19: Ecosystem Productivity

2nd law of thermodynamics? What does it assume?

energy changing will always proceed from a higher state of energy to a lower state

-assumes that a system is closed

Why do organisms seem to disobey 2nd law of thermodynamics?

organisms are open systems, receiving energy from outside

Is an ecosystem an open or closed system?

Open system w/ energy & organisms passing in & out

What is primary productivity?

Rate at which photosynthesis/chemosynthesis converts energy→organic compounds(biomass)

Gross primary productivity vs. Net primary productivity

GPP→total rate of photosynthesis assimilation by plants

NPP→ GPP-autotrophic respiration

What is standing crop biomass?

accumulated organic matter in a given area at a given time

How do phytoplankton allocate energy to biomass?

they reproduce asexually & biomass increases as population increases

How do annual plants allocate energy to biomass?

allocate energy to leaves 1st, then reproduction

How do herbaceous perennial plants allocate energy to biomass? (non-woody)

allocate energy to leaves 1st, then roots for storage, then reproduction

How do woody perennial plants allocate energy to biomass?

most energy goes into maintaining woody tissue

Do trees reproduce every year?

no, most can’t afford to

What kind of environment is a plant with a large shoot: root ratio in?

stable environment w/ low light

-more shoot increases primary productivity

ex// temperature deciduous forests

What kind of environment is a plant with a low shoot: root ratio in?

unstable environment, especially where water & nutrients is reduced

ex// tundra shrubs & grasses

Increase in woody tissue decreases ______

primary productivity

ex// corn has greater productivity than Douglas Fir tree

Moisture, temperature, photosynthetic period, & nutrient availability is _______correlated with productivity.

positively

In aquatic ecosystem, which ecosystem has the highest & lowest productivity?

highest= swamps/marshes & coral reefs

lowest=open ocean

Why are aquatic ecosystems less productive than terrestrial ecosystems?

limited by nitrogen, phosphorous & iron

Why are coastal waters more productive than open ocean?

1) nutrients uptake from rivers

2) vertical mixing

3) upwelling currents transport nutrients to surface

What is secondary productivity?

rate at which consumer converts energy from producer into organic compounds(biomass)

True or false: Much of primary productivity is lost to environment & energy is also lost thru feces, urine, gas,& heat.

TRUE

What factors affect secondary productivity?

1) primary productivity

2) birthrate of population

3) growth rate of individuals

4) assimilation efficiency

define assimilation efficiency. Which animals have higher assimilation efficiency?

efficiency with which a consumer extracts energy from food

-carnivores>herbivores

assimilation efficiency of ectotherms vs. endotherms?

ectotherms→lower at 42%
endotherms→higher at 77%

define production efficiency. Compare ectotherms vs. endotherms.

efficiency with which a consumer incorporates assimilated energy into secondary production

-higher in ectotherms than endotherms bc endotherms must consume more to maintain itself

What is an ecosystem engineer?

example?

an organism that substantially creates, modifies, maintains, or destroys a habitat

-may have large impact on species richness

ex// coral reefs, beavers, & grebes