Calculate the percentage increase in the use of liquid fuels from 1950 to 1975.

%

Referring to the data, compare and contrast the changes in the use of the different fuels between 1950 and 1975.

« $\frac{(2250-300)\times 100}{300}$ = » 650 «%» ✔

[Source: Boden T ; Marland G ; Andres R J (1999): Global, Regional, and National Fossil-Fuel CO2 Emissions (1751 - 2014) (V. 2017). Carbon Dioxide Information Analysis Center (CDIAC), Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). doi:10.3334/ CDIAC/00001_V2017]

A certain number provided reasonable answers considering the y-axis graduations, but too many had totally incorrect and unrealistic answers, showing that they could not calculate a percentage increase.

Most interpreted the graph correctly, but it was more difficult for some to include similarities, only focusing on differences. A certain number ignored to take only 1950 to 1975 into account, as specified in the question.

Describe the body length frequency of the B. italica worms collected in this study.

The relationship between A. pallipes and B. italica is mutualistic.

A. pallipes feeds on algae and another worm, B. exodonta, lives inside A. pallipes as a parasite. State the trophic level of B. exodonta in this food chain.

Distinguish between mutualism and parasitism, providing another example of mutualism and another example of parasitism.

a. higher frequency of medium length worms 
b. shows normal distribution 
c. lower frequency at extremes

Allow correct numerical description of these points.

secondary consumer / third trophic level

a. in parasitism only one organism benefits whereas in mutualism both benefit 
b. example for both parasitism AND mutualism

Do not allow B. italica or B. exodonta as examples.

eg parasitic: human tapeworms AND mutualism: bacteria in human digestive tract

In order to form galls, the insects choose a location where cell division occurs at a high rate. State the term for a region of rapid cell division within a plant.

Describe the relationship between gall diameter and percentage survival of E. solidaginis.

Explain the concept of directional selection with respect to this example.

«apical» meristem/shoot apex

a. percentage survival is higher with larger diameter galls
OR
positive relationship  

b. variation/outlier at the lower diameters  OWTTE

c. little variation in survival percentage at highest diameters OWTTE

a. directional selection is when an extreme phenotype/characteristic is favoured  OWTTE

b. flies that form small galls will be selectively predated  OWTTE – accept vice versa

c. over time, flies that produce small galls will become rarer
OR
mean gall size will increase

Compare and contrast the design of both mesocosms (vertical flow and horizontal flow).

Suggest with a reason which system best reproduces the conditions of the natural environment.

State two variables other than temperature and light that should be controlled in this experiment, in order to discover which system is more effective at removing nutrients from water.

Similarities [1 max]
a. both have similar design «input and output» ✔

b. both open systems ✔

Differences [1 max]
c. vertical flow/«figure» A has pump but horizontal flow/«figure» B does not/flows naturally ✔ Do not accept references to rate of flow or pressure as they are unknown.

d. horizontal flow/«figure» B has a larger «surface» area
OR
horizontal flow/«figure» B has more plants ✔ Accept vice versa.

e. vertical flow/«figure» A has a pre-treatment «with sedimentation tank» before treatment but not horizontal flow/«figure» B ✔ Accept vice versa.

a. horizontal flow/«figure» B because it is larger
OR
horizontal flow/«figure» B contains more/several plants ✔

b. horizontal flow/«figure» B because it works by natural flow
OR
horizontal flow/«figure» B because it works without a pump ✔ Do not accept river instead of flow.

a. type/number of plants ✔

b. type of soil/substrate ✔

c. pH level ✔

d. initial concentration of nutrients ✔

e. timespan of experiment ✔

f. volume of water/influent
OR
flow rate ✔ Do not accept amount instead of volume.

If more than two variables written, mark only the first two.

Suggest a hypothesis for the trend in the graph.

Mesocosm experiments using water from Narragansett Bay were completed in the laboratory during a six month period. Discuss advantages and limitations of carrying out mesocosm investigations.

a. decrease in chlorophyll concentrations as decrease in phytoplankton/plants 

b. due to increase in pollution / increase in sea temperatures / decrease in pH/climate change

Accept other reasonable reason for mp b.

Advantages of mesocosm experiments:

a. scientist can alter/manipulate/control environmental conditions 

b. allows carrying out experiments with many samples / replicates 

c. ease of collection of continuous data 

Limitations of mesocosm experiments:

d. difficult to mimic natural environmental conditions exactly 

e. Natural environments change /are not static

Needs to suggest advantage and limitation for full marks.

Each of the mesocosms is an open ecosystem. State the property that makes the mesocosms open ecosystems.

Assuming that the populations of bacteria are under bottom-up control, identify the mesocosms in which the bacterial populations will be highest.

Outline top-down effects on the bacteria in the four mesocosms. 

Suggest advantages of undertaking this experiment in the sea rather than in the laboratory.

there is exchange of matter/energy
OR
there is an exchange between the surface of the water and the atmosphere ✔

 eg: matter could be nutrients/gas/water/minerals/etc; energy could be heat or light

soil and no fish «mesocosm» AND soil and fish «mesocosm» ✔

Both mesocosms required

Accept answers such as “the two with soil”.

a. zooplankton feed on bacteria reducing their numbers ✔

b. fish feed on zooplankton «therefore» increasing bacterial population ✔

a. conditions closer to levels experienced naturally by the organism ✔
OWTTE

b. natural variation of abiotic variables ✔
Accept examples, eg: temperature, dissolved oxygen

c. more natural behaviour/interactions ✔

d. not harm organisms by removing them from natural habitat ✔