* the branch of biology that deals with the interactions between organisms and their environment
* this can be studied at different levels of organization with different factors at each


1) population:

* includes all the members of a species in a given area
ex. all of the white tail deer in the Adirondacks is a population

2) community:

* all of the populations in a given area
ex. all of the organisms in the Adirondacks-- deer, pine trees, rabbits, maple trees, squirrels, bears, blueberries, etc... is a community

3) ecosystem:

* the living (biotic) community and the nonliving (abiotic) physical environment functioning together is an ecosystem
ex. the Adirondack ECOSYSTEM is made up of the BIOTIC community and the ABIOTIC factors-- weather, rocks, water, soil

4) biosphere:

* the biosphere is the portion of the earth in which LIFE exists
* is made up of many complex ecosystems

* the ecosystem is the structural and functional unit that is studied in ecology
* they involve important interactions between biotic and abiotic factors
* an ecosystem can support itself and is stable (not much change) when three conditions are met...the E.A.R. conditions...

1) there must be a constant supply of Energy (the sun is this source for all life on earth)

2) there must be living organisms that can convert the energy into organic compounds (plants--Autotrophs--photosynthesis)

3) there must be a Recycling of materials between organisms and the environment

A balanced aquarium is an example of a very small ecosystem. It is self-supporting because the requirements for a stable ecosystem are present:

ENERGY (1) is supplied to the ecosystem by light. There are PLANTS (2) to change the light energy into the organic molecule of energy (glucose). RECYCLING (3) of materials occurs during photosynthesis and respiration. During photosynthesis, plants use light energy and carbon dioxide to form glucose. They give off oxygen, which is used by the fish and snail during respiration. Animals release the carbon dioxide that is used by plants.


What exactly is an ecosystem? Find out from one of the scientists who coined the phrase.
here is a cool ecosystem at the bottom of the ocean--one of the few ecosystems not based on the sun!



* the non-living parts of the environment
* they directly affect the ability of organisms to live and reproduce
* abiotic factors can vary from place to place

* abiotic factors can act as LIMITING FACTORS that keep a population at a certain level

ex. desert environment -- hot temperature and little water are examples of limiting factors -- different species living in the desert are LIMITED mainly to those types of plants and animals that need very little water and can survive extreme temperatures


* all the living things that directly or indirectly affect the ecosystem
* biotic factors interact with other living organisms and the physical environment

* can also be LIMITING FACTORS

ex. disease (bacteria), predators, food resources

there are 2 types of ways biotic factors interact: nutritional and symbiotic relationships
1) nutritional relationships:

* involves the transfer of nutrients from one organism to another within an ecosystem

* organisms that can synthesize organic molecules from inorganic molecules
* also called producers
* can be either photosynthetic or chemosynthetic

* organisms that cannot manufacture organic molecules
* there are 5 types of heterotrophs

* organisms that eat only producers (plants)
* also called a primary or first-level consumer
ex. cows, elephants, goats

* organisms that eat only other animals
* also called a secondary (or tertiary--3) consumer
ex. tigers, lions, wolves

* organisms that eat everything
* can be a 1st, 2nd, or 3rd level consumer
ex. bears, humans

* organisms that eat only other animals after they are already killed
* usually a 2nd or 3rd level consumer
ex. vultures, hyenas

* organisms that live on DEAD matter
* also called saprophytes
ex. include heterotrophic plants, fungi, and bacteria

* always starts with producers
* shows the pathway of energy from one organism to the next in a direct line of organisms

* shows the interactions and interconnections among the different food chains of a community

2) symbiotic relationships:
* an interaction among different species in an ecosystem that where they live in a close association with each other
* called SYMBIOSIS; at least one member of the association benefits (gains) by the association

a) MUTUALISM (+ , +)
* a symbiotic relationship in which both organisms BENEFIT
ex. nitrogen fixing bacteria that live in nodes (lumps) on the roots of certain plants (legumes)...the bacteria have a nice place to live (+), and the plants benefit from getting the nitrogen they need from the bacteria (+)

* a symbiotic relationship where one organism benefits (+) and the other organism is not harmed (0)
ex. the remora (a small fish) attaches itself to the underside of a shark...when the shark feeds, the remora disconnects and eats scraps that are left over (+) ... the shark is not affected (0); barnacles (+) on whales (0)

c) PARASITISM (+ , -)
* a symbiotic relationship where one organism, the parasite, benefits (+), while the other organism, the host, is harmed (-)
ex. athlete's foot, a fungus, grows on human feet for nutrients (+), while the human doesn't like it (-);
tapeworms (+) in humans (-); heartworms (+) in dogs (-)

* a symbiotic relationship where one organism eats another!
ex. predator--lions (+), prey--gazelles (-)



* in order for an ecosystem to be self-sustaining, it must have a continuous flow of energy and be able to recycle materials

A) energy pyramid:

* at each step of the food web, energy is transferred to the next higher level
* sun--->plant-->rabbit--->snake--->hawk
* this energy transfer is NOT EFFICIENT!
* only 10% of the energy is passed to the next generation to be used; most energy is lost in maintaining homeostasis and as the production of heat
* the amount of usable energy decreases at each higher feeding level

B) biomass pyramid:

* the amount of organic matter in an ecosystem is its BIOMASS
* the biomass pyramid shows the total amount of biomass at each feeding level
* the higher the level, the less the biomass...which is because there is less energy at this level

C) material cycles

* where the same materials are reused in an ecosystem

* involves the processes of photosynthesis (uses CO2 and produces O2) and respiration (uses O2 and produces CO2)

* involves the processes of photosynthesis, transpiration (movement of water through a plant), evaporation and condensation, respiration, and excretion

* involves decomposers and other soil bacteria which break down and convert nitrogenous wastes and the remains of dead organisms into material that is usable by autotrophs (nitrates)



take a look at vairous material cycles in action
take a look at this neat animation of the carbon cycle
here you can see the complexities of the nitrogen cycle

* by existence, each community modifies its environment, making it more favorable to other communities
* by the gradual replacement of one community to another, the entire ecosystem (community and abiotic factors) changes
* these changes are called ECOLOGICAL SUCCESSION (stages)
* this eventually leads to a stable community called a CLIMAX COMMUNITY

1) the first stage in land succession can begin with bare rock...lichens and bacteria are usually the first to appear...
* initial organisms that populate a given area are called PIONEER ORGANISMS
* pioneer organisms change the environment (break down rock to form soil---takes a while)

2) ...other types of organisms can now begin to grow in the pockets of soil formed...
* forms a different community which SUCCEEDS (comes after) the first
* this community of different organisms continue to modify the environment...

3) ...which leads to a new community...

4) ...until eventually, a stable, CLIMAX COMMUNITY is reached

* ecological succession happens as follows

New York state has an oak-hickory and hemlock-beech-maple climax community

* climax communities are named by the dominant type of vegetation that exists in the community
* as long as environmental conditions in an ecosystem remain stable over long periods of time, the same species of plant and animals will continue to interact with each other
* a climax community remains stable until a catastrophic change (drought, fire, overgrazing, volcano)

* as a result of evolutionary processes, there is a great deal of diversity (differences) of organisms and their roles called a NICHE
* because of such different roles, there is greater chance that some species will survive any large environmental changes that might occur.
* biodiversity increases the stability of an ecosystem
* as biodiversity decreases in an ecosystem, it becomes more fragile to any changes that can occur

think JENGA!


it is all about the great variety of life in an ecosystem!

* the biosphere is organized into smaller parts as BIOMES
* this is where animals live (habitats)
* a biome is a large geographical area of the earth identified by a particular type of dominant (most common) plant and animal life
* biomes can be terrestrial (land) or aquatic (water) and is determined by geography and climate

A) terrestrial biomes:

* climatic conditions change with latitude (how north/south a place is) and altitude (how high up)
* the higher the altitude, the colder it gets
* the further you travel north (above the equator--south below the equator), the colder it gets
* these variables affect moisture level and temperature

B) aquatic biomes:

* represent the largest biomes on earth
* 70% of the earth's surface is water
* includes marine (salt water) and freshwater biomes
* temperature variations are slight in aquatic biomes
* also, water is not a limiting factor!
* as a result, aquatic biomes are typically more stable

1) amounts of available oxygen and carbon dioxide
2) temperature
3) light--needed for photosynthesis
* area with light is called the PHOTIC ZONE
* area without light is called the APHOTIC ZONE
4) amounts of dissolved minerals

C) comparing freshwater and marine biomes

1) marine biomes

a) provide the most stable aquatic environment
b) absorbs and holds a large quantity of solar heat and stabilizes the atmosphere
c) contains a relatively constant supply of nutrient materials and dissolved salts
d) serves as a habitat for a large number of diverse organisms (lots of BIODIVERSITY!)

2) freshwater biomes

a) includes lakes, ponds, streams, and rivers
b) abiotic factors vary greatly in each
c) ponds and small lakes can fill in and become a land community over time



look at some different biomes and how various organisms are adapted to live there

* the relationship between humans and the environment

Although most ecosystems are capable of recovering from the impact of some minor disruptions, human activities have sometimes increased the level of such disruptions so as to bring about a more undesirable and longer lasting change in the environment upon which all life depends. Such disruptions will directly affect at least one part of an ecosystem and this in turn may affect other parts.

Environmental damage caused by humans has the potential to ultimately make our ecosystem less suitable for our species. Human activities have upset various natural systems and have had negative affects on the biotic and abiotic environment. Although most ecosystems can recover from minor disruptions, some human activities have caused changes that cannot be reversed.

* human population growth is not stable
* it is an exponential growth (doubling and doubling)
* exponential growth is shown by a J-shaped curve

* many ecosystems now are unable to produce enough food because of rapid population growth
* some scientists believe that we are rapidly approaching the limits of our ability to increase as a species--called a CARRYING CAPACITY
* limiting factors for this are: availability of: food, clean air, clean water

* technological oversights (things not planned for) have had consequences which have contributed to the pollution of the water, land, and air.
* a POLLUTANT is something that is put into the environment that make it unfit for living things

1) water pollution

* interferes with our ability to obtain pure water for drinking, washing, recreation, and industry
* water pollutants include: heat or thermal pollution, pesticides, sewage, heavy metals, chemicals such as phosphates or PCB's

2) air pollution

* air pollution interferes with our ability to obtain clean air for breathing
* air pollutants include: smoke, soot, ash, carbon monoxide (CO), hydrocarbons, carbon dioxide--leads to the greenhouse effect, raising the temperature of the planet "GREENHOUSE EFFECT", nitrogen oxides and sulfur dioxide--mixes with water vapor to form "ACID RAIN"

3) soil pollution

* interferes with our ability to obtain clean water from wells, may cause death of soil decomposers, and make areas inhabitable
* soil pollutants include: solid wastes--landfills, inorganic or radioactive chemicals, organic wastes--like pesticides

4) improper use of biocides

* pesticides, insecticides, and herbicides are most often used without fully knowing their effects ON THE WHOLE ECOSYSTEM!
* improper use of biocides have disrupted food webs
ex. DDT

DDT is an insecticide used in the early 1960's which built up in bald eagles and peregrine falcons. This caused the shells of their offspring to be born with thin and brittle shells. The shells would crack because they could not support the weight of the mother as she incubated the eggs. As a result, these species ALMOST became extinct.

* biological controls could be used instead
* biological controls uses another species to control other populations
* however, this can also sometimes backfire...a newly introduced species may overpopulate an area


Through increased awareness of potentially negative interactions with our environment, humans have attempted to prevent continued disruptions of the environment and to counteract the results of many of our past negative practices. If population growth and environmental pollution are not slowed down, they will probably become limiting factors for our species, as well as many others. Scientists are constantly at work to find ways to improve our environment. Attempts to correct problems caused by past negative activities include:

population control
conservation of natural resources
wildlife preservation
soil conservation (topsoil)

I've done my, it is up to you!


farming creates lots of food for us 6.5 billion people, but we should make sure we do it with the earth in mind