Essentials of Ecology

CONCEPT 4-1 79

Species diversity is the most obvious, but not the only,
component of biodiversity. Another important compo-

nent is genetic diversity (Figure 3-5, p. 53). The earth’s

variety of species contains an even greater variety of
genes. Genetic diversity enables life on the earth to

adapt to and survive dramatic environmental changes.
In other words, genetic diversity is vital to the sustain-

ability of life on earth.
Ecosystem diversity—the earth’s variety of deserts,

grasslands, forests, mountains, oceans, lakes, rivers,

and wetlands is another major component of biodiver-
sity. Each of these ecosystems is a storehouse of genetic

and species diversity.
Yet another important component of biodiversity

is functional diversity—the variety of processes such as

matter cycling and energy flow taking place within

ecosystems (Figure 3-12, p. 60) as species interact with

one another in food chains and webs. Part of the im-

portance of the American alligator (Figure 4-1) is its

role in supporting these processes within its ecosys-

tems, which help to maintain other species of animals

and plants that live there.

THINKING ABOUT

Alligators and Biodiversity

What are three ways in which the American

alligator (Core Case Study) supports one or more

of the four components of biodiversity within its

environment?

Functional Diversity

The biological and chemical processes such as energy

flow and matter recycling needed for the survival of species,

communities, and ecosystems.

Abiotic chemicals

(carbon dioxide,

oxygen, nitrogen,

minerals)

Decomposers

(bacteria, fungi)

Consumers

(herbivores,

carnivores)

Solar

energy

Heat

Heat

Heat

Heat Heat

Producers

(plants)

Ecological Diversity

The variety of terrestrial and

aquatic ecosystems found in

an area or on the earth.

Species Diversity

The number and abundance of species

present in different communities

Genetic Diversity

The variety of genetic material

within a species or a population.

Active Figure 4-2 Natural capital: the major components of the earth’s biodiversity —one
of the earth’s most important renewable resources. See an animation based on this figure at CengageNOW™.
Question: What are three examples of how people, in their daily living, intentionally or unintentionally degrade
each of these types of biodiversity?