BIO 4120 Lecture Notes - Species Richness, Ecosystem Services, Ecological Relationship

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25 Nov 2012
Chapter 57: Conservation Biology
57.1 What is Conservation Biology?
Devoted to preserving the diversity of life on Earth
Draws heavily on concepts and knowledge from population genetics,
evolution, ecology, biogeography, wildlife management, economics and
Conservation biology is a normative scientific discipline
Conservation biology is a normative discipline embraces certain values
and applies scientific methods to the goal of achieving these values;
motivated by the belief that preservation of biodiversity is good and that loss
is bad.
Is guided by three principles:
oEvolution is a process that unites all of biology.
oThe ecological world is dynamic.
oHumans are a part of ecosystems.
Conservation biology aims to prevent species extinctions
Organisms have always altered Earth’s ecosystems.
Very first organisms probably reduced the supply of energetically and
structurally useful compounds (replacing them with waste products).
Early photosynthetic prokaryotes and eukaryotes generated oxygen
(unsuitable for anaerobic organisms).
Plants colonized the land, accelerating the weathering of rocks thus, gaining
access to rock-bound nutrients.
Weathering of phosphorus increased global productivity = rise of oxygen
Rise of vascular plants increased oxygen concentration; lower carbon dioxide
Human beings cause extinctions of other species
oWhen first arrived in N. America (20 000 years ago), encountered a
rich fauna of large mammals.
oMost species were exterminated (overhunting) within a few thousand
The productivity and richness of Earth’s biota has increased during the long
course of life’s evolution, but current situation is unique: all environmental
changes are being caused by a single species.
That’s why now more and more people value biodiversity for many reasons:
oHumans depend on other species for food, fiber, and medicine
oSpecies are necessary for the functioning of ecosystems and its many
benefits and services.
oHumans derive enormous aesthetic pleasure from interacting with
other organisms.
oExtinctions deprive us of opportunities to study and understand
ecological relationships among organisms.
oLiving in ways that cause the extinction of other species raises serious
ethical issues
57.2 How Do Biologists Predict Changes in Biodiversity?
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To preserve Earth’s biodiversity, we need to both maintain the processes that
generate new species and provide conditions that will keep extinction rates
at a typical level
There are four reasons why scientists cannot accurately predict the number
of future extinctions:
oDo not know how many species live on Earth.
oDo not know where species live (i.e. animal ranges are poorly known).
oDifficult to determine when a species actually becomes extinct.
oDo not know what will happen in the future.
Regardless, there are some methods for estimating probable rates of
extinction resulting from human actions (e.g. habitat destruction).
Species area relationship—mathematical relationship between the size of
an area and the number of species that area contains.
Findings suggest that a 90 percent loss of habitat will result in the loss of half
of the species that live in and depend on that habitat.
Current rate of loss of tropical evergreen forests is about 2% of remaining
forest each year; if this continues, at least 1 million species there could
become extinct during this century.
To estimate the risk that a population will become extinct, conservation
biologists develop statistical models that incorporate information about pop.
size, its genetic variation, and the morphology, physiology and behaviour of
its members.
Species in imminent danger of extinction in all or a significant part of their
range are labelled endangered species.
Threatened species are likely to become endangered in the near future.
Rarity is not ALWAYS a cause for concern b/c some species that live in highly
specialized habitats (e.g. panda) have probably always been rare and are
well adapted to those conditions.
Species whose populations suddenly shrink at rapid rates (i.e. “newly rare”)
are usually at high risks.
Species with special habitats or dietary requirements are more likely to
become extinct that species with more generalized requirements.
Populations with only a few individuals confined to a small range can easily
be eliminated by local disturbances.
57.3 What Factors Threaten Species Survival?
Species are endangered by habitat loss, degradation, and fragmentation
Habitat loss is the most important cause of species endangerment.
A habitat loss also affects the remaining habitats that are not destroyed.
As habitats are progressively lost, the remaining habitat patches become
smaller and more isolated and becomes increasingly fragmented.
Small habitat patches are qualitatively different from larger patches of the
same habitat in ways that affect the survival of species.
Small patches cannot maintain populations of species that require large
areas; can support only small populations of many of the species that can
survive in small patches.
The fraction of a patch that is influenced by factors originating outside it
increases rapidly as patch size decreases So, species from surrounding
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