| Date | November 2017 | Marks available | 2 | Reference code | 17N.3.HL.TZ0.17 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Describe | Question number | 17 | Adapted from | N/A |
Question
Define fundamental niche.
Outline a reason for organisms seldom occupying their entire fundamental niche.
Describe the relationship between Zooxanthellae and reef-building coral species.
Markscheme
the potential/full range of conditions under which an organism can live
competition for resources/named resource
OR
competitive exclusion «limits the niche»
a. «endo»symbiotic/mutualistic relationship
b. zooxanthellae/photosynthetic algae/dinoflagellates live in coral tissues
c. coral provides protection for algae/dinoflagellates
d. algae/dinoflagellates provide minerals/products of photosynthesis/oxygen/sugars to coral
[Max 2 Marks]
| Date | May 2017 | Marks available | 1 | Reference code | 17M.3.HL.TZ2.15 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | State | Question number | 15 | Adapted from | N/A |
Question
Most reef-building corals contain photosynthetic algae, called Zooxanthellae, that live in their cells. Coral bleaching can occur as a result of human-induced changes leading to the Zooxanthellae being ejected from the coral.
State the type of interaction that occurs between Zooxanthellae and reef-building corals.
State the trophic level of Zooxanthellae.
When coral is bleached, certain organisms become more common in the ecosystem such as the cnidarian Gorgonia, the echinoderm Diadema, other algae and certain sponges. State the term that is used for organisms whose presence provides evidence of the existence of a particular environmental condition.
A coat of algae builds up on coral reefs as a consequence of eutrophication. Explain the relationship between eutrophication and algal growth.
Explain how an excessive growth of algae on coral reefs can be controlled by top-down factors.
Markscheme
symbiosis/mutualism
producers
indicator species
a. eutrophication is nutrient enrichment of a body of water
b. example of nutrients eg: nitrates
c. «nutrients» serve as fertilizer for the algae «promoting growth»
a. top-down factors refer to predation/herbivory/trophic level above another one
b. which limit/control population growth
c. named example of a top-down predator eg: parrotfish. Do not accept general names, like “fish”.
| Date | November 2016 | Marks available | 3 | Reference code | 16N.3.HL.TZ0.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Suggest | Question number | 14 | Adapted from | N/A |
Question
Cryptococcus neoformans and the closely related species Cryptococcus gattii are human fungal pathogens. The reproduction of these yeast species on increasing concentrations of pigeon droppings (PD) was examined to determine whether they occupy the same or different ecological niches. The results for reproduction are expressed as a percentage relative to the control.
Suggest how this experiment shows that pigeon droppings represent a realized ecological niche for C. neoformans and a fundamental (but not a realized) niche for C. gattii.
Markscheme
a. the realized niche is the actual while the fundamental niche is «all of» the potential
b. «shared» fundamental niche shown by equal reproduction on control
c. C. neoformans reproduces on PD indicating a realized ecological niche
d. competitive exclusion decreases realized niche of C. gattii
e. C. gattii reproduces poorly on PD representing a fundamental niche
OR
C. gattii reproduces poorly on PD so not a realized niche
| Date | May 2016 | Marks available | 2 | Reference code | 16M.3.HL.TZ0.15 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 15 | Adapted from | N/A |
Question
The figure shows the distribution of two species of freshwater flatworms, Planaria gonocephala and Planaria montenegrina, over a range of stream temperatures. Graph A and graph B show the distributions when each species is separate from the other. Graph C shows the distribution when they are found living together.
Using graph A and graph B, compare and contrast the temperature ranges of the two species when they are found separately.
Explain, with respect to the example of P. montenegrina, what is meant by realized niche.
Markscheme
P. gonocephala is found over a greater range of temperatures (Note: do not accept just numbers (T) of ranges without comparing/contrasting clearly).
P. gonocephala is found between 16.5 degrees and 23.0 degrees whereas P. montenegrina is not
OR
P. gonocephala is found at a higher temperature
Both are found in temperatures of 6.5 degrees to 16.5 degrees
Do not accept “both show a greater range” alone as this comes from graph C not A and B as the question asks.
Realized niche is that which organism actually occupies
Presence of another species/P. gonocephala narrows the niche
Limited by competition
OR
competitive exclusion
The realized niche is colder/smaller range in the presence of P. gonocephala
| Date | May 2015 | Marks available | 2 | Reference code | 15M.3.HL.TZ1.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Distinguish | Question number | 11 | Adapted from | N/A |
Question
Distinguish between the use of a quadrat and a transect in gathering field data.
State the change in species diversity and the change in production during primary succession.
Species diversity: ………………………………………..
Production: ………………………………………………..
State one difficulty in classifying organisms into trophic levels.
Markscheme
Accept any horizontal set of ideas, up to two sets.
Species diversity: rises
Production: rises
Both needed for [1].
an organism can occupy/feed at more than one trophic level
| Date | November 2012 | Marks available | 1 | Reference code | 12N.3.HL.TZ0.10 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | State | Question number | 10 | Adapted from | N/A |
Question
Knowledge of deep-water fish is important for fisheries and marine reserve management. Scientists analysed data from scientific trawls made from 1977 to 1989 (early period) and from 1997 to 2002 (late period). These were at depths from 800 m to 4800 m in the Porcupine Seabight and Porcupine Abyssal Plain area southwest of Ireland. The graphs represent the abundance of fish and the number of species for each of these trawls.
State the depth at which the maximum number of species per trawl were caught.
Compare the abundance of fish between the early period (1977 to 1989) and the late period (1997 to 2002).
Suggest one reason for the difference in the abundance of fish at depths down to 2000 m between the early period and the late period.
Discuss the evidence in these data for a decline in the biodiversity of fish between the early period and the late period.
State two types of interactions that are most likely to occur among deep-water fish.
1. …………………………………………………………
2. …………………………………………………………
Outline the concept of maximum sustainable yield in the conservation of fish stocks.
Markscheme
1550 (m) (accept answers in the range of 1450 (m) to 1650 (m))
both show decrease in abundance as depth increases;
both show similar/low abundance at depths greater than 3000 (m); (accept values in range 2500 (m) to 3000 (m))
for depths less than 2500 (m) the abundance is (much) greater in the early period than in the late period; (accept values in range 2000 (m) to 2500 (m))
the highest abundance occurs in the late period (although) this is isolated;
overfishing / pollution / change in sea temperature / change in food sources
no evidence that there are fewer species;
difficult to compare as more trawls in the early period /early period of longer duration than late period;
diversity may have increased from (around) 2000 (m) to 4000 (m) / outliers for greater species diversity are all late period;
not enough details about time of year/duration of trawls; (accept any other valid argument)
Do not accept answers stating only “not enough data”.
competition and predatory/predation (both needed)
is the maximum number of fishes of a species that can be caught/harvested without causing a population decline / still allowing a population to regenerate;
corresponds to the turning point of a population growth curve;
below that point yield is lower and population grows / above that point yield and population will decline;
used to determine fishing quotas;
difficulty in estimating populations;