Chapter 3Ecosystems

Case Study: Have You Thanked the Insects Today?

Insects play a vital role in helping sustain life on earth.

Many food plants rely on insects to pollinate flowers.

Insectivorous insects help control pest populations

ex: ladybugs eat aphids

Insects adapt rapidly and can thrive when other organisms would go extinct, though most other organisms would perish quickly without them.

Ecology is the science related to the relationships and interactions in biological communities in nature – such as those between insects, plants, and people.

3-1 The Nature of Ecology

What is Ecology?Ecology - The study of how organisms interact with one another and with their nonliving environment.

Organism – any form of life. The cell is the basic unit of life in organisms. An organism may consist of one cell or many cells

Prokaryotic Cells – surrounded by a membrane but has no distinct nucleus or other internal parts enclosed by membranes. Ex: all bacteria are single-celled prokaryotic organisms.

Eukaryotic Cells – surrounded by a membrane and has a distinct nucleus and several organelles. Ex: all organisms except bacteria and some algae.

Species – groups of organisms that resemble one another in appearance, behaviour, chemistry, and genetic makeup and are able to produce fertile offspring. There are most likely 10-14 million species in the world other than Homo sapien

Case Study: What Species Rule the World? Small Matters!

Microbes are bacteria, protozoa, fungi, and yeasts

Harmful microbes that cause illness are in the minority

Microbes provide you with important nutrients, and produce foods such as dairy products and bread.

They decompose waste into nutrients, purify water, and break down the food you eat.

They prevent harmful bacteria from making you ill, are the sources of antibiotics, can help

clean up toxic waste, and help control plant diseases and pests.

What is a Population?

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

In a natural population, genetic makeup is varied – this is called genetic diversity

The place a population lives is its habitat

The area where a certain species is found is called its distribution or range

What are Communities and Ecosystems?

A community, or biological community, consists of all the populations of the different species living and interacting in an area.

An Ecosystem is a community of different species interacting with one another and with their environment of matter and energy.

All of the Earth’s ecosystems together make up the biosphere

The Earth’s Life Support Systems

What Are the Major Parts of the Earth’s Life-Support Systems?

• The Earth is made up of several spherical layers.

• The atmosphere is the thin envelope of air around the planet.

• The atmosphere’s inner layer, the Troposphere extends 17 km above sea level. It contains most of the planet’s air.

• The atmosphere’s next layer, the stratosphere, is 17-48 km above Earth’s surface. It contains ozone to filter out ultraviolet radiation. This allows life to exist on land and in the surface layers of bodies of water.

What Are the Major Parts of the Earth’s Life-Support Systems?

• The hydrosphere consists of the earth’s water – liquid, ice, and water vapor.

• The lithosphere is the earth’s crust and upper mantle; the crust contains nonrenewable fossil fuels and minerals, as well as renewable soil chemicals and minerals needed for plant life.

• The biosphere is the portion of the earth in which all living organisms exist and interact with one another and with their nonliving environment.

• All parts of the biosphere are interconnected. The goal of ecology is to understand the interactions in the earth.

What Sustains Life on Earth?Life on Earth depends on three interconnected factors:

The one-way flow of energy from the sun through materials and living things in their feeding interactions, into the environment as low-quality energy and eventually back into space as heat. Energy cannot be recycled.

The cycling of matter through parts of the biosphere. Nutrients are constantly recycled.

Gravity, which allows the planet to hold onto its atmosphere and causes the downward movement of chemicals in the matter cycles.

How Does the Sun Help Sustain Life on Earth?Energy from the sun supports most life on Earth by lighting and warming the planet.

The light from the sun supports photosynthesis and powers the cycling of matter and drives the climate and weather systems that distribute heat and fresh water.

Most solar radiation is degraded into infrared radiation with long wavelengths. This interacts with “greenhouse gasses” and causes them to vibrate and release infrared radiation with longer wavelengths into the troposphere. As the radiation interacts with molecules in the air, it increases their kinetic energy, helping to warm the earth. This is the natural greenhouse effect.

3-2 Ecosystem Components

What are Biomes and Aquatic Life Zones?Biologists have classified the terrestrial portion of the biosphere into Biomes.

Biomes are large areas of land classified by a distinct climate and specific species adapted to it.

Biologists have divided the watery parts of the biosphere into aquatic life zones.

Aquatic life zones are the water equivalent to biomes.

What are the Major Components of Ecosystems?

Two types of components make up the biosphere and all ecosystems.

• Abiotic components consist of nonliving components (water, air, nutrients, solar energy…)

• Biotic components are all biological components (plants, animals, microbes…)

How Tolerant are Organisms to Environmental Conditions?

Populations of different species can thrive under different physical conditions.

Different organisms have different physical and chemical needs in their environment.

Range of Tolerance is the range of extremes an organism can survive in its physical and chemical environment.

LAW OF TOLERANCE: the existence, abundance, and distribution of a species in an ecosystem are detemined by whether the levels of one or more physical or chemical factors fall within the range tolerated by that species.

What Factors Limit Population Growth?A variety of factors can affect the number of organisms in a population.

• A limiting factor is more important in regulating population growth than other factors.

• 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 optimum range of tolerance.

Common Limiting factors on land : soil nutrients, water, sunlight

Common aquatic limiting factors : temperature, sunlight, nutrient availability, and dissolved oxygen content (the amount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure), as well as salinity (the amount of various inorganic minerals or salts dissolved in a given volume of water).

What are the Major Biological Components of Ecosystems?

The Earth’s organisms either produce or consume food.

Producers/Autotrophs – organisms that make their own food from compounds obtained from their environment.

On land, most producers are green plants. Near shorelines, algae and plants are the main producers. In open water, most producers are phytoplankton – microscopic organisms that float or drift in the water.

Most producers capture sunlight to make carbohydrates like glucose by photosynthesis.

6 CO2 + 6 H2O + solar energy C6H12O6 + 6 O2

A few other producers,

mostly bacteria, convert

simple compounds from their

environment into more complex

nutrient compounds without

sunlight through a process

called chemosynthesis deep

Ocean hydrothermal vents with

Sulfur.

What are the Major Biological Components of Ecosystems?

What are the Major Biological Components of Ecosystems?

Consumers/Heterotrophs – organisms that get the energy and nutrients they need by feeding on other organisms or their remains.

Decomposers – are specialized consumers that recycle organic matter in ecosystems by breaking down dead organic material – detritus – to get nutrients. This releases simpler inorganic materials into the soil and water where producers take them up as nutrients.

What are the Major Biological Components of Ecosystems?

Omnivores – play dual roles by feeding on both plants and animals. Pigs, rats, foxes, bears, and humans are examples of omnivores.

Detrivores – detritus feeders and decomposers that feed on detritus.

What are the Major Biological Components of Ecosystems?

Producers, Consumers, and Decomposers all use chemical energy stored in glucose and other organic compounds to fuel their life processes.

In most cells, this energy is released through aerobic respiration which uses oxygen to convert organic nutrients back into Carbon dioxide and water.

C6H12O6 + 6 O2 6 CO2 + 6 H20 + energy

What are the Major Biological Components of Ecosystems?

• Some decomposers get the energy they need by breaking down glucose or other organic compounds in the absence of oxygen through anaerobic respiration or fermentation.

• Instead of carbon dioxide and water, the end products of this process are compounds such as methane gas, ethyl alcohol, acetic acid, and hydrogen sulfide.

What are the Major Biological Components of Ecosystems?

• The survival of any organism depends on the flow of matter and energy through its body.

• An Ecosystem survives through a combination of matter recycling and one-way energy flow.

Decomposers eat waste and recycle nutrients, providing us with crucial ecological service by putting nutrients back into the cycle of nutrients, Thus ending andbeginning the cycle again.

What is Biodiversity?• Biodiversity – varieties of life (bio = life/ diverse = variety)

There are different kinds of diversity found throughout an ecosystem.

• Genetic Diversity – variety of genetic material within a species or population

• Species Diversity – the number of species present in different habitats

• Ecological Diversity – the variety of terrestrial and aquatic ecosystems found in an area

• Functional Diversity – the biological and chemical processes such as energy flow and matter cycling needed for the survival of species, communities, and ecosystems.

What is Biodiversity?

• Biodiversity is the biological wealth or capital that helps keep us alive.

• Biodiversity supplies us with food, wood, energy, raw materials, industrial chemicals, and medicines.

• It preserves the quality of air and water, the fertility of soils, disposes of wastes, and controls populations of pests.

• It is a renewable resource as long as we live off the biological income it provides

• Loss and degradation of biodiversity is the most important environmental problem we face – and it is linked to all other environmental problems.

3-3 Energy Flow in Ecosystems

What are Food Chains and Food Webs?• All organisms whether they are dead or alive are a a

source of food for other organisms. This results in little matter waste in natural ecosystems.

• Food Chain – the sequence of organisms in which each organism is a source of food for the next. This determines how energy and nutrients move from one organism to another in an ecosystem.

What are Food Chains and Food Webs?• Ecologists assign each organism in an ecosystem a

feeding level. This is the organism’s trophic level.

• Each organism’s level depends on whether that organism is a producer or consumer and what it eats or decomposes.

Detritivores

and decomposers

process detritus

from all

trophic levels.

What are Food Chains and Food Webs?

Most species operate in several different food chains.

Food Web – the complex network of interconnected food chains in an ecosystem. It shows how eaters, the

eaten, and the

decomposed are all

interconnected.

How Can We Represent the Energy Flow in an Ecosystem?

• Each trophic level in a food chain or food web contains a certain amount of biomass (the dry weight of all organic matter in an ecosystem’s organisms). The energy in biomass is transferred amoung the trophic levels.

• Energy transfer through the trophic levels is not efficient. Usable energy is degraded to unusable low-quality heat with each transfer.

• Ecological Efficiency - The percentage of usable energy transferred as biomass from one trophic level to another. It ranges from a loss of 60% to 98% depending on the types of species and ecosystem involved. Typically, it is 10%.

How can we Represent the Energy Flow in an Ecosystem?

• The more trophic levels in a food chain or web, the greater cumulative loss of usable energy as energy flows through the various

trophic levels.

• Pyramid of Energy Flow

illustrates the

energy loss for a

Simple food chain.

*Pyramid of numbers

*Pyramid of Biomass

3-4 Matter Cycling in Ecosystems

What are Biochemical Cycles?

• All organisms rely on nutrients supplied by nutrient cycles (biogeochemical cycles).

• They supply carbon, oxygen, nitrogen, phosphorous, and water.

The Water Cycle

How is Water Cycled in the Biosphere?

• The water cycle recycles the earth’s fixed supply of water.

• Some of the water returns to earth as rain or snow – in order for precipitation there must be condensation nuclei in the atmosphere on which water vapor can collect.

How are Human Activities Affecting the Water Cycle?

• We withdraw large quantities of fresh water from streams, lakes, and underground sources.

• We clear vegetation and lay asphalt and concrete. This increases runoff, reduces infiltration that recharges groundwater supplies, increases the risk of flooding, and accelerates erosion and landslides.

• We modify water quality by adding nutrients and other pollutants.

The Carbon Cycle

How is Carbon Recycled in the Biosphere?

• Carbon is the basic building block of the carbohydrates, fats, proteins, DNA, and other organic compounds essential to life.

• Carbon makes up .038% of the volume of the troposhpere.

• Carbon dioxide determines the temperature of the Earth – if there’s too little it gets really cold, and if there’s too much it gets really hot.

How are Human Activities Affecting the Carbon Cycle?

• In some areas we clear trees and other plants that absorb CO2 through photosynthesis faster than they can grow back.

• We add large amounts of CO2 to the atmosphere by burning fossil fuels and wood.

The Nitrogen Cycle

How is Nitrogen Cycled in the Biosphere?

• Nitrogen is the atmosphere’s most abundant element, making up about 78% of the volume of the troposphere.

• Nitrogen is a crucial component of proteins, many vitamins, and DNA and RNA.

• N2 cannot be absorbed and metabolized directly, and goes through two natural processes that convert is into compounds that can enter food webs.

How are Human Activities Affecting the Nitrogen Cycle?

• We add large amounts of nitric oxide to the atmosphere when we burn any fuel.

• We add nitrous oxide to the atmosphere through the action of anaerobic bacteria on livestock wastes and commercial inorganic fertilizers applied to the soil.

• We release large quantities of nitrogen stored in soils and plants as gaseous compounds into the troposphere through destruction of forests, grasslands, and wetlands.

• We upset aquatic ecosystems by adding excess nitrates in agricultural runoff and discharges from municipal sewage systems.

• We remove nitrogen from the topsoil when we harvest nitrogen-rich crops, irrigate crops, and burn or clear grasslands and forests before planting crops.

The Phosphorous Cycle

How is Phosophorous Cycled in the Biosphere?

• Phosphorous is typically found as phosphate salts containing phosphate ions in terrestrial rock formations and ocean bottom sediments.

• Phosphate can be lost from the cycle for long periods of time when it washes from the land into streams and rivers and is carried to the ocean.

• Phosphate is often a limiting factor for plant growth because most soil contains so little.

How are Human Activities Affecting the Phosphorous Cycle?

• We mine large quantities of phosphate rock to make commercial inorganic fertilizers.

• We reduce the available phosphate in tropical soils when we cut down areas of tropical forests.

• We disrupt aquatic systems with phosphates from runoff of animal wastes and fertilizers and discharges from sewage treatment systems.

The Sulfur Cycle

How Is Sulfur Cycled in the Biosphere?

• Much of the earth’s sulfur is stored in underground rocks and minerals

• Hydrogen sulfide is released from active volcanoes and in swamps, bogs, and tidal flats broken down by anaerobic decomposers.

• Sulfur dioxide comes from volcanoes.

How are Human Activities Affecting the Sulfur Cycle?

• We burn sulfur-containing coal and oil to produce elevtric power.

• We refine sulfur-containing petroleum to make gasoline, heating oil, and other useful products.

• We convert sulfur-containing metallic mineral ores into free metals such as copper, lead and zinc.

3-5How Do Ecologists Learn About

Ecosystems?

What is Field Research?• Field Research involves going into nature and observing the structure of

ecosystems and what happens in them.

• Sometimes Ecologists carry out controlled experiments by isolating and changing a variable in part of an area and comparing the results with nearby unchanged areas.

• Remote Sensing and geographic information systems gather information

from broad geographic regions

and store it in special databases.

The data is manipulated and

combined with ground and other

data by computers.

How are Ecosystems Studied in the Laboratory?• Simplified systems can be set up in container such as

culture tubes, bottles, aquarium tanks, and greenhouses in indoor and outdoor chambers where temperature, light, carbon dioxide, humidity, and other variables are controlled carefully.

• Lab experiments are quicker

and cheaper than field study.

• Lab research must be coupled

with and supported by field

research.

What is Systems Analysis?• Systems analysis helps to develop mathematical and other models

that simulate ecosystems.

• Computer simulation of such models can help us understand large and very complex systems that cannot be adequately studied and modeled in field and lab research.

• Simulations and projections made using ecosystem models are no better than the data and assumptions used to develop the models.

Why do We Need Baseline Ecological Data?• Before we can understand what is happening to an

ecosystem, community, or population and how best to prevent harmful environmental changes, we need to know its current condition.

• Baseline Data – information about components, physical and chemical conditions, and how well something is functioning.

• If we do not know how many tigers are in india, we cannot determine whether their populations are inclining or decreasing.

So Basically…

In order to achieve long-term sustainability we need to

1. use renewable solar energy as our energy source, and

2. recycle and conserve the chemical nutrients organisms need for survival, growth, and reproduction.

Bibliography

• http://www.emc.maricopa.edu/faculty/farabee/biobk/lactferm.gif

• http://www.uic.edu/classes/bios/bios100/lecturesf04am/lactica.jpg

• Living in the Environment, Fourteenth Ed. By G. Tyler Miller, Jr.

• www.bigelow.org/edhab/fitting_algae.html • www.google.com• http://www.fossweb.com/resources/pictures/163

27852.gif• www.wildnatureimages.com/.../C6CT4387..jpg