Ecosystems: What Are They and How Do They Work?

Chapter 3

3-1 What Is Ecology?



Concept 3-1 Ecology is the study of how organisms interact with one another and with their physical environment of matter and energy.

3-1 What Is Ecology?



Ecology

is a study of connections in nature.

• How organisms interact with one another and with their nonliving environment.

Species Make Up the Encyclopedia of Life

 

Organisms

– individual forms of life • Classified into species based on certain characteristics

Species

– a set of individuals that can mate and produce viable, fertile offspring • • 1.75 Million species identified Up to 10 –14 million species not yet identified??

• Insects make up most of the known species

Science Focus: Have You Thanked the Insects Today?

 Many times we classify insects as

pests

: • Compete with us for food • • • Spread human diseases Bite or sting us Can be a nuisance  However, they are VERY beneficial: • • • • Pollinators Eat other insects Loosen and renew soil Estimated $57 billion/yr in ecological services

Species Make Up the Encyclopedia of Life

 A

population

is a group of interacting individuals of the same species occupying a specific area.

• The space an individual or population normally occupies is its

habitat

.

Species Make Up the Encyclopedia of Life



Genetic diversity

• • In most natural populations individuals vary slightly in their genetic makeup.

These genetic diversity is crucial to the survival of the population.

Levels of Organization of Matter in Nature

  A community interacting with its physical environment of matter and energy is an

ecosystem

.

 Populations of different species living and interacting in an area form a

community

.

The •

biosphere

is where all of the Earth’s life is found A “global ecosystem”

3-2 What Keeps Us and Other Organisms Alive?



Concept 3-2 Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.

Natural Capital: General Structure of the Earth

 • • • The biosphere consists of several physical layers that contain: • • Air Water Soil Minerals Life

The Earth’s Life-Support System Has Four Major Components



Biosphere

– All of the life on the planet 

Atmosphere

• • – Membrane of air around the planet.

Troposphere

• – lowest layer - most gas of any layer where weather occurs

Stratosphere

– contains ozone to filter out most of the sun’s harmful UV radiation.



Hydrosphere

water vapor – All the earth’s water: liquid, ice, 

Geosphere

• •

Lithosphere

– The earth’s crust and upper mantle – hard outer crust

Asthenosphere

– molten interior

Three Factors Sustain Life on Earth

1.

• • One-way flow of energy beginning with the sun Follows the laws of thermodynamics Most is lost as heat 2.

• • Cycling of matter or nutrients Nutrients exist in a fixed amount Follows the law of conservation of matter 3.

Gravity

Flow of Energy to and from the Earth

 Solar energy flowing through the biosphere warms the atmosphere, evaporates and recycles water, generates winds and supports plant growth.



Natural greenhouse effect

– natural process that keeps the Earth warmer than it would otherwise be

Life Exists on Land and in Water

 Life exists on land systems called

biomes

and in freshwater and ocean aquatic life zones.

3-3 What Are the Major Components of an Ecosystem?



Concept 3-3A Ecosystems contain living (biotic) and nonliving (abiotic) components.



Concept 3-3B Some organisms produce the nutrients they need, others get their nutrients by consuming other organisms, and some recycle nutrients back to producers by decomposing the wastes and remains of organisms.

Ecosystems Have Living and Nonliving Components

 Ecosystems consist of living (

biotic

) and nonliving (

abiotic

) components.

• • • • • • • • •

Biotic or Abiotic?

Plants Water Animals Temperature Rocks/Minerals Bacteria Solar Energy Landforms Soil

Several Abiotic Factors Can Limit Population Growth

 Populations have a

range of tolerance

to variations in their physical and chemical environments.

Several Abiotic Factors Can Limit Population Growth

 Availability of matter and energy resources can limit the number of organisms in a population.



Limiting factor principle

• Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance

Several Abiotic Factors Can Limit Population Growth

 The physical conditions of the environment can limit the

distribution

( range ) of a species.

Producers and Consumers Are the Living Components of Ecosystems



Producers

, or

autotrophs

, make their own food from nutrients/energy obtained from the environment 

Most

producers capture sunlight to produce carbohydrates by

photosynthesis

:

** You must memorize this equation if you haven’t already. It will come up throughout the year.

Photosynthesis

 Chlorophyll molecules in the chloroplasts of plant cells absorb solar energy.

 This initiates a complex series of chemical reactions in which carbon dioxide and water are converted to sugars and oxygen.

Producers and Consumers Are the Living Components of Ecosystems

 Some organisms can obtain energy from inorganic compounds in their environment WITHOUT sunlight through a process called

chemosynthesis

.

• Deep ocean bacteria draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulfide (H 2 S) gas.

Producers and Consumers Are the Living Components of Ecosystems



Consumers

, or

heterotroph

, cannot produce their own food and, therefore, must obtain their nutrients by feeding on other organisms.

•

Herbivores

• Primary consumers that eat producers •

Carnivores

• • Secondary consumers eat primary consumers Third and carnivores higher-level consumers : carnivores that eat •

Omnivores

• Feed on both plant and animals

Producers and Consumers Are the Living Components of Ecosystems

• •

Detritivores

: Insects or other scavengers that feed on wastes or dead bodies ( detritus ) – physically break down

Decomposers

: Bacteria and/or fungi that use enzymes to recycle nutrients in ecosystems – chemically break down

Producers and Consumers Are the Living Components of Ecosystems

 Organisms break down carbohydrates and other organic compounds in their cells to obtain the energy they need.

 This is usually done through

aerobic respiration

.

•

Aerobic means “with oxygen” ** You must memorize this equation if you haven’t already. It will come up throughout the year.

Producers and Consumers Are the Living Components of Ecosystems

 Some decomposers get energy by breaking down glucose (or other organic compounds) WITHOUT oxygen through a process called

anaerobic respiration,

or

fermentation

•

Anaerobic means “without oxygen”

 The end products vary based on the chemical reaction: • • • • Methane gas Ethyl alcohol Acetic acid Hydrogen sulfide

Energy Flow and Nutrient Cycling Sustain Ecosystems and the Biosphere

 An ecosystem is sustained by a combination of a

one-way flow

of energy and the

cycling

of key nutrients.

Science Focus : Many of the World’s Most Important Species Are Invisible to Us

 • • • • Multitudes of tiny

microbes

such as bacteria, protozoa, fungi, and yeast help keep us alive.

• • Harmful microbes are the minority Soil bacteria (

nitrogen fixing bacteria

) convert nitrogen gas to a usable form for plants They help produce foods: bread, cheese, yogurt, beer, wine Make up 90% of all living mass on Earth Help purify water, provide oxygen, breakdown waste Live beneficially in your body (intestines, nose)

3-4 What Happens to Energy in an Ecosystem?



Concept 3-4A Energy flows through ecosystems in food chains and webs.



Concept 3-4B As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.

Energy Flows Through Ecosystems in Food Chains and Food Webs



Food chains

and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem.



The arrows point in the direction of the energy flow.

Energy Flows Through Ecosystems in Food Chains and Food Webs

 A

food web

shows the connections of all organisms within an ecosystem.

Usable Energy Decreases with Each Link in a Food Chain or Web



Biomass

– the dry weight of all organic matter contained in an organism(s).

 Chemical energy in biomass is transferred from one trophic level to another.

Pyramid of Energy Flow



Ecological efficiency

: percentage of useable energy transferred as biomass from one trophic level to the next.

• Typically, only 10% efficient (90% lost as heat)

Usable Energy Decreases with Each Link in a Food Chain or Web

 Food chains rarely have more than 4 steps or 3 trophic levels.

Why?

Usable Energy Decreases with Each Link in a Food Chain or Web

 In accordance with the

2 nd law of thermodynamics

, there is a decrease in the amount of energy available to each succeeding organism in a food chain or web.

• Cellular respiration - the breakdown of glucose to release energy – is only 38% efficient • Energy is lost as heat • Energy is also used for growth, reproduction, movement • Ultimately, only about 10% of the original energy is available for the next trophic level (

90% lost as heat

)

Some Ecosystems Produce Plant Matter Faster Than Others Do



Gross primary production

• (

GPP

) Rate at which an ecosystem’s producers convert solar energy into chemical energy (photosynthesis) as biomass.

Some Ecosystems Produce Plant Matter Faster Than Others Do



Net Primary Production

• (

NPP

) Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R).

 NPP = GPP – R

Estimated Annual Average NPP in Major Life Zones and Ecosystems

 What are nature’s most productive/least productive systems?

Info from notes handout

 Sample food chain

Info from notes handout

1.

Pyramid of Numbers 2.

Pyramid of Biomass 3.

Pyramid of Energy

3-5 What Happens to Matter in an Ecosystem?



Concept 3-5 Matter, in the form of nutrients, cycles within and among ecosystems and the biosphere, and human activities are altering these chemical cycles.

Nutrients Cycle in the Biosphere



Biogeochemical Cycles

recycle nutrients through the earth’s air, land, water, and living organisms.

• Nutrients are the elements and compounds that organisms need to live, grow, and reproduce.

• Biogeochemical cycles move these substances through air, water, soil, rock and living organisms.

 Connect past, present , and future forms of life

The Water Cycle

The Water Cycle

Effects of Human Activities on Water Cycle

 Humans alter the water cycle by: • Withdrawal of large amounts of freshwater at rates faster than nature can replace it • Clearing vegetation and eroding soils.

• Increased flooding when wetlands are drained • Polluting surface and underground water.

• Contributing to climate change.

• Increases melting, evaporation, precipitation, etc.

The Carbon Cycle

The Carbon Cycle

Effects of Human Activities on Carbon Cycle

 Humans alter the carbon cycle by adding excess CO 2 • to the atmosphere through: Burning fossil fuels • Clearing/burning vegetation faster than it is replaced

The Nitrogen Cycle

The Nitrogen Cycle

Nitrogen Cycles through the Biosphere: Bacteria in Action



Nitrogen fixation

– converting atmospheric N 2 into ammonia (NH 3 ) or ammonium (NH 4 ) that can be used by plants • • Lightning – ammonia falls to the ground with the rain

Nitrogen-fixing bacteria



Nitrification

–

Nitrifying bacteria

convert ammonium (NH 4 ) to nitrates (NO 3 ) and/or nitrites (NO 2 ) 

Denitrification

–

Denitrifying bacteria

convert ammonia, nitrates, or nitrites back into atmospheric N 2 .



Ammonification

– Decomposers convert ditritus into ammonia or ammonium.

Nitrogen Fixation: A Closer Look

Effects of Human Activities on the Nitrogen Cycle

 Humans alter the nitrogen cycle by: • • Adding gases that contribute to acid rain • NO and N 2 O Contaminating bodies of water with excess nitrates from inorganic fertilizers • Humans fix more nitrogen than all natural sources combined • Adding nitrogen to the troposphere through deforestation • Remove nitrogen from topsoil

The Phosphorous Cycle

The Phosphorous Cycle

Effects of Human Activities on the Phosphorous Cycle

 Cycles through water, the earth’s crust, and living organisms (

NOT the atmosphere like the others

)  May be limiting factor for plant growth  Humans alter the phosphorus cycle by: • We remove large amounts of phosphate from the earth to make fertilizer.

• We reduce phosphorous in tropical soils by clearing forests.

• We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

The Sulfur Cycle

The Sulfur Cycle

Effects of Human Activities on the Sulfur Cycle

 Sulfur found in organisms, ocean sediments, soil, rocks, and fossil fuels.

• Sulfur dioxide (SO 2 ) in the atmosphere  Humans alter the sulfur cycle by adding sulfur dioxide to the atmosphere through: • • • Burning sulfur-containing coal and oil Refining sulfur-containing petroleum Smelting sulfur-containing metallic mineral ores • These can all lead to acid rain • Sulfuric acid (H 2 SO 4 ) when SO 4 mixes with H 2 O