Understanding Ecosystems and Energy: Key Concepts in Ecology and Thermodynamics

1. Chapter 3Ecosystems 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 • “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 • 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, 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) • Focus is on quality

10. C6H12O6 + 6 H2O + 6 O2 Photosynthesis • 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 CO2 + 12 H2O + radiant energy

11. 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 • Creating new cells, reproduction, movement, etc. C6H12O6 + 6O2 + 6 H2O 6 CO2 + 12 H2O + energy

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

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

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

15. 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

16. 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

17. 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

18. 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

19. 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

20. Variation in NPP by Ecosystem

21. 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