Option C: Ecology and conservation

Option C: Ecology and conservation

Core

C.1 Species and communities

Nature of science:

• Use models as representations of the real world - zones of stress and limits of tolerance graphs are models of the real world that have predictive power and explain community structure.

Understandings:

• The distribution of species is affected by limiting factors.

• Community structure can be strongly affected by keystone species.

• Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species.

• Interactions between species in a community can be classified according to their effect.

• Two species cannot survive indefinitely in the same habitat if their niches are identical.

Applications and skills:

• Application: Distribution of one animal and one plant species to illustrate limits of tolerance and zones of stress.

• Application: Local examples to illustrate the range of ways in which species can interact within a community.

• Application: The symbiotic relationship between Zooxanthellae and reef-building coral reef species.

• Skill: Analysis of a data set that illustrates the distinction between fundamental and realized niche.

• Skill: Use of a transect to correlate the distribution of plant or animal species with an abiotic variable.

C.2 Communities and ecosystems

Nature of science:

• Use models as representations of the real world - pyramids of energy model the energy flow through ecosystems.

Understandings:

• Most species occupy different trophic levels in multiple food chains.

• A food web shows all the possible food chains in a community.

• The percentage of ingested energy converted to biomass is dependent on the respiration rate.

• The type of stable ecosystem that will emerge in an area is predictable based on climate.

• In closed ecosystems energy but not matter is exchanged with the surroundings.

• Disturbance influences the structure and rate of change within ecosystems.

Applications and skills:

• Application: Conversion ratio in sustainable food production practices.

• Application: Consideration of one example of how humans interfere with nutrient cycling.

• Skill: Comparison of pyramids of energy from different ecosystems.

• Skill: Analysis of a climograph showing the relationship between temperature, rainfall and the type of ecosystem.

• Skill: Construction of Gersmehl diagrams to show the inter-relationships between nutrient stores and flows between taiga, desert and tropical rainforest.

• Skill: Analysis of data showing primary succession.

• Skill: Investigation into the effect of an environmental disturbance on an ecosystem.

C.3 Impacts of humans on ecosystems

Nature of science:

• Assessing risks and benefits associated with scientific research - the use of biological control has associated risk and requires verification by tightly controlled experiments before it is approved.

Understandings:

• Introduced alien species can escape into local ecosystems and become invasive.

• Competitive exclusion and the absence of predators can lead to reduction in the numbers of endemic species when alien species become invasive.

• Pollutants become concentrated in the tissues of organisms at higher trophic levels by biomagnification.

• Macroplastic and microplastic debris has accumulated in marine environments.

Applications and skills:

• Application: Study of the introduction of cane toads in Australia and one other local example of the introduction of an alien species.

• Application: Discussion of the trade-off between control of the malarial parasite and DDT pollution.

• Application: Case study of the impact of marine plastic debris on Laysan albatrosses and one other named species.

• Skill: Analysis of data illustrating the causes and consequences of biomagnification.

• Skill: Evaluation of eradication programmes and biological control as measures to reduce the impact of alien species.

C.4 Conservation of biodiversity

Nature of science:

• Scientists collaborate with other agencies—the preservation of species involves international cooperation through intergovernmental and non-governmental organizations.

Understandings:

• An indicator species is an organism used to assess a specific environmental condition.

• Relative numbers of indicator species can be used to calculate the value of a biotic index.

• In situ conservation may require active management of nature reserves or national parks.

• Ex situ conservation is the preservation of species outside their natural habitats.

• Biogeographic factors affect species diversity.

• Richness and evenness are components of biodiversity.

Applications and skills:

• Application: Case study of the captive breeding and reintroduction of an endangered animal species.

• Application: Analysis of the impact of biogeographic factors on diversity limited to island size and edge effects.

• Skill: Analysis of the biodiversity of two local communities using Simpson’s reciprocal index of diversity.

Additional higher level

C.5 Population ecology

Nature of science:

• Avoiding bias - a random number generator helps to ensure population sampling is free from bias.

Understandings:

• Sampling techniques are used to estimate population size.

• The exponential growth pattern occurs in an ideal, unlimited environment.

• Population growth slows as a population reaches the carrying capacity of the environment.

• The phases shown in the sigmoid curve can be explained by relative rates of natality, mortality, immigration and emigration.

• Limiting factors can be top down or bottom up.

Applications and skills:

• Application: Evaluating the methods used to estimate the size of commercial stock of marine resources.

• Application: Use of the capture-mark-release-recapture method to estimate the population size of an animal species.

• Application: Discussion of the effect of natality, mortality, immigration and emigration on population size.

• Application: Analysis of the effect of population size, age and reproductive status on sustainable fishing practices.

• Application: Bottom-up control of algal blooms by shortage of nutrients and top-down control by herbivory.

• Skill: Modelling the growth curve using a simple organism such as yeast or species of Lemna.

C.6 Nitrogen and phosphorus cycles

Nature of science:

• Assessing risks and benefits of scientific research - agricultural practices can disrupt the phosphorus cycle.

Understandings:

• Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia.

• Rhizobium associates with roots in a mutualistic relationship.

• In the absence of oxygen denitrifying bacteria reduce nitrate in the soil.

• Phosphorus can be added to the phosphorus cycle by application of fertilizer or removed by the harvesting of agricultural crops.

• The rate of turnover in the phosphorus cycle is much lower than the nitrogen cycle.

• Availability of phosphate may become limiting to agriculture in the future.

• Leaching of mineral nutrients from agricultural land into rivers causes eutrophication and leads to increased biochemical oxygen demand.

Applications and skills:

• Application: The impact of waterlogging on the nitrogen cycle.

• Application: Insectivorous plants as an adaptation for low nitrogen availability in waterlogged soils.

• Skill: Drawing and labelling a diagram of the nitrogen cycle.

• Skill: Assess the nutrient content of a soil sample.