Species - Ecosystems

SPECIES ➙ ECOSystems Ecological Organisation Modes of Nutrition Species: A group of organisms that can interbreed and produce fertile, viable offspring Living organisms can obtain chemical energy by one of two methods of nutrition (a few species can use both methods): Population: Group of organisms of the same species, living in the same area at the same time Community: A group of different populations living together and interacting in a given area Autotrophs Autotrophs synthesise organic molecules from inorganic nutrients within the environment, using energy from either: • Light (photoautotrophs) • Oxidation reactions (chemoautotophs) Habitat: The environment in which a species lives or the normal location of an organism Heterotrophs Heterotrophs obtain their organic molecules from other organisms via a variety of feeding methods and food sources • Consumers ingest other living organisms • Detritivores ingest detritus (decomposing matter and faeces) • Saprotrophs externally digest dead organisms (decomposers) Ecosystem: A community and also its environment (all biotic and abiotic factors) Autotrophs are commonly referred to as producers, as they are responsible for the production of organic molecules • Heterotrophs could not survive without autotrophs Nutrient Cycling Mesocosms Nutrients are materials required by organisms for survival Ecosystems have the potential to be sustainable over long periods of time, however this requires three conditions: The supply of inorganic nutrients within the environment is finite and therefore must be constantly recycled: • Autotrophs convert inorganic nutrients into organic molecules (i.e. they are producers) • Heterotrophs ingest organic molecules and may release inorganic byproducts (e.g. carbon dioxide) • Saprotrophs break down the nutrients in dead organisms and return them to the soil (i.e. they are decomposers) • Energy availability (e.g. light source) • Nutrient availability (e.g. decomposers) • Waste recycling (e.g. detoxifying bacteria) Mesocosms are enclosed environments with controlled conditions (e.g. terrariums) • They can be used to study sustainability Species Associations Quadrat Sampling The presence of species in a habitat may be dependent on the interactions between them (either positive or negative) The presence of a species in a given area can be determined via quadrat sampling (to assess sessile/non-motile species) • Rectangular frame placed in an area (+ repeat sampling) • Species numbers within the frame are counted/estimated If species are always found in the same habitat, this suggests a positive association (such as): • Predator / prey relationships • Symbiotic interaction (mutualism, commensalism, parasitism) If species do not share the same habitat, this suggests there is a negative association (such as): • Competition (niche partitioning or competitive exclusion)