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Chapter 2
Fundamentals of Ecology
Karleskint
Turner
Small
Key Concepts
• Ecology is the study of relationships
among organisms and the interactions of
organisms with their environment.
• An organism’s environment consists of
biotic (biological interactions) and abiotic
(non-living, physical) factors.
• An organism’s habitat is where it lives, and
its niche is the role the organism plays in
its community.
Key Concepts
• All organisms expend energy to maintain
homeostasis, i.e., internal balance relative
to external changes.
• Physical factors of the environment, such
as sunlight, temperature, salinity,
exposure, and pressure, will determine
where organisms can live.
• Species interactions that influence the
distribution of organisms in the marine
environment include competition,
predation and symbiosis.
Key Concepts
• Marine ecosystems consist of interacting
communities and their physical
environments.
• Most populations initially grow at an
exponential rate, but as they approach the
carrying capacity of the environment, the
growth rate levels off.
• Energy in ecosystems flows from
producers to and through consumers.
Key Concepts
• The average amount of energy passed
from one trophic level to the next is
approximately 10%, limiting the number
and biomass of organisms at different
trophic levels.
• With the exception of energy, everything
that is required for life is recycled.
Study of Ecology
• Ecology
– from the Greek word oikos meaning “home”
• Environment
– biotic factors
– abiotic factors
• Habitat: where an organisms lives
• Ecosystems
– composed of living organisms and their nonliving environment
Study of Ecology
• The study of organisms interacting with
one another and their environment. This
entails:
– biological (biotic) factors
– environmental (abiotic) factors
– the organism’s behavior
• Niche: an organism’s environmental role
Higher
Zone of
overlap
Species B
Niche
Species B
Salinity
Niche
0
Stepped Art
Fig. 2-12, p. 26
Homeostasis and Distribution
of Marine Organisms
• Maintaining homeostasis
– changes in external environment
– internal adjustments to maintain a stable
internal environment
• optimal range
• zones of intolerance
Characteristics of the Physical Environment
that Affect Organism Distribution
• Sunlight
– photosynthesis
– vision
– desiccation
• Temperature
– ectotherms
– endotherms
Characteristics of the Physical Environment
that Affect Organism Distribution
• Salinity
–solutes
–osmosis
–solutes in the body fluids of organisms
–tolerance for variation ion environmental
salinity
–regulation of solutes in body fluids
Cell
membrane
Outside Inside
the cell the cell
No net water
movement
(a) Isotonic solution
Cell
membrane
Outside Inside
the cell the cell
Cell
membrane
Outside
Inside
the cell
the cell
Net water movement
out of the cell
(b) Hypertonic solution
Net water movement
into the cell
(c) Hypotonic solution
Stepped Art
Fig. 2-4, p. 19
Characteristics of the Physical Environment
that Affect Organism Distribution
• Pressure
–760 mm Hg or 1 atmosphere at sea level
–increases 1 atmosphere for every 10 meters
below sea level
Characteristics of the Physical Environment
that Affect Organism Distribution
• Metabolic requirements
–nutrients and limiting nutrients
–oxygen as a requirement for metabolism
–anaerobic and aerobic organisms
–eutrophication and algal bloom
• Metabolic wastes
–carbon dioxide is a common byproduct of
metabolism
Populations
• A group of the same species that
occupies a specified area
• Geographic range
• Population size
Distribution of Organisms in a Population
• Population density (abundance)
• Dispersion
– clumped
– uniform
– random
Changes in Population Size
• Can occur through:
– reproduction
– immigration
– death
– emigration
• Can be affected by:
– survivorship
– life history
– opportunistic and equilibrium species
Population Growth
• Many ways a population can increase in
size, depending on the carrying capacity of
the environment
– exponential/logarithmic growth
– logistic growth
Population Growth
• Density Dependent Factors
– have greater effect as population increases in
size
• Density Independent Factors
– not related to population size
Communities
• Composed of populations of different
species that occupy one habitat at the
same time
• Niche: what an organism does in its
environment
– fundamental niche
– realized niche
Communities
• Biological environment
– competition
• may be interspecific or intraspecific
• may result in competitive exclusion
• resource partitioning allows organisms to share a
resource
– predator-prey relationships
• balance of abundance of prey vs. predators
• keystone predators
Communities
• Symbiosis: living together
– mutualism – both organisms benefit
– commensalism – one organism benefits, the
other is nether harmed nor benefited
– parasitism – one organism benefits, the other
is harmed
Ecosystems: Basic Units of the Biosphere
• Energy flow through ecosystems
• Producers = Autotrophs
(auto = self, troph = feed)
– photosynthetic producers
– chemosynthetic producers
Sunlight
Chlorophyll
Produces
6 Carbon
dioxide
(CO2)
+
6 Water
(H2O)
Glucose
(C6H12O6)
+
6 Oxygen
(O2)
Stepped Art
Fig. 2-16, p. 32
Ecosystems: Basic Units of the Biosphere
• Measuring primary productivity
– rate at which energy-rich food molecules are
being produced from inorganic matter
– measuring carbon in organic products of
photosynthesis
• light-dark-bottle method
• radioactive tracers
• satellite images
Ecosystems: Basic Units of the Biosphere
• Consumers = Heterotrophs
(hetero = other, troph = feed)
–
–
–
–
first-order consumers
second- and third-order consumers
detrivores
decomposers
• Food chains and food webs
• Other energy pathways
– dissolved organic matter (DOM)
– Detritus
Seaweed
(producer)
Sea urchin
(first-order
consumer,
herbivore)
Helmet snail
(second-order
consumer,
carnivore)
Fish
(third-order
consumer,
carnivore)
Stepped Art
Fig. 2-17, p. 33
Ecosystems: Basic Units of the Biosphere
• Trophic levels
– number of levels is limited because only a
fraction of the energy at one level passes to
the next level
– ecological efficiency
• ten percent rule
– trophic pyramids
• as energy passed on decreases, so does the
number of organisms that can be supported
Biogeochemical Cycles
• Hydrologic cycle
– water is lost through evaporation
– carried north and south from equator
– carried west to east within each hemisphere
– returned through precipitation and runoff
Moist air
Evaporation from
rivers, soils, vegetation,
lakes, falling precipitation
Precipitation
Precipitation
Evaporation
from ocean
Salt
Sea
spray
Lakes
Ocean
Seepage
Seepage
Groundwater
Soak in and
percolation
Land
Stepped Art
Fig. 2-20, p. 36
Biogeochemical Cycles
• Carbon cycle
– carbon released from organisms through
respiration and decomposition
– recycled by photosynthetic producers
– carbon is used in shells, corals and skeletons
as part of calcium carbonate
– fossil fuels when burned release CO2 back
into atmosphere
CO2 in atmosphere to plants
for photosynthesis
CO2 in the atmosphere
Precipitation
Respiration
Decomposers
Limestone
Peat Plant residues
coal
Dissolved
CO2 forms
HCO3–
Shells
Dissolved
CO2
CO2 is
taken up by
phytoplankton
for photosynthesis
Decomposition
Sediments
Limestone
Stepped Art
Fig. 2-21, p. 37
Biogeochemical Cycles
• Nitrogen cycle
– producers use nitrogen to synthesize protein
forming amino acids
– bacteria recycle nitrogen from wastes and
decomposing, dead organisms
– fixation of atmospheric nitrogen by
microorganisms
Biosphere
• Includes all of earth’s communities and
ecosystems
• Examples of ecosystems:
– estuaries
– salt marshes
– mangrove swamps
– rocky and sandy shores
– kelp forests
– coral reefs
– open ocean
Distribution of Marine Communities
• Pelagic division
– neritic zone and pelagic zone
– photic zone, disphotic zone, and aphotic zone
– plankton and nekton
• Benthic division
– shelf zone, bathyal zone, abyssal zone, and
hadal zone
– epifauna and infauna