increases) ;
2. non-linear /eq ;
3. correct manipulation of the data ;

Front 56

Suggest a reason for using cloned plants rather than using seeds in this
investigation.

Back 56

removal of genetic variation / they are all genetically identical

Front 57

Suggest a reason for growing cloned plants at 2000 m in this investigation.

Back 57

to act as a control / to see if there is a difference at other heights / as a comparison / to check that clones grow the same as the parent plants

Front 58

During the testing of a new anti-bacterial drug, a double blind trial may be used.
Explain what is meant by a double blind trial and suggest why it is important

Back 58

1. some people with (new) drug and some without (new) drug ;
2. use placebo / description (e.g. sugar-coated dummy pill /old drug ;
3. doctors and subjects do not know who is on new drug or who is not ;
4. to see if new drug works better than placebo / old drug ;
5. reduces bias

Front 59

Suggest why bioplastic is described as a more sustainable form of packaging
than oil-based plastics.

Back 59

1. bioplastic / starch} comes from plants ;
2. plants / starch are renewable ;
3. oil-based plastic is from non-renewable resource

Front 60

Bioplastic is biodegradable. Suggest one environmental advantage of using
biodegradable packaging.

Back 60

will not accumulate / not contribute to landfill / can be decomposed

Front 61

During an infection, some white blood cells make glycoproteins which become part
of their cell surface membranes. To make glycoproteins, the white blood cells must
first synthesise proteins on the surface of their rough endoplasmic reticulum.
(a) Explain how these newly-made proteins end up as glycoproteins on the cell
surface membrane.

Back 61

1. protein release from ribosome ;
2. enter the rER ;
3. becomes packaged into (rER) vesicles ;
4. (vesicles / proteins) move to Golgi (apparatus) / {vesicles fuse with / protein enters} Golgi ;
5. protein {modified / carbohydrate added / named carbohydrate added};
6. then become packaged into (secretory) vesicles ;
7. glycoprotein becomes part of (vesicle) membrane ;
8. vesicles {move towards / fuse with} the cell (surface) membrane ;

Front 62

Explain what is meant by the term totipotent stem cell.

Back 62

1. totipotent (stem cells) can give rise to {all / any / 216} cell types ;
2. stem cells are undifferentiated / unspecialised ;
3. can keep dividing /

Front 63

Suggest why injecting totipotent stem cells may benefit a person with a
shortage of white blood cells.

Back 63

they can give rise to white blood cells

Front 64

Suggest one risk to the person receiving the stem cells.

Back 64

possible route to infection / rejection by recipient / increased chance of becoming cancerous

Front 65

cell walls are found in
A, plant cells only
B, prokaryotic cells only
C, plant and prokaryotic cells
D, animal, plant and prokaryotic cells

Back 65

C

Front 66

rough endoplasmic reticulum is consists of ribosome and?

Back 66

membrane/cisterna

Front 67

explain how the data in the table show the effects that genotype and the environment have on the phenotypes.

Back 67

1. non-identical twins are genetically different;
2. identical twins are genetically the same /
have the same genotype / same genes / same
alleles ;
3. so difference in height / mass / phenotype is due to environment factor ;
4. greater difference in traits for non-identical twins;
5. difference due to genetic effects e.g. genes have a bigger effect ;

Front 68

suggest why a drug can be tested on rats before testing on humans

Back 68

1. laboratory rats of reduced genetic variability ;
2. rats have a similar / well known metabolism
3. no harm to human ;
4. looking for potential toxicity / adverse effect;
5. legal / ethical issues ;

Front 69

state what is done during each of the following phases of testing on humans P1 P2

Back 69

Phase 1:
1. drug tested on a small number of healthy individuals ;
2. low concentration / monitor safety
Phase 2:
3. drug tested on small number of patients ;
4. monitor effectiveness of treatment

Front 70

describe and explain how xylem is adapted for the transport of water and support in a plant

Back 70

Water transport:
1. hollow tubes / no living contents / end walls
broken down;
2. allow movement of water e.g. columns of water / vertical movement
3. waterproof material;
4. keeps water in the vessel e.g. less water lost
5. pores ;
6. to allow sideways movement of water;

Support:
7. lignin / extra cellulose;
8. for strength ;
9. rings / spirals;
10. for strength / flexibility ;

Front 71

explain how differential gene expression could result in the specialisation of cells

Back 71

1. correct stimulus e.g. chemical ;
2. some genes switched off / switched on
3. mRNA from switched on genes ;
4. mRNA translated ;
5. protein synthesised / different proteins produced ;
6. which permanently modify cell to become specialised /description of a modification

Front 72

describe how you oculd use a plant tissue culture technique to show which of the two tissues is totipotent

Back 72

1. sample / explants from both tissues
2. aseptic conditions / named example ;
3. grow cells into a callus
4. growth regulators
5. cells / tissue can differentiate / cells can
become whole plants;
6. details of procedure e.g. agar / leave for a suitable length of time / suitable controlled variable ;

Front 73

explain why the DNA content of the cell doubles

Back 73

1. DNA replication ;
2. so that it can halve;
3. new cells will have same amount as
original /original DNA content restored;
4. during cytokinesis ;

Front 74

describe the events occur during prophase

Back 74

1. chromosomes /chromatids condense / become visible
2. nuclear envelope breaks down
3. nucleolus breaks down
4. spindle fibre begins to form ;
5. centrioles migrate to opposite poles

Front 75

structural differences between a human sperm cell and a human egg cell

Back 75

1. flagellum / eq ;
2. overall shape e.g. streamlined / eq ;
3. fewer mitochondria / other organelles / eq ;
4. acrosome / eq ;
5. zona (pellucida) / jelly layer eq ;
6. cortical granules / eq ;
7. differences in food store types / eq ;
8. sperm cell has less cytoplasm / eq ;

Front 76

when a sperm cell reaches an egg cell, enzymes are released from the head of the sperm. explain the reasons for the release of these enzymes

Back 76

1. enzyme digest zona pellucida;
2. sperm can get through to egg cell / nucleus ;
3. contact with / receptor on zona pellucida /
(glycoprotein) jelly coat / surface of ovum;
4. causes acrosome to rupture / open

Front 77

describe what happens in the egg cell once the sperm cell nucleus has entered it.

Back 77

1. meiosis (II) is completed
2. {male and female / chromosomes come
together / (both) nuclei fuse
3. {cortical granules / enzymes/ chemicals}
released (from cell surface membrane);
4. bind with zona pellucida
zona pellucida then thickens
/hardens
5. to form fertilisation membrane / to make cell
impenetrable (to other sperm) / prevents
polyspermy / egg cell membrane {changes its
charge / becomes positive

Front 78

in plants, a double fertilisation occurs. one fertilisation involves a male gamete nucleus fusing with the egg cell nucleus. give two functions of this fertilisation.

Back 78

1. to produce a zygote;
2. to produce {original / full} complement of
{DNA / chromosomes / genetic material } /
diploid / 2n number ;
3. to allow mixing of genes / genetic material
/ genetic variation

Front 79

in the second fertilisation, the other male gamete nucleus fuses with two polar nuclei forming a triploid structure. name the triploid structure formed.

Back 79

(triploid) endosperm nucleus ;

Front 80

using the information in the table. what is the evidence that ant diversity can be used as an indicator of environmental conditions?

Back 80

a lower ant diversity indicates a high copper / poor / environment

Front 81

it has been suggested that there is no direct effect of copper on ants. suggest how the data in the table support this suggestion

Back 81

1. idea that amount of vegetation affects the
number of ants ;
2. idea that the amount of vegetation is
affected by copper level ;
3. vegetation to copper is direct link

Front 82

suggest two reasons why the seeds need to be dried and then stored in cold conditions

Back 82

1. inhibits germination ;
2. slowing down enzymes / biochemical reactions ;
3. slows down rate of decay / microbial activity ;
4. therefore prolongs seed survival
5. drying reduces freezing effect

Front 83

suggest why seed germination is tested at regular intervals

Back 83

1. idea that checking {seed viability /
germination success / eq } ;
2. allows new seeds to be produced / eq ;
3. idea that stored seeds may need replacing
e.g. due to decay / death ;

Front 84

give two ways in which zoos help to conserve endangered species.

Back 84

1. maintaining the endangered species e.g.
protection from poachers/ predation ;
2. (captive) breeding programmes /eq ;
3. reintroduction into the wild / eq ;
4. scientific research / example given / eq ;
5. education / example given / eq

Front 85

using the information in the graph, compare the effect of calcium ion concentration on the mean dry mass of shoots and the mean dry mass of pods in bean plants.

Back 85

1. both increase / eq ;
2. qualification of increase e.g. both increase
most rapidly between 0 and 100 mg dm-3 /
converse / gradient decreases with increase
in calcium / eq ;
3. dry mass {equal / 10.6 g} in both at 150 mg
dm-3 ;
4. increase in mass very similar in both after
150 mg dm-3 / increase higher in pods after
150 mg dm-3 / eq ;
5. change in pod mass greater (than shoot) / eq
;
6. correct comparative manipulation of the data
e.g. shoot increased by {8.1 g to 8.3 g} whilst
pod has increased by 11 g ;

Front 86

suggest how calcium ions contributed to the change in mass in the shoot of the bean plant

Back 86

more / larger} cells / more {cell walls /
calcium pectate / middle lamella} / helps
uptake of other ions

Front 87

describe the relationship between calcium ion concentrations and total nitrogen uptake by the bean pods

Back 87

1. positive (relationship / correlation) / as
calcium ion concentration increases so does
total nitrogen uptake by pods [not other way
round] / eq ;
2. {non-regular /greatest increase in total
nitrogen uptake occurs between 0 and 75 mg
dm-3 of calcium

Front 88

suggest the form in which he nitrogen was supplied in the watering solution

Back 88

nitrate / ammonium / ammonia ;

Front 89

suggest how the protein content of the bean pods from plants grown in the watering solution containing a calcium ion concentration of 300mg dm-3 would differ from those watered with a lower calcium ion concentration. give an explanation.

Back 89

1. {greater / eq} (protein content) ;
2. greater nitrogen uptake / eq ;
3. nitrogen is {part / used in synthesis} of
{amino acids / protein} / eq ;
4. (amino acids) used to synthesise protein / eq
;

Front 90

suggest what is meant by the phrase suitably-prepared petri dish

Back 90

1. ref. to agar / eq ;
2. idea that bacteria need to be distributed ;
3. idea of {single / named} bacterial strain / eq
;
4. appropriate microbiological technique
employed e.g. aseptic / sterile plates

Front 91

describe the function of disc 3

Back 91

to allow a comparison with the other discs / to show
that any difference between the discs is due to the
treatment given to those discs

Front 92

explain why clear zones are found around disc 1 and disc 2

Back 92

1. (tea tree oil) { diffused / eq } (out of disc) ;
2. killed the bacteria / inhibits bacterial growth

Front 93

the clear zone around disc 1 is not a circle. suggest how you would calculate the mean diameter of this clear zone

Back 93

1. record several measurements / eq ;
2. divide by number of measurements (to obtain
mean)

Front 94

describe how you would determine the minimum strength of tea tree oil that would be as effective as the 100% tea tree oil.

Back 94

1. 3 (or more) dilutions of tea tree oil / eq ;
2. from 50% downwards / eq ;
3. looking for minimum strength when diameter
is same as original strength / eq ;
4. one other named variable kept constant ;

Front 95

suggest one reason why it was good safety practisce to incubate the petri dish at 25c rather than 37c

Back 95

1. 37°C is (human) body temperature ;
2. (this temp) allows growth of {pathogenic /
eq} bacteria / encourages more rapid {growth
/reproduction/ eq} ;