Biology
4.2 What shapes an Ecosystem?
I. Biotic and Abiotic Factors
Biotic Factors
Ecosystems are influenced by a
combination of biological and
physical factors
Biological influences an
organisms within an ecosystems
a.
b.
c.
d.
Ecological Community
Birds
Trees
Mushroom
bacteria
the entire living cast of
characters with which an
organism might interact.
Ex. Tadpole eats algae / plants
Abiotic Factors
Physical or nonliving factors that
shape ecosystems
Ex. Climate of an area:
a.
b.
c.
d.
e.
f.
g.
Temperature
Precipitation
Humidity
Wind
Nutrient availability
Soil type
Sunlight
***Together, biotic and abiotic
factors determine the survival
and growth of an organism and
the productivity of the
ecosystem in which lives.
Habitat
II. Niche
includes biotic and abiotic
factors
Full range of physical and
biological conditions in which an
organism lives and the way in
which the organism uses those
conditions
a. Range of temperatures the
organism needs to survive
b. Combination of biotic and
abiotic factors in an
ecosystem often determines
the number of different
niches in that ecosystem
1. Type of food the organism
eats
2. How it obtains this food
3. Which other species use
the organism as food.
III. Community Interactions
a. competition
b.predation
c.various forms of symbiosis
A.Competition
Organisms of the same or
different species attempt to use
an ecological resource in the
same place at the same time
Resource
Any necessity of life
a.
b.
c.
d.
e.
Direct Competition
Water
Nutrients
Light
Food
Space
Results in a winner /loser
a. Loser organism failing to
survive
Competitive Exclusion Principle
B. Predation
No two species can occupy the
same niche in the same habitat
at the same time
An interaction in which one
organism captures and feeds on
another organism
Predator
Organism that does the killing
and eating
Prey
Food organism that is eaten or
hunted
C. Symbiosis
Any living relationship in which
two species live closely together
“living together”
3 main classes:
a. Mutualism
b. Commensalism
c. Parasitism
Mutualism
Both species benefit from the
relationship.
Ex. Flowers -> provide insects
food
Commensalism
One member of the association
benefits and the other is neither
helped nor harmed
Ex. Barnacles attach to whale’s
skin
Parasitism
One organism lives on or inside
another organism and harms it
Host
Parasite obtains all or part of its
nutritional needs from the other
organism
Ex. Tapeworms live in intestines
of animals
IV. Ecological Succession
Series of predictable changes
that occurs in a community over
time
***Ecosystems are constantly
changing in response to natural
and human disturbances . As an
ecosystem changes, older
inhabitants gradually die out and
new organisms move in, causing
further changes in the
community
A. Primary Succession
Succession occurs on surfaces
where no soil exists
a. Volcanic eruptions build new
islands
b. Cover land with lava rock or
volcanic ash
c. Bare rocks exposed when
glaciers melt
Pioneer Species
First species to populate the
area
Ex. Lichen
B. Secondary Succession
Components of an ecosystem
can be changed by natural
events
1. Changes may affect the
ecosystem in predictable or
unpredictable ways
2. When it is over, community
interactions tend to restore
the ecosystem to its original
condition
Ex.
Wild Fires
Land cleared for farming
C. Succession in a Marine Ecosystem
1. Large whale dies and sinks to
the normally barren ocean
floor
2. Whale carcass attracts a host
of scavengers / decomposers
3. Within a year, whale’s tissues
have been eaten. Tissues
support a small number of
fishes
4. Whale’s skeleton supports a
third community –
heterotrophic bacteria
Chemosynthetic bacteria