Chapter 17.2 Outline Notes
Energy Flows in Ecosystems
I.
How energy Moves Through Ecosystems
a. The Primary Energy Source
i. Photosynthetic organisms capture the _____________ light energy and store it as
___________________energy in organic molecules – what we call food.
ii. ________________________is the rate at which organic material is produced by photosynthetic
organisms in an ecosystem.
1. This determines the amount of energy available in an ecosystem.
iii. _________________are organisms that first capture energy and include plants, some kinds of
bacteria and_____________.
iv. _____________________are organisms that consume plants or other organisms to obtain
energy to build molecules.
b. Trophic Levels
i. Trophic level – a specific level in an ecosystem that organisms are assigned to.
ii. _____________moves from one trophic level to another.
1. Draw an example of the energy/food chain illustrated on page 365.
iii.
II.
Food chain – the path of energy through trophic levels of an ecosystem.
1. ___________________are in the first or lower trophic level
2. ___________________– animals that eat plants or other primary producers are called
primary consumers and are in the second trophic level
3. ____________________– animals that eat herbivores are called secondary consumers
and are at the third trophic level
4. ____________________– both herbivore and carnivore
5. ____________________– organisms that obtain energy from organic wastes and dead
bodies that are produced at all levels (examples include worms, fungal and bacterial
decompeosers)
6. ____________________– cause decay (examples (bacteria and fungi)
7. The fourth trophic level contains carnivores that eat other_______________. These are
tertiary consumers.
8. __________________– shows the __________________relationships between many
organisms in an ecosystem
Energy is lost in a Food Chain
a. Energy Transfer
i. During every transfer of energy, energy is lost as_____________, which is not a useful source of
energy in biological systems. So, the amount of useful energy available to do work
_______________as energy passes from one organism to the next in an ecosystem.
ii. This limits the number of ______________ ________________an ecosystem can support.
iii. Only about _______%of energy from one organism (trophic level) is transferred to the next
organism (trophic level)
b. The Pyramid of Energy (also a biomass pyramid)
i. Energy _______________– diagram in which each trophic level is represented by a block and
the blocks are stacked on top of one another, with the lowest tophic level on bottom. Draw the
illustration on page 368.
ii.
Trophic levels are limited.
1. _________________ecosystems have only three and rarely four levels. Too much
energy is ____________at each level to allow for more levels.
2. _____________________– the dry weight of tissue and other organism matter found in
a specific ecosystem.