Chapter 3 Ecosystems and Energy

I. Ecology

• A. Ecology

– 1. “eco” house & “logy” study of

– 2. The study of interactions among and between organisms in their abiotic environment

• B. Biotic - living environment

– 1.Includes all organisms

• C. Abiotic - non living or physical environment

– 1. Includes living space, sunlight, soil, precipitation, etc.

• D. Ecologists are interested in the levels of life above that of organism

• E. Species

– 1. A group of similar organisms whose members freely interbreed

• F. Population

– 1. A group of organisms of the same species that occupy that live in the same area at the same time

• G. Community

– 1. All the populations of different species that live and interact in the same area at the same time

• H. Ecosystem

– 1. A community and its physical (abiotic) environment

• K. Landscape

– 1. Several interacting ecosystems – for example a pond next to a forest

• I. Biosphere contains earth’s communities, ecosystems and landscapes, and includes:

1. Atmosphere -

gaseous envelope surrounding earth

2. Hydrosphere - earth’s supply of water

3. Lithosphere - soil and rock of the earth’s crust

II. Energy

• A. The ability or capacity to do work

• B. Types of energy

– 1. chemical energy – energy stored in the bonds of molecules

– 2. radiant energy – energy, such as radio waves, visible light, and x-rays, that is transmitted as electromagnetic waves

– 3. solar energy – is radiant energy from the sun – includes uv radiation, visible light, and infrared radiation

– 4. thermal energy – heat that flows from an object with a higher temperature (source) to an object with lower temperature (sink)

– 5. mechanical energy – energy in the movement of matter

– 6. electrical energy – energy that flows as charged particles

• C. Energy exists as:

– 1. Potential energy (stored energy)

– 2. Kinetic energy (energy of motion)

• D. Potential energy is converted to kinetic energy as arrow is released

III. Thermodynamics

• A. Study of energy and its transformations

• B. System- the object being studied

1. Closed System - Does not exchange energy with surroundings (rare in nature)

2. Open System - exchanges energy with surroundings

• C. First Law of Thermodynamics

– 1. Energy cannot be created or destroyed; it can change from one form to another

• D. Second Law of Thermodynamics

– 1. When energy is converted form one form to another, some of it is degraded to heat

– 2. Heat is highly entropic (disorganized) – entropy is the measure of disorder or randomness – organized, usable energy has low entropy whereas disorganized energy such as heat has high entropy

IV. Photosynthesis

• A. 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

V. Cellular Respiration

• A. 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

V. Energy Flow

A. Passage of energy through an ecosystem

– 1. Producers – autotrophs – make organic molecules from simple inorganic molecules – photosynthesis, chemosynthesis

– 2. Consumers

• a. Primary consumers – herbivores – eat producers

• b. Secondary consumers – eat primary consumers

• c. Tertiary consumers – eat secondary consumers

• d. carnivores – eat only meat

• e. omnivores – eat both producers and meat

• f. detrivores – detritus feeders – consume organic matter that includes carcasses, leaf litter, and feces

– 3. Decomposers – saprophytes – saprobes – heterotrophs that break down dead organic material – help recycle nutrients

• B. Food Chains – The Path of Energy Flow

– 1.Energy from food passes from one organisms to another based on their Trophic Level

– 2.An organisms position in a food chain determined by its feeding relationships

– 3.First Trophic Level: Producers

– 4. Second Trophic Level: Primary Consumers

– 5. Third Tophic Level: Secondary Consumers

– 6. Decomposers are present at all trophic levels

C. Food Web – shows all of the food chains

• D. Ecological Pyramids

– 1. Graphically represent the relative energy value of each trophic level

– 2. Important feature is that large amount of energy are lost between trophic levels to heat

– 3.Three main types

• a. Pyramid of numbers

• b. Pyramid of biomass

• c. Pyramid of energy

– 4. Pyramid of Numbers - Illustrates the number of organisms at each trophic level

a. Fewer organisms occupy each successive level

b. Does not indicate:

1. biomass of organisms at each level

2. amount of energy transferred between levels

– 5. Pyramid of biomass - Illustrates the total biomass at each successive trophic level

a. Biomass: measure of the total amt of living material

b.Progressive reduction in biomass through trophic levels

– 6. Pyramid of energy - Illustrates how much energy is present at each trophic level and how much is transferred to the next level

a. Most energy dissipates between trophic levels

b. Explains why there are so few trophic levels

VI. Ecosystem Productivity

• A. Gross Primary Productivity (GPP) – 1. Total amount of energy that plants capture and

assimilate in a given period of time

• B. Net Primary Productivity (NPP) – 1. Plant growth per unit area per time

– 2. Represents the rate at which organic material is actually incorporated into the plant tissue for growth

• C. GPP – cellular respiration = NPP – 1. Only NPP is available as food to organisms

D. Variation in NPP by Ecosystem

E. Human Impact on NPP

• 1. Humans represent 0.5% of land-based biomass, but use 32% of land-based NPP!

– a. This may contribute to loss of species (extinction)

• 2. This represents a threat to planet’s ability to support both human and non-human inhabitants