39 terms

IB Environmental Systems and Societies Topic 2.1-2.4

What are biotic factors?
All the living components of an ecosystem
What are abiotic factors?
All the chemical and physical (non living) factors in an ecosystem
Define 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
Explain pyramids of numbers
A pyramid of numbers is constructed by counting the number of organisms at each trophic level
They give good, approximate representations of ecosystems
Can be misleading because they don't account for the sizes of organisms
Provides a quick overview
Explain pyramids of biomass
Pyramids of biomass are constructed by measuring the mass of all the organisms at each trophic level
Recorded as dry mass multiplied by number of organisms
Usually shaped like a traditional pyramid
Don't take into account seasonal variations in biomass because are taken at one time of the year
difficult to measure without killing organisms
some animals have lots of bones or shells
Explain pyramids of productivity
Most accurate model
Show the flow of energy in an ecosystems over time, usually a year
data is difficult to collect
many species feed at more than one trophic level(true for all)
How does the pyramid structure of ecosystems affect the functioning of ecosystems
Because energy is lost through food chains carnivores are at great risk of disturbances
Disturbances at the lowest level (producers) affect all above them
Define species
a group of organisms that interbreed and produce fertile offspring
Define population
a group of organisms of the same species living in the same area at the same time
Define habitat
the environment in which a species normally lives
Define niche
a species role in a habitat and it's share of the resources in it. This depends on where it lives, what it does and if there is competition for the resources it needs.
Define community
a group of populations living and interacting with each other in a common habitat
Define ecosystem
A community of interdependent organisms and the physical environment they inhabit
What is competition?
interspecific: different species fight for space, water, food or sunlight
intraspecific: where members of the same species fight for space, water, food, sunlight OR MATES
what is predation?
where one organism eats another organism (lynx eats a snowshoe hare) this is a negative feedback mechanism
What is symbiosis?
Where two organisms live together
What is parasitism?
Ectoparasites: on the outside of the organism they stay and mooch off it (ticks, fleas, leaches)
Endoparasites: on the inside of an organism they stay and mooch off it (tapeworms)
What is mutualism?
Where to organisms live together and benefit off of each other (clown fish and sea anemone)
what is commensalism?
When one animal benefits and nothing happens to the other
Define biome
A collection of ecosystems sharing similar climatic conditions
What are producers?
organisms that use sunlight energy to create food, bottom of the food chain
What are consumers?
Eat other organisms to obtain energy, herbivores eat plants and carnivores eat herbivores
What are decomposers?
Obtain energy from breaking down dead organic matter
Describe photosynthsis
Carbon Dioxide + Water --> Glucose + Oxygen
nitrogen cycle
The transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere
carbon cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among between living organisms, soil, fossil fuels, oceans, and atmosphere of the Earth.
Define gross productivity
The total gain in energy or biomass per unit area per unit time
Define net productivity
the gain in energy or biomass per unit are per time remaining after allowing for respiratory losses
Define primary productivity
the gain by producers in energy or biomass per unit area per unit time
Define secondary productivity
the gain by heterotrophic organisms in energy or biomass per unit area per unit time
How to calculate NPP from GPP
NPP = GPP - R where R is respiratory loss
How to calculate GSP and NSP
NSP = GSP - R where R is respiratory loss
GSP = food eaten - fecal loss
Describe Respiration
C₆H₁₂O₆ + O₂ --> CO₂ + H₂O + ATP + Heat
What is the carrying capacity of an ecosystem?
The number of individuals in a population that the resources in the environment can support for an extended period of time
What is a limiting factor?
When the demand for a particular resource is greater than the supply
What do J-curves depict?
The show the growth of a population which does not slow down. This is common in populations which are becoming established in new habitats, especially if that habitat has abundant resources
What do S-curves depict?
S-curves show rapid exponential growth which eventually slows down as limiting factors become pertinent. Eventually the population stabilizes at its carrying capacity.
How are stable ecosystems regulated?
feedback mechanisms (normally negative) which enable the system to rebalance itself if changes occur
Define maximum sustainable yield
the maximum amount that can be harvested without compromising the future availability of that resource. It is equivalent to the NPP or NSP of an ecosystem