1. Chapter 3 Ecosystems and Energy

2. Overview of Chapter 3 What is Ecology? The Energy of Life
Laws 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
Biotic - living environment
Includes all organisms
Abiotic - non living or physical environment
Includes living space, sunlight, soil, precipitation, etc.

4. Ecology
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
Chemical, Thermal, Mechanical, Nuclear, Electrical, and Radiant/Solar (below)

8. Energy Energy exists as:
Potential energy (stored energy)
Kinetic energy (energy of motion)
Potential energy is converted to kinetic energy as arrow is released

9. 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

10. Laws of Thermodynamics
First Law of Thermodynamics
Energy cannot be created or destroyed; it can change from one form to another
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)

11. Photosynthesis
Biological process by which energy from the sun (radiant energy) is transformed into chemical energy of sugar molecules
6 CO H2O + radiant energy
C6H12O6 + 6 H2O + 6 O2

12. Cellular Respiration
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
C6H12O6 + 6 O2 + 6 H2O
6 CO H2O + energy

13. Photosynthesis and Cellular Respiration

14. Energy Flow Passage of energy through an ecosystem Producers
Primary consumers
Secondary consumers
Decomposers

15. Food Chains - The Path of Energy Flow
Energy from food passes from one organisms to another based on their Trophic Level
An organisms position in a food chain determined by its feeding relationships
First Trophic Level: Producers
Second Trophic Level: Primary Consumers
Third Tophic Level: Secondary Consumers
Decomposers are present at all trophic levels

16. Food Web

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
Fewer organisms occupy each successive level
Does not indicate:
biomass of organisms at each level
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
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

21. 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

22. Variation in NPP by Ecosystem

23. Human Impact on NPP
Humans represent 0.5% of land-based biomass, but use 32% of land-based NPP!
This may contribute to loss of species (extinction)
This represents a threat to planet’s ability to support both human and non-human inhabitants