UNIT III: ECOSYSTEM ECOLOGY Chapters 3 Part I: Energy Transfer

Chapter Objectives 1. List the basic components of an ecosystem 2. Describe how energy flows through ecosystems. 3. Describe how carbon, nitrogen, and phosphorus cycle within ecosystems 4. Explain how ecosystems respond to natural and anthropogenic disturbances 5. Discuss the values of ecosystems and how humans depend on them

I. Ecosystems Particular location on Earth distinguished by mix of interacting biotic and abiotic components, Each ecosystem interacts with surrounding ecosystems through the exchange of energy and matter

Sustaining Life on Earth: 1) One-way flow of high-quality energy from the sun 2) Cycling of Nutrients (atoms, ions, molecules) through the biosphere. 3) Gravity: allows planet to hold onto atmosphere and helps movement and cycling of chemicals through air, water, soil, organisms

II. Energy Flows Through Ecosystems Producers (autotrophs) Convert inorganic carbon to organic carbon

One molecule of glucose can generate 38 molecules of ATP

Anaerobic Respiration / Decomposition Breakdown of glucose/cellulose in absence of oxygen. Products are methane (CH 4 ), ethyl alcohol ( C 2 H 6 O) and acetic acid (C 2 H 4 O 2 ) 2 molecules of ATP are released per one molecule of glucose

III. Trophic Levels, Food Chains and Food Webs Producers, Consumers, Decomposers (Heterotrophs) Consumers: 1 o, 2 o, 3 o Herbivore: Each plants Carnivore: Eat animals Omnivore: Eat plants and animals Scavenger: Consume dead organisms Detritivore: Break down dead tissues into smaller pieces. Dung Beetle, Earthworm, Acid, Poop, and Barf: Vultures' Secret Weapons

Decomposers: break organic compounds down into inorganic substances; Bacteria/Fungi Fruit and vegetable Decomposition

Food Webs & Energy Flow © Brooks/Cole Publishing Company / ITP

V. Productivity Different Ecosystems use solar energy to produce and use biomass at different rates. To understand how ecosystems function must understand where energy comes from and how it is transferred Primary Productivity- amount of energy that producers in an ecosystems capture via photosynthesis over a given amount of time. Can measure rate of photosynthesis or or rate at which plant increases in mass

Energy captured minus the energy respired by producers is Net Primary Productivity: NPP NPP=GPP-R

Why Productivity is Important The amount of sunlight that reaches a lake determines how much algae can live in the lake Amount of Algae determine the number of zooplankton the lake can support Size of zooplankton population determines size of fish population

Measuring Productivity Rarely does photosynthesis occur w/o respiration. Measure O 2 in dark (no photo means but still respiration means no O 2 produced but some O 2 used. ) Measure O 2 in light. (photosynthesis and respiration occur; O 2 produced and O 2 used) Light Bottle – Dark Bottle = photosynthesis

Factors Limiting Primary Productivity The planet’s NPP limits the number of consumers- including humans, that can survive on earth. Solar Radiation alone does not determine Primary Productivity Temperature: Relationship between forest net primary productivity and annual temperature. Precipitation Increasing Precipitation increases productivity

NASA Earth Observatory t/lectures/kling/energyflow/energyflow.html t/lectures/kling/energyflow/energyflow.html

Energy Transfer Efficiency and Trophic Pyramids The energy in an ecosystem can be measure in terms of biomass (total mass of all living matter) NPP establishes the rate at which biomass is produced over a given amount of time. The amount of biomass present in an ecosystem at a particular time is standing crop Not all energy contained in a trophic level is in a usable form-not digestible

Problem 1% solar energy striking a producer captured by photo 60% of GPP lost to respiration 40% of GPP supports the growth and reproduction of producers A North American Forest has a GPP of 2.5 kg C/m 2 /year How much is “lost” to respiration? What is the NPP?

An acre of cropland could produce 1,000 kg of soybeans. If that is fed to people, how much biomass is available? Of fed to a cow, how much biomass do we get from the beef? Since 1 kg of soybeans contains 2.5X as many calories as 1kg of beef, 1 acre of land can produce 25Xmore calories when used for soybeans than beef.