Ecology and environment

Organisms connected by food and place

Naming a plant or animal is only the beginning of an ecological explanation. You also need to ask where it lives, what it consumes, and which other organisms depend on it. These courses approach those questions at two scales. A food web follows connections within a community; a biome groups environments with broad similarities in climate and vegetation. Moving between them helps separate a local feeding relationship from a large pattern on a world map.

Start with feeding links, then compare regions

Food webs begins with producers, consumers and decomposers. It builds from food chains to webs before introducing the energy pyramid and the 10% rule. Predator and prey populations appear through rabbits and foxes, followed by keystone species and Yellowstone wolves. The last unit considers poisons and invaders in food webs. Keep the direction of each feeding link explicit as you read; a web is more than a collection of animals drawn close together.

Biomes starts by defining a biome, then compares tropical rainforests and savannas, deserts and chaparral, temperate grasslands and forests, and boreal forest and tundra. Ocean and freshwater biomes complete the course. Compare the conditions described in the units rather than assuming that two places at similar positions on a map must support identical communities.

Read a web and a graph differently

In the ecosystem lab, inspect the meadow web and explain the feeding relationships before changing the scene. The pyramid view lets you examine energy transfer, while the population view plots rabbits and foxes as separate lines. A line on the population graph answers a different question from an arrow in the web. Identify what each representation measures before describing a rise, a fall or a connection. The intertidal preset offers another setting for thinking about keystone species.

The biome units use a globe to locate examples. Find Brazil, Egypt and Canada in the opening unit, then follow the regional comparisons as the course moves through different environments. The globe helps place the discussion geographically; the accompanying text explains the ecological conditions. Do not ask the map alone to supply information that belongs to the unit’s account of a biome.

Explanations with more than one link

When a population changes, trace the relevant relationships instead of naming only the species that changed first. Return to producers and decomposers when explaining how a community works, and use the energy unit before treating every level of a pyramid as equivalent. For biome comparisons, say which conditions and living communities are being compared. The questions and summaries let you check both kinds of reasoning: explaining a connection within a system and distinguishing the larger environments in which systems occur.