| Date | November 2017 | Marks available | 2 | Reference code | 17N.3.HL.TZ0.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Identify | Question number | 14 | Adapted from | N/A |
Question
To assess the impact of introduced cats (Felis silvestris) that prey on native species, a study was carried out on 120 islands around the world. The graph shows the impact of F. silvestris on reptiles, birds and mammals.
The ‘Ua‘u petrel (Pterodroma sandwichensis) is considered to be an indicator species in the Hawaiian Islands.
Identify how the pattern in mammals is different from reptiles and birds.
Describe how invasive species such as F. silvestris can have a significant impact on native species.
Suggest a method to limit the impact of F. silvestris on native species.
State the role of an indicator species.
Identify possible approaches to maintain the population of P. sandwichensis.
Markscheme
a. more extinct than endangered «in mammals as opposed to reptiles and birds»
b. total percentage extinct plus endangered mammals lower than reptiles and birds
[Max 1 Mark]
a. cats/invasive species compete with native species for food/habitat/resources
OWTTE
b. invasive species/cats may reduce/endanger native populations
c. invasive species/cats may change the structure/balance of the food web/chain
[Max 2 Marks]
a. control population/sterilization «of cats»/culling/hunting
b. keep household cats indoors
[Max 1 Mark]
a. early warning system
b. provide information on environmental conditions/ecosystem
OWTTE
[Max 1 Mark]
a. ex-situ/zoos/captive breeding
b. control predators
c. in-situ/management of natural reserves/breeding habitats/parks/resources/clean-up pollution
d. education
OR
government legislation
Accept any other valid answer
[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 | May 2017 | Marks available | 2 | Reference code | 17M.3.HL.TZ1.15 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | State | Question number | 15 | Adapted from | N/A |
Question
Zoos devote much effort to preserving and breeding elephants in captivity. Data for births resulting from artificial insemination in zoos in the United States from 1960 to 2012 are shown below.
54% of successful artificial inseminations have resulted in miscarriages, stillborn births or premature deaths.
Evaluate the success rate of breeding elephants by artificial insemination using these data.
Discuss two advantages of ex situ conservation measures.
State the two components needed to calculate the biodiversity of an area.
Markscheme
a. «not very successful as» less than half of the artificial inseminations have resulted in live births
b. there are no data for artificial insemination that did not result in pregnancy / no data for normal breeding success «in zoos»
Accept answers in the converse: «not very successful as» more than half do not result in live births
a. raise awareness / gain widespread public/political support for conservation actions
b. breed endangered species in captivity «for reintroduction»
c. education/research opportunities
d. lower maintenance/cost than in situ conservation
e. protect endangered species
a. number of organisms of each species «present»
b. «total» number of species
OR
«total» number of organisms of all species found
| Date | May 2017 | Marks available | 3 | Reference code | 17M.3.HL.TZ1.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Discuss | Question number | 14 | Adapted from | N/A |
Question
Define indicator species.
Indicator species may be affected by biomagnification. Discuss biomagnification using a named example of a pollutant.
Determine whether islands are open or closed ecosystems.
Markscheme
organism that is present/absent when specific environmental conditions exist
OR
organism used to assess a specific environmental condition
a. example eg: DDT / mercury / cadmium
b. substance accumulates in «fat» tissue/not excreted «when consumed»
c. contaminated organisms consumed «in large quantities» by higher level consumers
d. pollutant becomes more concentrated at each higher trophic level / through the food chain
e. some pollutants are more likely to be biomagnified «accumulate in fat tissue»
OR
some organisms are more likely to be affected by biomagnification than others
OR
biomagnification not the same at each trophic level
Only [2] if verified example not given.
closed because islands do not exchange matter/nutrients with surroundings
OR
open because islands do exchange matter/nutrients with surroundings
| Date | November 2016 | Marks available | 2 | Reference code | 16N.3.HL.TZ0.16 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Compare and contrast | Question number | 16 | Adapted from | N/A |
Question
Forest fires are very common in the Amazon forest. A study was performed to see the relationship between forest fragmentation, fire and management
Describe one method that could have been used to estimate the population size of a given tree in a forest after fire damage had occurred.
Outline how the edge effect can affect diversity in forests.
The number of plants in two fields of approximately the same size was counted.
Compare and contrast the richness and the evenness of the two fields.
Markscheme
ALTERNATIVE 1
a. transect through a given area
b. trees counted on transect
c. calculation of total population considering area
ALTERNATIVE 2
d. random sampling using quadrats
e. trees counted in quadrat
f. population calculated using area
ALTERNATIVE 3
g. GPS/Google Earth used to map individuals of a tree species
h. data base of data obtained
i. population density calculated using area
a. edge effect are the changes in community structures that occur at the boundary of two habitats
b. areas with small habitat fragments exhibit especially pronounced edge effects
c. edge species will always have a habitat
OR
edge biodiversity increases
d. if patches of forest are too small the non-edge species cannot find a habitat
e. «then» overall non-edge biodiversity is lower
a. same richness as they have the same number of species/total of individuals
b. field 1 has more evenness as more even distribution of numbers among the species
Accept correct use 2 of Simpson diversity index.
| Date | November 2015 | Marks available | 1 | Reference code | 15N.3.HL.TZ0.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 11 | Adapted from | N/A |
Question
Outline how habitat corridors can aid conservation of biodiversity in a nature reserve.
Explain how living organisms can change the abiotic environment during primary succession.
Markscheme
a. they allow species to travel between habitats / OWTTE;
b. outline of an example of a habitat corridor;
a. lichens secrete chemicals/acid which break down inorganic material/rock;
b. lichens/plants/litter change pH of the soil (which prevents/assists some species to establish);
c. organisms increase the mineral/organic/humus content of the soil when they decompose;
d. (organic matter and humus) can increase water retention;
e. plant roots can bind soil preventing erosion / break down soil particles;
| Date | May 2013 | Marks available | 6 | Reference code | 13M.3.HL.TZ1.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Discuss | Question number | 11 | Adapted from | N/A |
Question
Discuss how international efforts can contribute to the conservation of fish stocks.
Outline the biogeographical features of nature reserves that promote the conservation of diversity.
Markscheme
a. oceans are huge ecosystems with no borders / many important fishing grounds are in international waters;
b. fishing vessels often have a large geographical range / operate outside of national jurisdiction;
c. marine organisms migrate so need protection across their full range / breeding sites may be distant from feeding grounds so both need to be protected;
d. agree on maximum sustainable yields/quotas;
e. apply the precautionary principle in determining the level of exploitation;
f. agree on allowed fishing sites and exclusion zones;
g. agree on fishing seasons and moratoriums;
h. identify and agree on species that may be fished and those that may not;
i. determine and agree on which fishing methods are allowed and which are not/net and mesh size limitations;
a. nature reserve is a well defined/limited region with a protective framework/legislative protection;
b. large reserves promote biodiversity more effectively than small reserves;
c. size must be enough to have a well defined community of organisms;
d. edge effect is seen at or near the boundary between ecosystems;
e. leads to differences in population densities/biodiversity/levels of predation in central areas compared to edges;
f. habitat corridors allow organisms to move between parts of a fragmented ecosystem;
g. example of habitat corridors such as hedges/canals/drainage channels/tunnels/underpasses/overpasses;
| Date | May 2013 | Marks available | 1 | Reference code | 13M.3.HL.TZ2.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Distinguish | Question number | 11 | Adapted from | N/A |
Question
Distinguish between in situ and ex situ conservation.
The Atlantic cod is considered in many countries to be endangered due to overfishing. Describe two methods that could be used to estimate the cod population.
Outline one reason for the extinction of a named animal species.
Markscheme
in situ within the organism’s natural environment whereas ex situ taken out of natural environment / OWTTE
a. record size of catches from fishing boats;
b. capture, tagging, releasing and recapturing fish / Lincoln index;
c. sample fishes with trawling nets;
d. estimate population with echo sounder/sonar/fish finder;
Award marks only for the first two methods if more than two written.
name of species and what caused it to become extinct (both needed)
The named species must be extinct and not endangered.
eg:
passenger pigeon (became extinct when) hunted as a source of food
| Date | November 2013 | Marks available | 6 | Reference code | 13N.3.HL.TZ0.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Discuss | Question number | 12 | Adapted from | N/A |
Question
Eight sub-species of tigers existed in 1950, but three of these former sub-species have now become extinct. Discuss the role of active management techniques to prevent the extinction of the remaining tiger species.
Markscheme
Award [1] for one argument for each of the following aspects:
identification/monitoring of tiger populations;
creation of in situ/nature reserves;
provision of corridors between nature reserves;
hunting/poaching;
development of ecotourism;
impact on local economy;
ban on tiger products trade / development of synthetic alternatives;
increase of public awareness;
need for international cooperation/funds to implement measures;
ex situ/captive breeding programs;
extraction of DNA for gene bank;
| Date | May 2011 | Marks available | 2 | Reference code | 11M.3.HL.TZ1.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Outline | Question number | 11 | Adapted from | N/A |
Question
Outline the consequences of the edge effect for small nature reserves.
Markscheme
edge effect is the contrast between different environments/from central area of reserve;
small reserves have more edge effect;
as fragmentation increases so does edge (effect);
example of edge effect (e.g. cowbirds that lay eggs in edge will increase);
| Date | May 2011 | Marks available | 2 | Reference code | 11M.3.HL.TZ2.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Outline | Question number | 11 | Adapted from | N/A |
Question
Define indicator species.
Outline, with a named example, biological control of invasive species.
Markscheme
species sensitive to certain environmental conditions / species used to monitor environmental change / species used to determine environmental conditions
name of species to be controlled;
method of biological control with species name of predator/parasite/pathogen;
e.g. rabbits (introduced into Australia);
controlled by release of myxoma virus / myxomatosis (from South America);
Allow any other verifiable example. Reject cane toads as a biological control agent and other unsuccessful cases.
| Date | May 2012 | Marks available | 6 | Reference code | 12M.3.HL.TZ1.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Discuss | Question number | 12 | Adapted from | N/A |
Question
Discuss the advantages of in situ conservation of endangered species, using examples.
Markscheme
in situ conservation is carried out in nature reserves/natural habitats;
named example of a species that is being conserved in situ;
in situ conservation reduces possibility that habitat disappears and the whole community is lost / may prevent the total number of species that become endangered from increasing;
allows species to live in an environment for which they are adapted / they are able to fit into their normal food chains;
threatened species in a reserve may be monitored for further deterioration in numbers / remedial steps can be taken;
offspring acquire skills from parents/peers around them / offspring acquire natural behaviour;
reserves and protected areas in various parts of the world can share experience on how to manage them successfully;
nature reserves are popular sites for the public to visit maintaining awareness/education/scientific study;
reserves are places to return endangered individuals from breeding programmes as they provide realistic conditions for re-adaptation / OWTTE;
| Date | May 2012 | Marks available | 6 | Reference code | 12M.3.HL.TZ2.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Explain | Question number | 12 | Adapted from | N/A |
Question
Explain, with examples, the use of specific indicator species and biotic indices to detect changes in the environment.
Markscheme
indicator species:
indicator species are sensitive to/need specific environmental conditions/have specific/limited range of tolerance;
their population growth/disappearance/reduction indicates specific changes in the environment;
example of indicator species and what it indicates; (e.g. decrease in the population of stonefly larvae indicates increasing pollution levels/dissolved oxygen loss)
Allow any other example.
biotic index:
compares the relative frequency of indicator species;
can be calculated for overall environmental assessment of an ecosystem;
multiply number of individuals of each indicator species by its pollution tolerance rating;
an abundance of intolerant species gives a high score / vice versa;
indicating an unpolluted environment / vice versa;
a change in the biotic index over time indicates a change in environmental conditions;
Award [4 max] if only indicator species or biotic indices are addressed.
| Date | May 2010 | Marks available | 6 | Reference code | 10M.3.HL.TZ1.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Evaluate | Question number | 12 | Adapted from | N/A |
Question
Evaluate the use of indicator species in monitoring environmental changes.
Markscheme
indicator species sensitive to/need specific environmental conditions to survive;
monitor population size of indicator species over time;
biotic index can be calculated;
low overall score when abundance of tolerant species / lack of indicator species / vice versa;
represent summation of factors/overall assessment of environmental conditions;
time consuming / species not easy to identify (need keys) / species may not be present for other reasons such as season / another disadvantage;
methodology is simple / minimum equipment needed;
needs a reference study/guide to compare;
example of variable e.g. oxygen level / temperature / heavy metals / sulphur dioxide in air / other;
example of appropriate indicator species e.g. Tubifex to heavy metals / Chironomis to low oxygen levels / lichens to sulphur dioxide / other;
| Date | November 2011 | Marks available | 6 | Reference code | 11N.3.HL.TZ0.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Discuss | Question number | 12 | Adapted from | N/A |
Question
Discuss international measures that would promote the conservation of fish stocks.
Markscheme
large areas of ocean under no government control therefore need for international agreement/legislation;
fish stocks are a renewable resource if managed properly/should not be overexploited;
total allowable catches/quotas to limit maximum catch;
regulation of mesh sizes/selective fishing gear/limit size of fish caught/ban drift nets;
limit fishing effort by reducing the number of fishing days at sea of fishing vessels;
fix the number and type of fishing vessels authorized to fish;
cooperation may be difficult as most laws made at national level;
closed areas/total ban on fishing in threatened areas;
closed seasons banning fishing during breeding season;
use of fish farms;
| Date | November 2011 | Marks available | 3 | Reference code | 11N.3.HL.TZ0.11 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 11 | Adapted from | N/A |
Question
In 1988 a fire destroyed large portions of forest in Yellowstone National Park, USA. Photograph A was taken soon after the fire and photograph B one year later. The photographs are of the same area.
Identify, with a reason, the type of succession that has taken place.
Outline a method that could be used to sample the plant population shown in photograph B.
Yellowstone National Park was the first national park in the world and is a designated biosphere reserve site. Outline the biogeographical features of nature reserves that promote conservation of diversity.
Markscheme
secondary succession as some plants/organic components were present before fire
describe method for ensuring random placement of quadrats in a grid; (do not accept transect)
different species present in quadrat identified and counted;
used to estimate species density/frequency/abundance/cover;
size:
large nature reserves usually promote conservation better than small ones;
large areas needed for far-ranging animals (e.g. grizzly bear);
larger areas have proportionally smaller perimeters/less affected by edges;
edge effect:
ecology of edges of ecosystems is different from central areas due to edge effects;
fragmentation (of forests) leads to increase in edges which will favour some species over others;
habitat corridor:
habitat/movement/wildlife corridors allow organisms to move between different parts of fragmented habitat;
To award [3] responses must refer to size, edge effect and habitat corridor.
| Date | November 2009 | Marks available | 6 | Reference code | 09N.3.HL.TZ0.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Discuss | Question number | 12 | Adapted from | N/A |
Question
Discuss international measures that would promote the conservation of fish, including methods used to measure conservation of fish stocks.
Markscheme
measures to promote conservation: [3 max]
reduce total allowable catch below maximum sustainable yield/MSY;
limit areas where fishing can take place;
decrease total net size;
increase mesh size to let immature fish through / set minimum landing sizes for fish;
reduce fishing effort;
reduce/stop subsidies for increasing size of fleet;
methods used to measure conservation: [3 max]
monitor fish catches;
calculate the mass of fish that can be removed annually / maximum sustainable yield;
required knowledge of birth rate, growth rate of fish and mortality rates;
can be estimated by looking at age structure of landed fish;
can be estimated by catch per fishing effort;
| Date | November 2010 | Marks available | 6 | Reference code | 10N.3.HL.TZ0.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Discuss | Question number | 12 | Adapted from | N/A |
Question
Discuss the role of ex situ conservation of endangered species.
Markscheme
a. named example (e.g. zoo/botanic garden/seed bank/aquarium/laboratory) / definition of ex situ;
Do not accept open parks e.g. Safari.
advantages: [3 max]
b. prevent extinction / help in conservation of species;
c. possible breeding;
d. reintroduction into the wild;
e. correct nutrition constantly;
f. veterinary care;
g. educational use / research use;
h. prevent poaching/picking rare flowers/damage to habitat by man;
disadvantages: [2 max]
i. difficulty in the reintroduction of the species to the wild;
j. increases inbreeding / restricted gene pool;
k. selection of organisms to be kept ex situ;
l. not their natural habitat / reduces evolution;
m. does not solve the cause/problem e.g. habitat loss;