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

2. Summary of Lecture The structure of ecosystems Ecosystem Relationships
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 Limits 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: Consumers: Decomposers:
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