Ecosystem EcologyCh. 3

I.I. General InfoGeneral InfoA. Life is sustained by the interactions of

many organisms functioning together, through their physical and chemical environments

B. Levels of Organization1. Species - any organism that is able to

interbreed and produce fertile offspring2. Populations - groups of the same species living

in the same area at the same time3. Communities - groups of populations that live

together in a defined area

4. Ecosystem - the relationship of the community with its nonliving environment

5. Biomes - ecosystems in different locations with similar climate and communities (e.g. desert, temperate forest, arctic, etc)

6. Biosphere - combined areas of planet where life exists

C. Ecosystem Structure and Boundaries1. Biotic and abiotic components provide ecosystem

boundaries and distinguish one from anothera. Abiotic - water, temperature, light, soil and

atmospheric conditions, pH, salinity, etc.b. Biotic – living organisms, food, predation,

competition2. Watersheds and topographic features are often

used to delineate the boundaries of an ecosystem3. Know boundaries to determine components, and

flow of energy and matter

4. Variety of scales, wide range of sizes

D. Ecosystem Processes1. Two basic types:

a. Chemical cycling – movement and recycling of elements between the environment and organisms

b. Flow of energy

II.II. Energy FlowEnergy Flow

A. Review1. Energy is the ability to do work or

transfer heata. Potential vs. kineticb. 1st and 2nd law of thermodynamics

2. Nearly all the energy that powers ecosystems comes from the Sun

a. Main energy source for most life on earth

3. Photosynthesis and respiration

B. Producers (autotrophs) use energy from the environment to produce their own food

1. Photosynthetic - plants, algae, and some bacteria use energy in sunlight to make complex organic molecules

2. Chemosynthetic - several types of bacteria use energy in inorganic chemical bonds to live(e.g. ocean floor thermal vents, Yellowstone hot springs, etc.)

C. Consumers (heterotroph) - any organism that consumes another organism to obtain energy through cellular respiration

1. Primary consumer - herbivore2. Secondary consumer - carnivore3. Tertiary consumer - eats 2° consumers 4. Omnivore5. Scavengers – carnivores that consume dead

animals6. Detritivores – break down dead tissues and waste

products (detritus) into smaller particles; e.g. crabs, snails, beetles, earthworms, etc.

7. Decomposer – any organism that breaks down dead organic material and recycles nutrients in to ecosystems; e.g. bacteria and fungi

D. Trophic levels – successive levels of organisms consuming one another

1. As organisms eat and in turn are eaten, energy is transferred

2. Flow of energy begins with the sun or inorganic compounds and travels in one direction

3. Illustrated by a food chain or food web

4. Food chain – linear sequence of consumption from producers through tertiary consumers

5. Food web - complex model of feeding relationships: how energy and matter move between trophic levels

6. Ecological Pyramids - diagram that shows the relative amount of energy or matter contained within each trophic level in a food chain/web

a. Pyramid of Numbersi. Based on the number of individuals at

each trophic level

b. Energy Pyramidi. Proportion of consumed energy that can be

passed to the next trophic level is ecological efficiency

ii. Only about 10% of energy available at one trophic level is transferred to the next Why? How does this relate to 2nd law?

CTI – “Should Humans Eat Lower on the

Food chain?

c. Biomass Pyramidi. Total amount of organic matter in an

ecosystem.ii. Represents the total amount of potential

food available for each trophic level

E. Ecosystem Productivity1. Amount of energy available in an ecosystem

determines how much life it can support2. Biological production is the capture of

usable energy from the environment to produce organic matter (increase biomass)

a. Gross primary production – total amount of energy captured by producers over a given period of time

b. Net primary production – energy captured minus the energy used to respire

c. NPP = GPP – R (where R = respiratory loss)

WORKING IT OUT 5.1 & 5.2

F. Ecosystem disturbances1. Event caused by physical, chemical or

biological agents that results in changes in population size or community composition

2. Natural vs. anthropogenic3. Short term or long term Why are ecologists interested in

studying disturbances?

5. Watershed Studiesa. All of the land in a given landscape that drains

into a particular stream, river, lake or wetlandb. Study biogeochemical cycles to determine

impact of disturbancec. Hubbard Brook ecosystem of New Hampshire

What did the researchers do? Outcome?

6. Resistance vs. Resiliencea. Not every disturbance is a disaster

Example? 1) Resistance - measure of how much a

disturbance can affect its flows of energy and matter

2) Net productivity remains constantb. Rate at which an ecosystem can recover to its

original condition = resilience Low vs. high?1) Depends on biogeochemical and hydrologic

cycles6. Severe anthropogenic disturbance requires

restoration ecology

7. Intermediate Disturbance Hypothesisa. Ecosystems experiencing intermediate levels of

disturbance are more diverse than those with high or low disturbance levels

What does this graph indicate?

A. Instrumental Values1. Referred to by economists as ecosystem services2. Benefits that humans obtain from natural ecosystems3. Have monetary value that must be considered

DO THE MATH pg. 784. Types:

a. Provisionalb. Regulatingc. Support Systemsd. Resiliencee. Cultural

B. Intrinsic Values

III.III. Ecosystem ServicesEcosystem Services