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1 Dynamics of Ecosystems Chapter 57. 2 Flow of Energy in Ecosystems First Law of Thermodynamics: energy is neither created nor destroyed; it changes forms.

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Presentation on theme: "1 Dynamics of Ecosystems Chapter 57. 2 Flow of Energy in Ecosystems First Law of Thermodynamics: energy is neither created nor destroyed; it changes forms."— Presentation transcript:

1 1 Dynamics of Ecosystems Chapter 57

2 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 3 Trophic levels: level an organism “feeds” at Producers (autotrophs): “self-feeders” make organic compounds (photosynthesis) Consumers (heterotrophs): must take in food Flow of Energy in Ecosystems

4 4 Consumers are classified by their diet Herbivores: first consumer level, eat plants Primary carnivores: eat herbivores Secondary carnivores: eat primary carnivores or herbivores Detritivores: eat decaying matter – Decomposers: microbes that break up dead matter – “CHONPS” Flow of Energy in Ecosystems

5 5 Trophic levels within an ecosystem

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

7 7 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 – Less biomass/fewer individuals at each trophic level Flow of Energy in Ecosystems

8 8 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 Flow of Energy in Ecosystems

9 9

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

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

12 12

13 13 Ecosystem productivity per year

14 14 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 Flow of Energy in Ecosystems

15 15 Trophic cascade in a large-scale ecosystem Flow of Energy in Ecosystems

16 16 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 Example: Top-down

17 17 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 Example: bottom-up

18 18 Bottom up effects Flow of Energy in Ecosystems

19 19 Species richness is influenced by ecosystem characteristics – Primary productivity – Habitat heterogeneity Accommodate more species – Climatic factors Biodiversity and Stability

20 20 Factors that affect species richness Biodiversity and Stability

21 21 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 Biodiversity and Stability

22 22 Latitudinal cline in species richness Biodiversity and Stability


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