Page 120 - Environment: The Science Behind the Stories

reviewing Objectives

you should now be able to: severely disturbed but where remnants of the original com-
munity remain. (pp. 103, 106)
Compare and contrast the major types of species • Ecologists today view succession as being less predictable
interactions and deterministic than they did in the past. (p. 106)
• Competition results when individuals or species vie for • If disturbance is severe enough, communities may undergo
limited resources. It can occur within or among species phase shifts involving irreversible change—or novel com-
and can result in coexistence or exclusion. It also can lead munities may form. (p. 106)
to realized niches, resource partitioning, and character dis-
placement. (pp. 94–95) Perceive and predict the potential impacts of invasive
• In predation, an individual of one species kills and con- species in communities
sumes an individual of another. Predation is the basis of • People have introduced countless species to new areas.
food webs and can influence population dynamics and Some of these non-native species may become invasive if
community composition. (p. 96) they do not encounter limiting factors on their population
• In parasitism, an individual of one species derives ben- growth. (pp. 106–107)
efit by harming (but usually not killing) an individual of • Invasive species such as the zebra mussel have altered
another. (p. 97) the composition, structure, and function of communities.
• Herbivory is an exploitative interaction in which an animal (pp. 106–107)
feeds on a plant. (pp. 97–98) • We can respond to invasive species with prevention,
• In mutualism, species benefit from one another. (p. 98) control, and eradication measures. (p. 110)
• In some mutualistic and parasitic interactions, the participants Explain the goals and methods of restoration ecology
are symbiotic, whereas in others they are free-living. (p. 98)
• Restoration ecology is the science of restoring communi-
Characterize feeding relationships and energy flow, ties to a previous, more functional or more “natural” condi-
using them to construct trophic levels and food webs tion, variously defined as before human impact or before
recent industrial impact. (p. 110)
• Energy is transferred among trophic levels in food chains.
(pp. 98–99) • The growing practice of ecological restoration, informed
by the science of restoration ecology, helps us restore eco-
• Lower trophic levels generally contain more energy, bio- logical systems. (pp. 110–111)
mass, and individuals. (p. 100)
• Food webs illustrate feeding relationships and energy flow Describe biomes and identify the terrestrial biomes of
among species in a community. (pp. 100–101) the world
• Biomes represent major classes of communities spanning
Distinguish characteristics of a keystone species large geographic areas. (p. 111)
• Keystone species exert impacts on communities that are far • The distribution of biomes is determined by temperature,
out of proportion to their abundance. (pp. 101–102) precipitation, and other factors. (p. 112) CHAPTER 4 • S PEC i ES i n TERA CT i on S A nd Co mmuni T y E C ology
• Top predators are frequently considered keystone species, • Aquatic and coastal systems can be classified in ways simi-
but other types of organisms also exert strong effects on lar to terrestrial biomes, but these systems are determined
communities. (pp. 101–102) by different factors. (pp. 112–113)

• Biomes include temperate deciduous forest, temperate
Characterize disturbance, succession, and notions of grassland, temperate rainforest, tropical rainforest, tropi-
community change
cal dry forest, savanna, desert, tundra, boreal forest, and
• Disturbances are varied, and communities respond to chaparral. (pp. 113–117)
disturbance in different ways. (pp. 102–103)
• Mountains, with their diversity of elevations and climate
• Succession describes a typical pattern of community conditions, host mixtures of ecological communities. (pp.
change through time. (p. 103) 117–118)
• Primary succession begins with an area devoid of life.
Secondary succession begins with an area that has been
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