Unit 4: Ecosystems // Visuals

Animation(s)

Common vs. rare tree species: On the rainforest plot of Barro Colorado Island, common tree species account for only 15% of the total tree population compared with 80% of the total tree population in a typical New England forest. View animation
Rainforests: Rainforests cover only 6% of the planet but are home to over half of the Earth's plant and animal species. View animation
Return of the wolf: Since the return of the wolf, the elk population has drastically decreased from 20,000 in the 1990s to less than 10,000 today. View animation

Photograph(s)

African fish eagle: The African fish eagle is a counterpart to the American bald eagle and fills the same ecological niche in areas where it is present. View image
Automeris moth: When the Automeris moth perceives a threat, it moves its forewings to reveal false eye spots on its hindwings and to frighten predators away. View image
Predators impose top-down control on ecosystems: Since they were reintroduced to Yellowstone National Park in 1995, gray wolves have reduced the number of elk and other prey species, with impact further down through the park's food web. View image
Tropical ecologist Stuart Davies in the field: Director of the Center for Tropical Forest Science at the Smithsonian Tropical Research Institute, Stuart Davies explains the symbiotic relationship between ants and a cecropia plant. View image

Graphic(s)

Biome type in relation to temperature and rainfall: Biome distribution is closely associated with climate. Each of the biomes shown in this figure represents a different combination of temperature and precipitation ranges. View image
Earth's major land biomes: Biomes are Earth's major habitat types. They are classified according to the predominant forms of vegetation that they support. View image
Earth's marine and freshwater biomes: Marine and freshwater biomes contain many different types of habitats, from forest bogs to abyssal zones in the deep oceans. View image
Energy and nutrient transfer through ecosystems: Nutrients (shown by light arrows) cycle through ecosystems in a closed loop, while energy (shown by dark arrows) is released at each stage. View image
Lake Michigan food web: Food webs illustrate the complicated feeding patterns within ecosystems, in which a single species may consume a variety of other creatures and in turn serve as prey for multiple predators. View image
Ocean net primary productivity, 1997-2002: In contrast to land, where vascular plants carry out most primary production, most primary production in the oceans is done by microscopic algae. View image
Plant species diversity: Many hypotheses have been proposed to explain why species richness is greater in tropical latitudes than near the poles. View image
Terrestrial net primary productivity: Many factors influence primary productivity rates, but the most important on land are temperature and water availability. View image
The nitrogen cycle: Nitrogen is abundant in the atmosphere but occurs in an inert form that living organisms cannot use directly. In the nitrogen cycle, some of this supply is converted to biologically useful forms. View image
The phosphorus cycle: Phosphorus is found in water, soil, and sediments. Like nitrogen, it must be converted to biologically useful forms before plants and animals can take it up. View image
Typical forest succession pattern: Left undisturbed, an abandoned field will regrow from a meadow into a scrub community, then become populated by pines and ultimately by hardwood trees. View image

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