Chapter 2Chapter 2Fundamentals of EcologyFundamentals of Ecology

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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 non-

living 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

Species B

Species B

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Size o

f sed

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t

partic

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Coarse

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Zone of overlap Niche

Niche

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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

• Salinity–solutes–osmosis–solutes in the body fluids of organisms–tolerance for variation ion environmental

salinity–regulation of solutes in body fluids

Characteristics of the Physical Environment that Affect Organism Distribution

No net watermovement

(c) Hypotonic solution(b) Hypertonic solution(a) Isotonic solution

Net water movementinto the cell

Net water movementout of the cell

Insidethe cell

Outsidethe cell

Cellmembrane

Outsidethe cell

Insidethe cell

Cellmembrane

Outsidethe cell

Insidethe cell

Cellmembrane

Stepped Art

Fig. 2-4, p. 19

• 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

Characteristics of the Physical Environment that Affect Organism

Distribution

• A group of the same species that occupies a specified area

• Geographic range

• Population size

Populations

• Population density (abundance)

• Dispersion– clumped– uniform– random

Distribution of Organisms in a Population

• Can occur through:– reproduction– immigration– death– emigration

• Can be affected by:– survivorship– life history– opportunistic and equilibrium species

Changes in Population Size

• 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

Population Growth

• 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

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

6 Oxygen (O2)

+Glucose (C6H12O6)

Produces

6 Water (H2O)

+6 Carbon dioxide (CO2)

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

Ocean

Lakes Soil moisture

Land

Precipitation

Moist air

Precipitation

Seaspray

Salt Runoff

Groundwater

Soak in andpercolation

SeepageSeepage

Evaporation fromrivers, soils, vegetation, lakes, falling precipitation

Evaporationfrom ocean

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 the atmosphere

Plant residuesPeatcoal

Limestone

Decomposers

SedimentsShells

CO2 in atmosphere to plantsfor photosynthesis

Precipitation

Limestone CO2 istaken up by

phytoplanktonfor photosynthesis

DissolvedCO2

Respiration

DissolvedCO2 forms

HCO3–

Decomposition

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