1. Chapter 3 Ecosystems and Energy

2. Overview of Chapter 3 Ecology Energy
First Law of Thermodynamics
Second Law of Thermodynamics
Photosynthesis and Cellular Respiration
Flow of Energy Through Ecosystems
Producers, Consumers & Decomposers
Ecological Pyramid
Ecosystem Productivity

3. Ecology Ecology Biotic- living environment
“eco” house & “logy” study of
The study of interactions among and between organisms in their abiotic environment
Broadest field in biology
Biotic- living environment
Includes all organisms
Abiotic- non living or physical environment
Includes living space, sunlight, soil, precipitation, etc.

4. Ecology Biology is very organized
Ecologists are interested in the levels of life above that of organism

5. Ecology Definitions Species Population Community Ecosystem Landscape
A group of similar organisms whose members freely interbreed
Population
A group of organisms of the same species that occupy that live in the same area at the same time
Community
Al the populations of different species that live and interact in the same area at the same time
Ecosystem
A community and its physical (abiotic) environment
Landscape
Several interacting ecosystems

6. Ecology
Biosphere contains earth’s communities, ecosystems and landscapes, and includes:
Atmosphere- gaseous envelope surrounding earth
Hydrosphere- earth’s supply of water
Lithosphere- soil and rock of the earth’s crust

7. Energy The ability or capacity to do work Energy exists as:
Chemical, radiant, thermal, mechanical, nuclear, electrical
Energy exists as:
Stored energy (potential energy)
Kinetic energy (energy of motion)

8. Thermodynamics Study of energy and its transformations
System- the object being studied
Closed System- Does not exchange energy with surroundings (rare in nature)
Open System- exchanges energy with surroundings

9. Laws of Thermodynamics
First Law of Thermodynamics
Energy cannot be created or destroyed; it can change from one form to another
Ex: organisms cannot create energy they need to survive- they must capture it from another source
Focus is on quantity
Second Law of Thermodynamics
When energy is converted form one form to another, some of it is degraded to heat
Heat is highly entropic (disorganized) Entropy Rules!
Focus is on quality

10. Photosynthesis 6 CO2 + 12 H2O + radiant energy C6H12O6 + 6 H2O + 6 O2
Biological process by which energy from the sun (radiant energy) is transformed into chemical energy of sugar molecules
Energy captured by plants via photosynthesis is transferred to the organisms that eat the plants
6 CO H2O + radiant energy
C6H12O6 + 6 H2O + 6 O2

11. Cellular Respiration C6H12O6 + 6 O2 + 6 H2O 6 CO2 + 12 H2O + energy
The process where the chemical energy captured in photosynthesis is released within cells of plants and animals
This energy is then used for biological work
Creating new cells, reproduction, movement, etc.
C6H12O6 + 6 O2 + 6 H2O
6 CO H2O + energy

12. The Energy of Life
Case-in-Point:
Life Without the Sun

13. Energy Flow
Passage of energy in a one-way direction through an ecosystem
Producers
Primary consumers
Secondary consumers
Decomposers

14. Food Chains- The Path of Energy Flow
Energy from food passes from one organisms to another
Each “link” is called a trophic level

15. Food webs represent interlocking food chains that connect all organisms in an ecosystem

16. The Path of Energy Flow
Case-in-Point: How Humans Have Affected the Antarctic Food Web
Baleen whales
What would happen if you eliminated krill?
Krill
Squid
Fishes
Toothed whales
Penguins
Seals

17. Ecological Pyramids
Graphically represent the relative energy value of each trophic level
Important feature is that large amount of energy are lost between trophic levels to heat
Three main types
Pyramid of numbers
Pyramid of biomass
Pyramid of energy

18. Pyramid of Numbers
Illustrates the number of organisms at each trophic level
Usually, organisms at the base of the pyramid are more numerous
Fewer organisms occupy each successive level
Do not indicate the biomass of the organisms at each level or the amount of energy transferred between levels

19. Pyramid of Biomass
Illustrates the total biomass at each successive trophic level
Biomass: measure of the total amt of living material
Biomass indicates the amount of fixed energy at a given time
Illustrates a progressive reduction in biomass through trophic levels

20. Pyramid of Energy
Illustrates how much energy is present at each trophic level and how much is transferred to the next level
Most energy dissipates between trophic levels
Explains why there are so few trophic levels
Energy levels get too low to support life

21. The Path of Energy Flow Example: Thermodynamics in Action
Temperate forest: Primary producers = 1,500 g / m2
Desert: Primary producers = 100 g / m2
Food webs very complex, more tertiary consumers, some quaternary.
Food webs very simple, very few tertiary consumers

22. The Path of Energy Flow Desert Biomass Pyramid
such as . . .
13.5 kg coyote must range ~12 ha to subsist (30 acres).
Desert Biomass Pyramid
Tertiary consumers = 0.1 g / m2
Tertiary consumers must range over large areas to obtain enough energy to subsist.
Secondary consumers = 1.0 g / m2
Primary consumers = 10 g / m2
Primary producers = 100 g / m2

23. The Path of Energy Flow Temperate Forest Biomass Pyramid
13.5 kg coyote only needs ~1 ha to subsist (2.5 acres).
Temperate Forest Biomass Pyramid
NOTE: just relative examples, not accurate
Tertiary consumers = 1.5 g / m2
Secondary consumers = 15 g / m2
Primary consumers = 150 g / m2
Primary producers = 1,500 g / m2
Also, possibility of quaternary consumers, like bears.

24. Ecosystem Productivity
Gross Primary Productivity (GPP)
Total amount of energy that plants capture and assimilate in a given period of time
Net Primary Productivity (NPP)
Plant growth per unit area per time
Represents the rate at which organic material is actually incorporated into the plant tissue for growth
GPP – cellular respiration = NPP
Only NPP is available as food to organisms

25. Variation in NPP by Ecosystem

26. Human Impact on NPP
Humans consume more of earth’s resources that any other animal
Humans represent 0.5% of land-based biomass
Humans use 32% of land-based NPP!
This may contribute to loss of species (extinction)
Humans’ high consumption represents a threat to planet’s ability to support both human and non-human inhabitants