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Ecosystems Biology/Env S 204 Spring 2009 Scale of relationships Molecules Genes Cells Organisms (individuals) Populations Species Communities Ecosystems Biomes Biosphere smallest largest Ecological Principles • Everything is connected to everything else. • Everything has to go somewhere. • There is no free lunch in nature. (Or, you don’t get something for nothing.) Communities Community: all of the organisms in a given area (habitat) and their interactions. Ecosystems Ecosystem = biotic community + abiotic environment e.g., flower + pollinator Energy from the sun Precipitation, etc. Nutrients such as carbon, etc. Ecosystems The scale can be… very small (a leaf) to very large (global) Ecosystems Energy flow is one-way through ecosystems. Materials (nutrients) are cycled through ecosystems. Ecosystems—1) Energy processes Photosynthesis Respiration Ecosystems—1) Energy processes Photosynthesis transforms radiant (solar) energy into chemical energy (stored as chemical bonds in sugars and carbohydrates. sun CO2 O2 plant sugars, starches in cells Ecosystems—1) Energy processes Respiration is a step-by-step process that allows organisms to use the energy stored the chemical bonds manufactured during photosynthesis. sugars, starches O2 energy for cellular work + heat Ecosystems—2) energy users There are three main categories of organisms according to the ecological roles they play: 1) Producers (primary producers, autotrophs) 2) Consumers (heterotrophs) 3) Decomposers (a special type of consumer) Ecosystems—2) energy users Producers capture the sun’s energy and transform it into chemical energy through photosynthesis. plants + algae + blue-green algae Ecosystems—2) energy users Consumers are organisms that eat other organisms. Herbivores eat producers directly, carnivores eat other consumers. Examples: panda eating bamboo, bird eating nectar or flowers snail grazing on algae Herbivores (grazers, primary consumers) Ecosystems—2) energy users Consumers are organisms that eat other organisms. Herbivores eat producers directly, carnivores eat other consumers. Examples: limpkin eating apple snails American alligator amoeba Carnivores (secondary or tertiary consumers) Ecosystems—2) energy users Decomposers (detritivores) are a type of consumer that feed on dead organic matter—they can obtain this from any of the other trophic levels. fungi and many bacteria but also scavengers such as vultures Ecosystems—3) Energy flow Energy flow is one-way through ecosystems. WHY? Ecosystems—3) Energy flow In any energy transformation (e.g., from one trophic level* to another) there is a net loss of usable energy. *Trophic level: feeding relationships, who is eating whom. Ecosystems—3) Energy flow Lost as heat decomposer sun plant decomposer cow Lost as heat decomposer jaguar Ecosystems—3) Energy flow Lost as heat decomposer decomposer decomposer 90% 90% 90% 10% 10% 10% sun 1-5% plant 10% cow 10% jaguar captured 90% 90% Lost as heat Ecosystems—3) Energy flow Carnivores, especially secondary or tertiary ones, are rare. carnivores herbivores producers Ecosystems—Materials Water and elements (e.g., carbon, nitrogen) and other materials are cycled through ecosystems. They move between organic and inorganic phases by both biotic and abiotic processes. The diversity of microorganisms (especially bacteria) controls key steps in various cycles (see textbook examples of the nitrogen cycle, the carbon cycle, etc.) Ecosystem Services • Services provided by biodiversity that keep ecosystems functioning. • Often thought of in terms of human wellbeing. • Indirect-use value of biodiversity (these services are not factored into the marketplace). Ecosystem Services—examples • Photosynthesis • Nutrient cycling • Decomposition
