Chapter 3 Ecosystems and Energy

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

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

Ecology  Ecologists are interested in the levels of life above that of organism

Ecology Definitions  Species  A group of similar organisms whose members freely interbreed  Population  A group of organisms of the same species that live in the same area at the same time  Community  All 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

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

Energy  The ability or capacity to do work  Chemical, Thermal, Mechanical, Nuclear, Electrical, and Radiant/Solar (below)

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

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

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 from one form to another, some of it is degraded to heat  Heat is highly entropic (disorganized)

Photosynthesis  Biological process by which energy from the sun (radiant energy) is transformed into chemical energy of sugar molecules 6 CO H 2 O + radiant energy C 6 H 12 O H 2 O + 6 O 2

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 C 6 H 12 O O H 2 O 6 CO H 2 O + energy

Photosynthesis and Cellular Respiration

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

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

Food Web

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

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

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

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

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

Variation in NPP by Ecosystem

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