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 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.

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

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

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 form 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 CO2 + 12 H2O + radiant energy C6H12O6 + 6 H2O + 6 O2

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 CO2 + 12 H2O + 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 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

Food Web

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

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