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Energy Flow Through
Ecosystems
Matter cycles.
Energy flows.
Energy


The ability to do work
Energy cannot be created or destroyed, only
changed from one form to another
Some Energy Roles


The sun: provides energy
Autotrophs (aka producers): make their own
food


Heterotrophs (aka consumers): organisms
get energy from eating other organisms


ex. Plants, phytoplankton, highly specialized bacteria
ex. Animals- herbivores, carnivore, omnivore
Decomposers: break down dead organisms,
recycle nutrients in ecosystems

ex. fungus, bacteria
Producers- Photosynthesis

Plants
use
energy
from the
sun to
make
glucose
(sugar
that
stores
energy)
Respiration- all organisms use
chemical energy (stored in glucose and
more) to fuel life processes.
Aerobic Respiration

Uses OXYGEN to convert
sugar to CO2, water and
usable energy
Anaerobic Respiration
 Breaks down sugars to
use their energy
WITHOUT OXYGEN


Aka. Fermentation
Products include
methane (CH4), Ethyl
alcohol, acetic acid, and
hydrogen sulfide
Consumers
Consumers

4 Types

Herbivore: consume producers (plants and algae)


Carnivore: consume animals




Ex. Cows, horses, deer rabbits and mice
Ex. Lions, polar bears, hawks
Obligate carnivores- unable to digest plants
Other carnivores can digest plants but do not commonly
eat them.
Omnivore: eats plants and animals

Ex. Humans, grizzly bears
Decomposer- break down the remains and other wastes
and release simple inorganic molecules back to the environment.

Scavengers consume the soft tissues of dead animals.


Detritivores consume detritus (dead leaves, animal
feces, and other organic debris that collects



Ex. vultures, raccoons, and blowflies.
Land-earthworms, millipedes, and dung beetles
Water, detritivores include “bottom feeders” such as sea
cucumbers and catfish.
Saprotrophs- feed on any remaining organic matter that
is left after other decomposers do their work. Saprotrophs
include fungi and single-celled protozoa.


final step in decomposition
Fungi- only organisms that can decompose wood
Energy flow through biological systems
Food Chains

Food Chain: single pathway through which
energy and matter flow through an
ecosystem.

Simpler than what happens in nature
Food Chains Continued

Arrows always
points in the
direction of energy
flow
food web represents multiple pathways through which
energy and matter flow through an ecosystem

Most
organis
ms eat
and are
eaten by
more
than one
species
Energy Transfer between tropic levels


2nd Law of Thermodynamics: energy is not
transferred from one object/organism to the
next with 100% efficiency
In an ecosystem, only 10% is transferred

What happens to the other 90 percent of energy?


It is used for metabolic processes
given off to the environment as heat
Sample Energy Pyramid
4th Trophic Level
3rd Trophic Level
2nd Trophic Level
1st Trophic Level
Trophic levels- feeding positions in
food chain or web
Trophic Level
Where It Gets Food
Example
1st Trophic Level:
Producer
Makes its own food
Plants make food
2nd Trophic Level:
Primary Consumer
Consumes producers
Mice eat plant seeds
3rd Trophic Level:
Secondary Consumer
Consumes primary
consumers
Snakes eat mice
4th Trophic Level:
Tertiary Consumer
Consumes secondary
consumers
Hawks eat snakes
Trophic Levels and Biomass

there are usually fewer organisms at higher
trophic levels. Why?


Less energy to support more organisms
Organisms tend to be larger in size at higher
trophic levels, but their smaller numbers
result in less biomass. Biomass is the total
mass of organisms at a trophic level. The
decrease in biomass from lower to higher
levels is also represented by Figure above .