Ecology
Ecology = the study of the relationships
between organisms and their interactions
with the environment
LEVELS OF ECOLOGICAL ORGANIZATION
Organism  population  community  ecosystem  biome  biosphere
Standards:
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Describe the levels of ecological organization (ie, organism, populations, community, ecosystem, biome, biosphere).
Describe characteristic biotic and abiotic components of aquatic (water) and terrestrial (land) ecosystems.
Organism - is any individual living thing.
Species - is a group of organisms so similar to one another that they can breed.
Population - are groups of individuals that belong to the same species and live in the same area.
Community - the different populations that live together in a specific area.
Ecosystem – a system composed of all the living and non-living components in an environment.
Biome - is a group of ecosystems that have the same climate and similar dominant communities.
Biosphere - is all living things and the places where they exist (air, land, water).
Biotic – A term that describes a living factor in an ecosystem.
Abiotic – A term that describes a nonliving factor in an ecosystem.
Abiotic Factors = soil, sun, water, rocks, temperature, air, gases
Biotic Factors = all plants, animals, fungi, protists and bacteria
Standard:
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Describe how energy flows through an ecosystem (e.g., food chains, food webs, energy pyramids).
Food Chain – A simplified (single) path illustrating the passing of potential chemical energy (food) from one organism to another organism.
Food Web – A complex arrangement of interrelated (multiple) food chains illustrating the flow of energy between interdependent organisms.
Energy Pyramid – A model that illustrates the biomass productivity at multiple trophic levels in a given ecosystem.
Food Chain
Food Web
Energy Pyramid
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Energy is lost as you move
up the energy pyramid
from one trophic level to
the next.
Only 10% of the energy
available within one
trophic level is transferred
to organisms at the next
trophic level.
There is much more energy
in the producer level of a
food chain than at the
consumer levels.
Standards:
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Trophic level – The position of an organism in relation to the flow of energy and inorganic nutrients through an
ecosystem (eg. producer, consumer and decomposer)
Consumer – organism that obtains energy by feeding on other organisms
Producer – organism that uses a primary energy source (sun or chemicals) to make their own food
Decomposer – organism that obtains nutrients by consuming dead/decaying organic matter
Competition – individuals or groups of organisms compete for similar resources such as territory, mates, water & food
Predation – predator/prey relationships (predators = consume prey; prey = get eaten by predators)
Symbiotic relationship – A relationship between two organisms
1. mutualism – both organisms benefit (ex.
2. parasitism – one organism benefits and the other organism is harmed (ex. tick on deer)
3. commensalism – one organism benefits and other organism is unaffected
Fitness – A measure of an organism’s ability to survive and reproduce (more fit = greater population size)
Limiting factors – Chemical or physical factor that limits the existence, growth, abundance or distribution of an
individual organism or a population
Population dynamics – study of the changes in the number of individuals in a population, as affected by birth, death,
immigration and emigration
Describe biotic interactions in an ecosystem (e.g. competition, predation, symbiosis)
Describe how ecosystems change in response to natural and human disturbances (e.g. climate changes, introduction of nonnative species, pollution, fires)
Describe the effects of limiting factors on population dynamics and potential species extinction.
Limiting factors: Ecological factors that limit
population growth. They include:
• Competition (Resource Availability – food,
water, etc…)
• Predation (Predator/Prey relationships)
• Parasitism
• Disease
• Unusual weather
• Immigration vs. Emigration
• Births vs. Deaths
• Natural disasters (volcanoes, tsunamis,
tornadoes and hurricanes)
• Human activities (urbanization, introduction
of non-native species, deforestation, etc…)
Limiting factors can cause ecosystems to reach carrying capacity or threaten a population’s existence.
 Carrying Capacity: The maximum amount of a particular species that an environment can support.
 Threatened Species: A populations numbers are declining.
 Endangered Species: A populations numbers are very low.
 Extinct Species: All organisms of a particular species have died.
Ecological Change
Ecosystems can change due to natural disturbances climate
change or natural disasters (hurricanes, tornados, volcanic
eruptions, earthquakes, etc… OR they can change due to human
disturbances such as fires, pollution, urbanization, deforestation,
introduction of non-native species.
These disturbances may result in any of the following: global
warming, succession, disruption of stable ecosystems.
Succession – A series of predictable and orderly changes within
an ecosystem over time
1. Primary Succession (never inhabited before)
2. Secondary Succession (occurs in a once developed
community following a disturbance)
Standards:
Habitat – area which provides an organism with its basic survival needs
Niche – job that an organism plays in its ecosystem
Non-native Species – species that was introduced (not found naturally) in an area
Pioneer Species – first species to thrive in an otherwise lifeless area (ex. moss, lichens)
Climax Community – stable, end stage of ecological succession (successful ecosystem)
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Describe how matter recycles through an ecosystem (i.e. water cycle, carbon cycle, oxygen cycle, nitrogen cycle)
BIOGEOCHEMICAL CYCLES
The Water (Hydrologic) Cycle:
• Evaporation – water separates into hydrogen and oxygen molecules due to a rise in temperature
• Condensation – water collects due to a drop in temperature
• Precipitation – water falls from the clouds due to changes in temperature and pressure
• Surface Water and Groundwater – water collects or runs from one region to another
• Transpiration – plants draw water up from the ground and release it through their stoma (openings) in the leaves
The Carbon Cycle:
- Carbon is added to the atmosphere (CO2) by the following:
• Combustion - Burning of Fossil Fuels (exhaust)
• Respiration – From ALL organisms, aquatic and terrestrial
• Natural Events – Volcanism
- Carbon is removed from the atmosphere (CO2) by the following:
• Photosynthesis – From aquatic and terrestrial organisms
- Carbon is transferred between the earth and living organisms by:
• Consumption - Carbon is transferred from plants to animals
through organic molecules like carbs, lipids and proteins..
• Decomposition – Carbon molecules from dead organisms
form fossil fuels.
• Carbon passes through food chains and food webs as one
organism consumes the next
The Oxygen Cycle:
• Oxygen is added to the atmosphere by the
following:
– Photosynthesis - From aquatic and
terrestrial organisms
• Oxygen is removed from the atmosphere:
– Respiration - From ALL organisms,
aquatic and terrestrial
– Decomposition – Oxygen is needed
to allow this process to continue
– Combustion – Oxygen is required to
fuel the fire!
• Oxygen is also found in organic compounds in
living things:
– Carbohydrates
– Lipids (Fats)
– Proteins
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The Nitrogen Cycle:
• All life requires nitrogen-compounds like
amino acids, proteins & nucleic acids.
• The majority of nitrogen, 79%, is supplied
by the air, but the nitrogen in the air is not a
usable form for most organisms.
• Nitrogen fixation = process of bacteria
converting nitrogen gas (N2) into usable
nitrogen compounds. Usable forms of
nitrogen include:
– Nitrates (NO3-)
– Nitrites (NO2-)
– Ammonia (NH3)
• Different types of bacteria help us convert
nitrogen into different forms:
– Nitrification = converts ammonia
into nitrites OR nitrites into
Plants get usable nitrogen compounds from nitrogen fixing bacteria.
nitrates
Animals get their nitrogen by consuming plants.
– Denitrification = converts nitrates
Decomposing plant and animal matter supplies a source of nitrogen.
back into nitrogen gas.
Animal waste also provided a source of nitrogen.