Ecosystem Ecology The biological and physical components of the environment are a single interactive system in the concept of the ecosystem A.G. Tansley coined ecosystem in 1935
Ecosystem =
Ecosystem = A group of interacting populations and their physical environment. All interacting by a flow of energy and with their physical and chemical environments.
Ecosystems can be Large Small
Ecosystem Ecology An ecosystem is a spatial concept. It has boundaries and can be viewed in the context of its surrounding environment It is sometimes difficult to clearly separate ecosystems
Simple Ecosystem Energy input from sun Model Producers Autotrophs (plants and other self-feeding organisms) Nutrient Cycling Consumers Heterotrophs (animals, most fungi, many protists, many bacteria) Energy output (mainly metabolic heat)
Ecosystem Materials Plants Animals
Ecosystem Ecology Community structure varies in response to environmental conditions Organisms, in part, define the abiotic environment through succession Tress affect temperature in a forest Phytoplankton can affect water temperature
Energy and Materials Inputs are exchanges from the surrounding environment into the ecosystem Outputs are exchanges from inside the ecosystem to the surrounding environment A closed ecosystem is one with no inputs; an open ecosystem receives inputs form the surrounding environment
Ecosystems 1. Population Interactions 2. Energy Flow 3. Material Cycles
Ecosystems 1. Population Interactions 2. Energy Flow 3. Material Cycles
Modes of Nutrition Autotrophs Capture sunlight or chemical energy Primary producers Heterotrophs Extract energy from other organisms or organic wastes Consumers, decomposers, detritivores
Role of Organisms Producers (photoautotrophs)
Primary Producers Photoautotrophs + + + = Sunlight + water + CO 2 + minerals = C 6 H 12 O 6 + O 2 sugar oxygen Energy Materials
Concept 21.1 Feeding Relationships Each feeding category, or trophic level, is based on the number of feeding steps by which it is separated from autotrophs.
Role of Organisms Consumers 1. Herbivore 2. Carnivores 3. Omnivores 4. Parasites 5. Decomposers
Role of Organisms Consumers 1. Herbivore 2. Carnivores 3. Omnivores 4. Parasites 5. Decomposers
Role of Organisms Consumers 1. Herbivore 2. Carnivores 3. Omnivores 4. Parasites 5. Decomposers
Role of Organisms Consumers 1. Herbivore 2. Carnivores 3. Omnivores 4. Parasites 5. Decomposers
Role of Organisms Consumers 1. Herbivore 2. Carnivores 3. Omnivores 4. Parasites 5. Decomposers
Concept 21.1 Feeding Relationships The 1 st trophic level consists of autotrophs or primary producers. Autotrophs generate chemical energy from sunlight or inorganic chemical compounds. This level also generates most of the dead organic matter in an ecosystem.
Concept 21.1 Feeding Relationships 2 nd trophic level: Herbivores that consume autotrophs; also includes detritivores that consume dead organic matter. 3 rd (and higher) trophic levels: Carnivores that consume animals from the level below.
Feeding Relationships Dead organisms and feces are consumed by organisms called detritivores (primarily bacteria and fungi), in a process called decomposition. Detritus is considered part of the 1 st trophic level, and detritivores are part of the 2 nd level.
Concept 21.1 Feeding Relationships Some organisms do not conveniently fit into trophic levels. Omnivores feed at multiple trophic levels. Example: Coyotes are opportunistic feeders, consuming vegetation, mice, other carnivores, and old leather boots.
Concept 21.1 Feeding Relationships All organisms are either consumed by other organisms or enter the pool of dead organic matter (detritus). In terrestrial ecosystems, only a small portion of the biomass is consumed, and most of the energy flow passes through the detritus.
Energy Flow through Detritus
Feeding Relationships Much of the detritus in streams, lakes, and estuaries is derived from terrestrial organic matter. These external energy inputs are called allochthonous inputs. Energy produced by autotrophs within the system is autochthonous energy.
Food Chain A straight-line sequence of who eats whom Simple food chains are rare in nature marsh hawk upland sandpiper garter snake cutworm plants
Trophic Levels Feeding relationships All organisms at a trophic level are the same number of steps away from the energy input into the system Autotrophs are producers closest to energy input first trophic level
Food Chain 4 th trophic level 3 rd trophic level 2 nd trophic level 1 st trophic level
Trophic Levels in a Desert Ecosystem
Food Webs A food web is a diagram showing the connections between organisms and the food they consume. It shows qualitatively how energy flows from one component of this ecosystem to another.
Food Webs As more organisms are added to a food web, complexity increases to reflect the complexity of real ecosystems. Feeding relationships can span multiple trophic levels (omnivory) and may even include cannibalism (circular arrows).
Food Web
Higher Trophic Levels upland sandpiper garter snake marsh hawk crow Connections in a tallgrass prairie food web frog Second Trophic Level First Trophic Level spider weasel badger coyote sparrow earthworms, insects prairie vole pocket gopher ground squirrel grasses, composites Fig. 30-4, p.529
Food Webs Are Complex
Trophic Cascades Trophic cascade: Series of trophic interactions that result in changes in biomass and species composition. Predation by a top carnivore (4 th level) decreases abundance of 3 rd level carnivores, which leads to an increase in herbivores (2 nd level), and then a decrease in primary producers.
Trophic Cascades What controls energy flow through ecosystems? The bottom-up view: Resources that limit producers determine energy flow through an ecosystem.
Trophic Cascades The top-down view: Energy flow is governed by predator consumption rates at the highest trophic level, which influences multiple trophic levels below them.
Trophic Cascades In reality, both controls are operating simultaneously in ecosystems. Top-down control has implications for the effects of trophic interactions on energy flow.
Biological Magnification Non-degradable or slowly degradable substances become more and more concentrated in tissues of organisms at higher trophic levels of a food web
DDT in Food Webs Synthetic pesticide banned in United States since 1970s Carnivorous birds accumulate DDT in their tissues, produce brittle egg shells