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Summary Chapter 56 campbell
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Summary chapter 56 Campbell
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Chapter 56Conservation biology integrates ecology, phycology, molecular biology,
genetics and evolutionary biology to conserve biological diversity at all levels.
Efforts to sustain ecosystem processes and stem the loss of biodiversity also
connect the life sciences with the social sciences, economics and humanities.
Concept 56.1
Extinction is a natural phenomenon that has been occurring since life first
evolved; it is the high rate of extinction that is responsible for today’s biodiversity
crisis.
Biodiversity can be considered at three main levels: genetic diversity, species
diversity, and ecosystem diversity.
Genetic diversity comprises not only the individual genetic variation within a
population, but also the genetic variation between populations that is often
associated with adaptions to local conditions.
Species diversity – the variety of species in an ecosystem or across the
biosphere.
Endangered species as one that is “in danger of extinction throughout
all or a significant portion of its range”
Threatened species are those considered likely to become
endangered in the near future.
Global extinction of a species means that it is lost from all the ecosystems in
which it lived, leaving them permanently impoverished.
Ecosystem diversity – the variety of the biosphere’s ecosystems, because of the
many interactions between populations of different species in an ecosystem, the
local extinction of one species can have a negative impact on other species in the
ecosystem.
Why should we care about the loss of biodiversity?
E. O. Wilson (biologist) because of biophilia, our sense of connection to nature
and all life.
Many species that are threatened could potentially provide medicines, food, and
fibers for human use, making biodiversity a crucial natural resource. Today, the
original disease-resistant population has apparently become extinct in the wild.
Ecosystem services encompasses all the processes through which natural
ecosystems help sustain human life. As human activities reduce biodiversity, we
are reducing the capacity of the planet’s ecosystems to perform processes critical
to our own survival.
Many different human activities threaten biodiversity on local, regional, and
global scales. The threats posed by these activities are four major types: habitat
loss, introduced species, overharvesting, and global change.
Human alternation of habitat is the single greatest threat to biodiversity
, throughout the biosphere. Habitat loss has been brought about by factors such as
agriculture, urban development, forestry, mining, and pollution.
In almost all cases, habitat fragmentation leads to species loss because the
smaller populations in habitat fragmentation leads to species loss because the
smaller populations in habitat fragments have a higher probability of local
extinction. Habitat loss is also major threat to aquatic biodiversity.
Introduced species also called exotic species, are those that humans move
intentionally or accidentally from the species’ native locations to new geographic
regions. Human travel by ship and airplane has accelerated the transplant of
species.
Human have deliberately introduced many species with good intentions but
disastrous effects.
The term overharvesting refers generally to the harvesting of wild organisms at
rates exceeding the ability of their populations to rebound.
Conservation biologists increasingly use the tools of molecular genetics to track
the origins of tissues harvested from endangered species.
Global change alters the fabric of earth’s ecosystems at regional to global scales.
Global change includes alterations in climate, atmospheric chemistry, and broad
ecological systems that reduce the capacity of earth to sustain life.
Global change concern acid precipitation = rain, snow, sleet, or fog with a pH
less than 5.2.
Resurrecting species is at least theoretically possible because of recent progress
in cloning living animals “Dolly” the lamb in 1997.
Concept 56.2
A small population is vulnerable to inbreeding and genetic drift, which draw the
population down an extinction vortex toward smaller and smaller population
size until no individuals survive. A key factor driving the extinction vortex is the
loss of genetic variation.
The minimal population size at which a species is able to sustain its numbers is
known as the minimum viable population (MVP).
The total size of a population may be misleading because only certain members
of the population breed successfully and pass their alleles on to offspring.
Therefore, a meaningful estimate of MVP requires the researchers to determine
the effective population size, which is based on the breeding potential of the
population.
Simply determining the total number of individuals in a small population is large
enough to avoid extinction. Conservation programs attempt to sustain total
population sizes that include at least the minimum viable number of reproducing
active individuals.
The declining-population approach requires that researchers carefully evaluate
the causes of a decline before taking steps to correct it.
The following steps can be used for analyzing declining populations:
1. Confirm, using population data, that the species was more widely distributed
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