Lecture 4: Ecosystems

1. Lecture 4: Ecosystems Concepts, Structure, and Relationships

2. Summary of Lecture • The structure of ecosystems • Definitions • Ecosystem Relationships • Trophic levels • Energy flow • Photosynthesis • Food Webs

3. Definitions • Ecology: study of the relationships between organisms and the environment, focus on interactions • Organism: any form of life

4. ECOSPHERE Ecosystems Communities Populations Organisms

5. Definitions (continued) • Species: group of organisms that resemble one another in appearance, behavior, chemistry, and genetic endowment. Under natural conditions, they can breed with one another and produce live, fertile offspring. • Sp. are the result of a long evolutionary process • Wild species vs. Domesticated species • How many species are there???? • 5-100 million species • 1.8 million species identified

6. Same Species

7. Species and Tolerance • Law of tolerance • The existence, distribution and abundance of a species is determined by whether the levels of physical and chemical factors fall within tolerable ranges for that species • Limits of tolerance • Species can’t survive beyond these limits • Range of tolerance • Minumum and maximum levels of tolerance • Law of limiting factors • Too much or too little of any abiotic factor can limit or prevent growth of a population, even if other factors are near the optimum

8. Tolerance Range

9. Definitions (continued) • Population: group of organisms of the same species living within a particular area. • Populations have genetic diversity • Populations are dynamic, not static • Examples: • All the people in a country • All the deer in a forest • All the cattails in a pond • Habitat: place where a population lives

10. Definitions (continued) • Community: complex of interacting populations of all plants, animals, and microorganisms living and in an area at a particular time • Ecosystem: all the elements of the community and the non-living environment • Rarely have distinct boundaries • Climate and species adapted to that climate • Ecotone: transition zone between ecosystems • High # of species and species density • Ecosphere: all of Earth’s ecosystems together

11. Figure 4.2

12. Components of an Ecosystem • Biotic (organic): living • Generally refers to those substances produced by the metabolism of a living organism, especially carbon-containing compounds. • Abiotic (inorganic): non-living • Physical and chemical factors effecting the ecosystem • Sunlight, temperature, water

13. Biotic Components • Producers: • Make their own food • Plants and other organisms • Consumers: • Depend on energy stored in tissues of producers • Decomposers: • Break down molecules (from producers or consumers) to simple materials which are recycled back to producers

14. Interdependence

15. Trophic Categories • Tropic level: all organisms that are the same # of energy transfers away from the original source of energy • # of levels is limited by amount of energy available • Producers: Any organism that is able to manufacture its own food. • photoautotrophic, using light energy to manufacture food, or chemoautotrophic, using chemical energy. • Green plants and algae • photosynthesis

16. Trophic Categories (continued) • Consumers: Any organism which must consume other organisms (living or dead) to satisfy its energy needs. • herbivore -- Literally, an organism that eats plants or other autotrophic organisms. The term is used primarily to describe animals • carnivore -- organism that eats meat. Most carnivores are animals, but a few fungi, plants, and protists are as well. • Primary, Secondary and Higher level consumers

17. Consumers (continued) • Omnivore -- organism that will eat both plants and animals. Refers to animals who do not restrict their diet to just plants or other animals. • Scavenger--organism that feeds on dead organisms • Detritivore -- organism which obtains most of its nutrients from the detritus in an ecosystem • Detritus feeders and decomposers • Bacteria, fungi, insects • Detritus: dead organisms or waste

18. Detritivores and Decomposers

19. Other Relationships • Predator-Prey • Parasite-Host

22. Freshwater Pond Ecosystem

23. Field Ecosystem

24. Food Chains and Webs • All the interactions of the predator and prey, including the exchange of nutrients.These interactions connect the members of the ecosystem and describe how energy passes from one organism to another • food chains: who eats whom? • food web: complexes of feeding relationships

25. Model of a Food Chain

26. Antarctic Food Web

27. Energy Flow and Nutrient Cycles • 1st principal of ecosystem function-sustainability: ecosystems use sunlight as their source of energy • 2nd: ecosystems dispose of wastes and replenish nutrients by recycling all elements

28. Energy Flow and Biomass Storage • Biomass: dry weight of all the organic matter of organisms in a trophic level • Transfer of energy from one trophic level to the next is low • Energy is lost as heat, waste, undigested food, etc • limitations on the transfer of energy to next trophic level creates the biomass pyramid • Ecological Efficiency: % of energy transferred from one trophic level to the next • About 5-20% energy transferred, 80-95% lost

29. Ecological Efficiency

30. Trophic Pyramid

31. Annual Pyramid of Energy Flow

32. Biomass for 2 Ecosystems

33. Energy flow and nutrient cycles • 1st principal of ecosystem function-sustainability: ecosystems use sunlight as their source of energy • 2nd: ecosystems dispose of wastes and replenish nutrients by recycling all elements

34. Nutrient Cycles and Energy Flow

35. Producers, Photosynthesis, and Primary Production • carbon dioxide + water • all oxygen in the atmosphere was put there by photosynthesis • rate of photosynthesis is proportional to the amount of light • Only ½ solar energy absorbed by plants • Only 1-5% of that energy is converted to chemical energy by photosynthesis . glucose + oxygen

36. Producers, Photosynthesis, and Primary Production • glucose combines with nitrogen, phosphorus, and other minerals (nutrients) to produce all other organic molecules • glucose also used for energy by the plants • glucose is converted to stored energy by the plants • primary production is the production of organic material by producers for the entire ecosystem

37. Photosynthesis

38. Energy Flow between Producers and Consumers • Cell respiration - • aerobic - nutrient organic molecules (mainly glucose) combining with oxygen to form CO2, H2O and energy • anaerobic respiration-breakdown of glucose in the absence of oxygen • Gross primary production (GPP)- total photosynthetic activity of producers-all the energy • Net primary production (NPP)-gross minus the amount of energy consumed by the plants themselves: the rate at which energy is available to the consumers in an ecosystem • Global NPP is the upper limit determining planet’s carrying capacity

39. Productivity of Different Ecosystems