Chapter 5 How Ecosystems Work

Lake Victoria Freshwater lake in Africa Freshwater lake in Africa Formerly home to ≈ 400 species of cichlids Formerly home to ≈ 400 species of cichlids 1960: Nile perch 1960: Nile perch introduced introduced 1990: water hyacinth 1990: water hyacinth invaded invaded Today, ecological Today, ecological imbalance; why? imbalance; why?

What Is Ecology? Literally study of one’s “house” Literally study of one’s “house” Interactions Interactions Two components Two components Biotic Biotic Abiotic Abiotic Broadest biological field of study Broadest biological field of study

Ecological Organization Organism Organism Population Population Community Community Ecosystem Ecosystem Landscape Landscape Biosphere Biosphere

Positive and Negative Feedback Loops Feedback Loop Feedback Loop circular process circular process Positive Feedback Loop Positive Feedback Loop change becomes more pronounced change becomes more pronounced Negative Feedback Loop Negative Feedback Loop change is reduced or inhibited change is reduced or inhibited

Landscape Ecology Studies the connections among ecosystems Studies the connections among ecosystems Ecosystem engineers Ecosystem engineers Organisms that create or modify habitat Organisms that create or modify habitat How are grizzly bears ecosystem engineers? How are grizzly bears ecosystem engineers?

Goals Of Ecologists Understand how ecosystems function Understand how ecosystems function Make connections: landscape ecology Make connections: landscape ecology Connections among ecosystems Connections among ecosystems Grizzly Bears Grizzly Bears

Energy Capacity or ability to do work Capacity or ability to do work Flows through ecosystems Flows through ecosystems Why do organisms need energy? Why do organisms need energy? Different kinds Different kinds Potential energy Kinetic energy

First Law of Thermodynamics Energy cannot be created or destroyed Energy cannot be created or destroyed Energy can be changed from one form to another Energy can be changed from one form to another

Second Law of Thermodynamics When energy is changed from one form to another, some is degraded into heat When energy is changed from one form to another, some is degraded into heat Heat is a less usable form of energy Heat is a less usable form of energy Increases entropy in the universe Increases entropy in the universe

Ecosystem Composition Producers Producers Consumers Consumers Decomposers Decomposers

Producers Make their own food Make their own food Photosynthesis Photosynthesis Examples? Examples? 6CO 2 + 6H 2 O > C 6 H 12 O 6 + 6O 2 Light energy

Consumers Feed on other things Feed on other things Herbivores Herbivores Carnivores Carnivores Omnivores Omnivores Detrivores Detrivores

Decomposers Break down dead organisms and waste products Break down dead organisms and waste products Examples? Examples?

Energy Flow Energy passes from one organism to the next Energy passes from one organism to the next Trophic level: each step in this flow of energy Trophic level: each step in this flow of energy Food chain: straight path Food chain: straight path Food web Food web Interconnected food chains Interconnected food chains More realistic than food chain; why? More realistic than food chain; why?

Food Chain

Biological Production Net Primary Production: amount of plant mass generated by photosynthesis and that remains after cellular respiration Net Primary Production: amount of plant mass generated by photosynthesis and that remains after cellular respiration Biomass: total amount of organic matter Biomass: total amount of organic matter NPP is measured by tracking the changes in biomass over time NPP is measured by tracking the changes in biomass over time (NPP = B2 –B1)

Food Web

Biogeochemical Cycles Matter cycles through ecosystems Matter cycles through ecosystems Five cycles Five cycles Carbon Carbon Hydrologic (water) Hydrologic (water) Nitrogen Nitrogen Sulfur Sulfur Phosphorus Phosphorus

Carbon Cycle Essential component for life Essential component for life Gas (CO 2 ) in atmosphere Gas (CO 2 ) in atmosphere Several forms in ocean Several forms in ocean Can take a long time—think fossil fuels Can take a long time—think fossil fuels CO 2 Sugar Photosynthesis Cellular respiration

Carbon Cycle

Hydrologic Cycle OceanAtmosphereLandOcean

Nitrogen Cycle Proteins, DNA Proteins, DNA Atmosphere is 78% N 2 Atmosphere is 78% N 2 Five steps Five steps Nitrogen fixation Nitrogen fixation Nitrification Nitrification Assimilation Assimilation Ammonification Ammonification Denitrification Denitrification

Nitrogen Fixation Specialized bacteria Specialized bacteria Split atmospheric nitrogen and combine it with hydrogen Split atmospheric nitrogen and combine it with hydrogen

Nitrogen Cycle

Phosphorus Cycle No atmospheric component No atmospheric component Phosphates used in DNA and ATP (chemical energy) Phosphates used in DNA and ATP (chemical energy) Phosphates move through the food chain Phosphates move through the food chainLandOrganismLandOrganism

Phosphorus Cycle

Ecological Niche Everything about an organism Everything about an organism Adaptations Adaptations Use of resources Use of resources Lifestyle Lifestyle Habitat Habitat

Ecological Niche Two species cannot occupy the same niche: why? Two species cannot occupy the same niche: why? Resource partitioning Resource partitioning Reduces niche overlap Reduces niche overlap Reduces competition Reduces competition

Resource Partitioning At Work!

Species Interactions No species lives in complete isolation No species lives in complete isolation Symbiosis Symbiosis Intimate relationship between members of at least 2 species Intimate relationship between members of at least 2 species Mutualism, commensalism, parasitism Mutualism, commensalism, parasitism Result of coevolution Result of coevolution Other interactions Other interactions Predation, competition Predation, competition

Mutualism Both species benefit Both species benefit

Commensalism One species benefits, other not affected One species benefits, other not affected

Parasitism Parasite benefits, host is “harmed” Parasite benefits, host is “harmed” Ectoparasites & endoparasites Ectoparasites & endoparasites

Species Interactions Predation: consumption of one species by another Predation: consumption of one species by another Coevolution: “arms race” Coevolution: “arms race”

Avoiding Predators Mechanical defenses Mechanical defenses Social groups Social groups Camouflage Camouflage Protective chemicals Protective chemicals

Species Interactions Competition: two or more organisms attempting to use the same resource Competition: two or more organisms attempting to use the same resource Intraspecific vs. interspecific Intraspecific vs. interspecific

Keystone Species Crucial to maintenance of an ecosystem Crucial to maintenance of an ecosystem Loss affects many other Loss affects many other species species Examples? Examples? What are the differences What are the differences between a keystone, umbrella or flagship species?

Adaptive Ecosystem Management Ecosystem Management: meeting the goals or objectives of the biotic community and their associated abiotic components Ecosystem Management: meeting the goals or objectives of the biotic community and their associated abiotic components Adaptive Ecosystem Management: Adaptive Ecosystem Management: developed by C.S. Holling and Carl J. Walters, University of B.C., 1970 developed by C.S. Holling and Carl J. Walters, University of B.C., 1970 acknowledges the uncertainty and the need for managers to learn while they manage acknowledges the uncertainty and the need for managers to learn while they manage passive and active passive and active

Eco Canada Career Focus Consider a career as an ecologist Consider a career as an ecologist Ecologists study the relationships between living things and their environments Ecologists study the relationships between living things and their environments

Case Study: Human Appropriation of Net Primary Productivity (HANPP) HANPP : indicator of are of land an the amount of biomass consumed by humans HANPP : indicator of are of land an the amount of biomass consumed by humans Valuable indicator of “human domination of ecosystems” on a global scale Valuable indicator of “human domination of ecosystems” on a global scale Many countries are consuming an excess of 100% of locally available NPP Many countries are consuming an excess of 100% of locally available NPP

Case Study: Human Appropriation of Net Primary Productivity (HANPP)