1. Ecosystems and Energy

2. Ecology: the study of one’s house –
- composed of biotic and abiotic components
Biotic: living components of the system
Abiotic: non-living components of the system – space, temperature, sunlight, soil, wind, precipitiation
- incorporates all the sciences and many other areas of study
- focus can be limited or large based on the purpose of the study – usually focuses on a specific level of interaction

3. Tying Ecology Together – movement of energy
Energy – ability to do work
Types: Chemical Electromagnetic (radiant)
Thermal
Nuclear
Mechanical
Electrical
Potential
Kinetic

4. Study of Energy = Thermodynamics
First Law of Thermodynamics:
- the amount of energy in the universe is constant
- an organism cannot create energy but must capture the energy from outside itself and then convert it into usable forms

5. Second Law of Thermodynamics
- the amount of energy available to do work decreases over time
- ordered systems of energy become disordered by becoming heat
- the amount of disorder is measured as Entropy
- theoretically all the energy in the universe will eventually be evenly distributed as heat and no work will be done (Heat Death of the Universe)
- thus no transformation of energy is 100% efficient
Ex: Car engine 20 – 30% efficient at converting chemical energy in the bonds of gasoline into mechanical energy – rest is lost as heat
- Human metabolism – 40 % efficient

6. Energy Exchange in the Ecosystem
Photosynthesis and Cellular Respiration
Photosynthesis: process of capturing photons (light energy) and using them to fix carbon dioxide into simple sugars
6 CO2 + 6 H2O  C6H12O6 + 6 O2

7. Photon capture is done by a system of proteins called pigments
main pigment is chlorophyll, which appears green because it reflects green light and best absorbs red and blue light
- chlorophyll is found in the chloroplast of plant cells
Organisms: Plants, algae, some protists, cyanobacteria (blue-green algae)
Process: CO2 is fixed to several organic molecules in order to form it into glucose, uses the ATP for energy
Glucose is used for energy for growth and reproduction – extra glucose is stored as starch
By products are Oxygen

8. Cellular Respiration
process of breaking down organic molecules into CO2 and energy –
- reverse of photosynthesis –
C6H12O6 + 6 O2  6 CO2 + 6 H2O
Glucose is broken down through a series of steps to ensure the slow release of the energy – slow release makes the process more energy efficient – carried out mainly by the mitochondria

9. Process:
Organisms: All eukaryotes (Plants, animals, fungus, most protists)
In the end - CO2 that was fixed by the photosynthesis is released by the cellular respiration, which also consumes the O2 that was generated
together they form the base process for the carbon cycle
However, the energy that is captured by the phototrophs is not transferred to the heterotrophs completely.
Much of it is lost as heat and through biological processes.

10. Energy Flow Through Ecosytems
Terms:
Producers/Autotrophs (self-feeders) – initial organisms that capture and store energy
Types: Photoautotrophs – capture solar energy and convert it to chemical energy Ex: plants and algae- some bacteria and protists
Chemoautotrophs – use the energy in other chemicals to build biological molecules
Ex: deep sea vent bacteria

11. Consumers/Heterotrophs (other feeders): must consume biological molecules for a source of energy – cannot make their own food
Types: Carnivores: meat eaters - cats
Herbivores: plant eaters - cows
Omnivores: any eaters – bears
Decomposers/Saprotrophes (rotten eaters):
Detrivores/Saprobes: break down dead things – fungus and bacteria

12. Microorganisms
and other
detritivores
Detritus
Primary producers
Primary consumers
Secondary
consumers
Tertiary consumers
Heat
Sun
Key
Chemical cycling
Energy flow

13. Trophic Levels 1. Primary Producers - autotrophs
2. Primary Consumers – herbivores
3. Secondary Consumers – carnivores – herbivore eaters
4. Tertiary Consumers – carnivores – eaters of other carnivores

15. 5. Keystone Predator – top of the food chain – presence helps regulate the populations of the lower trophic levels Ex: lions, wolves
removal of the keystone predator often causes a large disruption in the lower trophic levels
– removal of wolves from the United States causes a large upsurge of deer populations which in turn ate more and more plants making them less available for the other species

16. Number of species present
(a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates.
With Pisaster (control)
Without Pisaster (experimental)
Number of species present 5 10 15 20
1963
´64
´65
´66
´67
´68
´69
´70
´71
´72
´73
(b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity.

17. Observation of sea otter populations and their predation
Figure 53.17
Food chain before killer whale involve- ment in chain
(a) Sea otter abundance
(b) Sea urchin biomass
(c) Total kelp density
Number per 0.25 m2
1972
1985
1989
1993
1997 2 4 6 8 10
100
200
300
400
Grams per 0.25 m2
Otter number (% max. count) 40 20 60 80
Year
Food chain after killer whales started preying on otters

18. 6. Detrivores – complete the cycle of nutrients
- break things down which make nutrients available for the producers
- Together these make up a food chain (page 54) (consumer to decomposer) which more accurately portrayed as a food web (page 55).

20. Ecosystem “Engineers” (Foundation Species)
Some organisms exert their influence
By causing physical changes in the environment that affect community structure

21. Beaver dams can transform landscapes on a very large scale
Figure 53.18

22. Ecological Pyramids Biomass and Energy Transfer Between Trophic Levels
Producers: Trap and convert energy into usable forms
Producers use this energy for life functions (growth, repair, reproduction) which decreases the amount of energy that is available to the next level
Same is true for each consumer level
Result: As you move up in levels, the number of organisms, the overall biomass and the amount of energy decreases.

23. Types of Pyramids 1. Pyramid of Numbers: Figure 3.11
- typically, the organisms at the base of the food chain are most abundant

25. Biomagnification

27. Types of Pyramids 2. Pyramids of Biomass: Figure 3.12
- Biomass: amount of biological material – indicates the amount of fixed energy in an organism or system
- Average is about 90% decrease
- only 10% is passed to the next trophic level

28. Pyramid of Biomass Trophic level Dry weight (g/m2) Tertiary consumers
Figure 54.12a
(a) Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels, as illustrated by data from a bog at Silver Springs, Florida.
Trophic level
Dry weight
(g/m2)
Primary producers
Tertiary consumers
Secondary consumers
Primary consumers
1.5 11 37
809

29. Certain aquatic ecosystems have inverted biomass pyramids
Trophic level
Primary producers (phytoplankton)
Primary consumers (zooplankton)
Dry weight
(g/m2) 21 4

30. Types of Pyramids 3. Pyramid of Energy: Figure 3.13
- expressed as kilocalories per square meter
- since the producers are most abundant they will contain the most energy per square meter, but not per organism

31. Pyramid of Energy Figure 54.11 Tertiary consumers Secondary Primary
producers
1,000,000 J of sunlight
10 J
100 J
1,000 J
10,000 J

32. Ecological Pyramids allow us to look at an ecosystem and determine its productivity
Ecosystem Productivity:
Gross Primary Productivity (GPP) is the rate at which energy is captured during photosynthesis
Net Primary Productivity (NPP) is the amount of energy left over after the producers have used the amount they need for life functions
- measured by the kilocalories per square meter per year or the grams of biomass (dry weight of CO2) incorporated per square meter per year

33. Consumers eat the producers and the NPP becomes available for use (not all – depends on the efficiency of the consumers digestive system)
Consumer uses the energy for basic life functions (movement, tissue repair) and the remaining energy (Secondary Productivity) can be used for growth and reproduction

34. Worldwide agriculture could successfully feed many more people if humans all fed more efficiently, eating only plant material
Trophic level
Secondary
consumers
Primary
producers