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Ecology
Environmental Science
Mr. Vickers
Ecology
• The study of living organisms in the natural
environment, how they interact with one another
and how the interact with their nonliving
environment
Levels of organization
atoms
molecules
species
population
organelles
cells
community
tissues
organs
systems
organism
ecosystem
biosphere
ECOLOGY
Species
• A group of organisms that can reproduce and
produce fully fertile offspring
Great White Pelican Pelecanus onocrotalus
Population
• A group of organism of the same species which live in the
same habitat at the same time where they can freely
interbreed
• Habitat: the environment in which a species normally lives or the location
of a living organism
The black-veined white butterfly
(Aporia crataegi) mating
Community
• All the populations of the different species living and
interacting in the same ecosystem
7-spotted lady bug
(Adephagia
septempunctata)
Bean aphids
(Aphis fabae)
Red ant
(Myrmica rubra)
Broom plant
(Cytisus scoparius)
Ecosystem
• Community (Biotic) interacting with environment (Abiotic )
Components of an Ecosystem
• Biotic Factors: living or once living organisms
• Abiotic Factors: nonliving factors that have an effect on living things
Examples:
- Water: organisms have water in their bodies (50-95%) and chemical
reactions need water to happen.
- Soil: type of soil determines which plants and other organisms live in
that location
- Light and Temperature: affect photosynthesis (plant growth is limited
to amount of sunlight)
Energy + CO2 + H2O → C6H12O6 + O2
Energy and Organisms
• Autotrophs: organisms which can synthesize their own complex,
energy rich, organic molecules from simple inorganic molecules
(e.g. green plants synthesis sugars from CO2 and H2O; bacteria in
deep sea vents doing chemosynthesis) - PRODUCERS
• Heterotrophs: organisms who must obtain complex, energy rich,
organic compounds form the bodies of other organisms (dead or
alive).
– Ex: consumers and decomposers (saprotrophs and detritivores)
Decomposers
• Detritivores: heterotrophic organisms who ingest dead organic matter.
(e.g. earthworms, woodlice, large scavengers). Ingest first, then digest.
Earthworm
(Lumbricus terrestris)
• Saprotrophs: heterotrophic organisms who secrete digestive enzymes
onto dead organism matter and absorb the digested material. (e.g. fungi,
bacteria). Digest first, then absorb.
Chanterelle
(Cantherellus cibarius)
Consumers
• Omnivore: eats both plants and animals
• Carnivore: meat eater
• Herbivore: plant eater
Food Chains
• Sequence of relationships
between trophic levels.
• Show the flow of energy
from the SUN to the
heterotrophs
• Trophic level: an
organism’s feeding
position in a food chain
• Producers: essential to
every single food chain
Food Web
• Shows the feeding relationships in a community. Arrows show the flow of
energy.
Read the article and generate a food web:
http://ehp.niehs.nih.gov/members/2004/112-8/focus.html
How much is available to the caterpillar’s
predator?
Plant material
eaten by caterpillar
200 J
67 J
Feces
100 J
33 J
Growth (new biomass)
Cellular
respiration
Energy and Nutrients
• Energy enters ecosystems as light and usually
leaves as heat.
• Nutrients do not usually enter an ecosystem
and must be RECYCLED. Nutrients include:
carbon, nitrogen, phosphorus, magnesium...
The Carbon Cycle
The Nitrogen Cycle
Pyramids of Energy
Biomass
• Amount of dry matter in one organism
• Each bar represents: dry weight of all organisms in one
trophic level
Trophic level
Dry weight
(g/m2)
Tertiary consumers
1.5
Secondary consumers
11
Primary consumers
37
Primary producers
809
Populations
• Characteristics:
–
–
–
–
Size: number of individuals at a certain time
Density: number of individuals in a certain space at a particular time
Spacing: clumped, uniform, random
Age Structure
• Pop. Change = (birth + immigration) – (death + emigration)
• Limiting factor: prevents the continuing growth of a population in
an ecosystem
– Can be:
- water, air, light, food
- diseases, competitors, predators, parasites
Population Growth
•
Exponential Phase: population
increases exponentially because the
natality rate is higher than the mortality
rate.
•
Transitional phase: difference between
natality and mortality rates are not as
great, but natality is still higher so
population continues to grow, but at a
slower rate.
•
Plateau phase: natality and mortality
are equal so the population size stays
constant.
•
Carrying Capacity: the maximum
population size that can be supported
by the environment
The Greenhouse Effect
•
•
•
Light from the sun has short wavelengths and can pass through most of the
atmosphere.
This sunlight warms the earth which in turn emits long wave radiation.
This long wave radiation is bounced back by the greenhouse gases, such as carbon
dioxide, methane, water vapor, oxides of nitrogen and sulphur dioxide
The Greenhouse Effect
• Natural and essential to life
• Human pollution is making it worse = causing global
warming
– Oxides of nitrogen: industrial processes, burning fossil fuels,
fertilizers
– Methane: cattle, waste disposal, natural gas leaks
– CO2: burning fossil fuels
• Consequences:
–
–
–
–
Changes in climate = effects on the ecosystem
Extinction
Melting glaciers = rise in sea level
Increase in photosynthetic rates
Changes in atmospheric CO2
Precautionary Principle
• Action should be taken to prevent harm even if there is not sufficient data
to prove that the activity will have severe consequences
• If people want to do activities that may cause a change in the environment
they must prove first it won’t do harm
• We should take action now: reduce carbon emissions before it’s too late
• Should people invest money to reduce carbon emissions if we are not
100% sure about the consequences of global warming?
• More expensive to be eco-friendly
• What should consumers do?
Arctic Ecosystems
-
North America, Greenland, Iceland, Norway, Russia
Example: polar bears/seals/algae affected
Loss of ice habitat
Increased success of pests/pathogens/mosquitoes
Increased decomposition
Expansion of temperate species/reduced range for arctic species
Rise in sea levels
Climate change
Disturbance of food chains
Melting of permafrost

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