Essentials of Ecology

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

Sulfur

in animals

(consumers)

Processes

Reservoir

Pathway affected by humans

Natural pathway

Refining

fossil fuels

Burning

coal

Smelting

Mining and

extraction

Sulfur

in plants

(producers)

Decay

Uptake

by plants

Sulfuric acid

and Sulfate

deposited as

acid rain

Sulfur dioxide

in atmosphere

Sulfur

in soil, rock

and fossil fuels

Decay

Dimethyl

sulfide

a bacteria

byproduct

Sulfur

in ocean

sediments

Active Figure 3-22 Natural capital: simplified model of the sulfur cycle, with major harm-

ful impacts of human activities shown by red arrows. See an animation based on this figure at CengageNOW.

Question: What are three ways in which your lifestyle directly or indirectly affects the sulfur cycle?

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

Scientists use field research, laboratory research, and

mathematical and other models to learn about eco-

systems (Concept 3-6). Field research, sometimes called

“muddy-boots biology,” involves observing and mea-

suring the structure of natural ecosystems and what

happens in them. Most of what we know about struc-

ture and functioning of ecosystems has come from

such research. GREEN CAREER: Ecologist. See academic

.cengage.com/biology/miller for details on various

green careers.

Ecologists trek through forests, deserts, and grass-

lands and wade or boat through wetlands, lakes,

streams, and oceans collecting and observing species.

Sometimes they carry out controlled experiments by

isolating and changing a variable in part of an area and

comparing the results with nearby unchanged areas

(Chapter 2 Core Case Study, p. 28, and see The Habitable

Planet, Videos 4 and 9, http://www.learner.org/resources/

series209.html). Tropical ecologists have erected tall

construction cranes over the canopies of tropical forests

from which they observe the rich diversity of species

living or feeding in these treetop habitats.

Increasingly, new technologies are being used to col-

lect ecological data. Scientists use aircraft and satellites

equipped with sophisticated cameras and other remote

sensing devices to scan and collect data on the earth’s

surface. Then they use geographic information system

(GIS) software to capture, store, analyze, and display

such geographically or spatially based information.