Download Organic matter that enters into the composition of living organisms

Chapter 10
Ecosystems
What is an ecosystem?
• An ecosystem is a community of living
organisms interacting with one another and
with the nonliving components of the
environment that they inhabit.
• Examples of ecosystems:
– Forest
– Lake
– Island
Interactions within an ecosystem:
trophic relationships
• Trophic relationships are the feeding connections among
the living organisms in an ecosystem.
• Often represented by a food chain or food web
• The position of each organism in a chain corresponds to its
trophic level.
• Food chains contain:
– Producers
– Consumers
– decomposers
Trophe =
nourishment
Food Chain
Producers
• Producers are organisms with the ability to create organic matter
from inorganic matter
– Organic matter that enters into the composition of living organisms and
that is usually created by them (proteins, lipids)
– Inorganic matter is not necessarily produced by living organisms (water,
minerals, salts)
• Producers are also called autotrophs
• Autotrophs are at the bottom of the food chain because they are the
organisms that bring energy into the ecosystem
Auto= self
Trophe = nourishment
Photosynthesis
• In nature,
photosynthesis is
the process in
which producers
transform energy
from the sun into
organic matter.
– In this way plants
can feed
themselves and
grow.
Consumers
• Consumers are heterotrophic organisms that
feed on other living organisms.
• Primary, or first order consumers feed on
producers or their seeds and fruit.
– Herbivores are primary consumers.
• Second, third and fourth order consumers eat
consumers of the respective preceding order.
– Species in the second order or higher are usually
carnivorous.
• Some animals are
omnivorous.
• They are consumers of
several orders at once.
• Bears are an excellent
example of this because
they will eat berries one
day and salmon the next.
• The same animal can be a consumer of a
different order depending on its position in
another food chain.
DECOMPOSERS
• Decomposers are organisms that feed
on the waste and remains of other
living organisms.
• They feed on detritus, which is dead
organic matter.
– Ex: fallen leaves, dead animals, excrement
TROPHIC NETWORK
(food web)
• More than one food chain is possible in an
ecosystem.
• A representation of all
these relationships is
called a TROPHIC
NETWORK...or food web.
ECOSYSTEMS DYNAMICS
• Matter is transformed in an ecosystem
• Matter and energy within an ecosystem are
exchanged from one organism to another in a
process that is called material energy flow
• According to the LAW OF CONSERVATION OF
MASS, nothing is lost and nothing is gained;
matter is transformed
Chemical recycling: a
natural process by which
decomposers make
inorganic matter available
by breaking down organic
matter
•Producers convert energy from the Sun and inorganic matter from the environment into
organic matter.
•When producers die (or the consumers that eat them), decomposers break down the
organic matter in the detritus that they eat, producing new inorganic matter.
•This is called CHEMICAL RECYCLING
PRIMARY PRODUCTIVITY
• The biomass is the total mass of organic
matter in an ecosystem at any given time.
• The primary productivity of an ecosystem is
the amount of new biomass generated by its
producers.
The factors that influence primary
productivity are:
• The amount of light
• The amount of water available
• Access to nutrients
• Temperature
DISTURBANCES
• A disturbance is an event that damages an
ecosystem. It can lead to the elimination of
organisms and alter the availability of
resources.
• Disturbances can vary in three ways:
– Type
– Frequency
– Seriousness
NATURAL DISTURBANCES
• These are events triggered by natural
phenomena rather than by human activity.
• Examples of natural disturbances are:
– Storms
– Volcanic eruptions
– Droughts
– floods
HUMAN DISTURBANCES
• Many human activities have a damaging effect
on ecosystems.
• Examples of human disturbances are:
– Oil spills
– Deforestation
– Ozone depletion
– Flooding (hydroelectric dams)
ECOLOGICAL SUCCESSION
• Ecological succession is the series of changes
that occur in an ecosystem after a
disturbance and that continue until the
balance of the ecosystem is restored.
• After a disturbance, an ecosystem will go
through a series of gradual changes until
balance is restored…if possible.