Post on 04-Jan-2016
Chapters 55
Concept 5: Ecosystems – Analyzing productivity, energy flow, and chemical cycling.Ecosystems (Ch 55)
How energy flows though the ecosystem by understanding the terms that relate to food chains and food webs
The difference between gross primary productivity and net primary productivity
The carbon and nitrogen biogeochemical cycles
Ecosystemsconsist of all the organisms living in a
community, as well as the abiotic factors with which they interact
Ecosystems range from a microcosm (aquarium) to a large area such as a (forest, lake)
Ecosystem Dynamics involve two main processes: energy flow and chemical cycling
Flow of EnergyThe first law of thermodynamics states that
energy cannot be created or destroyed, only transformedEnergy enters an ecosystem as solar radiation, is
conserved, and is lost from organisms as heat
The second law of thermodynamics states that every exchange of energy increases the entropy of the universeIn an ecosystem, energy conversions are not
completely efficient, and some energy is always lost as heat
Cycling of Chemicals• The law of conservation of mass states that
matter cannot be created or destroyed• Chemical elements are continually recycled
within ecosystems• Ex) In a forest ecosystem, most nutrients enter
as dust or solutes in rain and are carried away in water
Overall: Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products
Trophic LevelsAutotrophs - build molecules themselves
using photosynthesis or chemosynthesis as an energy sourceEx) plants and algaeEx) chemosynthetic bacteria
on hydrothermal vents
Heterotrophs - depend on the biosynthetic output of other organisms
Trophic LevelsEnergy and nutrients pass from:
Primary producers (autotrophs) to Primary consumers (herbivores) to Secondary consumers (carnivores) to Tertiary consumers (carnivores that feed
on other carnivores)
Detritivores, or decomposers, are consumers that derive their energy from detritus, nonliving organic matterProkaryotes and fungi are important detritivoresDecomposition connects all trophic levels
Try This!Which of the following is absolutely essential
to the functioning of an ecosystem?A) producersB) producers and herbivoresC) producers, herbivores, and carnivoresD) detritivoresE) producers and detritivores
Primary Productivity (Lab 12!)The amount of light energy converted to
chemical energy (organic compounds) by an ecosystem’s autotrophs during a given period of time
Background:Photosynthesis (required light energy)
carbon dioxide + water → glucose + oxygenCellular Respiration (generates ATP – energy
currency) glucose + oxygen → carbon dioxide + water
Primary Productivity• Gross primary production (GPP)
– Total primary production of the ecosystem
• Net primary production (NPP) – GPP minus energy used by primary producers for respiration• Only NPP is available to consumers• Ecosystems vary greatly in NPP and
contribution to the total NPP on Earth
Ecological EfficiencyDescribes the proportion of energy represented at one
trophic level that is transferred to the next trophic level
On average, efficiency is only ~10%10 percent of the productivity of one trophic level is
transferred to the next level. The remaining 90% is consumed by individual metabolic activity or to detritovores
Applications: Farming: Energy required to raise and sustain carnivores is
far greater than that of herbivores… we eat cows, we ride horses
Bioaccumulation as you go up the trophic levels Ex)High mercury in tuna and swordfish Ex) High toxicity levels in orcas
Ecological PyramidsUsed to show relationship between trophic
levels
Horizontal bars or tiers: represent relative size in terms of either: Energy (productivity) Biomass Numbers of organisms
Tiers are stacked in the order in which energy is transferred.
Try ThisWhich of the following is not true of a pyramid of
production?A) Only about 10% of the energy in one trophic level is
passed into the next level.B) Because of the loss of energy at each trophic level,
most food chains are limited to three to five links.C) The pyramid of production of some aquatic
ecosystems is inverted because of the large zooplankton primary consumer level.
D) Eating grain-fed beef is an inefficient means of obtaining the energy trapped by photosynthesis
E) A pyramid of numbers is usually the same shape as a pyramid of production
Biogeochemical CyclesDescribes the flow of essential elements from the
environment to living things and back to the environment.p. 1209-1214 in Campbell
For each of the following essential elements, you
much know:The reservoirs (major storage location)The process of assimilation (incorporation into plants
and animals) The process of release (how it returns to the
environment)
Biogeochemical CyclesHydrolytic Cycle (water cycle)
Carbon Cycle (required for the building of all organic compounds)
Nitrogen Cycle (required for the manufacture the building blocks of proteins and nucleic acids)
Phosphorus Cycle (required for the manufacture of ATP and all nucleic acids. Cycle is similar to other mineral cycles like calcium)
Try ThisThe finding of harmful levels of DDT in
grebes (fish-eating birds) following years of trying to eliminate bothersome gnat populations in a lakeshore town is an example of...
Try ThisThe finding of harmful levels of DDT in
grebes (fish-eating birds) following years of trying to eliminate bothersome gnat populations in a lakeshore town is an example of...
BIOLOGICAL MAGNIFICATION
Concept 5: Ecosystems – Analyzing productivity, energy flow, and chemical cycling.Ecosystems (Ch 55)
How energy flows though the ecosystem by understanding the terms that relate to food chains and food webs
The difference between gross primary productivity and net primary productivity
The carbon and nitrogen biogeochemical cycles