Chapter 55

• Three Levels of
Biodiversity

• Genetic differences within a population
• Genetic variations between populations

• Is the variety of species in an ecosystem or throughout the biosphere

– Because of a number of alarming statistics regarding extinction and biodiversity

• Variety of ecosystems in the biosphere
• The local extinction of one species can have a negative impact on the overall species richness of the community
• Human activity is affecting ecosystem diversity

• Biophilia--our sense of connection to nature and other forms of life

• Ecosystem services encompass all the processes
– Through which natural ecosystems and the species they contain help sustain human life on Earth

– Purification of air and water
– Detoxification and decomposition of wastes
– Cycling of nutrients
– Moderation of weather extremes
– And many others

• Most species loss can be traced to four major threats
– Habitat destruction
– Introduced species
– Overexploitation
– Disruption of “interaction networks”

• Human alteration of habitat
– Is the single greatest threat to biodiversity throughout the biosphere
• Massive destruction of habitat
– Has been brought about by many types of human activity

• Those that humans move, either intentionally or accidentally, from the species’ native locations to new geographic regions

• That gain foothold usually disrupt their adopted community, often by preying on native organisms or outcompeting them for resources

• Human harvesting of wild plants or animals at rates exceeding the ability of population of those species rebound
Figure 55.7

• The extinction of one species can doom others, particularly when the extinction involves a keystone species

Concept 55.2: Population conservation focuses on population size, genetic diversity, and critical habitat
Two approaches:
•Conservation biologists who adopt the smallpopulation approach
– Study the processes that can cause very small populations finally to become extinct

• Small pops. Prone to
This positive feedback
Loop that draw pop
Down an extinction vortex
Reduction in individual fitness and population adaptability
Small population
Lower reproduction
Higher mortality
Smaller population
Figure 55.9
Inbreeding
Genetic drift
Loss of genetic variability

• The key factor driving the extinction vortex
– Is the loss of the genetic variation necessary to enable evolutionary responses to environmental change

• The minimum viable population
(MVP)
– Is the minimum population size at which a species is able to sustain its numbers and survive

• A population viability analysis (PVA)
– Predicts a population’s chances for survival over a particular time
– Factors in the MVP of a population

• The declining-population approach
– Focuses on threatened and endangered populations that show a downward trend , regardless of population size
– Emphasizes the environmental factors that caused a population to decline in the first place

• The declining-population approach
– Requires that population declines be evaluated on a case-by-case basis
– Involves a step-by-step proactive conservation strategy

• Landscape and regional conservation aim to sustain entire biotas

• The structure of a landscape can strongly influence biodiversity
• The boundaries, or edges, between ecosystems
– Are defining features of landscapes
Figure 55.14a, b
(a) Natural edges.
Grasslands give way to forst ecosystems in
Yellowstone National Park.
(b) Edges created by human activity.
Pronounced edges (roads) surround clear-cuts in this photograph of a heavily logged rain forest in Malaysia.

• As habitat fragmentation increases and edges become more extensive, biodiversity tends to decrease

• A movement corridor
– Is a narrow strip of quality habitat connecting otherwise isolated patches
– Can promote dispersal and help sustain populations

• A biodiversity hot spot is a relatively small area
– With an exceptional concentration of endemic species and a large number of endangered and threatened species hot spots
Equator
Figure 55.17

• Nature reserves are biodiversity islands
– In a sea of habitat degraded to varying degrees by human activity
• The zoned reserve model recognizes that conservation efforts
– Often involve working in landscapes that are largely human dominated

• Concept 55.4: Restoration ecology attempts to restore degraded ecosystems to a more natural state

• Bioremediation
– Is the use of living organisms to detoxify ecosystems

• Biological augmentation
– Uses organisms to add essential materials to a degraded ecosystem

• The newness and complexity of restoration ecology
– Require scientists to consider alternative solutions and adjust approaches based on experience

• Concept 55.5: Sustainable development seeks to improve the human condition while conserving biodiversity

• Acquire the ecological information needed for the development, management, and conservation

• Our innate sense of connection to nature may eventually motivate a realignment of our environmental priorities