Download Chapter 4 Notes

Chapter 4 Notes
Section 4-2
I. What Shapes an Ecosystem?
A. Biotic & Abiotic Factors
1. Biological, or living influences on an ecosystem are
called biotic factors.
a. Examples: birds, trees, mushrooms, bacteria
2. Physical & chemical, or nonliving factors that influence
an ecosystem are called abiotic factors.
a. Examples: climate, wind, sunlight, nutrient
availability
3. Together the biotic and abiotic factors determine the
survival and growth of an organism and the
productivity of the ecosystem in which that organism
lives.
4. A habitat is the area where an organism lives.
B. The Niche
1. A niche is the full range of physical and biological
conditions in which an organism lives and the way in
which the organisms use those conditions.
a. A niche includes the organisms place in the food
web.
b. The type of food it eats.
c. The physical conditions needed for survival.
d. When and how it reproduces.
2. Species cannot share niches in the same habitat.
C. Community Interactions
1. Competition occurs when organisms attempt to use the
same ecological resource at the same time.
a. Resources include water, food, nutrients, light,
and space.
b. Competitive Exclusion Principle states that no
two species can occupy the same niche at the
same time.
2. Predation is an interaction in which one organism
captures and feeds on another.
a. Predator - The organism that does the killing.
b.
3.
Prey - The organism that gets killed or the food
organism.
c.
A cheetah and a zebra: Which is the predator
and which is the prey?
Symbiosis is a relationship where two species live
closely together.
a. Mutualism – both species benefit.
i. Ex. Flowers and insects
b. Commensalism – one member benefits and the
other is neither helped nor harmed.
i. Ex. Whales and barnacles
c. Parasitism – one organism lives inside or on
another organism and harms it.
i. Ex. Dog and heartworms
II. Ecological Succession
A. Succession – species replacing each other in a developing
ecosystem
B. Primary Succession- when succession takes place where
there were no species before (ex: plants on land that a
volcanic eruption formed)
C. Secondary succession – succession in an area where there
has been previous life (ex: plants starting to grow in a field that
was destroyed by fire)
III. Limits to growth of a population:
A. *Recall: A limiting nutrient is a nutrient that is scare or
cycles slowly in an ecosystem. These can reduce the primary
productivity of an ecosystem. In terms of population, we call
these limiting factors.
1. Competition
2. Predation
3. Parasitism
4. Disease
5. Natural Disasters
6. Human Activities
B. Density – dependent factors – a limiting factor that
depends on the population size
1. Examples: competition, predation, parasitism & disease
2. Won’t affect small, scattered populations - only affects
large populations
C. Density – independent factors – a limiting factor that
affects all populations regardless of size
1. Examples: unusual weather, natural disasters, seasonal
cycles, and some human activities like the damming of
rivers & clear-cutting forests
IV. Biodiversity – all organisms in biosphere; variety
A. Value of biodiversity: food, medicine, other products
V. Threats to biodiversity
A. Habitat alteration – land development
B. Over fishing/hunting
C. Pollution
1. Biological magnification – amount of pollutant
increases as it moves to higher trophic levels
a. Example: DDT in Borneo or Mercury in Minimata,
Japan
D. Introduced Species – accidental or intentional introduction of
a plant or animal to a new area
1. Invasive species – reproduce rapidly due to no natural
predator
ex: Nutria in Louisiana; Fire ants (1918)