Ecosystems and Energy

Ecosystems and Energy3

© 2012 John Wiley & Sons, Inc. All rights reserved.

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 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 - 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 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 from bow


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 CO6 CO2 2 + 12 H+ 12 H22O + radiant energyO + radiant energy

CC66HH1212OO66 + 6 H + 6 H22O + 6 OO + 6 O22


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

CC66HH1212OO66 + 6 + 6 OO2 2 + 6 H+ 6 H22OO

6 CO6 CO22 + 12 H + 12 H22O + energyO + energy


Photosynthesis and Cellular Respiration


Energy Flow Through Ecosystems

Passage of energy through an ecosystem


Food Chains- The Path of Energy Flow

Energy from food passes from one organisms to another based on their Trophic Level Def: An organism’s position in a food chain, which

is 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

90% 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

Ecosystems and Energy

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