ECOLOGY
Ecology
• The study of organisms and their
interactions with the environment
• The biosphere is all the land, water and
air in which organisms live.
• All the living parts of an environment are
called biotic factors. The nonliving parts
are called abiotic factors (ex: water,
light, etc.)
Levels of Organization
in the Biosphere
• Population: consists of all the members
of a single species that live in one area
• Community: all populations that live and
interact in one environment
• Ecosystem: community + abiotic factors;
ex: forest, desert, ocean
Cycles
• Matter is recycled within and between
ecosystems
• Biogeochemical cycles show how
matter cycles through the biosphere
• There are 4 types of cycles:
– Water cycle
– Carbon cycle
– Nitrogen cycle
– Phosphorous cycle
Some Terms
• Habitat: type of environment in which a
particular species lives
• Niche: full range of physical and
biological conditions in which an organism
lives and the way in which the organism
uses those conditions
• Biodiversity: the variety of life--the
different plants, animals and microorganisms--and the ecosystems of which
they are a part
Food Synthesis
• Photosynthesis: use of light energy to
make food; process used by plants, algae
and some bacteria
• Chemosynthesis: use of chemical
energy to make food; process used by
some bacteria
Remember
• Autotrophs: use light energy to make
their own food; also called producers
• Heterotrophs: can’t make their own
food; also called consumers
Types of Heterotrophs
• Herbivores: eat plants
• Carnivores: eat animals
• Omnivores: eat both plants and animals
• Decomposers: break down organic
matter
• Scavengers: eat tissues of dead animals
Community Interactions
• Competition: organisms attempt to use
an ecological resource in the same place
at the same time
• Symbiosis: any relationship in which 2
species live closely together
• Predation: interaction in which one
organism (predator) captures and feeds
on another organism (prey)
Types of Symbiotic Relationships
• Mutualism: both organisms benefit
• Parasitism: one organism benefits while
the other is harmed
• Commensalism: one organism benefits
while the other is neither harmed nor
benefited
Food Chains
• A food chain models the flow of energy
through organisms in a community
• The flow is in one direction
• Each step in the transfer of energy and
matter in an ecological community is
called a trophic level
• Only 10% of the energy from one level is
transferred to the level above it
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Food Web
• Shows how food chains are connected
Ecological Pyramids
• Show the relationship between producers
and consumers at the trophic levels in an
ecosystem
• There are 3 types of pyramids:
– Energy Pyramid
– Biomass Pyramid
– Pyramid of Numbers
Growth Rate
• Growth rate = change in the number of
individuals divided by the time period
• Factors that play a role in growth
rate:
– Birth rate
– Immigration—movement of individuals into an
area
– Emigration—movement of individuals out of
an area
– Death rate
Exponential Growth
• Occurs when individuals
•
•
in a population reproduce
at a constant rate
Under ideal conditions
with unlimited resources,
a population will grow
exponentially
As resources become less
available, the growth of a
population slows or stops
The red bracket shows the area
of the graph that represents
exponential growth.
Carrying Capacity
• The number of individuals
•
in a population that an
environment can support
over a relatively long
period of time
Determined by limiting
factors
• Limiting factors are biotic
and abiotic resources in
the environment that limit
the size of a population
The red bracket shows the area
of the graph that represents the
carrying capacity.
Density-Dependent Limiting Factors
• Factors that become limiting only when
the population is large
• They include:
– Living space
– Disease
– Competition
– Predation
Density-Independent Limiting
Factors
• Factors that affect all populations in the
same way, regardless of their size
• They include:
– Weather
– Seasonal cycles
– Natural disasters
Ecological Succession
• As an ecosystem changes, older
inhabitants gradually die out and new
organisms move in
• This series of predictable changes that
occurs in a community over time is called
ecological succession
• There are 2 types:
– Primary succession
– Secondary succession
Primary Succession
• Occurs where no soil exists
• Ex: occurs on surfaces formed by volcanic
eruptions or on bare rock exposed when
glaciers melt
Primary Succession
Secondary Succession
• Occurs when a disturbance of some kind
changes an existing community without
removing the soil
• Ex: wildfires burn woodlands or field is
cleared for farming and then abandoned
Secondary Succession
Biological Magnification
• Buildup of a pollutant in organisms at
higher trophic levels in a food chain
ppm=parts per million