prinCiples of eCology 469summary
section 24.1 Ecology is the study of
interactions of organisms with one another
and with their physical environment.
The regions of Earth’s crust, waters, and
atmosphere where organisms live make up
the biosphere. Every kind of organism has a
habitat where it normally lives. The species in a given habitat
associate with each other as a community.
An ecosystem encompasses producers, consumers, and
decomposers and their physical environment. All interact with
their environment and with one another through a flow of
energy and a cycling of materials. A species’ niche consists of
the combined physical, chemical, and biological conditions it
needs to live and reproduce in an ecosystem.
In ecological succession, the first species that take hold in
a habitat are later replaced by others, which themselves are
replaced until conditions support a more or less stable array of
species in the habitat.
section 24.2 Ecosystems gain and
lose energy and nutrients. Sunlight is the
main energy source. Primary producers
(photosynthesizing plants or algae) convert
solar energy to forms that consumers can
use. Primary producers also assimilate many
of the nutrients that are transferred to other
members of the system.
Consumers include herbivores, which feed
on plants; carnivores, which feed on animals;
and omnivores, which have combination diets.
Consumers also include decomposers, such
as fungi and bacteria that feed on particles of
dead or decomposing material.expLoreon your oWn
Benjamin Franklin once remarked, “It’s not until the well
runs dry that we know the worth of water.” Everybody needs
water—an essential fluid that is in increasingly short supply. Have you
ever wondered about the impact of your own water use? You can get
an idea using the following average statistics:
In a typical U.S. home, flushing toilets, washing hands, and bathing
account for about 78 percent of the water used.
Nearly all toilets installed in the United States since 1994 use
1.6 gallons for each flush. Older toilets use about 4 gallons.
A shower uses about 5 gallons per minute (less if you have a low-
flow shower head). Brushing teeth with the water running uses about
2 gallons. Shaving with the water running full blast can use up to
20 gallons.
Washing dishes with an automatic dishwasher uses about 15 gallons;
handwashing dishes with the water running doubles that water use.
Using these numbers as a guide, keep track of your water use for
a typical day. Are there ways you could conserve and still meet your
basic needs?An ecosystem’s energy supply is transferred through
feeding (trophic) levels. Primary producers make up the first
feeding level, herbivores make up the next, carnivores the next,
and so on.
Organisms that get energy from more than one source
cannot be assigned to a single feeding level.
A food chain is a straight-line sequence of who eats whom
in an ecosystem. Food chains usually cross-connect in intricate
food webs.
section 24.3 Primary productivity is the
rate at which producers capture and store
a given amount of energy in a given time
period in an ecosystem. The amount of energy
flowing through consumer levels drops at each energy transfer
through the loss of metabolic heat and as food energy is shunted
into organic wastes. Energy relationships in an ecosystem can
be represented as an ecological pyramid in which producers
form a base for successive levels of consumers.
sections 24.4–24.6 In a biogeochemical
cycle, a substance moves from the physical
environment into organisms, then back to the
environment.
Water enters and leaves ecosystems through
the water cycle. In the carbon cycle and the
nitrogen cycle, where the elements exist mainly as atmospheric
gases, the elements move through food webs and then
ultimately return to the atmosphere.revieW Questions
- Explain what an ecosystem is, and name the central roles
that producers play in all ecosystems.
E.F. Benfield, Virginia TechCopyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).