Question
Vinegar is a water-based solution of ethanoic acid. Acetobacter aceti is used in the production of vinegar. This bacterium has the ability to convert ethyl alcohol, \(\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}\), into ethanoic acid, \(\mathrm{CH}_3 \mathrm{COOH}\).
$
\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}+\mathrm{O}_2 \rightarrow \mathrm{CH}_3 \mathrm{COOH}+\mathrm{H}_2 \mathrm{O}
$
In the generator method of ethanoic acid fermentation, Acetobacter aceti are grown over wood shavings in a fermenter to the point where they form a biofilm.
At the base of the fermenter oxygen is bubbled in, which then rises through the wood shavings. Ethanol drips through the wood shavings. At a suitable temperature the ethanol is converted to ethanoic acid, which is withdrawn from the bottom of the fermenter, and new ethanol is added at the top.
a.i. \(A\). aceti is a Gram-negative bacterium. If a Gram staining procedure were carried out on a sample of \(A\). aceti, predict the result that would be
observed after decolourization.[1]
a.ii \(A\). aceti is a Gram-negative bacterium. If a Gram staining procedure were carried out on a sample of \(A\). aceti, predict the result that would be
observed after counterstaining.[1]
b.i. List two abiotic variables that would need to be monitored during this fermentation process.[2]
b.ii.Describe one way in which microorganisms in this fermenter could be limited by their own activities.[2]
b.iiiDistinguish between batch fermentation and continuous fermentation.[2]
c. Outline the concept of an emergent property.[2]
▶️Answer/Explanation
Ans:
a.i.the bacteria would be clear/colourless
a.ii.would stain pink
Do not accept “violet” or “lilac”.
b.i.a. oxygen
b. temperature
c. \(\mathrm{pH}\) levels
d. \(\mathrm{CO}_2\)
b.ii.a. name of a factor
b. description
eg
a. \(\mathrm{pH}\)
b.lowered by “ethanoic» acid production.
eg
a. increase in temperature
b. due to metabolism.
eg
a. increased population size/reproduction
b. would limit resources.
eg
a. increased metabolic waste
b. reduce population.
b.iii
Table format is not required.
c. a. emergent properties arise from the interaction of the elements of a system
b. behaviours exhibited which are not shown by individuals
C. quoroum sensing
OR
matrix production
OR
water channels
OR
antibiotic resistance
OR
other correct example
Question
The model describes the fundamental and realized niches of a species of microscopic marine arthropod in the Northern hemisphere with respect to two different factors (X and Y). The abundance of the species is shown over twelve months. The fundamental niche is separated into five zones ranging from critical to optimal conditions. The population of the species in its realized niche each month is represented by an oval. The size of each oval shows the population abundance.
a. Distinguish between fundamental niche and realized niche.[1]
b. State the month where the population reaches its maximum.[1]
c.i. Outline how factor \(Y\) affects the species from January to April.[2]
c.ii.Suggest, with a reason, what factor \(Y\) could be.[2]
▶️Answer/Explanation
Ans:
a. fundamental niche is all potential conditions a species could live in whereas realized niche is actual conditions under which the species live
b. April
c.i. a. limited effect on low/stable population size from January to March
OWTTE.
b. large effect increases population size from March to April OWTTE.
c. niche conditions decrease from January to March
d. niche conditions improve from March to April
c.ii.a. factor eg temperature.
b. explanation
eg as temperature increases in spring “March to April» so the conditions for the species are more favourable.