IB Environmental Systems and Societies Topic 2
Terms in this set (71)
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
a group of organisms that interbreed and produce fertile offspring
a group of organisms of the same species living in the same area at the same time
the environment in which a species normally lives
a species share of a habitat and the resources in it. An organisms ecological niche depends on where it lives and what it does
a group of populations living and interacting with each other in a common habitat
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
List the most significant abiotic factors in an ecosystem
pH, temperature, light intensity, salinity, turbidity, dissolved oxygen, soil moisture, wind speed, slope, soil particle size, soil mineral content, drainage
How do you measure pH
pH meter (H+)
How do you measure temperature
How do you measure dissolved oxygen
oxygen meter (PPM)
How do you measure light intensity
light meter (LUX)
How do you measure salinity
salinity meter (ppt)
How do you measure turbidity
How would you estimate the abundance of an organism?
1. One day capture as many organisms of one species as possible
2. Tag each of those organisms
3. Release all of the organisms back into the ecosystem
4. The next day (or week) come back to the same spot and the same time and collect as many organisms of the same species as possible
5. Count the number of tagged organisms
6. Do this calculation:
(Total number captured 2nd time) x (number captured 1st time) / (total number captured with mark 2nd time)
How do you evaluate biomass of trophic levels
1. Estimate the abundance of each organism in the trophic level
2. Measure the average biomass of each organism in the trophic level
3. Multiply each average biomass by the number of organisms in the ecosystem and add together
A function of two components: the number of different species and the relative numbers of indidviduals of each species
What is simpson's diversity index?
Formula D = N(N-1) / ∑n(n-1)
D = diversity index
N = total number of organisms of all species found
n = number of individuals of a particular species
Higher D is more diverse
A collection of ecosystems sharing similar climatic conditions
Explain tropical rainforests
High precipitation (2500 mm/yr)
High temperature (26 C)
Good nutrient cycling=high rate of decomposure
Explain temperate forests
Good growing season in summer but limited in winter
High temperature and insolation in the summer = greater productivity
Rainfall between 500 and 1500 mm/yr
Second highest NPP
Lowest precipitation (50 mm/yr)
Low insolation (days are shorter)
Poor nutrient cycling because locked in permafrost
For 1-2 months the productivity is very high because the sun is up all day
Very low productivity
Low precipitation (under 250 m/yr)
High insolation, but all water is evaporated or absorbed by ground
Hot days and cold nights
Low nutrient cycle
Enough precipitation to prevent deserts, but not enough for forests
nutrient cycle is sufficient
insolation, precipitation and evaporation rates are balanced
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
Carbon Dioxide + Water --> Glucose + Oxygen
Glucose + Oxygen --> CO2 + H2O + ATP/Heat
draw the nitrogen cycle
draw the carbon cycle
draw the water cycle
draw the phosphorus cylce
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
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. Shows exponential, transition and plateau phase
What are density dependent factors in regulation of ecosystem populations?
Factors which control and regulate a population due to the size (density) of the population in a specific area.
What are density independent factors in regulation of ecosystem populations?
abiotic factors such as climatic or severe weather events.
What are internal factors in regulation of ecosystem populations?
Factors that act within the population or species. Things such as density dependent fertility or size of breeding territory
What are external factors in regulation of ecosystem populations?
Factors that come from outside the population such as predation and disease
How do we categorize survivorship strategies?
we divide them into K-strategists and r-strategists, based on the amount of time they invest in rearing offspring. As these are artificially created categories not all species will fit perfectly
How do K-strategists operate?
Organisms that have few offspring but invest a large amount of time in caring for them so that most of them survive. These species take a long time to mature and may reproduce several times in their life. The population size of K-strategists is usually close to the carrying capacity of the ecosystem and they are usually the predominant species in stable ecosystems
How do r-strategists operate?
They have a relatively short lifespan and reproduce once, producing large numbers of offspring. They are unlikely to car for their offspring, who mature quickly and are usually small. Only small numbers of offspring survive. They reproduce quickly and are most common in unstable ecosystesm
What is succession?
It is the long-term process by which communities in a particular area change over a period of time so that the appearance of the whole area evolves and changes. The different stages are known as SERAL STAGES and the final stable community is called a CLIMAX COMMUNITY. Each stage in the succession is known as a SERE
What is primary succession?
It's when an area of previously established land that was cleared (by fire or landslide or something) is colonized again.
What is zonation?
The spatial pattern of organisms over a particular area
how does energy flow in an ecosystem?
How does production and energy flow change with succession?
EARLY STAGES OF SUCCESSION:
- GPP low
- NPP high
- P:R ratio >1
- food chains simple and linear
- simple community structure
- many r-stratgists
LATE STAGES OF SUCCESSION
- GPP high
- NPP decreasing
- P:R ratio approaches 1
- large food webs established and decomposer food present
- K-strategists predominate
What are climatic and edaphic factors?
the physical, chemical and biological properties of soil
How are stable ecosystems regulated?
feedback mechanisms (normally negative) which enable the system to rebalance itself if changes occur
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