Chapter 2Ecosystems: What They Are

Copyright © 2008 Pearson Prentice Hall, Inc.

EnvironmentalScienceTenth Edition

Richard T. Wright

Ecosystems: What Are They?

• Ecosystems: A Description• The Structure of Ecosystems• From Ecosystems to Global Biomes• The Human Factor

Some Terms and Definitions

• Ecosystems: A grouping of plants, animals, and microbes occupying an explicit unit of space and interacting with each other and their environment.

• Ecosystem: a dynamic complex of plant, animal, and microorganism communities and the nonliving environment interacting as a functional unit within an explicit space.

• Ecosytems: Units of Sustainable life on earth

ECOSYSTEM: MA DEFINITION

• A dynamic complex of plant, animal, and microorganism communities and the nonliving environment interacting as a functional unit within an explicit space.– a lake, a wetland, a coral reef, …

• Humans are an integral part of ecosystems• Can be investigated ECOLOGY

– study of ecosystems and all processes that determine the distribution of species and their interactions.

How Ecosystems Are Formed

AbioticsAbiotic factors: non-living, chemical, physical

Plants

Animals

(moisture and temperature)

(+ moisture = forest)(temperature = forest type)

(lynx or bobcat)

predict

predict

Ecosystem Types in the United States

• Coasts and oceans• Farmlands• Forests• Fresh waters• Grasslands and shrub lands• Urban and suburban areas

Ecosystems: A Description

• Biotic communities: grouping or assemblage of plants, animals, and microbes.

• Species: different kinds of plants, animals, and microbes in the community

• One species: individuals that are similar in appearance and distinct form other individuals.

• Biological definition of a species: the entirety of a population that can interbreed and produce fertile offspring in the community.

Ecosystems: A Description• Population: number of individuals that make up

the interbreeding, reproducing group in a given area.

• Association: a plant community with definite composition, uniform habitat characteristics and uniform plant growth.– Is determined by abiotic factors.– (explains the nature of the biotic community, how it fits in

the landscape)

• Ecotone: Transitional region between different ecosystems.

Ecotones on Land

• Shares many of the species and characteristics of both ecosystems

• May also include unique conditions that support distinctive plant and animal species

Terrestrial-to-Aquatic-System Ecotone

• Shares many of the species and characteristics of both ecosystems

• May also include unique conditions that support distinctive plant and animal species

Landscape, Biomes and the Biosphere• Landscape: group of interacting ecosystems

– Lake, march, dry land• Biomes: similar or related ecosystems or landscapes

– deserts, tropical rain forests (Terrestrial) – Transitional zones between biomes

• Aquatic systems– Lakes, rivers, wetlands, Ocean

• Biosphere: Everything is connected in the Biosphere.– ALL ecosystems. Gigantic space (“dry” and wet) in which we

(all animals, plants, microorganisms) exist and the non-living matter in it.

The Structure of Ecosystems

• Trophic categories :• Trophic relationships: food chains, food webs,

trophic levels.• Nonfeeding relationships: symbiosis• Abiotic factors

AutotrophsAutotrophs = Producers = Self feeders= Producers = Self feeders

6CO2 + 6H2O + Sun light C6H12O6+6O2

-They make their own organic matter from inorganic molecules and energy from the sun (photosynthetic) or chemical reactions (chemosynthetic)

-PhotosynthesisChlorophyll: green pigment, site of light capture

Proteins, carbohydrates(Carbon, Hydrogen, C-H bonds)

Consumers = HeterotrophsFeed on organic matter for energy and growth

• Primary consumers = herbivores = rabbit: eat plant material

• Secondary consumers = carnivores = predators = coyotes: prey are herbivores and other animals.

Consumers = Heterotrophs

• Parasites = predator = either plant or animal: prey are plants or animals.

DoddlersAscarisLumbricoides

Lampreys

Detritus Food Web

• Detritus: dead organic matter

• Detritus feeders• Primary d feeders

– Decomposers:bacteriaand fungi- cause rotting

• Secondary d feeders

Trophic Relationships: Food Chain

Third-order Consumer

Secondary Consumer

Primary Consumer

Producer

Match Organisms with Trophic Level(s)Trophic Levels

Organisms Producer Primary Consumer

Secondary Consumer

Third-Order Consumer

Plants X

Rabbits X

Snakes X X

Owls X X

Bacteria X X X X

Food Webs = Food Chain Interrelationships

Trophic Level Energy Flow

Producer 10,000 Kcal

Third-order Consumer

Secondary Consumer

Primary Consumer- 100x

- 10x

- 10x

100 Kcal

10 Kcal

1Kcal

How do you measure energy?

How far can you go?

Biomass Pyramid

Biomass: total combined dry weight of all organisms at a trophic level

Running out ofBiomass!!!

Trophic Levels: Pyramid of Energy

1

2

3

4

5Which level is occupied by:producers?primary consumers?secondary consumers?third-order consumers?

Nutrient Cycles and Energy Flow

Nonfeeding (Symbiotic) Relationships

• + And + = Mutualism. Both species benefit by the interaction between the two species. Honey bee and flower, Lichens (alga and fungi)

• + And 0 = Commensalism. One species benefits from the interaction and the other is unaffected.

Barnacle riding on a turtle shell

Cattle Egret

Nonfeeding (Symbiotic) Relationships

• + And - = One species benefits from the interaction and the other is adversely affected. Examples are parasitism

Competitive Relationships

Resource Partitioning: Reducing Competition in a habitat by usage of different niche

Niche: the what, where, when of feeding and meeting other needs

Abiotic Factors

• Law of Limiting Factors: “Every species (both plant and animal) has an optimum range, zones of stress, and limits of tolerance with respect to every abiotic factor.”

Survival Curves Illustrate Law of Limiting Factors

Application of the Law of Limiting Factors

• Compare the “tolerance” differences for a trout and a catfish using water:– temperature (cold or warm).– oxygen concentration (high or low).– salinity (high or low).

Oxygen Tolerance Curves for Two Different Fish Species

Diagram the temperature tolerance curves for each fish species.

Temp-9-13ºC

From Ecosystems to Global Biomes

• The role of climate• Microclimate and other abiotic factors• Biotic factors• Physical barriers

Climate and Major Biomes

Identify Biomes A to E Based on Temperature and Precipitation Levels:

Precipitation

Tem

pera

ture

Low High

High

A

B

C

D

E

Answers• A has high temperature and low moisture = hot desert• B has low temperature and low moisture = cold desert

(tundra with permafrost)• C has medium temperatures and moisture = grassland• D has high temperature and moisture = rain forest• E has low temperature and high precipitation = arctic

poles

Effects of Latitude and Altitude

Microclimates

Exposed or sheltered siteVariation in ecosystems within a biome

The Human Presence

• Three revolutions– Neolithic – Industrial– Environmental

• Red Sky in the Morning by James Gustave

• The Inconvenient Truth by Al Gore

How Humans Modify Their Physical Environments to Meet Their Needs

• Produce abundant food• Control water flow rate and direction• Overcome predation and disease• Construct our own ecosystems• Overcome competition with other species