Ecology Final

ecosystem ecology

focuses on how organisms influence its abiotic environment and vice versa

what are the major emphases of ecosystem ecology?

1. energy flow through the system
2. nutrients cycle through the system
3. how disturbance effects both energy flow and nutrient cycles

Energy is captured and stored by autotrophs via

photosynthesis

photosynthesis refresher

plants capture energy from the sun to manufacture carbon-based molecules

energy capture from the sun gets transferred through the ecosystem, but is eventually lost to the ecosystem via

heat

gross primary productivity

the total rate of photosynthesis

net primary productivity

the rate of energy storage

formula for NPP

NPP \= GPP - Respiration (R)

standing biomass

simply how much plants in an environment weigh (amount of organic matter making up those plants)

In terrestrial system, NPP is often measured as the

change in standing biomass

What regulates NPP?

The length of the growing season

In northern states where winters are longer, what happens to NPP?

less overall NPP

In southern states where winters are shorter, what happens to NPP?

longer NPP

what controls NPP?

Both precipitation (water) and temperature

How does temperature affect NPP?

cold temperature reduces rates of photosynthesis (higher NPP in warmer environments)

How does precipitation affect NPP?

recall from earlier in the semester, in dry environments plants have to close their stomata to prevent water loss through transpiration

evapotranspiration

the combined effect of water movement through the plant (transpiration) and water evaporation from soil

How are rates of evapotranspiration affected by climate?

- warm and wet \= high rates of evapotranspiration therefore photosynthesis
- cold \= low rates of evapotranspiration
- warm and dry \= lowest rates of transpiration

Is there a latitudinal effect on NPP?

there is a strong latitude effect on NPP, but other factors control NPP at one given latitude

Is there an effect of latitude in ocean system?

No real effect on latitude

What happens in deep waters to photosynthesis and NPP?

Photosynthesis and NPP decline because less light

When is highest aquatic plant biomass achievable?

when both nutrients and light were added (suggests both limit biomass)

Why do coastal areas have the highest NPP?

1. shallower water
2. nutrient inputs from land

How does NPP vary throughout the year?

variation due to photosynthetic period caused by seasonal differences in day length, temp, rain, etc.

How does NPP vary among years?

variation due to hotter and dryer years, wetter or drier years, etc.

How does NPP vary among successional stages?

NPP increases with successional stage until late succession

What does NPP determine?

the biomass of productivity and biomass of secondary producers

Assimilation efficiency

how efficient consumers are in extracting energy for biomass and respiration versus waste

production efficiency

how efficient consumers are in converting food to biomass

trophic efficiency

how much energy is transferred and converted into biomass from one trophic level to the next

Where is energy lost?

energy is lost as it flows from herbivores to higher level trophic level

Processes important to nutrient cycling

1. Nutrient uptake
2. Retranslocation
3. Decomposition

Nutrient uptake

obtaining essential nutrients

nutrient uptake in plants

absorbed as solution in soil by roots

nutrient uptake in higher trophic levels

direct consumption of tissue

essential point of nutrient uptake

nutrients found in higher trophic levels were once found in the soil

retranslocation

process of recycling nutrients within an organism (nutrients are drawn back into the organism)

Where as translocation is cycling within an organism, nutrient cycling throughout the ecosystem is dependent on what?

Decomposition

decomposition

releases energy as heat and carbon dioxide back into the atmosphere

Different roles of decomposers

1. bacteria are major decomposers of animal tissue
2. fungi are major decomposers of plant tissue
3. other organisms (small invertebrates and worms) shred dead material into smaller bits

What indicates the amount of material that was decomposed?

about of mass lost

what does decomposition rate depend on?

the species

decomposing cellulose

makes up cell walls, simpler molecule, fewer chemical bonds, faster decomposition

decomposing lignin

makes up woody parts of plants, many more chemical bonds needed to break, decomposes much slower

what type of information does CO2 production measure?

total decomposition in a given area but doesn't separate types of material

Decomposition rates depend on:

1. air temperature throughout the day
2. region
3.

tundra decomposition rates

low decomposition rates, low rates of primary productivity

tropical forest decomposition rates

highest rate of decomposition, high rates of net primary productivity

mineralization

1. converts nutrients bound in organic molecules to their original form
2. done by bacteria and fungi

immobilization

uptake of nutrients by decomposing organisms

net mineralization formula

net mineralization \= total mineralization - immobilization

how does decomposition relate to NPP?

areas of higher decomposition have higher rates of NPP

What does SIR stand for?

susceptible, infected, recovered

Infection

how quickly susceptible individuals become infected

Recovery

how quickly infected people recover

SIR model

simple model that predicts how infections will move through the population

infection depends on

1. population density
2. transmission rate
3. infectious period

population density

number of individuals per unit area

transmission rate

depends on rate of contact between infected and susceptible individuals that leads to a new infection

infectious period

the average period of time an infected individual can transmit

Simple assumptions of SIR model

1. direct infection only (no vector transmissions)
2. no evolution (disease agents don't mutate)
3. doesn't consider new births or deaths
4. assumes one recovered you can never get disease again

epidemic curve

number of infections over time

Basic reproductive number

the average number of susceptible individuals that a single infected individual infects (R0)

R0 < 1

disease will decline and fizzle out

R0 \= 1

disease will remain in population, but no outbreak or epidemic

R0 \> 1

disease will increase and outbreaks are possible

R0 differs on:

1. differs depending on the disease
2. differs depending on the region/environment
3. often expressed as a range

herd immunity

when a large portion of the population becomes immune to the disease, making the spread of the disease unlikely

how do you achieve herd immunity?

1. through immunity as a result of recovering from infection
2. through vaccination

critical immunization threshold

minimum number of individuals that need to be vaccinated to reach herd immunity

small R0

less of the population needs to be vaccinated

larger R0

much more of the population needs to be vaccinated

largest number of species are found where?

near the equator

which species' diversity exceeds any other taxa?

insects

Tropical moist forests

- high biodiversity
- cover 6% of land surface
- 50% of all known species
- 90% of all non-human primates

latitudinal gradient in biodiversity

the global pattern where ecosystems near the equator have the highest diversity, but decreases as you move toward the poles

what groups peak at low altitudes

marine fish and mollusks

what group does not follow a general latitudinal pattern?

cacti: adapted to drier desert conditions

two classes of hypotheses that explain the latitudinal gradient in biodiversity

1. hypotheses that address why a latitudinal gradient exists in the first place
2. hypotheses that address what mechanisms reinforce and maintain existing patterns of diversity

hypotheses that address why a latitudinal gradient exists in the first place

focus largely on what factors allow for higher speciation rates near the equator

hypotheses that address what mechanisms reinforce and maintain existing patterns of diversity

focuses largely on the biotic and abiotic interactions that maintain high species diversity (mechanisms that explain coexistence)

what explains higher speciation rates and lower extinction rates toward the equator?

1. more stable climate through evolutionary history
2. climate in tropics is more stable in general than toward poles
3. the tropics have more available thermal energy than toward the poles

potential evapotranspiration

index used to describe amount of evaporation that would occur if provided enough water

there is a strong link between potential evapotranspiration and

species richness

areas of higher thermal energy leads to \__________________________________ which leads to \_________________________________

higher primary productivity, higher species richness

what 2 groups have exploded in recent times?

invertebrates and flowering plants (angiosperms)

is plant diversity related to animal diversity

yes

weather

combination of factors that occur in a specific place at a specific time

factors of weather

temperature, humidity, precipitation, wind, cloudiness

climate

long-term average pattern of weather (can be expressed locally, regionally, or globally

net radiation formula

net radiation \= (incoming SW - reflected SW) - (emitted LW - downward LW)

net radiation explanation

sum emits shortwave light, surfaces on earth (plants, buildings, oil, water) absorbs and then emits longwave (heat)

what causes the latitudinal differences in temperature?

the Earth's curvature

why is it hotter near the equator?

1. solar radiation is direct
2. travels shorter distance through atmosphere, therefore less chance of being reflected back away from earth

why is it cooler toward the poles?

1. the same amount of solar radiation is spread across a larger surface area because of angle
2. travels further distance through atmosphere, more is reflected back

what generates wind currents?

differences in thermal energy across latitude

Coriolis effect

inertia of rotating earth causes wind patterns to be much more complicated

northern hemisphere currents

clockwise

southern hemisphere currents

counter clockwise

what determines global patterns of precipitation?

thermal energy, wind, and ocean currents