PACKET #80CHAPTERS #54 & #50

Ecosystems &The Flow of Energy &

Matter

Introduction

Ecosystem Encompasses all the interactions among organisms

living together in a particular place, and among those organisms and their abiotic environments

Individual communities and their abiotic environments Earth, which encompasses the biosphere (all of

Earth’s communities) and its interaction with Earth’s water, soil, rock and atmosphere, is the largest ecosystem

ENERGY FLOW

Ecosystems

Energy Flow Through Ecosystems

The flow of energy is linear—as energy cannot be reused by organisms Energy begins as solar energy, which is trapped by

photosynthesis in the form of chemical energy Chemical energy is then available to do work

Energy Flow II

Energy flow describes who eats whom in ecosystems A food chain describes

the sequential passage of energy

A food web shows the complexity of interconnected food chains Remember that a food

web is composed of many food chains

Energy Flow III

Food Chain Refresher Primary producers are

autotrophs and comprise the first trophic level

Herbivores, primary consumers, comprise the second trophic level May find omnivores here

Carnivores and/or omnivores, comprise trophics level three and higher all the way to the decomposers

Energy Flow IV

Ecological Pyramid Illustrates the trophic

levels May be a pyramid of

Numbers

Energy Flow V

Ecological Pyramid Illustrates the trophic

levels May be a pyramid of

Biomass

Energy Flow VI

Ecological Pyramid Illustrates the trophic

levels May be a pyramid of

Energy

PRODUCTIVITY

Ecosystems

Productivity I

Energy flow begins with primary productivity The amount of light energy converted to chemical energy,

in the form of organic molecules, by an ecosystem’s autotrophs, over a given period of time.

Gross Primary Productivity (kilocalories fixed per area per time OR grams carbon fixed) Expresses the total rate of photosynthesis of an ecosystem

Net Primary Productivity (kilocalories fixed per area per time OR grams carbon fixed) The energy remaining after cellular respiration

Gross total productivity – energy used for cellular respiration

Productivity II

Primary Productivity is always expressed as a RATE and is represented via Kilocalories fixed per

area per time Joules per square meter

per year Grams carbon fixed

(Biomass) The dry weight of

vegetation added to an ecosystem per unit area per unit time Grams per square

meter per year

Productivity III

Rates of productivity are influenced by environmental factors

Tropical rain forests are the most productive terrestrial ecosystems

Wetlands, coral reefs, and estuaries are the most productive aquatic ecosystems

Productivity IV

Energy flow is never 100% efficient and results in the Pyramid of Productivity

Productivity V

Relationship of productivity to biological diversity is complex Ecosystems may be more diverse as productivity

increases, but after a certain point, diversity will decline with increasing productivity

Important when considering nutrient-enriched environments Especially those that are impacted by human application

of fertilizers and enrichment by animal wastes.

Cycles of Matter in Ecosystem

Introduction

Biochemical cycles are cycles of matter between the abiotic and biotic components of the environment

Carbon, nitrogen, phosphorus and water cycles are central to life on earth

Carbon, nitrogen and water cycles have atmospheric components and cycle on a global scale

Carbon Cycle

Carbon dioxide is the pivotal molecule in the carbon cycle

Human activities, since the beginning of the Industrial Revolution, have contributed an increasing amount of carbon dioxide to the atmosphere by burning fossil fuels

Nitrogen Cycle

Bacteria are essential to this cycle Nitrogen fixing bacteria

converts nitrogen gas to ammonia

Nitrifying bacteria converts ammonia to nitrate

Denitrifying bacteria converts, anaerobes, convert nitrate to nitrogen gas

Nitrogen is needed for the production of proteins

Nitrogen oxides are also an ingredient in photochemical smog

Phosphorus Cycle

Fertilizers, runoff containing animal wastes, and sewage introduce phosphorus into aquatic ecosystems

Phosphorus loss accelerated by clear cutting Brazil

Water Cycle

Enough said!

THE SUN

Abiotic Factors in Ecosystems

The Sun

Warms the earthSolar energy

biogeochemical cycles

Temperature changes with latitude Sun’s rays strike the

equatorial regions vertically which result in warmer temperatures

The Sun II

Temperature changes with season Tilting of the Earth’s axis

causes the amount of solar radiation to vary during the year

How does this help with the establishment of ocean currents?

How does temperature change help with support life in standing bodies of water? More to come

Review