Unit 4 Ecology
Option C: Ecology and Conservation
Understandings: Species, communities & ecosystems (4)
Ø Species are groups of organisms that can potentially interbreed to produce fertile offspring.
Ø Members of a species may be reproductively isolated in separate populations.
Ø Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).
Ø Consumers are heterotrophs that feed on living organisms by ingestion.
Ø Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
Ø Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.
Ø A community is formed by populations of different species living together and interacting with each other.
Ø A community forms an ecosystem by its interactions with the abiotic environment.
Ø Autotrophs obtain inorganic nutrients from the abiotic environment.
Ø The supply of inorganic nutrients is maintained by nutrient cycling.
Ø Ecosystems have the potential to be sustainable over long periods of time.
Understandings: Species and communities (C)
Ø The distribution of species is affected by limiting factors.
Ø Community structure can be strongly affected by keystone species.
Ø Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species.
Ø Interactions between species in a community can be classified according to their effect.
Ø Two species cannot survive indefinitely in the same habitat if their niches are identical.
Understandings: Energy Flow (4)
Ø Most ecosystems rely on a supply of energy from sunlight
Ø Light energy is converted to chemical energy in carbon compounds by photosynthesis.
Ø Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
Ø Living organisms cannot convert heat to other forms of energy
Ø Heat is lost from ecosystems.
Ø Energy losses between trophic levels restrict the length of good chains and the biomass of higher trophic levels.
Understandings: Communities and Ecosystems (C)
Ø Most species occupy different trophic levels in multiple food chains.
Ø A food web shows all the possible food chains in a community.
Ø The percentage of ingested energy converted to biomass is dependent on the respiration rate.
Ø The type of stable ecosystem that will emerge in an area is predictable based on climate.
Ø In closed ecosystems energy but not matter is exchanged with the surroundings.
Ø Disturbances influence the structure and rate of change within ecosystems.
Understandings: Carbon Cycling (4)
Ø Autotrophic convert carbon dioxide into carbohydrates and other carbon compounds.
Ø In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions.
Ø Carbon dioxide diffuses from the atmosphere or water into autotrophs.
Ø Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere.
Ø Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere or accumulates in the ground.
Ø Methane is oxidized to carbon dioxide and water in the atmosphere.
Ø Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils.
Ø Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas which accumulates in porous rocks.
Ø Carbon dioxide is produced by the combustion of biomass and fossilized organic matter.
Ø Animals such as reef-building corals and molluscs have hard parts that are composed of calcium carbonate and can become fossilized in limestone.
Understandings: Nitrogen and the Phosphorus Cycle (C)
Ø Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia.
Ø Rhizobium associates with roots in a mutualistic relationship.
Ø In the absence of oxygen, denitrifying bacteria reduce nitrate in the soil.
Ø Phosphorous can be added to the phosphorous cycle by application of fertilizer, or removed by the harvesting of agricultural crops.
Ø The rate of turnover in the phosphorous cycle is much lower than the nitrogen cycle.
Ø Availability of phosphorous may become limiting to agriculture in the future.
Ø Leaching of mineral nutrients from agricultural land into rivers causes eutrophication and leads to increased biochemical oxygen demand.
Understandings: Climate Change (4)
Ø Carbon dioxide and water vapour are the most significant greenhouse gases.
Ø Other gases including methane and nitrogen oxides have less impact.
Ø The impact of a gas depends on its ability to absorb long-wave radiation as well as on its concentration in the atmosphere.
Ø The warmed Earth emits longer wavelength radiation (heat).
Ø Longer wave radiation is absorbed by greenhouse gases, which retain the heat in the atmosphere.
Ø Global temperatures and climate patterns are influenced by concentrations of greenhouse gases.
Ø There is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution 200 years ago and average global temperatures.
Ø Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of fossilized organic matter.
Understandings: Impact of humans on ecosystems (C)
Ø Introduced alien species can escape into local ecosystems and become invasive.
Ø Competitive exclusion and the absence of predators can lead to reduction in the numbers of endemic species when alien species become invasive.
Ø Pollutants become concentrated in the tissues of organisms at higher trophic levels by biomagnification.
Ø Macroplastic and microplastic debris has accumulated in marine environments.
Understandings: Conservation of biodiversity (C)
Ø An indicator species is an organism used to assess a specific environmental condition.
Ø Relative numbers of indicator species can be used to calculate the value of a biotic index.
Ø In situ conservation may require active management of nature reserves or national parks.
Ø Ex situ conservation is the preservation of species outside their natural habitats.
Ø Biogeographic factors affect species diversity.
Ø Richness and evenness are components of biodiversity.
Understandings: Population Ecology (C)
Ø Sampling techniques are used to estimate population size.
Ø The exponential growth pattern occurs in an ideal, unlimited environment.
Ø Population growth slows as a population reaches the carrying capacity of the enfivonment.
Ø The phases shown in the sigmoid curve can be explained by relative rates of natality, mortality, immigration and emigration.
Ø Limiting factors can be top down or bottom up.