Transcript Chapter 5.1
Chapter 5.1
Energy Flow in Ecosystems
Environmental Science
Spring 2011
Describe how energy in transferred from the
sun to producers and then to consumers
Describe one way in which consumers
depend on producers
List two types of consumers
Explain how energy transfer in a food web is
more complex than energy transfer in a food
cycle
Explain why an energy pyramid is
representation of trophic levels
Ojectives
Energy from the sun enters an ecosystem
when a plant uses sunlight to make sugar
molecules in a process called photosynthesis.
Photosynthesis: solar
drives a series of
chemical reaction that
require carbon dioxide
and water and
produce sugars
(carbohydrates).
Life Depends on the Sun
Photosynthesis equatin:
Life Depends on the Sun
Producer: organism that makes its own
food
◦ Ex. Sunflower
◦ Also called autotrophs
Consumers: organisms that get their
energy from eating other organisms
◦ Ex. Deer, lion
◦ Also called heterotrophs
All organisms get their energy directly or
indirectly from the sun!
Life Depends on the Sun
Producer or consumer? Autotroph or heterotroph?
Life Depends on the Sun
Large communities of worms, clams,
crabs, mussels, and barnacles live near
deep ocean vents
Exist in total darkness, photosynthesis
can not occur
Where do they get energy:
◦ Bacteria live in some of the organisms and use
hydrogen sulfide to make their own food
◦ Bacteria are producers
◦ Bacteria are eaten by the other underwater
organisms
An Exception: Deep-Ocean
Herbivores: consumers that eat only
producers
◦ Ex. Rabbit, cow, sheep
Carnivores: eat only other consumers
◦ Ex. Tiger, wolf, shark
What Eats What?
Omnivores: eat both plants and animals
◦ Ex. Humans, chimpanzees
Decomposers: consumers get their food
by breaking down dead organisms
◦ Ex. Bacteria, fungus
What Eats What?
Cellular Respiration: Process of
breaking down food to yield energy
◦ Cells absorb oxygen and use it to release
energy from food
Cellular Respiration
Excess energy you obtain is stored as fat
or sugar
All living things use cellular respiration to
get the energy they need from food
molecules
◦ Even organisms that make their own food
Cellular Respiration
Each time one organism eats another
organism, a transfer of energy occurs
Food chains, food webs, trophic levels
◦ Trace transfer of energy
Energy Transfer
Food Chain: a sequence in which energy
is transferred from one organisms to the
next as each organism eats another
organism
Food Chains and Food Webs
Food Webs: includes more organisms
and multiple food chains linked together,
shows many feeding relationships that are
possible in an ecosystem
Food Chains and Food Webs
Trophic Level: each step through which
energy is transferred in a food chain
Each time energy is transferred from one
organisms to another, some of the energy
is lost as heat and less energy is available
to organisms at the next tropic level
About 90% of energy at each trophic level
is used up, remaining 10% is all that is
available to next trophic level
Trophic Levels
Trophic Levels
Each layer represents one tropic level
Producers: at base, lowest trophic level,
contains most energy
Herbivores: second level, contain less
energy
Carnivores: third level, feed on
herbivores, contain less energy
Carnivores that feed on carnivores:
highest level, contain less energy
Energy Pyramids
Energy Pyramids
Because so much energy is lost at each
level, there are fewer organisms at the
higher trophic levels
◦ Ex. 1,000 zebras for every 1 lion on African
savannah
◦ Must be enough herbivores to support
carnivores
Energy Loss in Ecosystems
Loss of energy from tropic level to trophic
level limits the number of trophic levels in
an ecosystem
Organisms that feed on organisms at the
top trophic level are usually small, such as
parasitic worms and fleas that require
small amounts of energy
Energy Loss in Ecosytems