Chapter 2Ecosystems: What They Are

Copyright © 2008 Pearson Prentice Hall, Inc.

2.1 - Ecosystems: What Are They?

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

• 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

• Ex. edge of a forest, marshland

Terrestrial-to-Aquatic-System Ecotone

How Ecosystems Are Formed

Abiotics

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.

• Populations: number of individuals that make up the interbreeding, reproducing group.

How Habitat and Animal Diversity Are Related

Hab

itat

Div

ersi

ty

Animal Diversity

Diversity = number of different species

2.2 - The Structure of EcosystemsAutotrophs are the basis for ecosystems.2.2 - The Structure of Ecosystems

Autotrophs are the basis for ecosystems.

Inorganic vs. Organic

*Some autotrophs can use energy in inorganic chemicals to form organic matter from CO2 and water = chemosynthesis. Ex. some bacteria

Consumers = Heterotrophs• 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.

Detritus Food Web

*decomposers are primary detritus feeders

Trophic Categories

Trophic Relationships: Food Chain

Trophic Relationships: Food Chain

Third-order Consumer (C3)

Secondary Consumer (C2)

Primary Consumer (C1)

Producer (P)

Trophic Relationships Among Producers and Consumers

Trophic Level Energy FlowTrophic Level Energy Flow

Producer 10,000 Kcal

Third-order Consumer

Secondary Consumer

Primary Consumer- 100x

- 10x

- 10x

100 Kcal

10 Kcal

1Kcal

Biomass Pyramid

Trophic Levels: Pyramid of Biomass or Pyramid of EnergyTrophic Levels: Pyramid of Biomass or Pyramid of Energy

1

2

3

4

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

Symbiotic Relationships

• + And + = Mutualism. Both species benefit by the interaction between the two species. Honey bee and flower

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

Symbiotic Relationships

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

• - And - = Competition. Both species are adversely affected by the interaction.

Resource Partitioning: Reducing Competition

*this allows organisms to avoid competition and all benefit.

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 biotic 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

What do you think the temperature tolerance curves for each fish species would look like?

2.3 - Climate and Major Biomes

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

Answers Next Slide

Precipitation

Temperature

Low High

High

A

B

C

D

E

Answers to Previous Slide• 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 AltitudeEffects of Latitude and Altitude

Microclimates

2.4 - 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 - agriculture• Control water flow rate and direction -

irrigation• Overcome predation and disease• Construct our own ecosystems• Overcome competition with other species