Dynamics of Ecosystems Chapter 57

1. Dynamics of EcosystemsChapter 57

2. Flow of Energy in Ecosystems • First Law of Thermodynamics: energy is neither created nor destroyed; it changes forms • Second Law of Thermodynamics: whenever organisms use chemical-bond or light energy some is converted to heat (entropy) • Sun our major source of energy (E)

3. Flow of Energy in Ecosystems • Trophic levels: level an organism “feeds” at • Producers (autotrophs): “self-feeders” make organic compounds (photosynthesis) • Consumers (heterotrophs): must take in food

4. Flow of Energy in Ecosystems • Consumers are classified by their diet • Herbivores: first consumer level, eat plants • Primarycarnivores: eat herbivores • Secondarycarnivores: eat primary carnivores or herbivores • Tertiary=Top-Level Consumer • Detritivores: eat decaying matter • Decomposers: microbes that break up dead matter –Create “CHONPS”

5. Trophic levels within an ecosystem

6. Flow of Energy in Ecosystems • Productivity: the rate at which the organisms in the trophic level collectively synthesize new organic matter • Primary productivity(GPP or PP): producers • Respiration: rate producers use org. compounds • Net primary productivity (NPP) = PP(GPP) – respiration • Secondary productivity: productivity of a heterotroph trophic level

7. Flow of Energy in Ecosystems • biomass: the amount of organic matter present at a particular time • Only small fraction of incoming solar energy is captured by producers ~ 1%/year • Used to make chemical-bond energy • As energy passes up the food chain, most is lost as heat and waste (90% lost at each level) • Less biomass/fewer individuals at each trophic level

8. Flow of Energy in Ecosystems • 50% of chemical-bond energy is not assimilated and is egested in feces • 33% of ingested energy is used for cellular respiration • 17% ingested energy is converted into insect biomass

10. Flow of Energy in Ecosystems Flow of energy through the trophic levels of Cayuga Lake

11. Human Impacts: Pollution • Biomagnification:becomes more concentrated at higher trophic levels • predatory bird species’ eggshells so thin that the shells broke during incubation

13. Ecosystem productivity per year

14. Flow of Energy in Ecosystems • Trophic level interactions • Trophic cascade: process by which effects exerted at an upper level flow down to influence two or more lower levels • Top-down effects: when effects flow down • Bottom-up effects: when effect flows up through a trophic chain

15. Yellowstone Park Wolves • *Trophic Cascade • www.youtube.com/embed/ysa5OBhXz-Q?feature=player_embedded

16. Flow of Energy in Ecosystems Trophic cascade in a large-scale ecosystem

17. Flow of Energy in Ecosystems • Human removal of carnivores produces top-down effects • Over fishing of cod - 10% their previous numbers • Jaguars and mountain lions absent on Barro Colorado Island • Smaller predators become abundant

18. Flow of Energy in Ecosystems • When primary productivity is low, producer populations cannot support herbivore populations • As primary productivity increases, herbivore populations increase • Increased herbivore populations lead to carnivore populations increasing

19. Flow of Energy in Ecosystems Bottom up effects

20. Biodiversity and Stability • Species richness is influenced by ecosystem characteristics • Primary productivity • Habitat heterogeneity • Accommodate more species • Climatic factors

21. Biodiversity and Stability Factors that affect species richness

22. Biodiversity and Stability • Tropical regions have the highest diversity • Species diversity cline: biogeographic gradient in number of species correlated with latitude • Evolutionary age of tropical regions • Increased productivity • Stability/constancy of conditions • Predation • Spatial heterogeneity

23. Biodiversity and Stability Latitudinal cline in species richness