Ecosystems: What Are They and How Do They Work? Chapter 3

Core Case Study: Tropical Rain Forests Are Disappearing  Cover about 2% of the earth’s land surface  Contain about 50% of the world’s known plant and animal species  Disruption will have three major harmful effects Reduce biodiversity Accelerate global warming Change regional weather patterns

Natural Capital Degradation: Satellite Image of the Loss of Tropical Rain Forest

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.

Cells Are the Basic Units of Life  Cell Theory  Eukaryotic cell  Prokaryotic cell

Structure of a Eukaryotic Call and a Prokaryotic Cell

Species Make Up the Encyclopedia of Life  Species  1.75 Million species identified  Insects make up most of the known species  Perhaps 10–14 million species not yet identified

Ecologists Study Connections in Nature  Ecology  Levels of organization Population Genetic diversity Community Ecosystem Biosphere

Some Levels of Organization of Matter in Nature

Fig. 3-3, p. 52 Parts of the earth's air, water, and soil where life is found Biosphere Smallest unit of a chemical element that exhibits its chemical properties Ecosystem Community Population Organism A community of different species interacting with one another and with their nonliving environment of matter and energy Populations of different species living in a particular place, and potentially interacting with each other A group of individuals of the same species living in a particular place Cell An individual living being The fundamental structural and functional unit of life Molecule Atom Chemical combination of two or more atoms of the same or different elements

Population of Glassfish in the Red Sea

Genetic Diversity in a Caribbean Snail Population

Science Focus: Have You Thanked the Insects Today?  Pollinators  Eat other insects  Loosen and renew soil  Reproduce rapidly  Very resistant to extinction

Importance of Insects

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.

The Earth’s Life-Support System Has Four Major Components  Atmosphere Troposphere Stratosphere  Hydrosphere  Geosphere  Biosphere

Natural Capital: General Structure of the Earth

Life Exists on Land and in Water  Biomes  Aquatic life zones Freshwater life zones Lakes and streams Marine life zones Coral reefs Estuaries Deep ocean

Major Biomes along the 39 th Parallel in the U.S.

Three Factors Sustain Life on Earth  One-way flow of high-quality energy beginning with the sun  Cycling of matter or nutrients  Gravity

What Happens to Solar Energy Reaching the Earth?  UV, visible, and IR energy  Radiation Absorbed by ozone Absorbed by the earth Reflected by the earth Radiated by the atmosphere as heat  Natural greenhouse effect

Flow of Energy to and from the Earth

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  Abiotic Water Air Nutrients Rocks Heat Solar energy  Biotic Living and once living

Major Biotic and Abiotic Components of an Ecosystem

Range of Tolerance for a Population of Organisms INSERT FIGURE 3-10 HERE

Several Abiotic Factors Can Limit Population Growth  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

Producers and Consumers Are the Living Components of Ecosystems (1)  Producers, autotrophs Photosynthesis Chemosynthesis  Consumers, heterotrophs Primary Secondary Third and higher level  Decomposers

Producers and Consumers Are the Living Components of Ecosystems (2)  Detritivores  Aerobic respiration  Anaerobic respiration, fermentation

Detritivores and Decomposers on a Log

Energy Flow and Nutrient Cycling Sustain Ecosystems and the Biosphere  One-way energy flow  Nutrient cycling of key materials

The Main Structural Components of an Ecosystem

Science Focus: Many of the World’s Most Important Species Are Invisible to Us  Microorganisms Bacteria Protozoa Fungi

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 chain  Food web

A Food Chain

Simplified Food Web in the Antarctic

Usable Energy Decreases with Each Link in a Food Chain or Web  Biomass  Ecological efficiency  Pyramid of energy flow

Pyramid of Energy Flow

Some Ecosystems Produce Plant Matter Faster Than Others Do  Gross primary productivity (GPP)  Net primary productivity (NPP) Ecosystems and life zones differ in their NPP

Estimated Annual Average NPP in Major Life Zones and Ecosystems

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, nutrient cycles Hydrologic Carbon Nitrogen Phosphorus Sulfur  Connect past, present, and future forms of life

Water Cycles through the Biosphere  Natural renewal of water quality: three major processes Evaporation Precipitation Transpiration  Alteration of the hydrologic cycle by humans Withdrawal of large amounts of freshwater at rates faster than nature can replace it Clearing vegetation Increased flooding when wetlands are drained

Hydrologic Cycle Including Harmful Impacts of Human Activities

Science Focus: Water’s Unique Properties  Properties of water due to hydrogen bonds between water molecules: Exists as a liquid over a large range of temperature Changes temperature slowly High boiling point: 100˚C Adhesion and cohesion Expands as it freezes Solvent Filters out harmful UV

Carbon Cycle Depends on Photosynthesis and Respiration  Link between photosynthesis in producers and respiration in producers, consumers, and decomposers  Additional CO 2 added to the atmosphere Tree clearing Burning of fossil fuels

Natural Capital: Carbon Cycle with Major Harmful Impacts of Human Activities

Nitrogen Cycles through the Biosphere: Bacteria in Action (1)  Nitrogen fixed Lightning Nitrogen-fixing bacteria  Nitrification  Denitrification

Nitrogen Cycles through the Biosphere: Bacteria in Action (2)  Human intervention in the nitrogen cycle Additional NO and N 2 O Destruction of forest, grasslands, and wetlands Add excess nitrates to bodies of water Remove nitrogen from topsoil

Nitrogen Cycle in a Terrestrial Ecosystem with Major Harmful Human Impacts

Annual Increase in Atmospheric N 2 Due to Human Activities

Phosphorus Cycles through the Biosphere  Cycles through water, the earth’s crust, and living organisms  May be limiting factor for plant growth  Impact of human activities Clearing forests Removing large amounts of phosphate from the earth to make fertilizers

Phosphorus Cycle with Major Harmful Human Impacts

Sulfur Cycles through the Biosphere  Sulfur found in organisms, ocean sediments, soil, rocks, and fossil fuels  SO 2 in the atmosphere  H 2 SO 4 and SO 4 -  Human activities affect the sulfur cycle Burn sulfur-containing coal and oil Refine sulfur-containing petroleum Convert sulfur-containing metallic mineral ores

Natural Capital: Sulfur Cycle with Major Harmful Impacts of Human Activities

3-6 How Do Scientists Study Ecosystems?  Concept 3-6 Scientists use field research, laboratory research, and mathematical and other models to learn about ecosystems.

Some Scientists Study Nature Directly  Field research: “muddy-boots biology”  New technologies available Remote sensors Geographic information system (GIS) software Digital satellite imaging  2005, Global Earth Observation System of Systems (GEOSS)

Some Scientists Study Ecosystems in the Laboratory  Simplified systems carried out in Culture tubes and bottles Aquaria tanks Greenhouses Indoor and outdoor chambers  Supported by field research

Some Scientists Use Models to Simulate Ecosystems  Computer simulations and projections  Field and laboratory research needed for baseline data

We Need to Learn More about the Health of the World’s Ecosystems  Determine condition of the world’s ecosystems  More baseline data needed

Biodiversity and Evolution Chapter 4

Core Case Study: Why Should We Care about the American Alligator?  Largest reptile in North America  1930s: Hunters and poachers  Importance of gator holes and nesting mounds  1967: endangered species  1977: comeback, threatened species

The American Alligator

4-1 What Is Biodiversity and Why Is It Important?  Concept 4-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth.

Biodiversity Is a Crucial Part of the Earth’s Natural Capital  Vital renewable resource  Species diversity  Ecosystem diversity  Functional diversity

Natural Capital: Major Components of the Earth’s Biodiversity

4-2 Where Do Species Come From?  Concept 4-2A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations.  Concept 4-2B Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

Biological Evolution by Natural Selection Explains How Life Changes over Time  Biological evolution  Natural selection Charles Darwin Alfred Russel Wallace  Tree of Life

Six Major Kingdoms of Species as a Result of Natural Selection

The Fossil Record Tells Much of the Story of Evolution  Fossils Physical evidence of ancient organisms Reveal what their internal structures looked like  Fossil record is incomplete: why?

Fossilized Skeleton of an Herbivore that Lived during the Cenozoic Era

The Genetic Makeup of a Population Can Change  Populations evolve by becoming genetically different  Genetic variations First step in biological evolution Occurs through mutations in reproductive cells

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring  Natural selection: acts on individuals Second step in biological evolution Adaptation may lead to differential reproduction Genetic resistance  When environmental conditions change, populations Adapt Migrate Become extinct

Evolution by Natural Selection

Case Study: How Did Humans Become Such a Powerful Species?  Three human adaptations Strong opposable thumbs Walk upright Complex brain

Adaptation through Natural Selection Has Limits  Genetic change must precede change in the environmental conditions  Reproductive capacity

Three Common Myths about Evolution through Natural Selection  “Survival of the fittest” is not “survival of the strongest”  Organisms do not develop traits out of need or want  No grand plan of nature for perfect adaptation

4-3 How Do Geological Processes and Climate Change Affect Evolution?  Concept 4-3 Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.

Geologic Processes Affect Natural Selection  Tectonic plates affect evolution and the location of life on earth Location of continents and oceans Species physically move, or adapt, or form new species through natural selection  Earthquakes  Volcanic eruptions

Movement of the Earth’s Continents over Millions of Years

Climate Change and Catastrophes Affect Natural Selection  Ice ages followed by warming temperatures  Collisions between the earth and large asteroids New species Extinction

Changes in Ice Coverage in the Northern Hemisphere During the last 18,000 Years

Science Focus: Earth Is Just Right for Life to Thrive  Certain temperature range  Dependence on water  Rotation on its axis  Revolution around the sun  Enough gravitational mass

4-4 How Do Speciation, Extinction, and Human Activities Affect Biodiversity?  Concept 4-4A As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity.  Concept 4-4B Human activities can decrease biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.

How Do New Species Evolve?  Geographic isolation  Reproductive isolation

Geographic Isolation Can Lead to Reproductive Isolation

Extinction is Forever  Extinction  Endemic species Particularly vulnerable

Golden Toad of Costa Rica, Extinct

Extinction Can Affect One Species or Many Species at a Time  Background extinction  Mass extinction How numbered is debated: 3–5

Science Focus: We Have Two Ways to Change the Genetic Traits of Populations  Artificial selection  Genetic engineering, gene splicing  Consider Ethics Morals Privacy issues Harmful effects

Genetically Engineered Mice

4-5 What Is Species Diversity and Why Is It Important?  Concept 4-5 Species diversity is a major component of biodiversity and tends to increase the sustainability of ecosystems.

Species Diversity: Variety, Abundance of Species in a Particular Place  Species diversity Species richness Species evenness  Diversity varies with geographical location Most species-rich communities Tropical rain forests Coral reefs Ocean bottom zone Large tropical lakes

Variations in Species Richness and Species Evenness

Science Focus: Species Richness on Islands  Species equilibrium model, theory of island biogeography Rate of new species immigrating should balance with the rate of species extinction  Island size and distance from the mainland need to be considered

Species-Rich Ecosystems Tend to Be Productive and Sustainable  Species richness seems to increase productivity and stability or sustainability  How much species richness is needed is debatable

4-6 What Roles Do Species Play in Ecosystems?  Concept 4-6A Each species plays a specific ecological role called its niche.  Concept 4-6B Any given species may play one or more of five important roles—native, nonnative, indicator, keystone, or foundation roles—in a particular ecosystem.

Each Species Plays a Unique Role in Its Ecosystem  Ecological niche, niche Pattern of living  Generalist species Broad niche  Specialist species Narrow niche

Specialist Species and Generalist Species Niches

Case Study: Cockroaches: Nature’s Ultimate Survivors  Cockroaches Generalists High reproductive rates  Giant panda and tiger salamanders Specialists Low reproductive rates

Cockroach

Specialized Feeding Niches of Various Bird Species in a Coastal Wetland

Niches Can Be Occupied by Native and Nonnative Species  Native species  Nonnative species; invasive, alien, or exotic species May spread rapidly Not all are villains

Indicator Species Serve as Biological Smoke Alarms  Indicator species Can monitor environmental quality Trout Birds Butterflies Frogs

Case Study: Why Are Amphibians Vanishing? (1)  Habitat loss and fragmentation  Prolonged drought  Pollution  Increase in UV radiation  Parasites  Viral and fungal diseases  Climate change  Overhunting  Nonnative predators and competitors

Case Study: Why Are Amphibians Vanishing? (2)  Importance of amphibians Sensitive biological indicators of environmental changes Adult amphibians Important ecological roles in biological communities Genetic storehouse of pharmaceutical products waiting to be discovered

Life Cycle of a Frog

Keystone, Foundation Species Determine Structure, Function of Their Ecosystems  Keystone species Pollinators Top predator  Foundation species Create or enhance their habitats, which benefit others Elephants Beavers

Case Study: Why Should We Protect Sharks?  Keystone species Eat dead and dying fish in the ocean Strong immune systems Wounds do not get infected Almost never get cancer Could help humans if we understood their immune system