Welcome to the Ecology Tutorial, an Environmental Systems Term Project

This is an introductory page to ecology.
Including terminology, ecological components, and links.

Project guidelines


Ecology is the science that attempts to answer such questions about how the nature works. In 1869, German biologist Ernst Haeckel coined the term ecology from two Greek words: oikos, meaning "house" or "place to live" and logos, meaning study.

Ecology is the study of how organisms interact with one another and with their non-living environment of energy and matter. The key word is interact. Scientist usually carry out this study by examining different ecosystems: communities with groups of different species interacting with one another and their non-living physical and chemical environment.

Ecosystem Components
Ecosystems consist of various non-living, abiotic, and living, biotic components. The abiotic components of an ecosystem include various physical and chemical factors.
The physical factors having the greatest effect on the ecosystem are:
  1. sunlight and shade
  2. average temperature
  3. average precipitation and distribution
  4. wind
  5. latitude and altitude
  6. nature of soil (for terrestrial ecosystems)
  7. fire (for terrestrial ecosystems)
  8. water current (for aquatic ecosystems)
  9. amount of suspended solid material (for aquatic ecosystems)
The chemical factors are:
  1. level of water and air in soil
  2. level of plant nutrients dissolved in soil moisture (for terrestrial) and in the water (for aquatic)
  3. level of natural or artifical toxic substances dissolved in soil moisture and in water
  4. salinity of water for aquatic ecosystems
  5. level of dissolved oxygen in aquatic ecosystems
Organisms that make up the biotic component of an ecosystem are usually classified as autotrophs and heterotrophs, based on how they get their food or organic nutrients they need to survive.

Autotrophs(producers)-are organisms that can manufacture the organic compounds they need as nutrients from simple inorganic compounds obtained from their environment. In most terrestrial ecosystems, green plants are the producers. In aquatic ecosystems, most of the producers are phytoplankton, consisting of various species of of floating and drifting bacteria and protist.
Most producers make their organic nutrients they need through photosynthesis. The overall net chemical change can be summarized as follows:

6 CO2 + 6 H2O + solar energy -----> C6H12O6 + 6 O2

Some producers , mostly specialized bacteria, can extract inorganic compounds from their environment and convert them into organic nutrient compounds without the presence of sunlight. These producers are called chemosynthesis. An example of this is around the hydrothermal vents in some parts of the deep ocean. Bacteria carry out chemosynthesis by converting inorganic hydrogen sulfide to organic nutrients.

Heterotrophs(consumers)-are organisms which cannot synthesize the organic nutrients they need and get their organic nutrients by feeding on the tissues of producers or other consumers. There are several classes of of consumers, depending on there food source.
  1. Primary consumers (herbivores) feed directly on plants or other producers.
  2. Secondary consumers (carnivores) feed only on primary consumers.
  3. Tertiary or higher level consumers feed only on animal-eating animals.
  4. Omnivores can eat both plants and animals.Examples are pigs, rats, cockroaches, and humans.
  5. Detrtivores (decomposers and detritus feeders) live off of detritus, parts of dead organisms and castoff fragments and waste of living organisms. Decomposers digest detritus by breaking down the complex organic molecules in these materials into simpler, inorganic compounds. Decomposers consist of various bacteria and fungi.



Types of Species Found in Ecosystems
  1. Native species-which normally live and thrive in a particular ecosystem.
  2. Immigrant species-which migrates into an ecosystem or which are deliberately or accidently introduced into an ecosystem by humans.
  3. Indicator species-which serves as a early warning that a community or an ecosystem is being degraded.
  4. Keystone species-which plays a role affecting many other organisms in an ecosystem. The loss of a keystone species can lead to sharp population drops and extinction of other species that depend on it for certain services.
Principal Ways Species Interact
  1. Interspecific competition-competition from one or more species for one or more to the limited resources it needs.
  2. Predation-an individual organism of one species, know as a predator, feeds on parts or all of a organism of another species, the prey, but does not live in or on the prey.
  3. Parasitism-A parasite is a consumer that feeds on another living organism (its host) by living on or in its host organism for all or most of the host's life.
  4. Mutualism-is a type of interaction in which both participating species generally benefit.
  5. Commensalism-one specie benefits, while the other is neither helped nor harmed to any great degree.

Ecosystem Cycling

Biochemical Cycle-Nutrients, the chemical essential to life, are cycled in the ecosphere and in the mature ecosystems. In these cycles, nutrients move from the environment,through organisms, and back to the environment.

Carbon Cycle-is based on carbon dioxide gas, which makes up only about 0.03% by volume of the troposphere and is also dissolved in water. Carbon is the basic building block of carbohydrates, fats, proteins, nucleic acids, and other organic compounds essential to life.

Nitrogen Cycle-The Earth's largest reservoir of nitrogen is the troposphere, with about 78% of its volume made up of nitrogen gas(N2). Nitrogen is required to synthesize proteins, and nucleic acids. The abundant form of nitrogen cannot be used directly. The conversion of atmospheric nitrogen gas into other chemical forms useful to plants is called nitrogen fixation. This is carried out mostly by certain kinds of bacteria (cyanobacteria) in soil and water and by rhizobium bacteria living swellings, called nodules. Lightning also plays a role in converting nitrogen gas.

Phosphorus Cycle-Various forms of Phosphorous is cycled through water, the earths crust, and living organisms.

Sulfur Cycle-Sulfur enter the atmosphere from natural sources. Hydrogen sulfide, from active volcanoes, and decay of organic matter by anaerobic decomposers.Sulfur dioxide from active volcanoes. Particulate sulfate from sea spray. About one-third of all sulfur compounds and 99% of all sulfur dioxide are sources from human activity.

Hydrologic Cycle (water cycle)-collects, purifies, and distributes the Earth's fixed supply of water. Water is an important medium for the movement of nutrients into and out of ecosystems.


4 Laws of Ecology by Barry Commoner
  1. You can't throw anything away
  2. Can't do just one thing (everything is connected to everything else)
  3. Nature know best
  4. No such thing as a free lunch



Page 2 is a list of interesting sites that deal with the Environment (lots of Links). You can get to page 2 by clicking below.

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Written by Scott M. Stoddard
Fall 1995