Biology 12

CHAPTER

13

Reflecting

Questions

Ecological Principles

428

To avoid the fate of the Easter

Islanders, we need to understand

the impact we have on Earth. The

study of Earth is challenging because

the planet is so large and difficult to

manipulate experimentally. One

possible solution may lie in an

enormous greenhouse, situated in the

Arizona desert. Its massive steel and

glass shell contains roughly 170 000 m^3

of atmosphere, 1 500 000 L of fresh

water, 3 800 000 L of salt water, and

17 000 m^3 of soil, all organized into

different zones that model natural

Earth environments. There is, for

example, a rain forest, a desert, and

an ocean.

This greenhouse, called Biosphere 2,

is one of the world’s biggest

laboratories. Since Earth is so complex

and unpredictable, it is difficult to

determine exactly how specific

organisms are affected by the types

of changes (in variables such as

temperature and carbon dioxide

concentration) we see occurring, or to

predict what might occur in the future.

By using Biosphere 2, scientists can

double the amount of a variable in

one area, while leaving it at a

“normal” level in another similar

area. Controlled experiments like

this are vital to understanding how

change affects organisms.

Originally built for another purpose

(see question 10 in the Chapter Review

section), Biosphere 2 was taken over

by Columbia University in 1996 and

is now a research and teaching

laboratory. With the participation of

many other universities, Columbia

has built a campus adjacent to the lab,

which provides unique educational

opportunities for students from around

the world. Conferences are also

held at the site, for those involved

in studying or managing Earth’s

resources. All of these activities are

designed to help people understand

global problems and consider the

challenges faced by our planet.

In this chapter, you will examine

concepts related to these challenges.

How can you learn about the

complexity of interactions among

organisms so you can understand

them better? How do conditions on

Earth affect its inhabitants? How do

living things affect their physical

environment?

Why are species

distributed as they

are on Earth?

Why are some species

rare while others are

abundant?

What impact does one

species have on other

species in its

environment?

What impact do

organisms have on

Earth itself?

Prerequisite

Concepts

and Skills

Before you begin this chapter,
review the following concepts
and skills:

understanding how

organisms will only

survive and reproduce in

environments to which

they have adapted,

therefore maintaining their

homeostasis (Chapter 6,

section 6.3), and

explaining why organisms

need to obtain energy and

specific nutrients from

their environment to

support normal metabolic

functions (Chapter 3,

section 3.4).

The portion of Earth inhabited by

living things is called the biosphere.

In a facility called Biosphere 2,

scientists are attempting to mimic

conditions on Earth (Biosphere 1) to

study them in a controlled manner.