- Why is there Life on Earth.
- Biomes: concept, main types on Earth.
- Ecosystems: concept and components.
- Habitats and ecological niches.
- Land ecosystems: main types and features. The formation of soil.
- Aquatic ecosystems: main types and features.
- Anthropogenic ecosystems: main types and features.
- Feeding interactions: producers, consumers and decomposers; food chains and food webs; trophic pyramids.
- Other biotic interactions: interspecific and intraspecific.
- Major human influences in the ecosystems.
One ecosystem is any area that happens to have an specific set of features (living species and physical-chemical conditions) that make it significantly different from its surroundings. Thus, a forest is an ecosystem, but a lagoon or a puddle of water in that forest, are themselves ecosystems too. A city is also an ecosystem: a man-made ecosystem.
The limits of many ecosystems are difficult to define. For instance, a lagoon in a forest can be fed with water from an aquifer that extends throughout an area much bigger than the forest itself, and that also feeds with water the farm-land that surrounds the forest. This way, the lagoon, the forest and the farm-land are connected. Ecosystems are not isolated in Nature: there are connections and transitional areas between them.
When an ecologist tries to describe an ecosystem, he/she has to describe the following sorts of facts:
- The set of living species in it, that is, the biocenosis. For instance, in a forest there could be pines, oaks, mice, doves, butterflies, kites, ants…
- The set of physical and chemical conditions, that is, the biotope. In a forest: the average temperature in the coldest month, the average temperature in the hottest month, the rainfall rate, the kind of salts that exist in the soil…
- The relationships between the living species: the pines holding the nests that doves make, the kites eating the mice, the mushrooms feeding on the fallen leaves…
- The relationships between the physical-chemical conditions: how temperatures alter the soil's humidity through evaporation, how wind wears away soil particles…
- The relationships between the physical-chemical conditions and the living species: the way in which the animal activity is affected by the day-night cycle, the way in which temperature affects the loss of water vapour by plants through evapotranspiration, the way plants retain the soil particles with their roots and prevent them from being worn away by the wind, the way in which the decomposition of fallen leaves or dead animals adds new salts and minerals to the soil…
Every ecosystem can have other ecosystems inside of it. The Earth itself is one ecosystem and comprises all the other ecosystems. The Ecosphere is the name we give to our planet when we think of it as an ecosystem, and it has a biotope and a biocenosis. The biotope of the Ecosphere is made up by the Geosphere, the Hydrosphere and the Atmosphere. The biocenosis of the Ecosphere is called Biosphere, and comprises all the living beings of the Earth.
If we wanted to split the Ecosphere in the biggest possible ecosystems, we would split it into the biomes. A biome is a large ecosystem made up of all the ecosystems belonging to the same climatic zone. There are, for instance, the tropical rainforest biome, the mediterranean forest biome and the desert biome.
What Are Ecosystems and How They Work
Analyzing an ecosystem. Excellent quizz to test your knowledge on the basics of ecosystems.
Jack and the beanstalk. Cartoon film that uses the traditional pantomime story of "Jack and The Beanstalk" to link different types of feeding relationship. Includes reference to autotrophs, herbivores, carnivores, parasites, symbionts and saprotrophs.
Marine food web. Interactive activity to place different marine species in their correct trophic levels.
Ecosystems and Biomes of the World
World biomes interactive map. Another great interactive map to see the occurence and learn the main characteristics of the world's biomes. With many activities.
Water ecosystems. A brief introduction to fresh-water and marine ecosystems.
How wetlands work. Water lilies, turtles, frogs, ducks, snakes, dragonflies, minnows, herons, sticky black muck, monsters… What do these things have in common? Wetlands.
National marine sanctuaries. Collection of select videoclips and still images from USA's underwater treasures.
How the Galapagos islands work. One of the world's most famous ecosystems is the place that inspired Charles Darwin's theory of evolution. But there's more to it than just finches and tortoises.
Scenes from Antarctica. A great set of 32 stunning photos taken in the Antarctica.
The Man and the Ecosystems
10 of today's most important environmental issues. A list that neatly summarizes some of our most pressing environmental concerns.
Disappearing forests of the world. Google Earth file showing deforestation data for different countries.
Interactives: Garbage. Good lesson with coverage of topics such as solid waste, hazardous waste, sewage and waste reduction efforts.
What's the biggest threat to freshwater habitats? Learn what ar the freshwater habitats, why are they important, and how agriculture endangers them.
Why could China's Three Gorges Dam cause an environmental disaster? Is it a milestone of modern engineering or a potential environmental disaster?
Ocean debris turning Hawaiian beach into plastic. Consumer waste from the "Great Pacific Garbage Patch" is turning a Hawaiian beach "into plastic".
Preserving the Environment
Protected areas of the world. Google Earth file showing the protected area network for a number of countries.
Biodiversity hotspots. Google Earth file showing information about the Earth's 34 Biodiversity Hotspots, as defined by Conservation International. These are the most important areas for conservation, with very large numbers of endemic species. Each of the hotspots has lost more than 70% of its original forest.
Protected Planet. Protected Planet lets you view the world's protected areas on a Google Map. If you click on one of the mapped protected areas then you are taken to a close-up of the selected area, which includes photographs, points of interest in the area and links to related protected areas.
WWF - Have fun while making a point. Are you looking for games to find out more about key conservation issues such as endangered species, global warming and pollution? If you are, then go right ahead and indulge yourself!
Recycle City. See how the people of Dumptown turned their town around, reducing waste and saving money or play the Dumptown game and create your own scavenger hunt.
How composting works. Composting is a method that transforms solid organic waste into a product that can benefit the environment as a natural fertilizer for gardening and farming. Learn more.
50 ways to help the planet. 50 actions that people can carry on in their daily lives to help preserve the Ecosphere.
Top 5 green myths. Many of us have adopted small, easy habits to help make our lives a little more environmentally friendly. But how can you be sure your choices are right for the planet?
Top 10 myths about sustainability. In-depth article explaning the real meaning of such a popular word.
How do you clean up an oil spill? Despite stricter penalties and better ship design, oil spills haven't been eliminated. And when they happen, what can be done to clean up that mess?