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Chapter 2
SECTION 2
NUTRITION AND ENERGY FLOW
Ecology is the study of interactions between
organisms and their environment.
Ecology combines the science of
biology, chemistry, physics, geology and
others.
Ecology involves the interaction of the
biotic and abiotic factors:
Biotic and Abiotic Factors
• Biotic factors
are all living
things that
inhabit an
environment
• Abiotic factors
are all non
living things
that inhabit an
environment.
Biosphere
Ecosystems
Communities
Populations
Organisms
Biosphere
Levels of
organization
Levels of Organization
• Biosphere – The portion of the Earth that supports
life.
• Ecosystem – populations of plants and animals
that interact with each other in a given area and
with the abiotic components of that area
• Communities – All the populations of different
species that live in the same place at the same time
• Population – A group of organisms, all of one
species, which can interbreed and live in the same
place at the same time
• Organism – An individual living thing that is
made of cells, uses energy, reproduces, responds,
grows and develops
Biotic Factors
• Living things are
adapted to their
environment and
impact their
community
Abiotic Factors
• Changes in abiotic
factors can change
environment
• No rain can lead to
drought.
Where and How Organisms Live
• Niche - the role a • Habitat - the
species plays in
place where an
its community
organism lives
out its life
How Do Organisms Obtain
Energy?
Autotroph
Heterotroph
Autotrophs
• Organisms that
use energy from
the sun or
chemicals to
make their food;
also called
producers
Heterotrophs
• Organisms that
depend on
autotrophs for
nutrients and
energy; also
called
consumers.
Types of Heterotrophs
• Carnivores
• Herbivores
• Scavengers
• Omnivores
• Decomposers
Carnivores
• Only eat
meat
Herbivores
• Only eat
plants.
Scavengers
• Feed on
carrion, refuse,
and similar
dead organisms
Spotted Hyena chasing away a
vulture.
Omnivores
• Eat a variety
of plants and
animals
Decomposer
• Break down
complex
compounds of dead
and decaying
organisms into
small, absorbable
molecules; these
are fungi or
bacteria.
How Does Matter and
Energy Flow in
Ecosystems?
Food Chain
• A model that shows how
matter and energy move
through an ecosystem.
• algae  fish  bird
• Arrows show direction of energy
There are usually no
more than 5 links
because the amount of
energy has been lost.
Trophic Levels
• A feeding step in a food chain.
• Many different species occupy
each trophic level in an ecosystem.
• Many organisms feed from several
different trophic levels.
Quaternary Consumers
(hawks, lions, killer whales)
Tertiary Consumers
(organisms that eat secondary consumers)
Secondary Consumers
(carnivores that eat the consumers
from the level below)
Primary Consumers
(herbivores)
Producers
(autotrophs)
Food Web
• Food webs express all of
the possible feeding
relationships at each
trophic level in a
community.
Ecological Pyramids
• Show energy conversion in a
ecosystem.
• Pyramid of energy - energy decreases
at each higher trophic level.
• Pyramid of numbers - population size
decreases or increases at each higher
trophic level.
Pyramid of Energy
• The total transfer of
energy from one
trophic level to the
next is 10%. What
happens to the rest of
the energy? Lost as
heat or by living
• Producers using
sunlight constantly
adds energy back to
the ecosystem.
Pyramid of
Biomass/Numbers
• Populations and
biomass amounts will
usually decrease as
you go up the trophic
levels.
• Can you think of an
example where the
pop. Size will increase
at each higher trophic
level?