14.9.4 Productivity Pyramids: Pyramid of Numbers

Question 1

Productivity Pyramids: Pyramid of Numbers

Answer 1

• Analyzing various productivity (food) pyramids reveals that approximately 10% of the energy present in a trophic level is incorporated into biomass in the next trophic level.
• The number of primary producers in an ecosystem is a limiting factor for the number of organisms in higher trophic levels.
• A census taken of a Michigan bluegrass field indicated that approximately 6 million primary producers supported only three tertiary consumers.

Question 2

note

Answer 2

• Review: The primary producers are green plants and other organisms than can bind energy from inorganic sources into the chemical bonds of organic compounds. Using the sun’s energy, plants convert carbon dioxide into carbohydrates.
• Primary producers supply food either directly or indirectly for all of the other organisms on the planet.
• Trophic levels are feeding levels used to categorize
  organisms according to their source of nutrition.

Question 3

note 2

Answer 3

• Question: Which trophic level has the greatest number of organisms?
• The producers make up the largest trophic level. A census taken of a Michigan bluegrass field (results shown on the left) indicated that close to 6 million primary producers supported only three tertiary consumers.
• Because primary producers make energy available to all of the other levels of the food chain, the number of primary producers in an ecosystem limits the number of organisms in the other trophic levels.

Question 4

Which of the following would be expected to be placed at the top of an ecological pyramid?

Answer 4

• the trophic level with the smallest numbers

Question 5

The Michigan bluegrass grassland study examined

Answer 5

• the numbers of individuals at each trophic level.

Question 6

It is generally accepted that only about __________% of the energy available at one trophic level is incorporated into the tissues of the organisms at the next level.

Answer 6

• 10

Question 7

Which of the following types of organisms occupies the trophic level with the least biomass?

Answer 7

• tertiary consumers

Question 8

Which of the following statements concerning the energy in food chains is incorrect?

Answer 8

• Energy transfer along the food chain is extremely efficient, and as much as 75% of the energy fixed by producers, is available to primary consumers.