IB Environmental Studies/Ecosystem
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[edit] Topic 2: The Ecosystem
[edit] 2.1. Structure
biotic factor - A living, biological factor that may influence an organism or ecosystem.
abiotic factors – A non-living or physical factor that may influence an organism or ecosystem. For example, precipitation, wind, sunlight, soil, temperature, pH, salinity.
Trophic level - The position that an organism occupies in a food chain, or a group of organisms in a community that occupy the same position in food chains. And is mainly considered as feeding level.
Producers/Autotrophs - Organisms that make their own food. Usually plants through photosynthesis. Primary consumers - Organisms that consume producers. Secondary consumers - Organisms that consume primary consumers.
Herbivores - Organisms that eat plants, but no meat. Carnivores - Meat-eaters. Omnivores - Organisms that eat both plants and meat.
Heterotrophs - Decomposers -
species - A group of organisms that interbreed and produce fertile offspring.
population - A group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding.
community - A group of populations living and interacting with each other in a common habitat.
ecosystem - A community of interdependent organisms and the physical environment they inhabit.
habitat - The environment in which a species normally lives.
niche - A species' share of a habitat and the resources in it. An organism's ecological niche depends not only on where it lives but on the role it plays in the ecosystem.
fundamental niche - The part of the habitat in which a species can live in the absence of competitors and predators realized niche - The part of the habitat that the organism actually occupies.
biome – large, relatively distinct terrestrial region characterized by similar climate (temperature and precipitation), soil, and organisms.
competition – [– ,–] Two species (interspecies competition) or two populations of the same species (intraspecies competition) compete for the same resources. Both sides are harmed.
symbiosis – biological interaction where two different species are in direct contact with each other.
commensalism – [0 , +] One species benefits, the other is unaffected amensalism – [0 , –] One species is harmed, the other is unaffected mutualism – [+ , +] Both species benefit predation – [+ , –] One species benefits, the other is harmed. The prey is usually killed quickly. parasitism – [+ , –] One species benefits, the other is harmed. The host is killed slowly if at all.
[edit] 2.2. Function
photosynthesis – 6CO2 + 6H2O + light energy ⇒ C6H12O6 + 6O2 + heat – Carbon Dioxide, Water and Sunlight go in, Glucose, Oxygen and Heat are produced.
respiration – C6H12O6 + 6O2 ⇒ 6CO2 + 6H2O + released energy (heat) – Glucose and Oxygen go in, Carbon Dioxide and Water and Heat are produced.
[edit] 2.3. Changes
Reproductive Strategies: r and K
r-selection
- Short-lived - Large broods - Reproduce early in life - Little to no care for young - Relatively small
K-selection
- Long-lived - Few offspring per reproductive period - Reproduce later in life - Nurture young - Relatively large
succession – a change over time in the types of species that occupy a given area.
primary succession – ecological succession in an environment that has not been previously inhabited (no soil is present). pioneer communities – the first organisms to colonize (or recolonize) an area. secondary succession – ecological succession in an environment that was exposed to some type of disturbance (soil is already present).
sere – a sequence of communities over ecological time. Each stage of succession is called a seral stage.
lithosere – succession on bare rock hydrosere – succession in freshwater lakes psammosere – succession on sand dunes halosere – succession on salt marshes
climax community – species composition no longer changes over time; secession stops. Community retains an overall uniform appearance.
