1. CHAPTER 38 Conservation Biology
Modules 38.6 – 38.8

2. 38.6 There are two approaches to studying endangered populations
CONSERVATION OF POPULATIONS AND SPECIES
38.6 There are two approaches to studying endangered populations
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
Figure 38.6A

3. 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

4. The small-population approach
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

5. The red-cockaded woodpecker requires three habitat factors
38.7 Identifying critical habitat factors is a central goal in conservation research
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
Figure 38.7A

6. Low growth of plants among the mature pine trees
Controlled fires to reduce forest undergrowth
Figure 38.7B, C

7. Increased fragmentation threatens many species
38.8 Connection: Increased fragmentation threatens many populations: A case study
Increased fragmentation threatens many species
This includes those whose populations were historically highly fragmented

8. One example is the endangered bull trout
It inhabits lakes, rivers, and mountain streams in northwestern Canada and the United States
Figure 38.8A

9. The bull trout requires cold, fast-flowing streams with pebble-covered bottoms and little or no silt
Figure 38.8B

10. Before human intervention, the bull trout population consisted of four subpopulations
Egg-laying sites in mountain streams
Regular, frequent dispersal and gene flow between subpopulations
Irregular, infrequent dispersal; minimal gene flow between subpopulations
Figure 38.8C, left

11. The bull trout population has been further fragmented and reduced by
Mill site for silver mine
the construction of hydroelectric dams
logging
road building
mining s3 s5 s4
Hydroelectric dam
Hydroelectric dam
Egg-laying sites in mountain streams
Clear-cut (logged) areas
Roads
Irregular, infrequent dispersal; minimal gene flow between subpopulations
Figure 38.8C, right

12. 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