14.9.2 Ecosystems: Productivity and Energy Flow

Question 1

Ecosystems: Productivity and Energy Flow

Answer 1

• Detritivores obtain their energy from nonliving things.
• Primary productivity is a measure of the incorporation of energy (usually solar) into bodies of organisms.
• The transfer of energy from trophic level to trophic level is 10% on average. Most of the remaining energy is expended on respiration and growth.
• “Warm-blooded” organisms expend more energy on respiration than “cold-blooded” organisms.

Question 2

note

Answer 2

• Only a fraction of the energy that leaves the sun hits the earth; plants intercept only a fraction of that energy. It is estimated that about 1% of the energy in sunlight is available for primary producers. From this small amount, plants produce 170 billion tons of biomass.
• The illustration on the left shows the flow of energy through trophic levels. The relative amount of energy obtained by each trophic level is reflected in the graphic.

Question 3

primary producers

Answer 3

• green plants and other organisms that can bind energy from inorganic sources into the chemical bonds of organic compounds. Plants convert solar energy into chemical energy in the form of carbohydrates. Plants produce a relatively large amount of chemical energy.
  Overall, the transfer of energy from trophic level to trophic level is 10% on average. Energy that is consumed on respiration, growth, and waste matter at any previous trophic level is no longer available to the subsequent trophic levels.

Question 4

detritivores

Answer 4

• consume the energy available from all of the other trophic levels after organisms in those levels die.
  Because plants are the primary producers in many
  communities, it is of great interest to measure the amount of chemical energy they produce and how much of that is available to higher trophic levels.

Question 5

gross primary productivity

Answer 5

• a measure of the energy that is bound (and organic matter created) per unit area by the photosynthesis of green plants. As discussed earlier, not all of the energy obtained by the plants is available for the other trophic levels. The plants use some of the energy for respiration

Question 6

net primary productivity

Answer 6

• gross primary productivity minus plant respiration. The more efficient a plant is at conserving energy, the greater its net primary productivity

Question 7

The quantitative estimate of the total amount of living material is

Answer 7

• biomass

Question 8

Which of the following statements best explains why there are so few top-level predators?

Answer 8

• Only a small fraction of the energy is transferred from one trophic level to the next.

Question 9

Energy transfers from one trophic level to the next are, on average, how efficient?

Answer 9

• 10%

Question 10

True or false?

Energy flows, rather than cycles, through an ecosystem.

Answer 10

• true

Question 11

Efficiency of energy conversion from the lower trophic level is expected to be higher in

Answer 11

• snakes