Essentials of Ecology

74 CHAPTER 3 Ecosystems: What Are They and How Do They Work?

among key variables that they will use to develop and

test ecosystem models.

RESEARCH FRONTIER

Improved computer modeling for understanding complex

environmental systems. See academic.cengage.com/

biology/miller.

We Need to Learn More about the

Health of the World’s Ecosystems

We need baseline data on the condition of the world’s

ecosystems to see how they are changing and to de-

velop effective strategies for preventing or slowing their

degradation.

By analogy, your doctor needs baseline data on

your blood pressure, weight, and functioning of your

organs and other systems, as revealed through basic

tests. If your health declines in some way, the doctor

can run new tests and compare the results with the

baseline data to identify changes and come up with a

treatment.

According to a 2002 ecological study published by

the Heinz Foundation and the 2005 Millennium Eco-

system Assessment, scientists have less than half of the

basic ecological data they need to evaluate the status of

ecosystems in the United States. Even fewer data are

available for most other parts of the world. Ecologists

call for a massive program to develop baseline data for

the world’s ecosystems.

RESEARCH FRONTIER

A crash program to gather and evaluate baseline data for

all of the world’s major terrestrial and aquatic systems. See

academic.cengage.com/biology/miller.

All things come from earth,

and to earth they all return.

MENANDER (342–290 B.C.)

REVIEW

1. Review the Key Questions and Concepts for this chapter
   on p. 51. What are three harmful effects resulting from
   the clearing and degradation of tropical rain forests?


2. What is a cell? What is the cell theory? Distinguish
   between a eukaryotic cell and a prokaryotic cell.
   What is a species? Explain the importance of insects.

Defineecology. What is genetic diversity? Distin-

guish among a species, population, community (bio-

logical community), habitat, ecosystem, and the

biosphere.

3. Distinguish among the atmosphere, troposphere,
   stratosphere, greenhouse gases, hydrosphere, and

Tropical Rain Forests and Sustainability

This chapter applied two of the scientific principles of sustain-

ability (see back cover and Concept 1-6, p. 23) by which the

biosphere and the ecosystems it contains have been sustained

over the long term. First, the biosphere and almost all of its eco-

systems use solar energy as their energy source, and this energy

flows through the biosphere. Second, they recycle the chemical

nutrients that their organisms need for survival, growth, and re-

production.

These two principles arise from the structure and function of

natural ecosystems (Figure 3-12), the law of conservation of mat-

ter (Concept 2-3, p. 39), and the two laws of thermodynamics

(Concepts 2-4A and 2-4B, p. 40). Nature’s required adherence

to these principles is enhanced by biodiversity, another sustain-

ability principle, which also helps to regulate population levels of

interacting species in the world’s ecosystems—yet another of the

sustainability principles.

This chapter started with a discussion of the importance of

incredibly diverse tropical rain forests (Core Case Study), which

showcase the functioning of the four scientific principles of

sustainability. Producers within rain forests rely on solar energy

to produce a vast amount of biomass through photosynthesis.

Species living in the forests take part in, and depend on cycling

of nutrients in the biosphere and the flow of energy through

the biosphere. Tropical forests contain a huge and vital part of

the earth’s biodiversity, and interactions among species living in

these forests help to control the populations of the species living

there.

REVISITING