1. Chapter 54
Ecosystems

2. Ecosystems
Ecosystem - consists of all the organisms living in a community as well as all the abiotic factors with which they interact.
Trophic structure - all the feeding relationships within an ecosystem.
Trophic levels - divides the species of an ecosystem by what their main source of nutrition is.

3. Trophic Relationships in Ecosystems
Primary Producers - 1st trophic level consisting of autotrophs; “the base” (photosynthesize)
Primary Consumers - herbivores
Secondary Consumers - carnivores that eat herbivores
Tertiary Consumers - carnivores that eat other carnivores

4. Trophic Relationships in Ecosystems (con’t)
Quarternary Consumers - high order carnivores that consume larger carnivores
Detritovores - derive energy by consuming dead organic material such as leaves, feces, and dead organisms from all trophic levels.

5. Food Chains and Food Webs
Food Chain - pathway by which food energy is passed from trophic level to trophic level
Example
dandelion - grasshopper - mouse - snake - hawk (terrestrial)
phytoplankton - zooplankton - small fish - medium sized fish - large fish (marine)
Food Webs - elaborate feeding relationships between all trophic levels

6. Food Chains and Food Webs (con’t)

7. Ecosystem Processes
Production - rate of incorporation of energy and materials into bodies of organisms
Consumption - metabolic use for growth and reproduction of assimilated organic materials
Decomposition - breakdown of organic material into inorganic material
bacteria, fungi, and some animals
links all trophic levels recycling nutrients back into the abiotic environment

8. Energy Flow in Ecosystems
An ecosystem’s energy budget depends on the amount of primary productivity.
the amount of light energy converted to chemical energy (organic compounds)
Biomass - term used to describe primary productivity
the amount of new vegetation added to the ecosystem in terms of dry weight per unit time

9. Productivity of Different Ecosystems

10. Energy Flow through Ecosystems
Most of the energy is lost as it flows through each trophic level due to heat.
metabolic rate of the organism
Secondary Productivity - rate at which consumers convert chemical energy into their own new biomass.
Herbivores can only eat a fraction of the plant biomass produced, and can only digest a fraction of what they eat.

11. Energy Partitioning in a Caterpillar
lost as heat
recycled by detritovores
converted to biomass

12. Energy Flow through Ecosystems (con’t)
Ecological efficiency - percentage of energy transferred from one trophic level to the next (~10% is transferred)
Pyramid of Productivity - food chain is diagrammatically represented using blocks where the primary producers form the base
Biomass pyramid - representation of the standing crop biomass in a trophic level

13. Pyramid of Net Productivity
Consumers convert ~10% of chemical energy into biomass.
Primary Producers only convert ~1% of light energy into biomass.

14. Biomass Pyramid

15. Biogeochemical Cycles
Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle

16. Biological Magnification
Biological magnification - concentration of toxins at successive trophic levels
top-level carnivores tend to be the organisms most severely affected .
These toxins, such as DDT and PCBs, are pesticides that may accumulate in tissues after ingestion. (fat tissue)

17. Biological Magnification of DDT in a Food Chain
Food Chain Concentration of DDT in A Long Island Marsh sprayed for Mosquito Control 1967
ppm
Water
Plankton .04
Silverside Minnow .23
Sheephead Minnow .94
Pickerel 1.23
Needlefish 2.07
Heron 3.57
Tern 3.91
Osprey 13.8
Merganser 22.8
Cormorant 26.4

18. Human Impact-Ozone Depletion
Ozone (O3) - bottom layer of the stratosphere that protects Earth from UV radiation.
Depletion since 1975 is due to CFC’s, chlorflourocarbons, chemicals used in refrigerators, aerosol, and styrofoam.
Chlorine reacts with the O3 molecules reducing them to O2 molecules
Reactions allow the chlorine to dissociate from the O2 molecules allowing the chlorine to react with more ozone.

19. Human Impact-Ozone Depletion (con’t)
Ozone is constantly produced and destroyed, however, atoms, such as Cl & Br, siphon ozone away faster than it is being produced.

20. Ozone Depletion - Antarctica