Download unit 2: ecology

UNIT 2: ECOLOGY
THE BIOSPHERE
NOTES
WHAT IS ECOLOGY?
Ecology = the scientific study of interactions among organisms and between organisms
and their environment
Ecological Levels of Organization
- Species = a group of organisms so similar to one another that they can breed and
produce fertile offspring
- Populations = groups of individuals that belong to the same species and live in
the same area
- Communities = assemblages of different populations that live together in a
defined area
- Ecosystems = a collection of all the organisms that live in a particular place,
together with their nonliving, or physical, environment.
- Biomes = a group of ecosystems that have the same climate and similar dominant
communities
- Biosphere = the combined portions of the planet in which all of life exists,
including land, water, and atmosphere (extends about 8km above Earth’s surface
and as far as 11km below the surface of the ocean)
o Interactions within the biosphere produce a web of interdependence
between organisms and the environment in which they live
Ecological Methods
- Ecologist use three basic approaches:
- 1. Observing (use to form hypothesis)
- 2. Experimenting (test hypothesis)
- 3. Modeling (use of current collected data for extended experiments)
ENERGY FLOW
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At the core of every organism’s interaction with the environment is its need for
energy to power life’s processes.
The flow of energy through an ecosystem is one of the most important factors that
determines the system’s capacity to sustain life.
Producers
- Without a constant input of energy, living systems cannot function.
- Sunlight is the main energy source for life on Earth
- Autotrophs = produce their “own” form of energy (make their food)
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o Photosynthetic Autotrophs = Sunlight  Food
 Plants, Protists (Algae), Bacteria
o Chemosynthetic Autotrophs = Inorganic chemical compounds  Food
 Oceanic volcanic vents, sulphur springs, marshes, etc.
 Bacteria
Producers = Autotrophs
Essential to the flow of energy through the biosphere
Consumers
- Heterotrophs = organisms that rely on other organisms for their energy and food
supply (eat their food)
- Consumers
- Bacteria, Protists, Fungi, Animals
- Herbivores = eat plants
- Carnivores = eat animals
- Omnivores = eat both plants and animals
- Decomposers = break down organic matter
- Detritivores = feed on plant and animal remains and other dead matter
Feeding Relationships
- What happens to the energy in an ecosystem when one organism eats another?
- It moves along a one-way path
- Energy flows through an ecosystem in one direction, from the sun or inorganic
compounds to autotrophs (producers) and then to various heterotrophs
(consumers)
- Food Chains = a series of steps in which organisms transfer energy by eating
and being eaten
- Food Webs = links all the food chains in an ecosystem together
- Trophic Levels = each step in a food chain or food web
o 1st Level = Producers
o 2nd , 3rd , or Higher Level = Consumers
Ecological Pyramids
- The amount of energy or matter in an ecosystem can be represented by an
ecological pyramid
- Ecological Pyramid = a diagram that shows the relative amounts of energy or
matter contained within each trophic level in a food chain or food web
- 1. Energy Pyramids = represents the amount of energy that is transferred from
one trophic level to the next
o Only about 10% of the energy available within one trophic level is
transferred to organisms at the next trophic level
o Organisms use much of the energy they consume for life processes and
release some as heat
o 1/10th solar energy captured by grass  cow
o 1/10th of the energy from cow  human
o Human obtains 1 percent (10% of 10% percent) of the “original” energy
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o The more trophic levels, the less energy that remains from the original
amount
2. Biomass Pyramids = represent the amount of potential food that is available
for each trophic level in an ecosystem
o Biomass = the total amount of living tissue within a given trophic level
o Biomass is usually expressed in terms of grams of organic (living) matter
per unit area
3. Pyramid of Numbers = represents the numbers of individual organisms at
each trophic level in an ecosystem
o Doesn’t always “fit” the same shape of energy or biomass pyramids (i.e. a
forest tree contains a large amount of energy/biomass, but it is only one
organism)
CYCLE OF MATTER
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Organisms need more than just energy to survive
They also need water, minerals, and other life-sustaining compounds
More than 95% of the body is made up of just four elements: oxygen, carbon,
hydrogen, and nitrogen
Although these elements are common on Earth, organisms cannot use them unless
the elements are in a chemical form that cells can take up.
Recycling the Biosphere
- Unlike the one-way flow of energy, matter is recycled within and between
ecosystems.
- Biogeochemical Cycles = biological, geological, and chemical aspects of the
biosphere
- Biological systems do not “use up” matter, they “transform” it.
- Example: Carbon atom  CO2 in Atmosphere  Leaf  Fruit  Caribou 
CO2  Atmosphere
The Water Cycle
- All living things require water to survive.
- Water moves between the oceans, atmosphere, and land.
- Evaporation/ Transpiration  Condensation  Precipitation
Nutrient Cycles
- Nutrients = all the chemical substances that an organism needs to sustain it’s life
- “Chemical building blocks”
- Every living organism needs nutrients to build tissues and carry out essential life
functions.
- 1. The Carbon Cycle
o Carbon is a key ingredient of living tissue
o Calcium Carbonate (CaCO3) in bones is found in rocks
o Humans breathe out Carbon Dioxide (CO2)  Plants  Sugar  Humans
o
o
o
o
Biological Processes: Photosynthesis, Respiration, and Decomposition
Geochemical Processes: Erosion and Volcanic Activity
Mixed Biogeochemical: Burial and decomposition
Human Activities: Mining, Cutting/Burning Forests, Burning Fossil Fuels
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2. The Nitrogen Cycle
o Nitrogen is required to make protein
o Nitrogen gas (N2) makes up 78% of Earth’s atmosphere
o Ammonia (NH3) is found in the waste products of many organisms and in
dead/decaying matter.
o Nitrogen Fixation = the process in which nitrogen gas (N2) is converted
into ammonia (NH3)
o Nitrogen gas cannot be used by organism (except certain bacteria) so it has
to be converted to ammonia (which then can be used)
o Denitrification = soil bacteria converts nitrates into nitrogen gas
(released into the atmosphere)
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3. The Phosphorous Cycle
o Phosphorous forms DNA and RNA
o Phosphorous doesn’t enter the atmosphere
o Exists as inorganic phosphate in rocks, soil, and ocean sediment.
o Rocks erode which releases phosphate  dissolves  taken up by
organisms
Nutrient Limitation
- Primary Productivity = the rate at which organic matter is created by producers.
- The amount of available nutrients is one factor that controls the primary
productivity of an ecosystem
- If a nutrient is in short supply, it will limit an organism’s growth
- Limiting Nutrient = a nutrient that is scarce or cycle slowly
- Farmers apply fertilizers to overcome the limiting nutrients and boost productivity
- Fertilizers usually contain nitrogen, phosphorous, and potassium
- Open oceans are considered “nutrient-poor” environments compared to land
- Sea water contains at most only 0.00005 percent nitrogen, or 1/10,000 of the
amount typically found in soil.
- Nitrogen is often the limiting nutrient in oceans
- Within streams and lakes (freshwater), phosphorous is usually the limiting factor
- Fertilizers run-off into the freshwater ecosystem  off balance  algal bloom