Modules38-06to38-08 Conservation of Populations and Species

BIOLOGYCONCEPTS & CONNECTIONS

Fourth Edition

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor

From PowerPoint® Lectures for Biology: Concepts & Connections

CHAPTER 38Conservation Biology

Modules 38.6 – 38.8


• Habitat degradation can lead to population fragmentation

– Portions of populations are split and subsequently isolated

– It often results in species being designated as threatened or endangered

38.6 There are two approaches to studying endangered populations

CONSERVATION OF POPULATIONS AND SPECIES

Figure 38.6A


• The Endangered Species Act (ESA) defines an endangered species as one that is in danger of extinction throughout all or a significant portion of its range

– Example: the northern spotted owl

• The ESA defines a threatened species as one that is likely to become endangered in the foreseeable future

Figure 38.6B


• Some conservation biologists believe that the smallness of a population will ultimately drive it to extinction

• The small-population approach

– Identifies the minimum viable population size for a threatened species

– Focuses on preserving genetic variation

• The declining-population approach diagnoses and treats the causes of a population's decline


• Identifying the specific combination of habitat factors that is critical for a species is pivotal in conservation biology

• The red-cockaded woodpecker requires three habitat factors

– A mature pine forest

38.7 Identifying critical habitat factors is a central goal in conservation research

Figure 38.7A


– Low growth of plants among the mature pine trees

– Controlled fires to reduce forest undergrowth

Figure 38.7B, C


• Increased fragmentation threatens many species

– This includes those whose populations were historically highly fragmented

38.8 Connection: Increased fragmentation threatens many populations: A case study


• One example is the endangered bull trout– It inhabits lakes, rivers, and mountain

streams in northwestern Canada and the United States

Figure 38.8A


• The bull trout requires cold, fast-flowing streams with pebble-covered bottoms and little or no silt

Figure 38.8B


• Before human intervention, the bull trout population consisted of four subpopulations

Figure 38.8C, left

S1

S3 S2

S4

Egg-laying sites in mountain streams

Regular, frequent dispersal and gene flowbetween subpopulationsIrregular, infrequent dispersal; minimal geneflow between subpopulations


• The bull trout population has been further fragmented and reduced by– the construction

of hydroelectric dams

– logging

– road building

– mining Figure 38.8C, right

s1

s3

s2

s5s4

Mill sitefor silvermine

Hydroelectricdam

Hydroelectricdam

Egg-laying sites in mountain streams

Clear-cut (logged) areasRoadsIrregular, infrequent dispersal; minimal geneflow between subpopulations


• Conservation biologists often use computer simulations in a population viability analysis (PVA)

– PVA incorporates as much information about a population's current status as available

– It predicts a species' chance for long-term survival

Modules38-06to38-08 Conservation of Populations and Species

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