Concepts, Structure, and Relationships Lecture 4: Ecosystems Concepts, Structure, and Relationships

Summary of Lecture The structure of ecosystems Ecosystem Relationships Definitions Ecosystem Relationships Trophic levels Energy flow Photosynthesis Food Webs

Definitions Ecology: study of the relationships between organisms and the environment, focus on interactions Organism: any form of life

ECOSPHERE Ecosystems Communities Populations Organisms

Definitions (continued) Species: group of organisms that resemble one another in appearance, behavior, chemistry, and genetic endowment. Under natural conditions, they can breed with one another and produce live, fertile offspring. Sp. are the result of a long evolutionary process Wild species vs. Domesticated species How many species are there???? 5-100 million species 1.8 million species identified

Same Species

Species and Tolerance Law of tolerance Limits of tolerance The existence, distribution and abundance of a species is determined by whether the levels of physical and chemical factors fall within tolerable ranges for that species Limits of tolerance Species can’t survive beyond these limits Range of tolerance Minumum and maximum levels of tolerance Law of limiting factors Too much or too little of any abiotic factor can limit or prevent growth of a population, even if other factors are near the optimum

Tolerance Range

Definitions (continued) Population: group of organisms of the same species living within a particular area. Populations have genetic diversity Populations are dynamic, not static Examples: All the people in a country All the deer in a forest All the cattails in a pond Habitat: place where a population lives

Definitions (continued) Community: complex of interacting populations of all plants, animals, and microorganisms living and in an area at a particular time Ecosystem: all the elements of the community and the non-living environment Rarely have distinct boundaries Climate and species adapted to that climate Ecotone: transition zone between ecosystems High # of species and species density Ecosphere: all of Earth’s ecosystems together

Figure 4.2

Components of an Ecosystem Biotic (organic): living Generally refers to those substances produced by the metabolism of a living organism, especially carbon-containing compounds. Abiotic (inorganic): non-living Physical and chemical factors effecting the ecosystem Sunlight, temperature, water

Biotic Components Producers: Consumers: Decomposers: Make their own food Plants and other organisms Consumers: Depend on energy stored in tissues of producers Decomposers: Break down molecules (from producers or consumers) to simple materials which are recycled back to producers

Interdependence

Trophic Categories Tropic level: all organisms that are the same # of energy transfers away from the original source of energy # of levels is limited by amount of energy available Producers: Any organism that is able to manufacture its own food. photoautotrophic, using light energy to manufacture food, or chemoautotrophic, using chemical energy. Green plants and algae photosynthesis

Trophic Categories (continued) Consumers: Any organism which must consume other organisms (living or dead) to satisfy its energy needs. herbivore -- Literally, an organism that eats plants or other autotrophic organisms. The term is used primarily to describe animals carnivore -- organism that eats meat. Most carnivores are animals, but a few fungi, plants, and protists are as well. Primary, Secondary and Higher level consumers

Consumers (continued) Omnivore -- organism that will eat both plants and animals. Refers to animals who do not restrict their diet to just plants or other animals. Scavenger--organism that feeds on dead organisms Detritivore -- organism which obtains most of its nutrients from the detritus in an ecosystem Detritus feeders and decomposers Bacteria, fungi, insects Detritus: dead organisms or waste

Detritivores and Decomposers

Other Relationships Predator-Prey Parasite-Host

Freshwater Pond Ecosystem

Field Ecosystem

Food Chains and Webs All the interactions of the predator and prey, including the exchange of nutrients.These interactions connect the members of the ecosystem and describe how energy passes from one organism to another food chains: who eats whom? food web: complexes of feeding relationships

Model of a Food Chain

Antarctic Food Web

Energy Flow and Nutrient Cycles 1st principal of ecosystem function-sustainability: ecosystems use sunlight as their source of energy 2nd: ecosystems dispose of wastes and replenish nutrients by recycling all elements

Energy Flow and Biomass Storage Biomass: dry weight of all the organic matter of organisms in a trophic level Transfer of energy from one trophic level to the next is low Energy is lost as heat, waste, undigested food, etc limitations on the transfer of energy to next trophic level creates the biomass pyramid Ecological Efficiency: % of energy transferred from one trophic level to the next About 5-20% energy transferred, 80-95% lost

Ecological Efficiency

Trophic Pyramid

Annual Pyramid of Energy Flow

Biomass for 2 Ecosystems

Energy flow and nutrient cycles 1st principal of ecosystem function-sustainability: ecosystems use sunlight as their source of energy 2nd: ecosystems dispose of wastes and replenish nutrients by recycling all elements

Nutrient Cycles and Energy Flow

Producers, Photosynthesis, and Primary Production carbon dioxide + water all oxygen in the atmosphere was put there by photosynthesis rate of photosynthesis is proportional to the amount of light Only ½ solar energy absorbed by plants Only 1-5% of that energy is converted to chemical energy by photosynthesis . glucose + oxygen

Producers, Photosynthesis, and Primary Production glucose combines with nitrogen, phosphorus, and other minerals (nutrients) to produce all other organic molecules glucose also used for energy by the plants glucose is converted to stored energy by the plants primary production is the production of organic material by producers for the entire ecosystem

Photosynthesis

Energy Flow between Producers and Consumers Cell respiration - aerobic - nutrient organic molecules (mainly glucose) combining with oxygen to form CO2, H2O and energy anaerobic respiration-breakdown of glucose in the absence of oxygen Gross primary production (GPP)- total photosynthetic activity of producers-all the energy Net primary production (NPP)-gross minus the amount of energy consumed by the plants themselves: the rate at which energy is available to the consumers in an ecosystem Global NPP is the upper limit determining planet’s carrying capacity

Productivity of Different Ecosystems