Chapter 3 Ecosystems and Energy

The diamondback tarrapin

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

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.

Ecology Biology is very organized 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 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 Energy exists as: Chemical, radiant, thermal, mechanical, nuclear, electrical Energy exists as: Stored energy (potential energy) Kinetic energy (energy of motion)

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

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

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 CO2 + 12 H2O + energy

Energy Flow Passage of energy in a one-way direction 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 Each “link” is called a trophic level

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

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 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

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

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

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 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