#13 Ecosystem Energetics

Question 1

What composes a system?

Answer 1

biotic and abiotic. composed of autotrophs, heterotrophs, and the abiotic environment

Question 2

Autotrophs are ______ producers

Answer 2

Primary - green plans and algae

Question 3

Heterotrophs are _______?

Answer 3

decomposers or consumers

Question 4

The abiotic system consists of ________

Answer 4

air, water, and soil

Question 5

What is the driving force of the ecosystem?

Answer 5

Sun’s energy - photosynthesis

Question 6

input vs output in the ecosystem

Answer 6

inputs are exchanges from the surrounding environment into the ecosystem.
outputs are exchanges from the ecosystem to the surrounding environment

Question 7

What is the first law of thermodynamics?

Answer 7

energy is neither created nor destroyed, it is merely transferred or transformed.

Question 8

What is the second law of thermodynamics?

Answer 8

When energy is transferred or transformed, part of the energy assumes a form that cannot pass on any further (usually through heat)

Question 9

The total rate of photosynthesis, or the energy assimilated by autotrophs

Answer 9

Gross primary productivity (GPP)
Autotrophs must expend energy in the process of respiration (R)

Question 10

The rate of energy storage after respiration is known as?

Answer 10

Net primary production (NPP)
NPP = GPP - R

Question 11

GPP and NPP are ____ in older (mature) ecosystems

Answer 11

low because energy is used to the maintenance of order and less used for the production of new materials

Question 12

What environmental factors would give the highest primary production?

Answer 12

Warm temperatures and adequate water supply.

Question 13

What does it mean if more energy is allocated to the leaves relative to the stems and roots?

Answer 13

the greater net carbon gain and plant growth

Question 14

What does less moisture mean for plants in order of energy usage

Answer 14

more energy allocated to the roots (think of the desert plants)

Question 15

What is a root to shoot ratio? What are the estimated root-to-shoot ratio (R:S) range for:
- tropical rainforest
- arid shrublands
- desert

Answer 15

It measures the proportion of a plants biomass allocated to its roots compared to its shoots.
- 0.20 tropical rainforest
- 1.2 arid shrublands
- 4.5 desert (more invested in root systems to compensate for not a lot of water)

Question 16

Disturbances can lead to year-year _______ in NPP

Answer 16

variations (recall herbivory and fires)

Question 17

As woody plants age, much of the energy goes into _______?

Answer 17

support and maintenance - the ratio of leaves to woody tissue decreases

Question 18

leaves account for _____ percent of the total mass of the mature tree?

Answer 18

1-5%

Question 19

As the stand ages, photosynthesis and respiration rates _____?

Answer 19

decline - more of productivity goes towards maintenance than growth

Question 20

NPP is the energy available to ______?

Answer 20

heterotrophs (organic matter energy)

Question 21

When is secondary productivity the highest?

Answer 21

When the birth rate of the population and the growth rate of individuals are highest - depends on primary production for energy

Question 22

herbivore biomass and consumption _____ with primary productivity

Answer 22

increases

Question 23

Secondary productivity of herbivores ______ with primary producitivty

Answer 23

increases

Question 24

distinguish the difference between autotrophs, herbivores, and carnivores

Answer 24

Autotrophs - primary producers
Herbivores - First-level consumers
Carnivores - Second-level consumers

Question 25

Where does detritus come from

Answer 25

the input of dead organic matter and waste materials from the grazing food chain

Question 26

how to figure out how much energy is available for grazing herbivores?

Answer 26

NPP = available energy

Question 27

what is the calculation for energy available to a given trophic level?

Answer 27

its the production of the next lower level (n-1)

Question 28

what is assimilation efficiency?

Answer 28

assimilation to ingestion (A/I)
- Ingested food (I) –> Assimilated (A) and Expelled (E)

Question 29

How to calculate assimilated energy (A) for production?

Answer 29

the ratio of production to assimilation (P/A)
- Assimilated energy (A) –> respiration (R) and production (P)

Question 30

consumption efficiency

Answer 30

the ratio of ingestion to production (ln /Pn – 1)

Question 31

what does consumption efficiency define?

Answer 31

the amount of available energy produced by any given trophic level (Pn – 1) which is consumed by the next higher level (ln)

Question 32

What percent of biomass in a given trophic level is converted at the next higher trophic level?

Answer 32

10% - so if herbivores eat 1000kcal = 100kcal converted to herbivore tissue = 10kcal into the first-level carnivore production = 1kcal into the second-level carnivore production