Download ECOLOGY

Study of interactions among organisms, and
between organisms and their environment.
Organism
Lowest level of
organization
studied in
ecology
Three important aspects of the ecology of
an organism are its:
 Habitat—physical area in which the organism lives
 Niche—way of life of a species. Includes its
habitat, feeding habits, reproductive behavior
 Trophic level—the relationship between what an
organism eats and what it is eaten by, it’s feeding
level.
Two basic trophic levels are:
Producer or autotroph
Consumer or heterotroph
Two types of autotrophs:
 Photoautotrophs-manufacture their own food
by photosynthesis (sunlight is the main energy
source for life on Earth).
 Chemoautotrophs-manufacture their food by a
process called chemosynthesis which utilizes
chemicals in their environment. Certain
bacteria can do this.
Types of consumers include:
Herbivores—eat
primary
producers
Types of consumers include:
Carnivores—eat
other consumers
Types of consumers include:
Decomposers—
break down
dead tissues into
fundamental
elements or
compounds
Types of consumers include:
Omnivores—eat
both producers
and consumers
Types of consumers include:
Detritovores
(scavengers)—
feed on
organisms that
have recently
died
Population
 A group of organisms of the same species that are living
in a particular place at a particular time.
 A population may also be defined as a group of organisms
that can interbreed.
Characteristics of populations
 Population density—number of individuals per unit area
 Growth rate—three factors may affect the population
size:
1. Birth rate
2. Death rate
3. Immigration or emigration
 Geographic distribution—(range) area inhabited by a
population
Types of growth
Exponential growth—
occurs slowly at first, and
then increases rapidly (J
shaped curve on graph).
Under ideal conditions
with unlimited resources,
a population will grow
exponentially.
Types of growth
Logistic growth—occurs
when a population’s
growth slows or stops
following a period of
exponential growth (S
shaped curve on a graph)
Carrying capacity
Largest number of individuals that
an ecosystem can support.
Occurs when the population
reaches the limit of what
available resources can support.
Growth limiting factors—factors in an ecosystem
that causes population growth to slow down,
stop, or decrease.
 Density-dependent factors—depend on population
size. Include competition, predation, parasitism, and
disease.
 Density-independent factors—affect all populations in
similar ways regardless of population size. May include
unusual weather, natural disasters, seasonal cycles, and
certain human activities (clear cutting forests, damming
rivers, etc…).
Communities
Different populations that
live in the same defined
area and can interact with
one another.
Biotic relationships—all relationships among
organisms in a community
 Competition—use or defense of a resource by one
organism that reduces the availability of that resource to
other organisms
 Predation—one organism feed upon another. The
predator feeds upon the prey
 Symbiosis—relationship in which two dissimilar
organisms live in close association
Types of symbiosis include:
Parasitism—harmful,
close, long-term
relationship in which one
organism receives its
nutrition from another
organism. The one
receiving the benefit is
called the parasite. The
providing organism is
called the host.
Types of symbiosis include:
Commensalism—
relationship in which one
organism benefits and the
other neither benefits or
suffers harm.
Types of symbiosis include:
Mutualism—relationship
in which both organisms
benefit.
Ecosystem
An ecosystem is a community of living
things and their
physical environment.
*In an ecosystem, matter is recycled but
energy is lost.*
Two types of factors that influence an
ecosystem:
 Biotic factors—biological (living) influences that shape an
ecosystem. Biodiversity refers to the variety of organisms
in a given ecosystem.
 Abiotic factors—physical or non-living influences that
shape an ecosystem.
Keystone Species—a species that has an
unusually large effect on its ecosystem
Ecological succession—a series of
predictable changes that occurs over time.
 Primary succession (bare
rock succession)—occurs on
volcanic islands or on bare
rock as glaciers melt
 Secondary succession—
occurs when a disturbance
of some kind (fire, land
clearing or plowing) changes
the community without
removing the soil. Begins
with grasses and then
follows the same pattern as
a primary succession.
Ecological Succession
Pioneer organism—first
organism to populate an
ecosystem. The pioneer
organism in a primary
succession is lichen which
is a mutualistic
relationship between an
alga and a fungus.